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Tuatara aims to stimulate and widen interest in the natural sciences in New Zealand, by publishing articles which (a), review recent advances of broad interest; or (b), give clear, illustrated, and readily understood keys to the identification of New Zealand plants and animals; or (c), relate New Zealand biological problems to a broader Pacific or Southern Hemisphere context. Authors are asked to explain any special terminology required by their topic. Address for contributions: Editor of Tuatara, c/o. Victoria University of Wellington, Box 196, Wellington, New Zealand. Enquiries about subscriptions or advertising should be sent to: Business Manager of Tuatara, c/o. Victoria University of Wellington, Box 196, Wellington, New Zealand.
(This issue edited by
is the journal of the Biological Society, Victoria University of Wellington, New Zealand, and is published three times a year. Joint Editors:
Part 2
(continued from Vol. 11, p. 207)
Jubula. couplet 9. This genus which has characters of both Frullania and Lejeunea is now considered to be closer to Lejeunea. The discovery of this genus in Stewart Island by W. Martin, is, I understand, the first in the Southern Hemisphere.
Drepanolejeunea couplet 11. Stephani's Harpalejeunea colensoi is considered to be a Drepanolejeunea.
Leptolejeunea couplet 14. This genus is included on the basis of an identification by the late Dr. Herzog of an undescribed species from Kauri Valley on kie-kie leaf, coll. H.
Cheilolejeunea couplet 16. Strepsilejeunea and Euosmolejeunea are now included in Cheilolejeunea. All three were originally Spruce's subgenera of Lejeunea.
Taxilejeunea couplet 18 is retained, not because of Stephani's T. colensoana which is a Lejeunea, but because of an undescribed species, Herzog's T. seriata with a series of perianths and innovations along the stem.
Arachniopsis couplet 1. It is now accepted that Lepidozia herzogii, with a complete absence of a basal discus in the leaf, is an Arachniopsis. Evans (1939) placed this genus in the Cephaloziaceae, but its non-exclusively ventral branching, and the fusiform-cylindrical (not trigonous) perianth are characteristics of the Lepidoziaceae. The sporophyte of Arachniopsis has not yet, I think been investigated morphologically.
With the introduction of Arachniopsis to the New Zealand flora, the transference of Lepidozia herzogii to this genus is made accordingly.
Arachniopsis herzogii (Hodgson) Hodgson comb. nov. Type: From Russel. Bay of Islands, North Island, leg. V. W. Lindauer (No. 281).
Lepidozia herzogii Hodgson Trans. Roy. Soc. N.Z., 78, 500, 1950, nom. nov. pro L. bisetula Herzog, Trans. Roy. Soc. N.Z., 68, 44, 1938, non L. bisetula Stephani, Spec. Hep., vi, 323, 1924.
Telaranea herzogii (Hodgson) Hodgson Rec. Dom. Mus., 4, 11, pp. 101-132. 1962.
The class Anthocerotopsida which includes five or six genera, according to opinion, is represented by about 300 species, comprising one order Anthocerotales.
Plants (gametophytes) thalloid, dorsiventral, lobed, internal tissues not differentiated. Rhizoids small, smooth-walled, ventral scales absent. Air-chambers and pores absent. Cells usually each with a single chloroplast with a pyrenoid. Antheridia endogenous in closed cavities on the thallus. Archegonia sunk in the tissue of the thallus. The sporophyte indeterminate in growth, consists of a foot, an intercalary meristematic region and a long cylindrical capsule with a central columella. Stomata present in the capsule wall. Capsule splitting along one side and liberating the spores.
Family Anthocerotaceae, Anthoceros, Phaeoceros, Megaceros, Dendroceros.
Professor H. B. Fell recently left Victoria University of Wellington to take up a position at Harvard University. Professor Fell had been editor of Tuatara since April, 1961, and the present healthy state of the journal, both financially and editorially, is in large part due to his efforts. Professor Fell combined efficiency with imagination in his approach to the post of editor and his success is attested by the commendable regularity of appearance of issues, the greatly improved format and the fact that support for the journal has increased to the point where there is now a steady supply of largely unsolicited manuscripts.
The Biological Society greatly appreciates Professor Fell's contributions to the success of its journal and wishes him every success in his new position.
Many New Zealand Shrubs have branching patterns which are recognisably distinctive, but difficult to describe. Observations of the habit of shrubs and particularly of divaricating shrubs have suggested differences which could be used as the basis for a classification.
In a ‘normal’ shrub each new branch makes an acute angle with the branch it springs from, so that the pattern of branches is a three-dimensional spreading fan. In some extreme cases where new branches are set at a very narrow angle, the branches may all come to stand more or less erect and parallel to one another. This form of growth is known as fastigiate. If on the other hand the angle of divergence of secondary branches is as much as 90 degrees or more, the branchlets will grow amongst each other and become increasingly intermeshed to produce a twiggy shrub regardless of the structure which underlies that divaricating form. The term divaricating itself refers to the wide branching angle but it has come to be used of any tangled, appearance. In juvenile Sophora microphylla and
The following is not presented as exhaustive, but may be useful as a basis for critical observation and description of plant habits.
(1) Normal branching (at an acute angle):
(a) with straight twigs e.g. (b) with zig-zag twigs e.g. juvenile
(2) Branches set at a narrow angle to the parent axis and tending to be parallel (fastigiate) e.g.
(3) Branches set at right angles to the parent axis:
(a) branching distantly placed or lax e.g. (b) branching close-set e.g. (c) branching tends to be sympodial as there is regular die-back of the tips e.g.
(4) Branches reflexed at an angle of more than 90 degrees e.g.
The term ‘divaricating’ is used of all the types 1 (b), 3 (a), 3 (b), 3 (c) and 4 in the classification.
G. M. Taylor
(continued from Vol. II, p. 177)
Beauty has been accused by being ‘only skin deep.’ The theories of Lorenz and Tinbergen soon came under attack from a number of directions and new facts began to accumulate which would clearly not fit the theoretical systems unless these were revised.
In the writings of Lorenz the impression conveyed to many was that behaviour was either innate or learned and that these classes were exclusive and exhaustive. At least he claimed that the essence of ethology was the discovery of ‘a distinct and particulate physiological process … a certain type of innate, genetically determined behaviour patterns’ (Lorenz, 1950: 221) which was independent of individual experience in the life of an animal. It was soon pointed out that there is a sense in which all behaviour is both innate and the product of experience — the outcome of interaction between inheritance and the environment in which the inherited material finds itself (e.g. Hebb, 1953). Tryon (1929) had already shown that learning ability has a genetic basis: from a single population of rats he selected pairs with similar maze-running performances and allowed them to mate. After several generations of such matings selected on the basis of maze learning he had two groups: one contained ‘maze-bright’ rats and the other ‘maze-dull’ rats and divergence between the two groups had reached the point where there was no overlap in maze running scores between them. On the other hand von Senden (1932) and Riesen (1947) had shown that an ‘inborn’ reaction could be dependent on prior learning to perceive certain stimuli. At a certain age chimpanzees show a fear response to snakes or snake-like objects. They show this reaction without any previous experience of snake-like objects or of opportunity to imitate the reactions of others to such objects. But the capacity to show the reaction is dependent on ability to perceive the object visually, and this ability is acquired through experience.
Beach (1955) complained that the crux of the definition of innate behaviour is that it (innate behaviour) is unlearned — a negative definition or definition by exclusion. Such a two-class divisions of behaviour is indefensible, Beach said, unless one is thoroughly clear about what constitutes learning and learned behaviour, and this no one could claim to be. Further, the confidence with which it is asserted that a particular behaviour pattern is innate tends to be inversely related to the extent to which the development of this behaviour pattern, in the life of the animal, has been studied. Lehrman (1953, 1955) made this same point by citing experiments which indicated the roles of interaction between organism and environment in the development of responses which, by all the standards accepted by the ethologists, would be classified as innate, e.g. the pecking of chicks (Kuo, 1932), the parental behaviour of rats (Birch, unpublished observations cited by Lehrman, 1955: Riess, 1949).
Lehrman (1953) and Schnierla (1956) made the further point that classification according to the innate-learned dichotomy tends to emphasise superficial resemblances at the expense of profound differences between different kinds of animals. For example Schnierla (1959) showed that ants and rats could learn to run the ‘same’ maze but that they went about the process in quite different ways. Moreover, whereas this experience tends to improve the rat's performances in subsequent encounters with new mazes, the ant performs worse, if anything, when it is given a new maze to learn. The apparent differences in the processes underlying the maze-learning of these two animals is masked by unqualified use of a blanket term to cover both. These workers warned that uncritical use of such question-begging terms as ‘innate’ and ‘learned’, when applied to events in the ontogenies of individuals, could act as a damper on curiosity — an invitation to consider a problem solved before it had been investigated It is a nice irony that Lorenz, who claimed that it was possible (let alone an ‘inviolable law’) for science ‘to begin with pure observation, totally devoid of any preconceived theory and even working hypothesis’ (Lorenz, 1950: 232), should be taken to task for selecting examples to demonstrate an a priori principle and for failure to take account of the facts because of rigid and preconceived ideas (Lehrman, 1953).
Although the distinction between ‘appetitive’ and ‘consummatory’ behaviour provided useful pigeon holes in the initial stages of descriptive ethology, it was soon shown to be a difference of degree rather than of kind, and that a number of
The notion of consummatory act was questioned when it was shown that the terminations of many behaviour sequences are not actions involving the expenditure of muscular energy, but situations which provide a specific pattern of stimulation (Moynihan, 1953; Bastock, Morris & Moynihan, 1954; Kortlandt, 1955, Hinde, 1954). The work of von Holst and his students (von Holst & Mittelsteadt, 1950; von Holst, 1954) introduced the concept of Reafferenz or negative feedback into ethological thinking. Roughly speaking the Reafference Theory says that a particular act is ‘ordered’ by the central nervous system with the ‘expectation’ (Sollwert) of a certain result; the stimulus changes effected by the performance of the act are fed back into the CNS and ‘compared’ with those expected. Subsequent action depends on this comparison: if there is discrepency between received and ‘expected’ stimuli further action is instituted in the direction which will correct the discrepancy, Von Holst and Mittelsteadt took as one of their examples the optomotor reflex of the house fly. If a pattern of vertical stripes is moved across a fly's visual field the fly will reflexly turn in the same direction as the moving stripes. When the fly itself moves and the stripes stay still the effect, as far as the fly's visual receptors are concerned, is again movement of stripes across the visual field, but in this case the turning ‘reflex’ is not shown. The reason given for this by classical reflex theory was that, when the fly moved, the turning reflex to moving visual patterns was inhibited. Von Holst thought there might be another explanation. If the fly's movements were affected by discrepency between ‘expected’ and received visual stimuli then the optomotor reflex might be absent when the fly moved because then the changes in its visual field were changes that it ‘expected’ to result from its movements. To test this hypothesis von Holst and Mittelsteadt rotated the head of a fly through 180° and glued it to the thorax so that its left-hand eye was now on the right side and its right hand eye on the left side. This meant that a stripe that was actually crossing the visual field from left to right seemed to the fly to be crossing from right to left. If the classic reflex theory held, this should make no difference to the fly's behaviour when it moved. In fact, however, whenever the fly moved, it very quickly began spinning in small circles and would go on doing this until exhausted, and this is according to the predictions of the reafference theory. Twisting the head of the fly had caused it to misread its visual information so that the movement it made to correct a discrepency between input and Sollwert made the discrepency worse instead, which re-stimulated the movement to give further augmentation of the discrepency, and so on in a never ending vicious circle. The reafference model is similar in principle to the servo-mechanisms
homeostasis and is illustrated by such things as the control of circulation and respiration.
The application of this sort of thinking to animal behaviour tended to change the concept of the end In a recent discussion of the concept of consummatory act Sevenster-Bol (1962) has argued that if the term continues in use it should have no more than a descriptive sense — it can refer to the end act of a behaviour sequence without implying anything about factors or mechanism involved in the termination of the sequence.act or consummatory act in the direction of consummatory stimulus situation — the stimulus input cancelling further action of a certain sort
With the change of emphasis from the action at the end of a behaviour sequence to the stimulus input, the idea of consumption of energy or exhaustion of motivational impulses, came to look out of place. Moreover some of these ideas were at variance with what was known about the functioning of nervous systems. By drawing analogies with hydraulic systems and electrical circuits, Lorenz and Tinbergen had been led to attribute properties to nervous systems which neurophysiology had shown they could not possess — to talk of ‘damming up’ of impulses, ‘sparking over’, accumulation and ‘consummation’ of energy, was to take little account of what was known about nerve impulses and the functioning of neurones and neuronal systems. These shortcomings were pointed out in a series of papers by Robert Hinde (1956, 1959, 1960b), in which he also showed the inability of the ethological models, and the notion of ‘unitary drives’ that went with them, to do justice to other facts. He showed, for example, that where a behaviour pattern could be measured in a number of ways — frequency of performance per unit time, intensity of performance along some scale, latency after presentation of stimulus, duration of performance, strength of stimulus required to elicit performance, strength of stimulus required to inhibit the reaction or release an incompatible reaction — there was often considerably less than complete correlation between the values of the different measures (e.g. Hinde, 1958). Such degrees of independent variability between measurable aspects of a behaviour pattern were difficult to reconcile with the notion that an account of performance of a behaviour pattern could be reduced to fluctuation in a single variable, the ‘drive’, level of ‘action specific energy’, ‘motivational impulses’ or
A further objection to the use of drive concepts is that frequently vagueness of definition and inconsistency of reference are barriers to clear thinking. Two writers rarely employ the term in the same sense, and even within a single publication one is likely to find the term sliding between two or more, sometimes incompatible, senses: ‘drive’ can refer to extraneural state or intraneural state or both together, it can refer to a mechanism or to a quantity of energy, to tissue needs or ‘deprivation interval’ or deviation from a homoeostatic level (see Peters, 1958, for a linguistic philosopher's critique of the uses of ‘drive’). The concept of instinct presents similar ambiguity; Tinbergen, in a recent discussion (1960: 191) pointed out four quite different meanings of this term and he probably could have added more.
To overcome the bad features of early formulations of drive concepts in ethology a conference of animal behaviour workers (Cambridge in 1949 — see Thorpe, 1951) recommended that Specific Action Potential(ity) (SAP) replace the older terms and that the reference of this term should be to the readiness to perform, or the probability of performance of, a particular behaviour pattern in a particular situation; it was to imply nothing definite about internal mechanisms but was to be an objective variable based on observed behaviour. As a counter to imputations of teleological thinking (Lehrman, 1953: 352) and vitalism (Kennedy, 1954), Specific Action Potential was offered as an ‘operational’ term — a concept defined solely in terms of observations and measuring procedures In the language of MacCorquodale & Meehl (1948) the older notions of Action Specific Energy and Motivational Impulses were To illustrate this distinction consider an example from physics. By making simultaneous measurements of the current and e.m.f. in a wire we find that there is a regular relationship between these two variables: E ഗ I. We can express this relationship as an equation by adding a constant so that E = 1R, where R is our constant which we call the Resistance. This is Ohm's Law. So far R is defined solely in terms of E and I; it is an intervening variable that enables us to make an equation. If, now, we try to explain the relationship between current and e.m.f. by some such notion as obstruction to the flow of electrons, we give the term Resistance additional information content (surplus meaning) and to this extent it becomes a hypothetical construct.hypothetical constructs — terms that postulated the existence of entities not immediately available to observation — and they had been found wanting because the supposed properties of these entities were inconsistent with certain already known properties. SAP, on the other hand, was an intervening variable only; a term which linked independent variables (such as time) with dependent variables (such as response strength) without carrying any further meaning.
The SAP concept acquired current usage. It is now more often referred to as tendecy. In principle its use signifies a quantitative aspect of a piece of behaviour, based directly or indirectly on past observation. For instance if it is said that in a certain situation an animal shows a strong tendency to flee (say), or shows a high fleeing tendency, this means that we think that the animal is very likely to flee and we make this judgment because the animal has frequently fled when observed in this situation in the past.
Now Hinde (1960b) has pointed out than an explanatory model can err in two directions: as already mentioned it can be misleading if it attributes unreal properties to the explicandum; on the other hand if its properties correspond too closely to those of the explicandum it fails to illumunate it. For a model to explain it must have a wider reference or information content than the phenomena to be explained (e.g. see Braithwaite, 1959: 302; Harré, 1960: 101-2), otherwise all we are given is simply a re-presentation or redescription of our puzzle. Similarly a
Perhaps awareness of the necessity for an explanatory hypothesis to refer to something outside the explicandum accounts for some inconsistent use of the SAP or tendency concept and some circular argument that has resulted from such inconsistency. For example van Iersel & Bol (1958), in a study of preening in terns, use the concepts of tendency to approach the nest and tendency to withdraw from the nest and one assumes that what is meant when it is said that the tendencies are at certain levels is that the probability of approach is so and so and the probability of withdrawal such and such and that these are judgments based on past observation. But when these authors attempt to say why the probability of approach is so and so, and the probability of withdrawal such and such, the ‘explanation’ is usually in terms of approach and withdrawal tendencies. Clearly, for this to be of any use, the senses of approach and withdrawal tendencies, in the explanatory statements, must include more than they started out with. In the theoretical part of this paper it seems that the terms take on the properties of unitary drive factors although the nature of these added properties is not made explicit. Similarly the notion of inhibition, as used by van Iersel and Bol, seems to start out as an operational concept, grounded in the fact that two particular responses do not occur simultaneously, and then, later, is put to use to account for the fact that these two responses are incompatible. This type of argument occurs also in a recent treatment of displacement activities, by another member of the Leiden laboratory (Sevenster, 1961).
In practice, also, the concept of SAP or tendency is frequently taken to refer to a quantity that can be measured equivalently in a number of ways, with little attempt to test the correlation between these different measures. Thus van Iersel & Bol (1958) use a number of measures as equally good indicators of ‘incubation tendency’: ‘sitting tendency’, the landing distance after alarm, the readiness to depart at nest relief, the time a bird has gone without incubating. My studies of incubation behaviour in gulls
Similar jumps were made, in some of the older work, when it was assumed that all the responses serving a particular function are expressions of the same instinct. This was usually taken to mean that these responses were controlled by the same underlying mechanism or drive, from which it followed that they had a closer causal affinity to one another than any had to responses grouped in other instincts. Tests of this assumption have shown that a classification of responses according to the ends they serve need not correspond to a classification according to common casual factors (Beer, 1963, in press).
Confusion between the cause and goal of behaviour, between efficient and final causes, seems difficult to avoid, and is perhaps due, in part, to the fact that we account for our own actions by stating the ends we had in view when we carried them out. If used carelessly some of the technical jargon of behaviour studies can help this confusion rather than dispel it; when we meet terms like‘ expectancy ’ and ‘intention movements’ applied to fish or insects it is an easy step to anthropomorphic thinking. The term motivation has a number of connotations. It is derived, etymologically, from the verb ‘to move’ which has also given rise to ‘motor’ and ‘motive’. Both of these notions — the idea of something that drives like an engine, and the idea of the end in view of an agent doing or planning something — attach to the idea of motivation so that the study of motivation can mean the study of motives and the study of the physical and chemical mechanisms underlying behaviour. No doubt in some contexts this is a false opposition but most of the time it seems wise to observe and maintain the distinction between the causes and goals of behaviour (for another view on this question see Hinde, 1957).
The ethologist, with his zoological background, emphasises the role of natural selection, and hence functional adaptation, in the explanation of behaviour. This was and is an important and necessary emphasis, but it encourages the tendency to identify proximate causes with ultimate causes, to assume that because a certain set of responses has been selected because they together achieve a certain adaptive end, these responses must be controlled by a unitary causal mechanism inside the animal. For example the fact that a particular posture occurs in a situation where two responses are equally likely to occur (e.g. approach and withdrawal) is often accounted for by saying that the posture arises because of the balanced conflict of these two tendencies (e.g. van Iersel
As I have tried to point out for similar cases, if ‘conflict’ here means simply equivalence of probabilities for the two tendencies then we are given no new information; if, on the other hand, it means something more than this, we are entitled to ask what this something is and what independent evidence there is or could be for it. The term ‘conflict’ is particularly liable to cause confusion because there are at least four senses that it can have in such a context as territorial fighting: it can refer to the fact that two animals are clashing — we might speak, in this sense, of a conflict of interests; it can refer to the fact that two incompatible tendencies are equally aroused (e.g. the animal is equally likely to attack or flee) —a conflict of possible outcomes; it could refer to conflict between the internal mechanisms underlying the two tendencies (‘fleeing drive’ and ‘attack drive’); or it could refer to opposition of selection pressures in the evolution of the behaviour — conflict of functions.et al, 1962), and that the posture in question has been evolved as a ‘compromise’ solution. Again it seems to me that clear thinking will be achieved only when we can hold apart the functional or historical explanation on the one hand, and explanation in terms of proximate causal mechanisms on the other.
‘It does not seem over-optimistic to suggest that ethology is now entering a period of rapid expansion — a process which may, however, require a thorough revision of some of the concepts which have grown up with it and seen it through its teething troubles’ (Hinde, 1956: 321). The results of criticism of the older ethological concepts and theory, and the accumulation of new data, have been revision of the concepts and theory, increase in the precision of statements, increase in the detail of descriptive analysis, and application of the techniques and ways of thinking developed in other fields. This, together with the steadily increasing numbers of students, in both America and Europe, applying themselves to study of animal behaviour, has meant that instead of the small, rather homogeneous group of investigators that assembled for the first international ethological conference, we now find ethologists to be a large ill-defined group within which there has developed a number of special interests and considerable differences of opinion on many points. There is no general adherence to a specific structure of theory, as there was in 1950; technical terms have been brought much more into line with those used in related fields such as physiology and psychology and there is increasing cross-fertilisation with these related fields.
Is ethology losing its identity as a separate field of study then?
Perhaps it is to some extent, but the many present-day developments are clearly continuations of the ways of thinking about animal behaviour that were pioneered by Lorenz, and within the diversity one can see a unity of approach or attitude that derives from a common background of general zoology: the animals are still regarded from the standpoint of natural selection, as creatures that can be understood only if seen against the background of their natural setting.
This attitude is most clearly apparent in the students who try to explain behaviour in terms of its function, or use behavioural data to help in working out the adaptive value of some feature of form or function. Tinbergen's attention has been devoted to this sort of problem in recent years. One of his students has worked on the question of why so many sea birds have white plumage: from a study of the feeding habits of the birds and the visual responses of fish to differently coloured models he showed that the whiteness of the birds is very likely an adaptation to a certain kind of fish-catching way of life (Unpublished work by Phillips cited to me in a personal communication by Dr. Tinbergen). Tinbergen and a team of co-workers have examined the question of why Black-headed Gulls carry the broken egg-shells from their nests after hatching (Tinbergen et al, 1962). In a preliminary study (unpublished) I had found that carrying of shells from the nest could be released by placing shells in the nests at any time during the breeding season (not just at hatching), and that the reaction was shown not only to egg shells but to a range of conspicuous objects. Tinbergen and his students systematically tested the responsiveness of the gulls to a wide range of objects and found two peaks in this range: the more conspicuous an object was against the background of the nest the greater its releasing value, and the more like a real egg shell it was the greater its releasing value. Real egg shells were better releasers than any of the other objects even though they were considerably less conspicuous than some of them. This suggested that two selection pressures have acted in the evolution of the response; one favouring responsiveness to conspicuous objects in the nest, the other favouring responsiveness specifically to egg shells. The first suggested a visual predator and there were several obvious candidates for this role in the region such as carrion crows and herring gulls. To test the possibility that removal of conspicuous objects from the nest is advantageous because such objects might catch the eye of an egg-predator, the following experiment was set up: a number of artificial nests were made outside the gullery and eggs were placed in these nests, some containing a conspicuous object and others not. After a time these nests were examined and it was found that significantly more of those containing a conspicuous object had been robbed of their eggs. This result confirms that
This study illustrates how a question of the form ‘Why does the animal do so-and-so?’ can be put in different ways: it can be directed to the causes acting directly, here and now, to produce the behaviour and these can be divided into those external to the animal and those acting within the animal; it can be directed to the function served by the behaviour — in the natural life of the animal and this in turn leads to consideration of the evolutionary history of the behaviour; it can be directed to the individual history of the animal — how has this behaviour developed in ontogeny? In the egg shell study, investigation of proximate causes (external stimuli) led Tinbergen and his colleagues to reach conclusions bearing on the function of the behaviour and hence on its ultimate causes in the history of the species.
Other workers have directed their attention mainly to unravelling the organisation of proximate factors underlying behaviour and here we can make a division between those who are concerned to make correlations between external factors, physiological states or events and behaviour, and those who are concerned to work out the formal properties that any physiological mechanism must have if it is to account for a particular behaviour pattern. This division is not a hard and fast one; there are various combinations of method and interpretation. In the first group we should include, as ground floor members, the many descriptive studies that establish the quantitative and qualitative regularities of animal behaviour (e.g. Lind, 1959; Manley, 1960; Wickler, 1962). Then there are numerous studies of the effects of natural or experimentally induced differences in such things as the available external stimuli (e.g. Beer, 1961, 1962 a & b, 1963; Hinde, 1958; Lehrman et al, 1961), hormone levels in the blood (e.g. Warren & Hinde, 1959; Lehrman & Brody, 1960), tissue needs (e.g. Tugendhat, 1960a), previous experience (e.g. Tugendhat, 1960b). Notable combinations of observational and experimental techniques are to be found in the studies of ‘biological clocks’ (see Cold Spr. Harb. Symp.
In the second group of workers are first of all the students who have been influenced by Cybernetics and information theory — the models of animal functions, particularly the functions of the brain, that have been drawn up by making analogies with the operations of telephone systems and electronic computers (e.g. Wiener, 1948). By tracing the patterns of qualitative and quantitative relations between dependent and independent variables that describe a behaviour pattern, students such at Mittelsteadt (e.g. 1958) and Hassenstein (e.g. 1960) attempt to work out the range of formal models that would produce such relationships. If these models are genuinely different they will lead to different predictions, and testing of these predictions should eventually eliminate all but the only adequate model. The best known and most accessible example of this type of thinking in ethology is still the Reafference Theory (von Holst, 1954) I mentioned in the last section. Such formal or mathematical models for behaviour tend to remain untranslated into terms of flesh and blood. Until they can be their heuristic value is probably limited.
A second approach to a formal model of the underlying organisation of a behaviour pattern has been by way of statistical methods. The increasing availability of electronic computers and data recording devices has allowed the analysis of a great deal more of the detail of behaviour patterns than was possible in the past, and also more comprehensive statistical treatment of such data (see Beer, 1962c). By application of the techniques of multiple correlation analysis and factor analysis it has been possible, in
Although the use of electronic recording devices and computers increases the accuracy and detail of description immensely it has not removed the element of arbitrariness that enters into any analysis of behaviour. Measurement involves the division of behaviour into units that can be counted or timed. Behaviour is a continuum that can be broken up in an infinite number of ways; every classification, of necessity, ignores some ranges of variation — the notion of a complete description is really a contradiction in terms. The selection of units for measurement will not be made at random; there will be some prior idea of what is useful or relevant to the problem on hand. But here there enters a danger if one is not self-critical of one's criteria of selection; it is possible to ensure that you get the answer you expect or hope for by unwittingly sorting the information to that end. If, for example, you want to know how often two postures are associated and you find that one of these postures occurs in a number of situations that seem to have nothing to do with the other posture you might want to leave the latter occurrences out of account. Unless you can find an objective way of making the separation into two classes of occurrences — one relevant and the other not — your result is likely to reflect no more than the association that you think tendency with respect to a particular behaviour pattern: if a tendency is identified with one of these variables it remains an operational concept but, at the same time, makes more profound conditions about the properties that a physiological model for the underlying mechanism of the behaviour should possess.ought to obtain between the two postures. Before units are selected for measurement it should be insisted that the student spend as much time as possible in familiarising himself with the whole behaviour of the animal, preferably in its natural habitat or under conditions which reproduce the essentials (a question-begging word!) of the natural situation. If this is well done the student will be in no doubt about the complexity of the problem with which he has to deal and he will regard his efforts at measurement with a healthy scepticism.
The study of the ontogeny of behaviour has not received the attention that one might have expected from the emphasis that was placed on the innate elements of behaviour in the earlier ethological writings. Tinbergen (e.g. 1955: 102) now admits the term ‘innate’ to be useful only when applied to In a recent review Hess (1962) differs from me in being much more impressed by this paper of Lorenz's. We apparently differ also in our assessments of Hinde's examinations of unitary drive concepts; for Hess makes no reference to Hinde's papers on the subject, and uses the term drive throughout his review without any attempt to qualify its vagueness and ambiguity. I also object to his classification of Hebb, Lehrman, and Schnierla as ‘behaviourists’. This is either capricious or reflects profound misunderstanding of the work of these people.differences in behaviour between animals (the differences in behaviour between identical twins are clearly not due to differences in genetic factors) or between species (the differences between a man and an ape are clearly not due only to differences in up-bringing) and not when applied to processes of development which give rise to behaviour patterns in the life of an individual. However Lorenz has recently published a rather polemical paper (Lorenz, 1961) in which he defends his dichotomy between innate and learned behaviour and ridicules ‘many modern ethologists, mainly those publishing in English’ who have not had the courage of their convictions. There is little that is new in his arguments except perhaps his
that adaptation must be secured in the germ plasm does not answer the question how adaptation is secured in the germ plasm in any instance. Perhaps Lorenz is not really concerned to ask such a question. But when he points out that for certain behaviour patterns to be adaptive they must be ‘environment resistant’, or for others that they must be performed perfectly at the first time of asking without prior experience of trial and error learning, and hence that the information for the developments of such patterns must reside solely in the genotype, he perhaps invites yet another confusion between ultimate and proximate causation — between the problem that was set by Nature and the nature of the solution in terms of the developmental processes in the individual. Further, the notion of information, as used in his paper, is so vague that in saying that the basis of adaptive responses must be genetically carried information Lorenz seems frequently to be saying no more than that the behaviour is the product of evolution, which surely is true of all behaviour in some sense. In spite of the suggestion of technical precision that it imports from the context of information theory, Lorenz's genetically carried ‘information’ seems to be little more than a blank cheque into which he can write any regularity which is species specific or species characteristic irrespective of the precise ontogenetic basis of such regularity. The translation of the ‘information rsquo; (whatever it is) into structure and function is a problem that cannot be decided in advance but can be worked out only by study of the development of individual behaviour patterns through ontogeny.
The roles of experience in ontogeny have been extensively studied in the development of song in birds. This has been greatly assisted in recent years by the application of sound spectrography, a technique which enables one to get a pictorial record of sound as well as a measure of its frequency ranges. The consequent detail and precision of description and quantification are greater than is possible for most types of behaviour (see Marler & Isaac, 1960). By raising birds in isolation in sound proof conditions (what the Germans call the Kaspar-Hauser experiment) it has been shown that, with variations from species to species, certain features of a bird's song are affected by hearing the singing of other birds and other features are not (Thorpe, 1961; Blase, 1960; Thielke-Poltz & Thielke, 1960). A study of the ontogeny of responsiveness to a releasing stimulus, in birds, has shown that experience can be involved (Schaller & Emlen, 1961). Eibl-Eibesfeldt's (1956 a & b) studies of the ontogeny of certain behaviour patterns in mammals have shown that certain kinds of experience do not seem to be involved in the appearance of unit acts but that learning may enter into the linking of these acts into a functional sequence.
Imprinting has captured the attention of a number of ethologists; recent work in this field has been reviewed by Hess (1962). Hess's interpretation of the evidence is that the critical period is determined by the relationship between the development of locomotor ability and the development of fear of strange objects; when a certain degree of locomotion is possible, and fear responses are still relatively undeveloped, imprinting can take place. Sluckin & Salzen (1961) consider that imprinting is just a special case of perceptual learning. Hinde (1961) has pointed out that several different, although interrelated questions may be confused in these studies; of the tendency of a duckling to follow a moving object that it sees in early life it may be asked ‘Why does it follow?’, ‘Why does it learn to follow?’, ‘What limits the sensitive period?’, and ‘How does the early learning affect later experience?’ According to Hinde all of these questions are far from solution.
The influences of genes on behaviour have been demonstrated in studies of the behaviour of hybrids and also by selection experiments. Crosses between strains or species that differ in behavioural characteristics have produced hybrids that showed behaviour that was a mixture of that of the parents (e.g. Dilger, 1962, has crossed different species of lovebirds, Agapornis, and found that the hybrids showed ineffective combinations of the
Drosophila melanogaster. Mrs. Crossley, one of Bastock's students at Oxford, eliminated the progeny of all hybrid matings in a mixed population of two mutant strains of Drosophila and she found, after 40 generations of such selection against crossing, that the survivors showed differences in behaviour, between the two strains, that were not present in the original population, and that these differences were of the sort that would decrease the probability of crossing (personal communication). This result confirmed that of Knight et al (1956) who had shown that selection against hybrids between these two mutants resulted in progressive decrease in the numbers of hybrids produced from generation to generation; it also showed that anti-hybrid selection can result in the evolution of reproductive isolation of two strains as a consequence of changes in behaviour or responsiveness to stimuli (c.f. Mayr, 1942). These studies, of course, show only that genes are involved in the ontogeny of behaviour; they say little about how they operate in development or about the roles of organismenvironment interactions. Recent examples of comparative studies may be found in Tinbergen's review (1959) of the work on gulls, Andrew's review (1961) of hostile displays in passerine birds, and his study (Andrew, 1963) of the calls and facial expressions of primates. Wynne-Edwards (1962) has used behavioured data extensively in a new theory on the natural regulation of population densities and Klopfer (1963) has also recently applied a behavioural viewpoint to ecology.
The divergence of interests and methods that has developed within ethology has meant that in some parts of its range it has drawn closer to other fields of study. Concern with internal causes has resulted in liaison between ethologists and physiologists, particularly neurophysiologists and endocrinologists. Ethology now profits from developments in statistics and communications engineering. The traffic has not all been one way. Some of the generalisations that were made about behaviour on the basis of early discoveries in neurophysiology are now untenable in view of the work of ethologists. As psychologists and ethologists have come to realise that they have many areas of common interest, emotional and terminological barriers have given way to fruitful exchange of ideas. Ethologists are paying more and more attention to the discoveries, techniques and theories of psychologists (e.g. Hinde, 1959) and increasing numbers of papers by psychologists appear in the ethological journals and at ethological conferences. On the other hand the findings of ethology receive increasing attention in the writings of psychologists of all varieties (e.g. Carstairs, 1963; Gombrich, 1959) and ethologists are being appointed to the staffs of psychology departments at some American
The most securely established achievements of ethology to date have been the precise and detailed descriptions of behaviour of a wide range of animals, discoveries of regular quantitative relationships between units of behaviour and between units of behaviour and other factors, recognition and experimental testing of adaptive functions of behaviour patterns and the use of behaviour in working out the adaptive significance of morphological features, recognition of behavioural homology and the use of this in working out evolutionary origins and in taxonomy. These achievements follow from the general zoological background of ethology: training in accurate and detailed observation, concern with comparative anatomy, with questions of phylogeny. adaptation, selection and ecology. It may well be that the future of ethology as a distinct discipline will also prove to be bound up with questions concerning what animals do and why they do it, in terms of functional adaptation, rather than in terms of causal mechanisms.
Explanation starts with generalisations based on observed regularities, e.g. the association of a particular environmental change with a particular response. But these generalisations explain their instances only to the extent that they can be derived from grounds other than just these instances. This usually means that such a generalisation is an instance of another more comprehensive or higher level generalisation, e.g. when we claim that a particular external stimulus causes a particular response we can appeal to the general principle that there are classes of events or things in the environment that can affect behaviour. This generalisation, in its turn, illuminates those subsumed under it only when it is related to an even wider field of knowledge, e.g., in our example, the relations between energy changes in an animal's perceptual field and events going on in its receptors. In the case of explanation of behaviour in terms of causal mechanisms the higher-level generalisations that we build into our pyramid of laws and hypotheses tend to be in terms of lower and lower levels of structure and function; we start with the whole animal and its environment, then go to stimuli and responses, then to the properties of the nervous system, or part of it, and so on. The problems sorted out by the ethologist at the level of overt behaviour will tend to be translated into problems about the fine structure and function of the animal body and hence to become the property of other specialists — the physiologists, embryologists, biochemists and biophysicists. The causal mechanisms propounded in some of the
explain behaviour, they describe it or summarise it. When explanation is attempted with only statements of this sort we get either circular argument or the assumption of some unspecified reference outside the sphere of overt behaviour. Which ever choice is made we are likely to find that beliefs about proximate causes have been most strongly dictated by appreciation of the ways in which behaviour serves the biological functions of the animal. The zoological emphasis on the biological relevance of behaviour can mislead the ethololist when he moves from the description and measurement of behaviour, and the formulation of questions presented by such data, to the answering of these questions in terms of underlying causal mechanisms in the animal. Either he must acquire adequate knowledge of the ontogeny, physiology and fine structure of his animal, or he must hand his questions to someone who has such knowledge.
But questions about the proximate causation are not the only ones that can be asked about behaviour; equally important are questions about function, adaptation and evolution, and it is difficult to see how many of these questions can be translated into, or reduced to, questions of proximate causes. Indeed premature effort to make such translation or reduction could hinder our understanding of these questions rather than assist it. The kinetic theory of gases would not have been discovered if the behaviour of individual molecules had not been ignored in favour of the statistically probable behaviour of populations of molecules. The strength of Darwin's theory over those of his predecessors was that it showed the statistical implications of the presence of random variations in a population without, at the same time, trying to account for the origins of such variation (Gillispie, 1958). Similarly, if one accepts certain aspects of behaviour as given, one can
Recent advances in physiology, in biochemical genetics and biophysics, have produced a current fashion in favour of physicochemical explanation in biology. The history of biology shows oscillation between emphasis on low-level analytic studies on the one hand, and emphasis on high-level synthetic or ‘organismic’ studies on the other. Both of these viewpoints have their blind spots. Perhaps the present swing in favour of fine structure and function will be followed by renewed interests in problems peculiar to whole organisms or populations of organisms. In the meantime it would be unfortunate to lose sight of such problems. Ethologists are well placed to keep them in view.
Acknowledgment: I am grateful to Professor
As introductory reading I recommend ‘King Solomon's Ring’ by Konrad Lorenz (Methuen, London, 1952). ‘Curious Naturalists’ by Niko Tinbergen (Country Life, London, 1958). As basic reading for a study of ethology I recommend ‘The Study of Instinct’ by N. Tinbergen (Oxford, 1951), ‘Learning and Instinct in Animals’ (second edition) by W. H. Thorpe (Methuen, London, 1963), ‘Instinctive Behaviour’ edited by C. H. Schiller (International Universities Press, New York, 1957), ‘Current Problems in Animal Behaviour’ edited by W. H. Thorpe and O. L. Zangwill (Cambridge, 1961), Symposia of the Society for Experimental Biology IV: Physiological Mechanisms in Animal Behaviour (Cambridge, 1950). A large proportion of the ethological work is published in three journals: Behaviour, Zeitschrift für Tierpsychologie, and Animal Behaviour (formerly The British Journal of Animal Behaviour).
The seals are carnivores highly adapted to an aquatic environment, mainly marine. They simulate the smaller cetaceans very closely in shape and in the storage of fat, blubber, under the skin, thereby insulating the body against low temperatures; very little fat is stored in the mesenteries or in the body cavity, as land mammals normally do. But, unlike cetaceans, seals have retained their external coating of hair and the osteological identity of all four limbs, down to, at least, the rudiments of claws; they have also retained the flexibility of the limbs and, to a varying degree, that of the spinal column. In addition seals have retained their differentiated teeth, but the molars (postcanines) have deviated from the true carnassial form; they are more adapted to the seizure of slippery food. The prey consists largely of cephalopods, crustaceans, fish and marine birds. (The Crabeater Seal feeds largely on ‘Krill’ (Euphausia) and the Leopard Seal has been reported to eat other seals and carrion).
With the stream-lining of the body for rapid progression through water, all likely ‘obstructing’ organs have been modified or dispensed with. The limbs have been transformed into flippers or paddles: the fore limbs, no longer required to carry the weight of the body (except when on land), as with terrestrial mammals, into propelling or balancing organs and when not in use, they are tucked out of the way, alongside the body when the animal is travelling through water at speed. The hind limbs, in keeping with terrestrial animals, have retained their locomotory function, but are turned backwards and brought parallel with vertebral column, the ‘feet’ serving as efficient propellers. Even the tail is reduced to almost vestigial proportions. Although some seals proceed clumsily on all fours when on land, others have been ‘condemned’ to be ‘belly-walkers’, progressing like gigantic caterpillars, with undulating abdominal movements, aided by the fore flippers, but in water they are equally, if not more efficient swimmers than their more favoured brethren. Speed in water, where food is obtainable and enemies are to be avoided,
The external ears or pinnae, so marked a feature on the head of most terrestrial mammals, would, if retained in seals, not only offer some resistance to the water, but would be wholly unsuited to under water hearing and against pressure, when sounding. Accordingly, some species have modified these appendages very considerably, till they are almost rudimentary, while others, the pelagic forms, have dispensed with the pinnae entirely. Although the pinnae have been reduced or discarded, the hearing of seals is fairly acute. (Perhaps, a parallel to this form of reduction of the pinnae is found in the camels, among land mammals, which are subject to high winds accompanied with blown sand). Science has seized on this character and divided the Pinnipedia into two groups: the Eared-seals, such as Arctocephalus and the Earless-seals, such as Hydrurga. Likewise the presence or absence of underfur (wool) has been used as a means of classification — fur-seals and hair-seals.
In addition to the external modifications observed above, numerous other external and internal changes have occurred in the course of the evolution of seals from terrestrial to aquatic animals. The accompanying plate (Pl.1) shows clearly the modifications which have taken place in the formation of the teeth and scapulae. The great differences in the teeth probably betray a variation in the diet of the various species. However, it is significant that in the two genera, Arctocephalus and Neophoca the spine of the scapula is more posterior and the acromion more ventrally situated (more in Arctocephalus than in Neophoca) than in the remaining four seals illustrated, in which the spine is more centrally placed and the acromion less developed and more distant from the glenoid cavity. The change in position appears to be associated with the mode of progression: a greater use of the fore limbs in Arctocephalus and Neophoca on land, and, perhaps, in water, than the ‘belly-walking’ genera. Regardless of the distance the seals have travelled along the road of their evolution, unlike the cetaceans, they still have to return to the land (or ice) to rest, moult and to give birth to their young.
Polygamy is rather the rule than the exception. The males are normally larger than the females, but with the Crabeater Seal, the Leopard Seal and Weddell's Seal, the females appear to be the larger of the two sexes (Scheffer, 1958: 8). With the advent of the breeding season the males normally select the breeding sites and on the arrival of the females establish large or small harems, according to species. The territory and the harem is zealously guarded against all intruders as long as the season lasts, after which, the breeding animals disperse to form mixed or ‘bachelor’ colonies, or to roam as lone animals.
Breeding takes place during the late spring and summer of the Southern Hemisphere. Normally, a single pup is produced annually, but twins have been known to occur, occasionally. At birth the pup is approximately one-third the length of the parent. The pup is weaned after several weeks during which time it has grown rapidly and is enormously fat. In some species there is evidence of a pre-natal moult. Moulting of the adults usually takes place during the autumn and winter. During the moult solitary animals may be found resting among the rocks or on beaches. In some species the moult proceeds gradually, little change being noticed in the appearance of the animal, while in others the moult is pronounced, the coat being shed in patches — the Sea Elephant is a good example of the second form.
Apparently, most feeding is done at night which suggests that the eyes are accommodated to darkness or feeble light. The animals are able to survive long periods of fasting; this is particularly true of the bulls during the breeding season, for, they do not feed for several weeks, not till the season is over. The greatest enemies of seals (apart from Man) are Killer Whales (Orcinus orca), Sharks and other species of seals (Leopard Seal).
The commonest seal in New Zealand waters is Forster's Fur Seal (Arctocephalus forsteri (Lesson)). The Sea Lion (Neophoca hookeri Gray) is next in order of freqency but it is more southern in its distribution, frequenting the Sub-Antarctic Islands and southern and south western parts of the South Island. The Sea Elephant (Mirounga leonina (Linn.)), particularly young animals, frequently haul ashore during the moulting season — to wit, the celebrated, ‘Blossom’ which spent several weeks in Wellington Harbour, till it completed its moult, in spite of the efforts of the Marine Department and the S.P.C.A. to dissuade it from remaining in the area. ‘Blossom’ was a young bull. Perhaps, the next in order of frequency is the Leopard Seal (Hydrurga leptonyx (Blainville)) which makes its appearance as an occasional visitor. On rare occasions the Crabeater Seal (Lobodon carcinophaga (Hombron and Jacquinot)) has been recorded. Lastly, on very rare occasions, Weddell's Seal (Leptonychotes weddelli (Lesson)) has forsaken its Antarctic ice to appear in New Zealand waters.
Although much has been published (in the Press and elsewhere) and rumoured to the contrary that seals (Forster's Fur Seal) have a serious adverse effect on commercial fisheries, there is no substantial proof of such an effect. Some mathematical genii have even estimated the amount of fish each seal eats daily and divined astronomical figures to show the annual destruction of (‘commercial’) fish — in hundreds of thousands of tons! The seals and fish have lived together in the same waters for eoans, in a natural economic balance — long before the advent of the
The investigations of several scientific observers have produced no evidence that the seals subsist entirely on fish, leave alone commercial fish. On the contrary, these researches prove that the seals are largely molluscan feeders, subsisting mainly on cephalopods (octopus and squid) which diet is supplemented by a modicum of small fish and crustacea. The evidence for this statement is based on the examination of the stomach and intestinal contents. Again, there are large numbers of seals which (during the breeding season, for example) do not feed at all for several weeks! Normally, Nature provides a seasonal respite from predators in the case of most animals, else all animal life would soon disappear!
The ‘depletion’ of marketable commercial fishes at the regular fishing grounds, falsely attributed to the presence of seals in the vicinity, appears to be largely due to one of two factors, or both: a) the seasonal movement of the fish themselves to and from spawning and feeding grounds; b) the wholesale capture of fish by most modern methods and equipment all the year round with little or no respite for breeding or recuperation of stocks. Nature is bountiful but not inexhaustable—She is not proof against the ingenuity of scientific devices! Lack of knowledge and exploitation to the extreme ring the death knell of commercialisation—the present position of the whaling industry to wit!
However, there is the possibility that seals may damage fishing nets, occasionally, when accidentally trapped, in their efforts to escape, but this aspect has little or no bearing on commercial fishing. The fur seal itself, a national asset, has been a victim of ruthless commercial exploitation in the past. Protection, in time, has given it a chance to survive and make a come back, and judicious conservation of stocks will, it is hoped, enable it to survive and remain a national asset.
Incidentally, it is worthy of note, by way of warning, that all seals are strictly protected by law and molesting or the killing of seals may result in a very heavy fine—up to £500.
The author's thanks are due to Mr. J. H. Sorenson of the Marine Department and to Mr.
Neophoca hookeri (Gray). The New Zealand Sea Lion.
Distribution: New Zealand region, breeding between 51 and 53 degrees south: Enderby Island, Auckland Islands, straggling northwards to Campbell Island, Stewart Island and the southern shores of the South Island.
Arctocephalus forsteri (Lesson). Forster's Fur Seal.
Distribution: Widely spread in both New Zealand and south Australian waters and Subantarctic Islands as far south as 55 degrees south. Breeding in some of the Subantarctic Islands and since its spread and increase there is good reason to suspect it is breeding in some other suitable localities of its present range. At one time the Fur Seal was close on extinction due to the activities of sealers, but since its protection it has increased rapidly and is spreading to new localities.
Lobodon carcinophagus (Hombron and Jacquinot, 1842) Crabeater Seal.
Distribution: Circumpolar in the Southern Ocean. Occasionally seen as far north as Wanganui along the coast of the North Island, in New Zealand waters.
Hydrurga leptonyx (Blainville, 1820). Leopard Seal or Sea Leopard.
Distribution: Very widely distributed in the Southern Hemisphere. Occasionally, it appears along the New Zealand coasts. It has been recorded as far north as Lord Howo Island.
Leptonyx weddelli (Lesson, 1826). Weddell's Seal.
Distribution: Circumpolar, Antarctic Continent and adjacent islands. There have been four records of this species in New Zealand waters, one was recorded from Titahi Bay and another in Wellington Harbour.
Mirounga leonina (Linn., 1758). The Southern Sea Elephant.
Distribution: Circumpolar and Subantarctic waters. Breeding on many of the Subantarctic Islands. A still-born pup was found at Castle Point, east coast of the North Island, on September 18, 1961 (Dom. Mus. 1455). Young animals frequently visit the New Zealand coasts during the moulting season, late summer and autumn. Mr. J. H. Sorenson (1950) made a special study of these interesting animals and his paper is of special interest to any one seeking information on the life of them at Campbell Island.
We have all at one time or another heard it stated that New Zealand has a unique fauna. This is true, as it is true of any other island or continent. But the statement often carries an implication that somehow the fauna is extraordinary and strange—quite different from what might be expected by a rational man.
Let us examine this connotation by resorting to a stratagem. Suppose that by some accident of history New Zealand was not discovered until last year and that a biologist is asked to comment on what vertebrates are likely to be discovered in this new unexplored land. As yet no expedition has landed, and he has nothing to guide his predictions other than his knowledge of animals in other countries. I am presumptuously casting myself in the role of this biologist. With what, I hope, is a minimum of unconscious cheating, I shall reconstruct what I guess would be his conclusions and the reasoning by which he would arrive at them.
From a knowledge of other faunas, several principles can be derived to help in predicting the nature of the New Zealand fauna:
(a) A high proportion of the forms occurring on islands, but seldom all of them, are derived from the fauna of the nearest land mass. If the island has been linked to the mainland in the past, the fauna will be more diverse than if the island is truly oceanic. [The rocks on the east coast of Australia argue for the existence of the Tasman Sea at least since the beginning of the Cretaceous (Glaessner, 1962) and so, from a strictly biological viewpoint, New Zealand can be treated as an oceanic island.]
(b) The probability of extinction on large islands is less than on small islands (Mayr, 1954). [New Zealand would therefore have a better chance of retaining an invading species than would for instance, a small volcanic island in a comparable position].
(c) The probability of a species reaching an island from a continent is intimately related to the distance between the two, and to the climate of the intervening region. [New Zealand is about 1,000 miles from Australia. This fact is probably the most important in deciding what might be here].
(d) ‘Dispersal of individual land animals over water is largely accidental … but in the course of time statistical probability comes into play and determines what sort of animals cross water most often and what islands they most often reach’ (Darlington, 1938). But for any process conforming to statistical laws the end result cannot be exactly predicted. Some effects will be very likely while others will be most unlikely, but one can never say ‘this is absolutely certain’ or ‘this is theoretically impossible’.
With considerable confidence I would predict the absence of strictly fresh-water fish. In most cases they are incapable of crossing salt-water gaps of more than a few miles. Where they do occur on islands it is usually possible to prove that at one time the island was connected to the mainland (Darlington, 1957).
My prediction is correct: there are no strictly fresh-water fish in New Zealand. Some species do spend their entire lives in fresh water, but are members of widespread families (Galaxiidae, Eleotridae and Retropinnidae) many species of which are tolerant of salt water (Stokell, 1955). The presence of the Galaxiidae is expected as this family is almost ubiquitous within the Southern Temperate Zone.
Frogs have reached the Seychelles from Africa (500 miles), but do not disperse widely in the temperate zone. The inference is obvious: there is little likelihood of frogs occurring in New
Leiopelma) are of an ancient stock that has no close relatives elsewhere. They may therefore have dispersed to New Zealand at some time in the distant past when the distribution of land differed from now.
One must first decide whether any reptiles are likely to be here at all. The distance from Australia would rule out fresh-water turtles and probably also land snakes. Snakes have crossed some wide gaps in the tropics (e.g. 600 miles to the Galapagos) but in temperate zones they appear to be incapable of dispersing far across water. There are none on the Azores or Madeira. 800 and 350 miles respectively from a continent, and even the Canary Islands (60 miles) have none. Hence the presence of snakes seems improbable, and conveniently none are here.
Lizards disperse further than do snakes. They have reached the Galapagos in the tropics but have not colonised Hawaii, 2,000 miles from a continent. Skinks and geckos have crossed to New Caledonia, presumably from Australia (800 miles), but outside the tropics they are less successful colonisers. They have reached Bermuda from North America (600 miles) but do not occur on the Azores. Thus New Zealand is very near their limit of dispersal, or beyond it. If New Zealand were smaller I would predict the absence of lizards, but as it has a fairly long coastline oriented across the prevailing wind, the probability of lizards reaching here is thereby increased.
I would probably be non-committal about the possible presence of lizards, but would add a rider that if they are here at all they will be represented only by those groups in Australia that have powers of wide dispersal. The monitors and agamids can be dismissed because although they occur in Australia and are widespread they have not managed the crossing from Africa to Madagascar. Dismissed too are the pygopods which have not reached New Caledonia from Australia. Only skinks and geckos survive this trial by elimination.
In fact, skinks have reached here at least twice (two Australian genera are represented) and geckos at least once (three endemic genera). I am ignoring the records of Lepidodactylus lugubris and Gehyra oceanica (McCann, 1955) whose distributions in New Zealand suggest that they may have received an assisted passage.
I would not have suspected the presence of the tuatara (Sphenodon) in my most irresponsible imaginings. Like the New Zealand frogs it is completely unexpected.
Of all vertebrates, birds are by far the widest dispersers. Very few islands large enough to retain vegetation are completely lacking in land birds.
Following the principle that most of the fauna should be derived from Australia, I can list the families of land birds most likely to occur in New Zealand (Table 1). My rule of thumb is to assign a high probability to widespread families that breed in the south-east of Australia (Bassian province).
Of the 38 families listed, all but 11 are represented. Considering the chance processes with which we are dealing, this is a most gratifying proportion.
The following families are reported from New Zealand but are not on the list of high probabilities: Apterygidae, Acanthisittidae, Callaeidae, Turnagridae, Anhingidae, Glareolidae and Phaloropodidae. The first four are restricted to New Zealand while the last three do not breed here and have been reported only as stragglers.
Birds are zoogeographically the most predictable of all groups and I can therefore risk predicting down to the species level. There is a reasonable probability of an Australian species occurring in New Zealand if it is fairly wide ranging (showing that it has good powers of dispersal) and breeds in Tasmania (showing that it could probably tolerate the New Zealand climate). My criterion for the ability to disperse—that the species has penetrated into the Sunda Chain or the Western Pacific—is not a very satisfactory one as it tends to favour tropical species. It is forced on me by circumstance, for there is no convenient chain of temperate islands extending out from Australia.
By my count there are 43 species that qualify; they are listed in Table 2.
The score of 33 out of 43 is high and even I (in my capacity as the hypothetical biologist) am agreeably surprised. But my exuberance is dampened somewhat by finding in the list of wrong predictions one whose presence I would most confidently predict. This is the peregrine falcon which by its wide distribution and tolerance of a broad range of habitats earns a high place in the list of probabilities.
It should be noted that although the prediction about the scarlet robin was wrong, some of the robin's ancestors reached here at least twice in the past, giving rise to forms now specifically distinct from Petroica multicolor (Fleming, 1950).
On most islands of any size there is a stratified order of endemism ranging from endemic sub-species to endemic families, reflecting differing periods of time that the stocks have been isolated. I would correctly expect the same to occur here. Falla (1953) has shown that there is a continuous gradation of relationships, mainly with Australian birds, and Fleming (1962a) has tentatively dated the postulated invasions.
I would not have predicted the occurrence of the two endemic orders (kiwis and moas), even though the occurrence of flightless birds has a parallel in Madagascar. Loss of flight is not a common consequence of island colonisation except in rails, and there is no reason therefore to predict it. But the New Zealand bird fauna in this respect does not form an exception—only an uncommon case. Although failing to predict the presence of moas and kiwis, I would not be greatly surprised to find them here.
New Zealand and South America are separated by about 4,000 miles. This gap is a little wide even for birds, especially as they would fly into westerlies most of the way. Birds of South American derivation would hardly be expected here. Predictably, there are no land birds in New Zealand with unambiguous South American affinities.
The presence of large mammals can be virtually discounted. The farthest they have dispersed across water is only 200 miles (the Malagasy hippopotomus). Similarly, the presence of small mammals is rather unlikely as they have not colonised New Caledonia from Australia, a much less arduous task than reaching New Zealand. The marsupials do not appear to have great powers of dispersal for they have not reached Asia from Australia, although phalangers have reached the Celebes.
Of the flightless small mammals, the only possible (though not highly probable) contenders are the rats. One might expect that the Australian water-rats (Hydromyinae) would be well suited to dispersal, but their failure to enter the Sunda Chain rules against this contention. The genus Rattus, however, is widespread in the Pacific and travelled along the Sunda Chain in the late Tertiary or Pleistocene. If there are any flightless land mammals in New Zealand they should belong to this genus. But Rattus has not dispersed here; the three species in New Zealand have been introduced by man.
Bats disperse widely and have crossed water gaps as great as 2,000 miles (America to Hawaii). They are therefore likely to be an element in the New Zealand fauna. There are but two genera here, both of which are widespread in New Zealand (Dwyer, 1962). One is a species that occurs also in Australia while the other is the sole representative of a presumably autochthonous family. The problem is not that bats are here but that there are so few; by analogy with New Caledonia I would have expected about twice as many genera.
Any seal breeding on the New Zealand coast should be a sea lion (Otariidae). The walruses (Odobenidae), northern seals (Phocinae) and monk seals (Monachinae) occur only in the
Of the sea lions, Arctocephalus is almost certain to occur as various species of this genus breed at the margins of most southern temperate lands (Davies, 1958). The genus is represented here by Arctocephalus forsteri. I would also expect one of the larger sea lions to be present. Neophoca is the most likely as it occurs on the coast of Australia, and Eumetopias is another, though lesser, possibility. But the coast of New Zealand is devoid of breeding sea lions of these genera, although Neophoca hookeri breeds at the sub-antarctic islands to the south. Why this species has not extended farther north is a mystery. No other species of the genera of larger sea lions (Otaria, Zalophus, Neophoca, and Eumetopias) are restricted to sub-polar regions.
How have the predictions stood up against the facts? I can claim success with fish, poor scoring with the amphibians, and reasonably accurate predictions for reptiles, birds and mammals. A few occurrences are quite unexpected, but these are mostly of members of Fleming's (1962b) endemic or archaic grouping—forms that have been here for a long time and have no close relatives in other areas. Most countries have their quota of such forms, and I might have predicted that there would be a residual group defying individual prediction.
In all, I have been fairly successful. There have been surprises but probably no more than would be produced by a similar analysis of another fauna. There would be no way of predicting, for instance, the occurrence of that remarkable bird, the kagu, in New Caledonia, or iguanas in Madagascar and Fiji. The New Zealand vertebrate fauna cannot therefore be considered a special case for it conforms to the same zoogeographic principles that operate elsewhere.
In this investigation of the vertebrate fauna, the main working hypothesis has been that most forms were derived from Australia. This is a fair assumption but should not be extended to imply that all animals in New Zealand share this history. It is a mistake to assume that forms necessarily arose elsewhere and migrated to the particular region being considered, but this assumption is implicit in much of the zoogeographic literature. For instance, a
Conceptual clichés are common in zoogeography and often lead to inaccurate conclusions. The three unwarranted assumptions most often encountered, usually in heavily disguised form, are as follows:
genera migrate outward from the type locality of the family,
forms always migrate from elsewhere to the region being considered, and
centres of evolution tend to be near the larger universities. Stated in this way, these axioms are obviously absurd and would mislead no-one. But the student of zoogeography must continuously guard against being seduced by them in their more plausible guises.
I am grateful to Mrs. M. Grange, Dr.