Tuatara: Volume 12, Issue 2, July 1964
A Coincidental Distributional Pattern of Some of the Larger Marine Animals
A Coincidental Distributional Pattern of Some of the Larger Marine Animals
The problems involved in the study of animal distribution and migration are too familiar to most biologists to warrant any explanation.
The distribution of the genus or species is largely dependent on the suitability of the habitat at a given season, either for feeding or breeding — self preservation and procreation — the two fundamental laws in Nature. I think it will be conceded that the breeding ground or grounds may be assumed to be the centre or centres of distribution — the focus from which migration proceeds. In many animals there is an interval of non-feeding during which the reserve fat (energy) accumulated at the feeding ground gradually recedes and gives place to the developing gonads. In such animals the body cavity is ‘filled’ with reserve fat at the feeding ground occupying the space freed by the receding or atrophying gonads, the reverse taking place with the approach of the breeding season. However, this generalisation does not hold good in the case of pinnipedes and cetaceans for their reserve is built up ‘outside’ the body by way of a thick layer of blubber between the muscles and the skin. No reserve is built up within the body cavity for there is little or no mesenteric fat in such animals. Nevertheless, little or no feeding is done after leaving the feeding grounds. In these animals the body cavity appears to be devoted to the development of the precocious foetus which, at birth, is frequently about one third the size of the parent.
At the breeding grounds the food is normally suited to the diet of the young. As already indicated, the adults, having laid in their store of reserve at the feeding grounds, are no longer interested in food during the breeding season. In fish, in which parental care is virtually absent, (there are some which exhibit a degree of parental care) the young of migratory species set out on their migration soon after hatching keeping up with the food supply (which itself is also migratory, or there is a change in the diet) either under their own steam or by drifting along with the ocean currents. Such migrations only cease when the cycle is closed once more on the return of the animals to the breeding grounds, when sexually mature. The migration may page 120 be altitudinal or dimensional or both. The time spent on migration varies in accordance with the species — it may be short or protracted over several years. The migration of the European eel to and from its breeding grounds is a classical example of this life-long migration.
The periodic migration of birds is well-known, but again the migration is largely governed by the food supply for the adults on the one hand, during the non-breeding period, and the suitable food supply and general environmental conditions for the young on the other. In many instances the quality of the food differs, not only between the young (nestlings) and the adults, but, in the chicks, it changes with advancing age. The migration may be ‘local’ or far-flung, according to species. However, I am fully aware of the numerous other factors involved in the study of bird migration which contribute to this interesting problem.
Terrestrial mammals are, perhaps, less migratory than many other forms of animal life (except Man who is invading most environments). In mountainous regions the seasonal migration is more altitudinal whereas on plains it is more dimensional. In either case it is in order to escape the weather conditions which curtail the food supply. With mammals the food of the young is secured by the provision of milk by the mother till they are able to fend for themselves; it is the food of the adult that matters.
Marine mammals, living as they do in a liquid medium, display great dimensional migration, for it is well-known that some of the cetaceans travel, periodically, through several degrees of latitude (and longitude) between their breeding and feeding grounds — breeding in warmer and feeding in colder latitudes. Again, the right food for the adult is the important factor for the young are suckled. The foetus is precocious and the young is only suckled for a comparatively short time after birth. The ample provision of stored reserve is adequate to tide the animals over the long period away from the feeding grounds. This periodical movement of cetaceans to and fro from the feeding grounds to the breeding grounds is taken advantage of by the whaling industry.
Along the course of migration, between the breeding and feeding grounds, marine animals usually leave a trail of weaklings or diseased comrades which fall out of the migratory stream, floundering at or near the surface, too weak to resist the currents and winds, and eventually strand along the nearest coasts unless devoured by scavengers. Such strandings give us a ‘line’ on the probable migratory route of the species involved. It is the similar pattern of stranding of various species of the larger animals along certain stretches of coast and not on others which I refer to as the ‘coincidental distributional pattern’.
Fig. 1: To illustrate the New Zealand pattern, I have taken eight taxa; 1) Trachypterus, 2) Regalecus, 3) Mola. 4) Mesoplodon gravi, 5) M. layardi, 6) M. stejnegeri, 7) Tasmacetus, 8) Berardius. The figures representing these have been arranged approximately in the region of stranding (not the exact spot). The dotted arrows indicate the surface currents taken from J. W. Brodie's paper: ‘Coastal Surface Currents Around New Zealand’. (N. Zeal. Journ. Geol. & Geophys, 1960, 3: 235).
In the course of some studies on three large pelagic fishes, the Dealfish (Trachypterus), the Oarfish (Regalecus) and the Sunfish (Mola) and among the mammals, of some of the Beaked Whales (Mesoplodon, Tasmacetus and Berardius), I was struck by the similar pattern of stranding displayed by these animals in New Zealand waters. Looking further afield, the same animals, at a generic level, followed a similar ‘global pattern’, particularly in the northern portion of the Atlantic Ocean, in the Caribbean, along the eastern shores of the United States of America and around the British Isles and the western shores of Europe. In passing it is worthy of note to observe that the New Zealand Archipelago holds a similar position in the Pacific Ocean, in the Southern Hemisphere, as does the British Archipelago in the Northern Hemisphere. However, in the New Zealand region the animals approach the area from the south following the East Australian Current, whereas, around the British Isles the animals appear to approach from the north, following the southern bend of an arm of the Gulf Stream, and strand mainly along the eastern shores. A feature common to both the areas is that the animals generally strand along the eastern shores. Stranding on the western shores is comparatively rare. However, it may be postulated that, in New Zealand, the western shores are sparsely populated and therefore fewer observations are available, but this certainly cannot be said of the British Isles! The lack of observations alone cannot account for this similarity in the two regions. The problem requires a lot more observation and knowledge of the species before any satisfactory conclusions can be reached.
Below, I give the years of stranding and locality of the various species selected for the purpose of this paper. Many others could, doubtless, be added, but this small number will suffice to illustrate the point. In addition to those mentioned, there have been other strandings for which only the date alone has been recorded, but no locality — just ‘New Zealand’. The records have been compiled from literature, museum specimens and specimens examined by myself. It is, of course, obvious that literature and museum materials have contributed the major portion of the data. In some species the period covered exceeds a hundred years. The causes of stranding are fortuitous: in some it is caused by disease or weakness; in others, accident. In mass stranding, witnessed page 123 with some cetaceans, such as Black Fish (Globicephala) or False Killer (Pseudorca), the reasons for the mass ‘suicides’, often witnessed, are not clearly understood, but, there is the possibility that the accidental (?) stranding of one from a school may result in the stranding of the whole school, the supersonic distress calls of the ill-fated attracting the others to their doom as did the sirens of mythology !
1. Dealfish (Trachypterus)
1880, Jackson Bay; 1917, Queen Charlotte Sound; 1923, Picton; 1929, Stewart Island; 1929, Plimmerton; 1935, Nelson; 1936, Makara Coast, Wellington; 1937, Eastbourne, Wellington; 1937, Island Bay, Wellington; 1943, French Pass; 1944, Island Bay, Wellington; 1944, Plimmerton; 1950, Milton Bay, Queen Charlotte Sound; 1950, Petone Beach, Wellington; 1951, Paraparaumu; 1956, Tory Channel.
Since the last date, several other specimens have appeared in Cook Strait area. As both sexes and very young specimens have been taken in the area, there is good reason to suspect that Trachypterus breeds in the area. It is remarkable that only two specimens have been reported outside the Cook Strait area.
2. Oar Fish (Regalecus)
1860, Nelson; 1874, Jackson Bay; 1876, New Brighton Beach, Christchurch; 1877, Nelson; 1877, Cape Farewell; 1881, 1883, Moeraki, Otago; 1886, Portobello; 1889, Nelson; 1891, Banks Peninsula; 1895, New Plymouth; 1897, Waikanae; 1930, Otago; 1949, Chatham Islands.
3. Sunfish (Mola)
1872, Auckland; 1872, Dunedin; 1885, Port Napier; 1889, Gisborne; 1895, Otago Harbour; 1896, Napier; 1918, Paraparaumu; 1919, Queen Charlotte Sound; 1923, Bay of Islands; 1923, Seatoun, Wellington;?, Napier; 1924, Otago; 1930, Palliser Bay; 1934, Island Bay, Wellington; 1940, Raumati Beach; 1946, Gore Bay; 1949, Palliser Bay; 1959, Rakaia River Mouth; 1951, Oyster Bay; 1951, Muritai, Wellington; 1951, Flat Point; 1952, Pakawau Beach, Nelson; 1953, Marlborough Coast; 1953, Hawke's Bay; 1953, off Kahu Rock; 1954, Blue Bay, Park Beach; 1954, Hawke's Bay; 1954, Waitara; 1954, off Waitangi, Chatham Islands; 1955, Island Bay, Wellington; 1957, Hick's Bay; 1958, Napier; 1958, Plimmerton; 1958, off Kahu Rock; 1959, Titahi Bay; 1959, Otago Harbour; 1960, Otago; 1962, Farewell Spit.
Details of the strandings of Mola in New Zealand waters are given by the author in the Records of the Dominion Museum, 4(1961): 7-20.
The New Zealand Archipelago appears to be the rendezvous for many cetaceans, particularly, some of the Ziphiidae, some of which are known to calve in the area, during the spring and early summer.
4. Gray's Beaked Whale, Mesoplodon grayi Haast
1873, Kaikoura; 1875, east coast of the North Island; 1875, Saltwater Creek; 1875, Lyall Bay, Wellington; 1911, near North Cape; 1926, Chatham Islands; 1931, Waverley Beach, Wanganui; 1935, Hawera; 1956, Palliser Coast; 1961, Kenny's Creek, Southland; dates unknown, Kaiapoi; Kawau; Great Barrier Island; Orewa; Plimmerton; Wellington; Stewart Island.
5. Layard's Beaked Whale, Mesoplodon layardi (Gray)
1872, Pitt Island, Chatham Islands; 1874, Saltwater Creek; 1879, Marlborough; 1901, Titahi Bay; 1912, Lyttelton Harbour; 1924, Porirua Harbour; 1937, Nukumaru Beach, Wanganui; 1943, Waikanae; 1954, Paraparaumu; 1955, Castle Point; 1960, Makara Coast, Wellington: dates unknown, Napier; Milton; Queen Charlotte Sound.
6. Stejneger's Beaked Whale, Mesoplodon stejnegeri True
1904, New Brighton, Christchurch; 1930, Waitotara Beach, Wanganui; 1937, Manawatu Heads; 1951, Stewart Island.
The 1904 specimen was the type of M. bowdoini Andrews (= M. stejnegeri True). This species is more widely ranging than the two previous species for it occurs in both the Northern and Southern Hemispheres.
7. Shepherd's Beaked Whale, Tasmacetus shepherdi Oliver
1933, Ohawe, Wanganui; 1933, Mason Bay, Stewart Island; 1950's, New Brighton Beach, Christchurch; 1962, Sumner Spit, Christchurch.
Tasmacetus is, perhaps, the rarest of cetaceans and has been recorded four times only since its first discovery. It was described by the late Dr. W. R. B. Oliver from the Ohawe specimen.
8. Arnoux's Beaked Whale or Porpoise Whale, Berardius arnouxi Duvernoy
1840, Otago; 1846, Akaroa; 1866, Titahi Bay; 1868, New Brighton, Christchurch; 1870, Worser Bay, Wellington; 1871, Porirua Harbour; 1873, Banks Peninsula; 1877, Wellington; 1920, coast near Wanganui; 1929, Stewart Islyand; 1931, Te Horo Beach; 1934, Otaki Beach; 1937, Plimmerton; 1944, Thames coast; 1960, Pukerua Bay.
B. arnouxi is restricted to the Southern Hemisphere. It was first described in 1846 from a specimen obtained at Akaroa.