Reappraisal of the reptiles on the islands of the Houtman Abrolhos, Western Australia

2004·1.7 MB·English

by  R A How

REAPPRAISAL OF THE REPTILES ON THE ISLANDS OF
THE HOUTMAN ABROLHOS, WESTERN AUSTRALIA
By R.A. HOW1, D.J. PEARSON2, A. DESMOND’and B. MARYAN1
'Department of Terrestrial Vertebrates, Western Australian Museum,
Francis Street Perth, WA, 6000
2Science and Information Division, Department of Conservation and
Land Management, P.O. Box 51 Wanneroo, WA, 6946
department of Conservation and Land Management, P.O. Box 72,
Geraldton, WA6531.
INTRODUCTION The recent publication by Harvey
ec al (2001) provides a compre¬
The islands of the Houtman
hensive background on the
Abrolhos have a long history of
history of the Houtman Abrolhos
European visitation dating back
as well as detailed descriptions of
to their initial description by
the geological and botanical
Fredrick de Houtman in 1619.
diversity of islands making up
They were brought to prominence
this archipelago. The geology of
by the wreck and subsequent
islands in the Abrolhos indicates
mutiny among the survivors of
that those defined as belonging to
the Dutch ship Batavia in 1629.
the 'Central Platform' type, such
The Houtman Abrolhos consists
as the Wallabi, Rat and Gun
of some 170 islands and islets 60 to
Islands, consists of Cretaceous and
80 km off the Geraldton coast.
Tertiary limestones, siltstones and
The islands lie between 28°15'
marls of mainland landforms and
South and 29°05‘ South latitude
these have been isolated by rising
and west of 114°05' East longitude
sea levels for the past 8000-10 000
and are arranged in four groups
years. In contrast the newly
(North Island, Wallabi Group,
created adjacent islands, such as
Easter Group, Pelsaert Group) that
Long, Suomi and Pelsaert, consist
are separated from each other and
of coral rubble of more recent
the mainland by sea depths of up
origin.
to 40 metres. Between the mid I9'h
and 20th centuries there was a The vertebrate fauna of the
thriving guano industry on Houtman Abrolhos was detailed
islands of the Pelsaert, Easter and by Alexander (1922), and more
Wallabi groups and mining for comprehensive appraisals of the
this fertilizer was responsible for birds were compiled by Storr et al
considerable alteration to the (1986) and Fuller et al. (1994).
habitats on many islands (Harvey Nearly 100 species of land and sea
etal 2001). birds are recorded from the
172
archipelago. Two terrestrial of species. These are “taxa which
mammal species are known from are considered to have been
the Abrolhos islands: the Tammar adequately surveyed, or for which
Wallaby (Macropus eugenii sufficient knowledge is available,
derbianus) occurs on East and West and which are considered not
Wallabi and was introduced to currently threatened or in need of
North Island; while the Bush Rat special protection, but could be if
(Rattus fuscipes) occurs on West present circumstances change".
and East Wallabi. The reptiles of The Carpet Python (Morelia spilota
the island groups were first imbricata) is considered as a species
documented by Alexander (1922) in need of special protection.
and subsequently by numerous The Abrolhos islands are the type
surveys of the islands by Storr and locality of six reptile taxa, Pogona
the Aquinas College, Perth, which minor minima, Hcteronotia binoei,
were summarized and re¬ Christinus marmoratus, Strophurus
evaluated by Storr et al. (1983). A spinigerus subsp. spinigerus, Egernia
total of 23 terrestrial species and stokesii stokesii and Eremiascincus
the marine Green Turtle, Chelonia richardsonii. There are no recent
mydas occur on or around the records of the latter species from
islands. Two species of frogs, the Abrolhos. The gecko
Limnodynastes dorsalis and Crenadactylus bilineatus, also with
Myobatrachus gouldii, are its type locality on the Abrolhos
represented by specimens from islands, has been synonomised
the Abrolhos islands in the British with C. ocellatus by Cogger ct al
Museum (Alexander 1922) but (1983).
there have been no recent records
of frogs from the islands. The
mainland remnant islands appear METHODS
to have the most diverse
A brief examination of the
herpetofauna and retain
herpetofauna of twelve of the
populations of species known to
Abrolhos islands was undertaken
occur on the adjacent mainland.
between 15-17 April 2003, by six
Two threatened vertebrate species, herpetologists. It was determined
the Abrolhos Island Painted that ‘Central Platform’ islands
Button-quail (Turnix varia would be the focus of the sampling
scintillans) and the Lesser Noddy program with the aim of enhancing
Tern (Anous tenuirostris melanops) knowledge of the reptile fauna of
are endemic to the archipelago these limestone islands, in
(both are classified as ‘Vulnerable’). particular those of the Pelsaert
The Brush Bronzewing Pigeon Group, and to provide additional
(Phaps elegans), Tammar Wallaby, information on the CALM Priority
Abrolhos Dwarf Bearded Dragon Four Taxon, Egernia s. stokesii.
(Pogona minor minima) and the Sampling on the islands was
Abrolhos Spiny-tailed Skink undertaken opportunistically with
(Egernia stokesii stokesii) are all up to four hours spent searching all
classed as Priority Four Taxa major habitats on the islands. All
under the CALM priority ranking records of specimens from the
173
islands have been re-examined and both Murray and Middle Islands.
their identity validated by a recent The extensive removal of guano
audit of the herpetological from Gun Island probably
collections of the Western accounts for the failure to locate
Australian Museum by one of us either of the two larger skinks, E.
(BM). kingii and E. s. stokesii, at this
location where habitats had been
drastically altered and recently
RESULTS
created rock piles were evident.
A total of 195 captures were made Only one specimen of E. kingii
of 17 species during sampling in from Gun Island is in the
April 2003. No new species were collections of the Western
collected for the Houtman Australian Museum.
Abrolhos, although important Fourteen species were document¬
new records of species were made ed from the six islands examined,
for several islands, particularly increasing the number of known
those defined as ‘central platform' species in the Pelsaert Group of
type in both the Wallabi and islands from the previous ten.
Pelsaert groups. New records for the Pelsaert
Group were Delma australis, Lerista
Pelsaert Group elegans, Lerista lineopunctulata, and
Menetia greyii.
Six limestone islands were
examined for between two and
four hours by up to six people. Easter Group
These islands were Middle, A brief search for reptiles was
Murray, Gun, One, Two and Three made on Dry Island, as well as the
Islands. The number of reptile two coral rubble islands of Keru
species known on Gun Island was and Suomi nearby. No species
increased from 5 to 7 with the were located on the ‘Central
addition of Lcrista lineo[)unctulata Platform' type Dry Island and a
and Menetia greyii: on Murray single individual of Menetia greyii
Island from 4 to 8 with the was located on each of Keru and
addition of Crenadactylus ocellatus Suomi islands. None of these
subsp. ocellatus, Cryluoblepharus represent new records for the
carnabyi, Lerista elegans and islands or the group. Dry Island
Morethia obscura; and on Middle has been dramatically altered by
Island from 6 to 8 with the guano mining with little remnant
addition of Delma australis and vegetation remaining and is
Morethia obscura. No previous covered with numerous rock piles
information was available for created during mining. Earlier
One, Two or Three Islands but reports by Alexander (1922)
they probably represent the three indicate that Egernia stokesii
islets south of Gun Island referred occurred on Rat Island before the
to by Storr et al. (1983). Of introduction of cats, sometime
particular significance was the between 1889 and 1913, however,
documentation of healthy the Museum has no collections of
populations of the E. 5. stokesii on this species from the island.
174
Wallabi Group skink, E. richardsonii, in their
Reptiles were surveyed on East compilation of the Abrolhos
Wallabi, Tattler and Oystercatcher herpetofauna. The lack of recent
Islands. Six species, all previously records of these taxa suggests that
recorded, were collected from East they were incorrectly attributed
Wallabi. Tattler Island was known or are now locally extinct on the
to have populations of both the archipelago.
gecko Christinus marmoratus and There are numerous island records
skink Egernia s. stokesii. Both of noted by Storr et al. (1983) that are
these species as well as the skinks not represented in the Western
Cryptoblepharus carnabyi and Australian Museum collections,
Ctenotus fallens were collected and these records appear as an asterix
Egernia kingii was observed. in Table 1, while those species
No previous records of reptiles observed but not collected during
were available for Oystercatcher the present survey are denoted by
Island and our brief survey a hash. There is recent
collected the geckos, Under- photographic evidence of a Carpet
woodisaurus milii, Crenadactylus Python on East Wallabi Island but
ocellatus and Christinus marmoratus the population density appears to
and the skinks Ctenotus fallens and be very low and none were
Egernia kingii. The skink C. observed during our search of this
carnabyi was observed but not island. Seagull Island, immediately
collected. to the north of Oystercatcher
Island and separated by less than
20 metres of sea, was not visited
by us but is recorded as having
DISCUSSION
populations of the geckos,
The total number of terrestrial Christinus marmoratus, Crena¬
reptile species known to occur on dactylus ocellatus and Under-
the Houtman Abrolhos is 23 woodisaurus milii; the skinks
species, all but three of which are Ctenotus fallens and Egernia stokesii
recorded on the large islands of subsp. stokesii; and the python
East and West Wallabi (Table 1). Morelia spilota imbricata. Our brief
survey of Oystercatcher Island
Storr et al. (1983) report on the
indicates that such records, with
Western Australian Museum
specimen R188 from the Wallabi the likely exception of Morelia
islands as belonging to Lerista spilota, are very probably accurate.
greeri, however, the validity of this As well as the earlier records of E.
identification cannot be verified stokesii from Rat Island in the
as the specimen is lost and, since Easter group, Storr et al. (1983)
noted the former occurrence of
all other specimens of this species
occur in the Kimberley, we have the python, Morelia spilota, on
North Island; however, no recent
discounted the record. Similarly,
Storr et al (1983) do not recognize records exist.
the British Museum specimens of Storr et al. (1983) indicated the
the two frog species noted by impoverished reptile fauna
Alexander (1922) nor that of the recorded from the Easter group
175
Table 1. Records of species from specific islands in the Houtman Abrolhos repre¬
sented by specimens in the Western Australian Museum collections. An * repre¬
sents un-vouchered records presented in the literature and * species sighted dur¬
ing the present survey. Two amphibians and the skink, Eremiascincus richardsonii,
mentioned in text, are of doubtful origin and not included in this Table.
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Pogona minor 12 38 54 95
Christinus marmoratus 34 1 11 * 8 2 4 11 37
Crenadactylus ocellatus 1 * * * 6 7
Gehyra variegata 3 8 11
Heteronotia binoei 17 7 7
Strophurus spinigerus 1 11 14
Underwoodisaurus milii 2 3 * 11 98 116
Delma australis
Delma grayii 1 1
Lialis burtonis 1 6 7
Cryptoblepharus carnabyi # 1 1 2 3 9
Ctenotus fallens 10 3 1 * 2 6 27 39
#
Egernia kingii 5 1 2 * 1 2 15 17 38
Egernia stoke si i 1 * 11 54 82 153
Lerista distinguenda
*
Lerista elegans 1 1 1
Lerista lineopunctulata 2 1 1
Lerista praepedita 4 3 * 3
M enetia greyii 1 1 1
Morethia lineoocellata 4 6 * 7
Morethia obscura
* *
Morelia spilota 5 5
Simoselaps littoralis 2 1 3
SPECIES 11 116 1 3 2 8 6 1 15 19 20
GRAND TOTAL 90 1 1 9 11 4 2 3 22 2 148 338 556
but pointed out that two taxa distributions on the adjacent
occur on these islands (Delma mainland. They also noted that
australis and Lcrista distinguenda) Mcnctia greyii is known only on
that are absent on adjacent groups Eastern Island in the Wallabi
and have restricted or absent group apart from several records
176
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1112 2 7 1 3 4
5 3 2 16 26
1113 8 4 1 1 8 1 7 8 8 3 3 1 3 2 14
6 118 71 13 2 8 110 1 33 57 27 5 35 1 14 6 188
in the Easter group. Our survey There is considerable information
has recorded D. australis from still to be gathered on the reptile
Middle Island in the Pelsaert fauna of the Houtman Abrolhos
group and M.greyiion two islands islands as detailed sampling
in the Pelsaert group. involving pitfall trapping has not
177
been undertaken on this remote REFERENCES
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add substantially to our
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Catalogue of Australia Volume 1:
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Amphibia and Reptilia. Australian
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ACKNOWLEDGEMENTS of the Houtman Abrolhos,
Western Australia: 1991-1993.
The survey was undertaken with
Corella 18:97-113.
the assistance of Zoe Hamilton,
Dave Algaba, Rochelle Clifford HARVEY. J.M., ALFORD. J.J.,
and Kevin Marshall; their LONGMAN V.M. and KEIGHERY,
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provided great sustenance. The
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178