Newsletter of the AUSTRALIAN PLATYPUS CONSERVANCY
ISSUE
30 - June 2005
TRANSLOCATION TRENDS
A project aiming to re-establish a platypus population
along Cardinia Creek—a small, self-contained catchment located southeast of
Melbourne—received a boost in April 2005 when three more juveniles were
successfully translocated from the neighbouring Tarago River. Working in close partnership with Melbourne
Water, APC staff released two young males and a young female at a site located
roughly 2 kilometres upstream of the 2004 release site. This spacing was considered to be ideal in
terms of encouraging the development of a single population while reducing the
potential for aggressive encounters occurring between newly liberated animals
and those already established in the area.
Protocols
governing the translocation process and post-release monitoring were
essentially identical to those employed the previous year, with one
exception. Given that the carefully
excavated manmade burrows into which animals were released in 2004 were quickly
abandoned, juveniles were liberated directly into the stream in 2005, at a site
providing plenty of natural cover in the form of partly submerged logs and
branches and plants overhanging the water.
The results of radio-tracking and live-trapping studies undertaken in the weeks since the young platypus were released indicate that all three animals quickly settled into a normal pattern of life in their new surroundings. Importantly, the post-release behaviour of this year’s trio has been quite similar to that recorded in 2004, suggesting that it may be broadly representative of young translocated platypus.
Some
of the main conclusions to date are as follows:
·
Translocated juveniles
may initially move either upstream or downstream.
·
In both 2004 and 2005,
animals have established home ranges within a fairly short distance (about 1-2
kilometres) of the release site.
·
Post-release foraging
patterns and use of burrows have been entirely normal from the outset,
suggesting that newly released juveniles require little (or no)time to become
accustomed to their new environment.
·
Juveniles have
consistently gained weight in the weeks following release. However, this finding may at least partly
reflect the provision of supplementary food (in the form of worms left near
burrows) in the same period.
·
No post-release
mortalities have been documented to date.
The animals translocated in 2004 are all known to have survived for a
minimum of 5 weeks, with two definitely surviving for periods of more than six
months. Based mainly on radio-tracking
data, those released in 2005 are known to have survived for a minimum of 4, 5.5
and 7 weeks, respectively.
Given the favourable outcomes
in both 2004 and 2005, we believe that a good case can be made for
translocating two or three more animals to Cardinia Creek in 2006, to boost
both the size and genetic variability of the population. With a little luck, the first home-grown
juveniles may also appear next year.
PLATYPUS GO WITH THE FLOW
What
is the effect of catastrophic natural events, such as major bushfires and
floods, on platypus populations?
In
the case of fire, a growing body of anecdotal evidence suggests that large
fires which burn substantial amounts of a catchment can cause platypus numbers
to drop dramatically.
For
example, platypus appear to have become extinct along Cardinia Creek in the
aftermath of the 1983 “Ash Wednesday” bushfire which incinerated nearly the
entire valley (see page 1).Similarly, people residing in the upper reaches of
the much larger Yarra River system (which also suffered severe damage in the
1983 fire) have reported that platypus sightings ceased after vast quantities
of ash and cinders were deposited in the channel, with the animals not
reappearing for several years.
In
the case of floods, observations by Dr Tom Grant in New South Wales and APC
staff in Victoria suggest that adult platypus are unlikely to be permanently
displaced from an area even by very
high flows—though some individuals may die through misadventure (for example,
drowning after becoming tangled in debris) or by contracting aspiration
pneumonia.
By
the same token, the fact that the mothers of small juveniles routinely block
all tunnels leading to the nesting chamber with a series of compacted soil
“pugs” presumably confers at least short-term protection from rising water
levels.
The
effect of flooding on juvenile platypus at a slightly more advanced stage of
development—when the animals are old enough to leave the burrow, but still
quite small and weak—was put to the test in early February 2005, when Melbourne
received over 120 millimetres of rain in less than 24 hours (the highest
one-day total in the city since weather records began to be kept in 1855).
The
timing of the storm coincided precisely with the period when juvenile platypus
are starting to emerge from their natal burrows in the Melbourne area (and
typically weigh in the order of just 450-650 grams).
Conservancy staff heard of only a single platypus carcass (and one living but apparently displaced juvenile) being found by members of the public in the aftermath of the high flows.
However, the results of live-trapping surveys carried
out over the following weeks suggest that flooding may have been responsible
for many juvenile deaths: the average capture rate for first-year platypus
along four annually monitored streams in Melbourne’s outer suburbs from 2000
through 2004 (0.31 juveniles per site per night) was ten times greater than
that recorded in 2005 (0.03 juveniles per site per night).
In contrast, little difference was observed in the
average capture rate for adult and subadult platypus along the same four
streams from 2000 through 2004 (0.49 animals per site per night) as compared to
their capture rate in 2005 (0.43 animals per site per night).
The varying response of the two age classes presumably
reflects the fact that greater size, strength and experience are all predicted
to be advantageous to the platypus in surviving flood waters.
Further surveys in the Yarra
catchment next year, conducted as part of the ongoing Melbourne Water Platypus
Research Program, should help to shed light on any longer-term effects of the
February flood on population age structure in the urban area.
Did You Know
That....
Platypus could be seen outside Australia from 1947 (when naturalist David Fleay was successful in conveying two juvenile females and a young male captured in Victoria to the Bronx Zoo in New York City) to 1957 (when the male—named Cecil—was found dead in his enclosure, a few weeks after the sole surviving female managed to escape). During their years in America, the animals mainly dined on earthworms, mealworms, crayfish, egg custard and (in the case of Cecil) frogs.
PLATYPUS: THE WORLD VIEW
The
Australian media recently featured images of Prime Minister John Howard happily
posed next to a giant platypus sculpture at the Australian pavilion at the
Aichi World Expo in Japan. The use of
the platypus as the nation’s “ambassador” at this major international event is
a pertinent reminder of the world-wide appeal of this uniquely Australian
mammal.
Reflecting
this global interest, the Conservancy often receives queries as to whether
platypus can be seen anywhere outside Australia.
The
last platypus known to be taken overseas from Australia died in 1957 (see Did
You Know That?, above). No
platypus has since been sent abroad.
After consulting widely with platypus experts, the Australian government
imposed a formal ban in the mid-1990’s on the export of the species for any purpose,
including display in foreign zoos or transfer to research institutions.
It
seems unlikely that this policy will be reviewed until a self-sustaining
captive population has been established.
Given that only a handful of platypus have been bred in Australian zoos
in the last decade, it may be many years yet before that point is reached. For the foreseeable future, Australia is
likely to remain the only country where platypus can be seen.
However,
one intriguing possibility is yet to be fully investigated: Does the platypus
exist in New Guinea?
The
occurrence of monotremes in New Guinea in the form of various echidna species
(including the short-beaked echidna Tachyglossus
aculeatus, which is also found across Australia) is a reminder that Australia
and its island neighbour to the north once formed part of the same
landmass. Hence, it is certainly
plausible that the range of the platypus once extended to what is now New
Guinea.
Furthermore,
reports of recent sightings of platypus in New Guinea do emerge from time to
time. Checking the accuracy of such
information is generally quite difficult.
When further enquiries have been possible, it has been concluded that the
animals concerned were very probably water-rats. In addition, no hard evidence (in the form of fossils, bones or
skins) has ever been made available to support the past or present occurrence
of platypus.
However,
new species of echidnas have been identified by scientists working in
previously inaccessible parts of the island in recent times. Such findings suggest that it is not totally
impossible that platypus could still be discovered in remote rivers or
lakes.
WEBBED WONDER ON THE WEB
The
Australian Platypus Conservancy’s official website—www.platypus.asn.au—provides
information to suit people of all interest levels.
You
can learn more about the biology and ecology of the species in the Platypus
Fact File. Special topics include:
Discovery and Naming, Distribution and Status, Life in the Water, Matters of
Life and Death, Out of the Water, Poison, The Search for Food, Status in
Country Areas, and Status in Urban Areas.
Practical
advice on how best to assist platypus in the wild is provided in Platypus
Conservation Guidelines, while Looking for Platypus offers suggestions about
how to monitor local platypus populations using visual survey methods. Platypus sightings can also be reported
online.
For
those seeking additional detailed information on the species, a reading list provides references for relevant books, popular
articles and scientific publications.
Articles from back issues of the APC newsletter can be found in the Ripples
archive section.
You
can also find basic information about the Australian water-rat Hydromys
chrysogaster, the largest native mammal to
share the platypus’s freshwater habitat.
The
website provides details about how to join Friends of the Platypus or sponsor a
platypus. Items which can be purchased from the APC—including T-shirts,
sweatshirts, cards and posters, and the Living With Platypus booklet—can
also be viewed and ordered.
SPECIAL THANKS TO OUR SUPPORTERS!
The
Australian Platypus Conservancy is a non-profit research and conservation
organisation. The success of the APC’s
programs relies on the support of businesses, management agencies and
individuals sharing our interest in one of the world’s most amazing animals.
We
gratefully acknowledge special recent help by the following supporters:
- Corangamite CMA
- Healesville Toyota
- Melbourne Water
- Project Platypus Landcare Group
- R.E. Ross Trust
The
APC also thanks the many other groups which continue to assist its work,
including:
Austvet; City of Banyule; Cumberland Stationery; Danks Trust; Decor Corporation; ESRI Australia; Gillette (Duracell Products); Glenelg Hopkins Catchment Management Authority; Goulburn Broken CMA; Greenworld Office Products; JLM Paper Tubes; Kevron Plastics; City of Knox; City of Manningham; Microchips Australia; Myer Foundation; Nature’s Own (Mayne Consumer Products); North Central CMA; North East CMA; Parks Victoria; Platypus Technology; John T Reid Charitable Trust; Self Adhesive Markings; Shire of Nillumbik; Shire of Yarra Ranges; Helen Macpherson Smith Trust; Sonoco Australia; Upper Maribyrnong Catchment Group; Victorian State Government; Wilderness Wear; West Doncaster & Templestowe Veterinary Centres; West Gippsland CMA; City of Whittlesea; Wimmera CMA; Carl Zeiss.
Australian Platypus Conservancy
P.O. Box 84, Whittlesea VIC
3757
Tel: (03) 9716 1626 Fax: (03) 9716 1664
E-mail: platypus@vicnet.net.au www.platypus.asn.au