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Studies on the Two New Zealand Bats

Interpretation of Data

Interpretation of Data

Table I. Summary of bat distribution records for New Zealand
Colonies or large flights. Small flights and isolated sightings.
District Before 1930 After 1930 Before 1930 After 1930
M C U M C U M C U M C U TOTAL
N. Auckland - 2 - - - 1 - 2 1 - - 4 10
Gt. & L. Barrier ls. 1 - - - - 2 1 - - - - 5 8
S. Auckland - - 1 - - 2 4 1 5 3 3 7 26
Rotorua-Taupo - - 3 1 - 8 - - 7 3 2 16 40
Gisborne - - - - - 8 - - 4 - 1 11 22
Taranaki - - - - - 1 - - 2 - - 2 5
Hawkes Bay - - 2 - - 1 - - 2 - - 9 14
H. Wellington - - 1 - - - - - 5 - 5 12 23
S. Wellington - 1 4 - - - 2 - 3 1 - 16 27
Kapltl I. - - - - - - 1 - 1 - 2 5 9
Marlborough - 1 1 - - - - - 3 - - 5 10
Nelson - - 4 - - 1 1 1 9 3 3 30 52
Westland - - 1 - - - 3 1 6 - 3 10 24
Canterbury - - - - - - - 4 3 1 1 2 11
Otago - - - - - - - 1 3 - - 3 7
Southland - - - - - - 3 1 2 - 1 9 16
Stewart I. etc. - - - - - - 1 - 3 5 - 3 12
Totals: 1 4 17 1 - 20 17 11 59 16 21 149 316
page 13

Maps 1 and 2 record the localities from which sightings of bats have been reported, and Table I summarises the details of the distribution records for each of the seventeen districts shown on these plates.* It also incorporates details of the numbers of bats observed at a single time. "M", "C" and "U" are used for Mystacina, Chalinolobus, and unidentified bats respectively. Large flights are taken, quite arbitrarily, as those including twelve or more animals.

Date Locality District Species
About 1949 Eglinton Valley S. Unidentified
Dec., 1950 Doctor's Gamp, 6 miles from Te Whaiti R.T. Unidentified
Dec., 1952 Doctor's Gamp, 6 miles from Te Whaiti R.T. Unidentified
Dec., 1952 Dale's Run, Te Whaiti R.T. Unidentified
Apr., 1955 Hidden Falls R., Lower Hollyford Valley Ot. Unidentified
About 1957 Lake Marora S. Unidentified
Apr. 26, 1957 North branch Tutaki Valley, slopes of Mt Murchison N. Unidentified
Nov. 28, 1958 Morgano Flat on Durville River N. Unidentified
Dec., 1958 Leslie River area N. Unidentified
Dec. 26, 1958 Lake Rotoroa, mouth of Durville River N. Unidentified
Oct., 1959 Pourakino Valley S. Unidentified

Two individuals of Mystacina tuberculata on Little Barrier Island during early 1958 are recorded by Watson (in N.Z. Dep. Sci. Industr. Res. Bull. 137: 132-5, 1961). May (N.Z. Speleological Bull. 37: 175-176, 1961) refers to a live bat (probably Chalinolobus tuberculatus) sighted in a limestone tunnel (Wai-tomo district) during February, 1961.

Note that sightings along the Wanganui River on the boundary of Taranaki and North Wellington are considered in Table I as being in North Wellington.

* Details of the actual distribution records are included as an appendix to the thesis "Studies on New Zealand Ghiroptera", by P. D. Dwyer, deposited at Victoria University of Wellington, New Zealand. Since the completion of this thesis the following additional records have been made available by the New Zealand Deer Stalkers' Association. These records are incorporated in the totals of Tables I and II, but are not shown on the distribution maps.

page 14
Map 1.

Map 1.

North Island of New Zealand, showing distribution of bats.

Abbreviations: N.A., North Auckland; B.Is., Great Barrier and Little Barrier Islands; S.A., South Auckland; R.T., Rotorua and Taupo districts; G, Gisborne; T, Taranaki; H.B., Hawke's Bay; N.W., North Wellington; S.W., South Wellington; K.Is., Kapiti Island.

References to symbols as for Map 2. A larger circle indicates a series of records from a single locality.

page 15
Map 2.

Map 2.

South Island of New Zealand, showing distribution of bats.

Abbreviations: M., Marlborough; N., Nelson; W., Westland; C, Canterbury; Ot., Otago; S., Southland; S.Is., Stewart Island and subsidiary islets.

page 16
Map 3.

Map 3.

New Zealand, showing bat distribution and forest.

Only observations of bats since 1930 are shown. A large circle indicates a series of records from a single locality. Forest areas at 1955 are based on Masters, Holloway and McKelvey (1957).

page 17
Map 4.

Map 4.

New Zealand, showing bat distribution and rivers and lakes.

A large circle indicates a series of bat records from a single locality.

page 18

Maps 3 and 4 illustrate the relationship of observations to forested areas and to rivers and lakes. In Map 3 only observations since 1930 have been used, and the forested areas illustrate the position at 1955 according to Masters, Holloway and McKelvey (1957).

A number of problems in interpretation are at once apparent from an examination of the distribution records available. The most obvious of these is that records must tend to reflect the distribution of observers, and for animals such as bats which become active after dusk this is particularly relevant. Both species are forest inhabiting and the greater percentage of observations of bats in flight have been made over lakes, in river valleys, or in open clearings within or adjacent. to forest. It is only in such open areas that the rapid movement of the bats may be observed against the background of the sky. There is a tendency, therefore, for observations. to fringe the forests (post 1930 records of Map 3) or to follow major river valleys where these are surrounded by forest (Map 4). Thus in the North Island, Lake Waikaremoana (Gisborne), Lake Rotorua (Rotorua-Taupo) and the Wanganui River drainage (North Wellington) provide numerous records. It is obvious that the Urewera records (Rotorua-Taupo and Gisborne) lie along the settled Rotorua-Waikaremoana road route at the head waters of the Rangi-taiki and Whakatane Rivers. In the South Island, the Wairau and Pelorus River Valleys (Marlborough), the Buller and Grey River Valleys (Nelson), and the Lake Rotoroa district (Nelson) account for many records. Within forest, observations are usually of roosting animals or, rarely, the entry of solitary foraging animals into tents or huts.

Table II
Total number of records in five-yearly intervals
Myetaoina. Chalinolotous Unidentified Total
1870-74 2 0 3 5
1875-79 0 0 5 5
1880-84 0 1 5 6
1885-89 0 0 4 4
1890-94 2 5 4 11
1895-99 1 0 7 8
1900-04 4 0 5 9
1905-09 2 2 9 13
1910-l4 0 0 9 9
1915-19 1 0 1 2
1920-24 1 0 9 10
1925-29 1 0 13 14
1930-34 2 0 15 17
1935-39 0 0 17 17
1940-44 1 0 11 12
1945-49 2 6 47 55
1950-54 2 6 27 35
1955-59 10 8 51 69
Totals 31 28 242 301
page 19

Table II groups the total numbers of observations in five yearly intervals.* The sudden increase in the number of observations from 1945-49 is a direct result of a survey by Mr. W. Phillipps, Dominion Museum. The increase during the last five years results, in part, from the present survey as reflected by the numerous records from the New Zealand Deer Stalkers' Association and also from general public interest and the consequent accumulation of information by the Internal Affairs Department. The table certainly cannot be taken to suggest an increase in numbers during the last hundred years.

The second problem arising in interpretation of distribution records is that the total number of observations for different districts may give a false impression of the relative densities of bats in these districts. Thus a comparison of the records for the South Auckland and Gisborne districts (Table I) indicates fewer observations, 22 against 26, for Gisborne, but more colonies or large flights, 6 against 3. In addition the percentage of observations since 1930 is far greater for Gisborne than for South Auckland.

Sight records are not sufficient to enable species identification. Therefore most of the observations are of unidentified bats. Species records have only been accepted in the light of good evidence. Mystacina has long been popularly legarded as the rarer species, but I feel this stems from its structural peculiarities and the popular synonymy of "unusual" and "rare". There is no great difference between the numbers of records since 1930 for the two species; 17 for Mystacina, 20 for Chalinolobus.

With these problems in mind, I have attempted to assess the distribution of bats in New Zealand, in relation to time and physical characters of the environment.

* The discrepancies in the totals between Tables I and II and between the tables and the maps result from differences in the details supplied by individual records.