Koolan Island Zoological notes 
265 
mammals known from Koolan Island comprise one 
dasyurid, one rodent and 12 bat species. They are a 
biased sub-set of the Torresian mammal fauna 
found on the adjacent mainland. 
Considering the extent, intensity and duration of 
human activity on the island, and the number of 
natural historians that have searched for ground¬ 
dwelling mammals there since 1965, the list may be 
complete. A field survey in 1983 found only three 
such species on the largest of the other islands in 
the Archipelago (Hidden Island, 2003 ha; Peradorcas 
concinna, Dasyurus hallucatus and Mesembriomys 
macrurus), two on Long (1380 ha; Peradorcas 
concinna and Rattus sp.), and only one species on 
smaller islands such as Irvine (940, Zyzomys 
woodwardii), Bathurst (580, Zyzomys zvoodwardii ), 
and Margaret (270, Mesembriomys macrurus). The 
voucher specimens from this survey are lodged in 
the WA Museum (M23001-23059, M23150-23167). 
In contrast to its non-volant mammals, Koolan is 
rich in bats, especially cave-dwelling species 
(Taphozous georgianus, Hipposideros ater gilberti, H. 
stenolis, Rhinonicteris aurantius, Macroderma gigas 
and Vespadalus caurinus). Even so, future surveys 
will probably reveal additional species because 
Miniopterus schreibersii and Pteropus scapulatus are 
known from nearby islands (Gibbings and King 
Hall respectively), and other species occur in 
adjacent areas of the mainland: Chaerephon jobensis, 
Vespadalus douglasi, Pipistrellus westralis, Scotorepens 
sanborni, Myotis adversus and N. geoffroyi pallescens 
(McKenzie and Rolfe 1986). 
Little is known about the natural history of 
Hipposideros stenotis in the Kimberley. The sites and 
small colony-sizes we recorded on Koolan are 
consistent with previous observations (Kitchener et 
al. 1981, Hall 1983), including a June 1982 record 
from Bathurst Island (16°03'S, 123°02'E), 15 km 
west of Koolan, where a female (M 23057) was 
taken from a pair found in a small sandstone (Pky) 
cave overlooking the coast. 
Our data show that animal-eating bats that 
forage in the island's open microhabitats have 
higher wing loadings and aspect ratios, but lower 
tip indices, than bats of more obstructed air-spaces 
(Table 3). These attributes relate to flight speed, 
energy-cost of flight and manoeuvrability, 
respectively (Norberg and Rayner 1987). Non- 
parametric ranked correlation analysis revealed a 
strong correlation between mean "wing loading" 
and "lowest frequency" in free-flight (Kendall Tau 
= -1.0, P = 0.014), and a significant correlation 
between mean "aspect ratio" and "lowest 
frequency" in free-flight (Kendall Tau = -0.8, P = 
0.05), for the five bats we recorded foraging in 
"edge" and "open" microhabitats on Koolan 
(Tables 3 and 4). Such relationships are well 
documented from work on bat communities 
elsewhere (e.g. Aldridge 1987, Fullard et al. 1991, 
McKenzie et al. 1995). The data presented in Table 
4 suggest that the microbats known from the island 
can be readily distinguished in terms of the 
average lowest frequency of their ultra-sounds, and 
will facilitate future survey work. 
The bias towards large land snails and 
butterflies, snakes and cave-dwelling bats in the 
Koolan Island fauna lists is a sampling artefact. 
Nevertheless, the richness of these groups indicates 
that the numerous rugged sandstone islands along 
this tropical, sub-humid coastline support much 
richer faunas than were revealed by the brief 
surveys carried out to date (e.g., Burbidge and 
McKenzie 1978). 
ACKNOWLEDGEMENTS 
We thank Patrick Warrand (Broken Hill Pty Ltd) 
for arranging accommodation and transportation 
during our field work, DEST for assistance with 
funding under National Rainforest Conservation 
Program, and Peter Agnew (ICI) for his assistance 
in locating the cave at 16°07T0"S, 123°44’30"E. We 
also thank Norah Cooper, Mark Cowan, Mark 
Salotti, Mark Harvey, Terry Houston, Darryl 
Kitchener, Ron Johnstone and Laurie Smith for 
access to W.A. Museum collections. Barbara York 
Main provided advice on spider determinations 
and contributed data from her records. Mike Lyons 
drafted Figure 1. Ron Johnstone and the two 
referees provided helpful comments on the 
manuscript. 
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