Newsletter of the AUSTRALIAN PLATYPUS CONSERVANCY
ISSUE
37 - March 2008
In theory, floods could either have a positive or negative impact
on platypus populations, depending on their severity and duration.
For example, positive effects could arise if accumulated silt is
washed away to reveal a more diverse channel substrate, or the quality of
platypus habitat is improved by logs and large branches that are carried down
and left in the channel. However,
populations could also be harmed if young platypus drown in their nursery
burrows, or stream and river habitats are degraded by erosion.
In practice, very little is known about how flooding actually
affects this species, either directly or over the longer term.
As reported in Ripples 30, the capture rate for juveniles
around Melbourne dropped sharply in 2005 after streams and rivers flooded in
early February—the time of year when most baby platypus are old enough to leave
the burrow, but are still quite small and weak. Little change was noted in the corresponding adult and subadult
capture rates, suggesting that size and strength may help this species cope
with flood waters.
Similarly, along the Shoalhaven River in New South Wales, juveniles
failed to be captured in surveys conducted after floods occurred in late
December and January, despite the fact that half of all adult females had been
found to be lactating (and hence caring for young) just before the floods took
place. However, the case for adults
being directly harmed by flooding in this area is again more tenuous—while at
least one platypus carcass has been recovered along the Shoalhaven immediately
after a flood occurred, many other marked adults have been recaptured after
floods none the worse for wear.
Major flooding affected several river catchments in eastern
Victoria in the winter and spring of 2007, just a few months after much of the
area was incinerated by bushfires. To
investigate the impact of this sequence of events on platypus populations, the
Conservancy has commenced a research project in partnership with the Department
of Sustainability and Environment and Parks Victoria.
To determine if platypus continue to inhabit streams that were
first burnt and then flooded, APC staff will undertake replicated live-trapping
surveys along a representative range of water bodies in the region. This fieldwork is being carried out in late
summer and autumn, when juveniles are easiest to detect if successful breeding
did occur.
To ascertain if platypus still survive along rivers that are too
deep or fast-flowing for nets to be set safely, visual surveys will be carried
out at sites where there are credible pre-flood reports of platypus being seen
(indicating that animals lived in the vicinity).
Last but not least, anecdotal information relating to possible
changes in the number of platypus seen in flood- and fire-affected habitats
will be obtained from individuals who are particularly well-placed to notice
such changes, including property owners with stream and river frontage, members
of canoeing and angling clubs, and field staff working for DSE, Parks Victoria
and regional water authorities.
Persons having information about how platypus numbers may have been
affected by fire and flood in Gippsland (or elsewhere) are urged to get in
touch with the APC, so their knowledge can be used to help assess the impact of
large-scale natural disasters on this most remarkable mammal.
PRIME PLACES FOR PLATYPUS
The Conservancy and Melbourne Water have been undertaking platypus
research since 1994, resulting in a dauntingly large number of reports on the animals’ distribution. To make this vast mass of data easier for
its staff and contractors to access and use, Melbourne Water recently asked the
APC to prepare a comprehensive summary of where platypus are found and where
they breed in the urban area. Based on
the information in this review, we thought it might be of interest to suggest a
list of what (at least in our opinion) are the top five water bodies supporting
platypus in the greater Melbourne region:
Yarra River.
Platypus have been seen since 2000 on a regular or occasional basis by one or
more persons living at View Bank, Lower Plenty, Eltham, Templestowe,
Warrandyte, Kangaroo Ground, Yarra Glen, Yarra Junction, Warburton and East
Warburton. Accordingly, we confidently
predict that platypus occupy all parts of this river upstream of about
Heidelberg, though numbers presumably vary locally depending on factors such as
habitat integrity and channel width and depth.
More generally, the importance of the Yarra River to the long-term
survival of platypus around Melbourne cannot be overstated: this river
comprises a very sizable chunk of platypus habitat in its own right, is an
important corridor allowing dispersing juveniles to travel from crowded
locations to less populated sites, and provides a life-saving refuge in dry
summers for platypus occupying small tributary streams.
Tarago River.
The Tarago joins the larger Bunyip River (which in turn flows into Western Port)
in Melbourne’s southeastern fringes. Many platypus have been seen in recent
years along both the Tarago River and its main tributary, Labertouche
Creek. As well, the Conservancy has
received several accounts of platypus occupying farm dams located 100 metres or
more from these two water bodies, suggesting that the local platypus population
is both large (increasing the likelihood that an animal finds a farm dam in the
first place) and reasonably crowded (providing motivation for the animal to
stay in the dam rather than return to the natural channel). The results of live-trapping studies
conducted from 2000 to 2007 confirmed that the Tarago system is associated with
a highly productive platypus population, with many breeding age females and
juveniles recorded. Their abundance presumably reflects in part the reliable
environmental flows released in recent years from Tarago Reservoir.
Woori Yallock Creek system. Woori Yallock Creek flows north to join
the Yarra approximately midway along the river’s length. From the viewpoint of a platypus, this creek
system has at least two desirable attributes: riparian corridors often support
substantial numbers of indigenous trees, and the headwaters are located at the
edge of the relatively damp Dandenong Ranges.
This location means that the Woori Yallock system as a whole generally
flows quite reliably. Platypus have
reportedly been seen in Woori Yallock Creek at numerous localities since 2000,
and also in many of the catchment’s smaller streams, including Wandin Yallock
Creek, Sassafras Creek, Emerald Creek, Menzies Creek, Cockatoo Creek, Shepherd
Creek, Tomahawk Creek, Clark Creek and Sheep Station Creek.
Werribee River. Live-trapping surveys conducted in 1998
and 2000 in and downstream of Werribee township confirmed that platypus were
widespread and occurred at a reasonably high
density (estimated to be around three adults or subadults per kilometre
of channel). Elsewhere along this
river, many platypus sightings have been reported since 2000 from Werribee township
upstream to Cobbledicks Ford and near
Bacchus Marsh. The animals have also
been recorded to occur downstream of Melton Reservoir and in Werribee Gorge.
Jacksons Creek. Jacksons Creek arises near Gisborne and joins Deep Creek west of Tullamarine Airport, forming the Maribyrnong
River. Based on sightings reports and
live-trapping surveys conducted in the late 1990s, particularly large numbers
of platypus occur in and around Sunbury township, with many juveniles and
breeding age females encountered in this area.
The animals presumably benefit from the numerous rocky riffles and
sizable pools in this basalt-dominated catchment, as well as reasonably intact
riparian vegetation which helps to protect the creek from impacts of
development.
Did You Know That....
Many platypus in parts of Tasmania are infected by a fungus
(Mucor amphibiorum) which causes large skin ulcers to develop and can result in
death. This fungus is also known to
occur in frogs on the Australian mainland (where Mucor infections in platypus
have not been recorded) and may have been introduced to Tasmania by green tree
frogs transported accidentally in shipments of bananas.
NEW PLATYPUS BOOK
Platypus (written by Tom Grant, available from
CSIRO Publishing, 159 pages)
Tom Grant has been a key figure in platypus-related research since
1978, when he produced two important papers on platypus temperature regulation,
based on his Ph.D. thesis.
Many readers will have enjoyed his book The Platypus: A Unique
Mammal, published in 1989 as part of the University of New South Wales
Press Natural History series, with a revised edition appearing in 1995. Persons familiar with these books will
recognise some of the same illustrations and drawings in Platypus. However, the rest of the book has been
thoroughly revamped, with an enormous amount of up-to-date information provided
in chapters organised around traditional subject areas: breeding biology, spurs
and venom, sensory organs, diving and foraging, ecology, evolution and
conservation. The text is complemented
nicely by a final chapter devoted to FAQ’s (Frequently Asked Questions) and a
comprehensive bibliography.
As a conservation organisation, we’re especially pleased that an
entire chapter is devoted to the effects of various human activities on
platypus populations.
It starts off by summarising what is known about how Australia’s
original inhabitants regarded the platypus—some aboriginal groups seem to have
considered them to be very good to eat, whereas others were less enthusiastic
about the platypus’s culinary merit—and continues with the impact of early
European hunters. Many platypus were
slaughtered to fashion hats and slippers, with 40 to 60 pelts required to make
a single lap rug. Fortunately, the
thickness of the platypus’s skin (and resulting stiffness of the tanned hide)
meant that platypus fur was not in high demand for most types of clothing or
export.
The platypus was declared a legally protected species in Victoria
in 1892, with New South Wales, Queensland and Tasmania following suit by
1907. Nonetheless, many platypus
continue to die today after drowning in crayfish traps or fish nets, becoming
impaled on fishing hooks or entangled in litter, or being run over by vehicles
after leaving the water to travel around vertical weir walls or elevated
culverts.
This publication will be valued by anyone with an interest in the
platypus. The author is to be commended
for clearly explaining a broad range of scientific findings and also indicating
where the boundaries of current knowledge lie—for despite the wealth of facts
in this book, much remains to be discovered about this amazing animal.
FORTHCOMING PLATYPUS TALK
Friday 6 June 2008, starting 7.30 pm at Gwen Webb Art Centre,
Market Street, Sale. For more details,
please contact the Conservancy.
OUR CONTACT DETAILS:
In 2007, the Conservancy relocated its research base to Gippsland
(see Ripples 35). Please note
(if you haven’t previously done so) that our new contact details are as
follows:
Australian Platypus Conservancy
P.O. Box 22
Wiseleigh VIC 3885
Tel: (03) 5157 5568
Email: platypus.apc@westnet.com.au
Website: www.platypus.asn.au