262 
N.L. McKenzie, L. Fontanini, N.V. Lindus, M.R. Williams 
Leporidae 
Oryctolagus cuniculus Lilljeborg. European (White) 
Rabbits were brought onto Koolan as cage pets. 
Despite some escapes, there is no evidence of a 
feral population. 
DISCUSSION 
Koolan supports a sub-set of the Kimberley 
fauna. Although maco-invertebrates and 
vertebrates are incompletely sampled, its bird and 
snake faunas are surprisingly rich considering the 
island's small size and restricted range of habitats. 
The indigenous earthworms all belonged to the 
genus Diplotrema (Acanthrodrilinae sensu. Jamieson 
1971) and are new to science. This genus is 
ubiquitous in rainforest patches elsewhere in the 
Kimberley where each patch has its own endemic 
species (McKenzie and Dyne 1991). The 
earthworm populations in Koolan Island 
rainforests were equivalent in terms of their 
density and abundance to those reported from 
rainforest patches on similar sandstone lithologies 
elsewhere in the Kimberley (mean +/- s.e. = 35.7+/ 
-5.8 m 2 , 9.2+/-2.0 g m 2 , n = 42; from Tables 4 and 6 
in McKenzie and Dyne 1991). 
The Koolan savanna woodland specimen is the 
first Diplotrema recorded outside a rainforest 
environment in the Kimberley. This reflects the lack 
of previous attempts to survey earthworms in 
Kimberley savannas, exacerbated by their presence 
near the surface only after heavy rains and their 
relatively low density (Table 2). Unfortunately, the 
specimen was so sexually immature that it could 
not be placed taxonomically in relation to the 
island's other Diplotrema: D. "koolanl" and D. 
"koolan2". 
Dichogaster bolaui, an introduced earthworm that 
is cosmopolitan in tropical and subtropical parts of 
the world, was the only species recorded in the 
gardens of houses in the town. These lush tropical 
gardens had been established for up to 20 years, 
and included many species of broad-leaf trees and 
shrubs such as Banana palms, Sausage Trees and 
Frangipani. Most had reticulated watering systems 
to overcome the annual seven month drought of 
the dry season. Our failure to find Diplotrema in 
these gardens may have related to the presence of 
the D. bolaui. This species was probably introduced 
with potted garden plants during the 1960's, 
although a box of earthworms was brought onto 
the island in the early 1980's (L.F., pers. obs.). 
Elsewhere in Australia, introduced earthworms are 
known to displace native species from disturbed 
soil profiles (Wood 1974, Abbott 1985). Dichogaster 
bolaui was not recorded outside the town 
boundaries. 
Only seven species of indigenous land snail have 
been recorded from Koolan Island. Their 
phylogenetic affinities are with taxa on the adjacent 
Kimberley mainland (Solent 1991). Three species 
are known only from Koolan (Kimboraga 
koolanensis, Setaubaudinea sp. and Amplirhagada 
astuta). 
In 1988, V. Kessner (pers. comm.) recorded five 
other non-camaenid species on islands elsewhere 
in the Buccaneer Archipelago: Gastrocopta 
Table 5 Syntopic land snail assemblages from other islands in the Buccaneer Archipelago (collected by V. Kessner in 
1988). 
Species 
Cockatoo 1 
"Unnamed" 2 
Dunvert 3 
Pupillidae 
Nesopupa mooreana Pilsbry 
X 
X 
Gastrocopta macrodon Pilsbry 
X 
X 
X 
Pupoides pacificus (Pfeiffer) 
X 
- 
- 
Subulinidae 
Eremopeas interioris (Tate) 
_ 
X 
X 
Helicodiscidae 
Stenopylis coarctata (Moellendorff) 
X 
- 
- 
Charopidae 
Discocharopa aperta (Moellendorff) 
_ 
- 
X 
Helicarionidae 
Westralcystis lissus (E.A. Smith) 
X 
X 
X 
Camaenidae 
Torresitrachia bathurstensis (E.A. Smith) 
X 
X 
X 
Kimboraga yampensis Solem 1985 
X 
X 
X 
1 16°05T5“S, 123°35'20"E. Under shady bushes on a steep sandstone (Pky) slope (23 July 1988) 
2 16°1215' S, 123°32’40"E. Vine thicket on a mudstone substrate (26 July 1988). 
3 16°17’45"S, 123°30’50"E. In a small patch of vine thicket on a very steep sandstone scree slope (26 July 1988). 
