Newsletter of the AUSTRALIAN PLATYPUS CONSERVANCY
ISSUE 29 - February 2005
PLATYPUS WEIGHT
WATCHERS
The APC recently reached a major milestone when staff carried out
the 400th night of platypus live-trapping surveys since such work began in 1994.
A review of the data collected over eleven field seasons
indicates that nets have been set on one or more occasions at nearly 750 sites,
distributed across thirteen major drainage divisions on the Australian mainland
and two rivers on Kangaroo Island. To
date, nearly 1400 data sheets describing the size and other physical attributes
of individual platypus have been completed, with one or more animals
encountered at nearly 38% of all netting sites.
While live-trapping surveys have focused on providing baseline
data to assist improved conservation management, the fact that APC researchers
always use standard protocols to capture and measure platypus means that information from different areas can also be
combined to reveal basic biological patterns.
For example, based on the characteristic size and shape of
pointed spurs found on the hind legs of males and young females, 18% of the
platypus captured to date have been classified as juveniles (less than one year
old), with the remainder comprising adults or subadults.
The overall juvenile sex ratio is very nearly 1:1, with males
comprising 49.6% of animals less than one year old.
By comparison, males make up slightly more than half (54.7%) of
the adults and subadults examined, suggesting that a lower proportion of
females survive to adulthood and/or that females are somewhat less likely to
enter nets—for example, as a by-product of their generally more sedentary
lifestyle.
The smallest platypus ever recorded in our work has been a
juvenile female captured in February 2004 along the Yarra River, which weighed
just 311 grams and measured 31 centimetres in total body length—about as long
as a standard ruler.
By comparison, the smallest confirmed adult female (also captured
in the Yarra system) weighed 769 grams, while the largest adult female
(captured along the Mackenzie River in western Victoria) tipped the scales at
1635 grams.
Reflecting the fact that male platypus typically are 15-20%
longer and weigh 60-90% more than females at any given locality, the smallest
adult male encountered to date (along the Rocky River on Kangaroo Island)
weighed 1060 grams, while the biggest male (captured and released along Deep
Creek in the Maribyrnong River catchment) weighed in at a robust 2640 grams.
Besides being of general scientific interest, reliable estimates
of demographic attributes such as age structure and sex ratio are of practical
value when trying to assess how platypus populations will be affected by
chronic or catastrophic disturbance.
With respect to conservation, the relatively small size of
platypus (particularly juveniles) highlights the potential vulnerability of
these animals to a range of terrestrial predators, including cats. Especially in the case of streams or rivers
that are characterised by extensive stretches of very low (or no) flow in
summer, the best action that can be taken to protect local platypus populations
is to ensure that plenty of protective cover is present along the banks in the
form of shrubs and other plants overhanging the water.
PLATYPUS
AND PLANNING
Protecting environmental conditions for platypus should be a
feature of good planning throughout the species’ range in eastern
Australia. Unfortunately, it currently
tends to be the exception rather than the rule for the animals’ needs to be
taken into account when applications for rezoning or new developments are
considered.
Because the platypus is officially classified as
"Common", Environmental Impact Reviews (EIR’s) for proposed
developments frequently fail to consider the species. Consequently, planning authorities and regulatory agencies often
do not appreciate that platypus populations may be threatened locally and need to be managed with care if they are
to survive.
The inclusion of platypus in the EIR process for relevant
planning schemes and development application procedures also makes good sense
for a number of practical reasons.
Firstly, conditions that are right for the platypus - a top
predator in freshwater ecosystems - will by definition favour many other
indigenous species. This generalisation
is especially important given the increasing importance placed on protecting
biodiversity values in planning (for example, see Victoria Planning Provisions
Biodiversity Note, 2002).
Secondly, failure to ensure at an early stage in the planning
process that platypus will be protected can lead to highly acrimonious
community conflict. This has been
recently exemplified by two ongoing disputes, respectively involving a new
creekside supermarket in a town north of Brisbane and plans to decommission a
small urban weir in central Victoria.
Thirdly, with
very little extra effort and cost, many developments can be modified at the
planning stage to make them more “platypus-friendly” - for example, by redesigning
bank stabilisation works, siting roads and walking trails more sensitively, and
creating wetlands that can be used by the species. Even if platypus do not currently occupy a stream or river,
allowance should be made for the fact that animal populations are dynamic:
improved management may make it possible for platypus to reside there in the
future. Such an approach can result in
a “win/win” outcome for both the environment and developers. (See Case Study: Monbulk Creek Wetland
on this page.)
To provide initial assistance to planners and those undertaking
approved works along waterways, the APC website: (www.platypus.asn.au) features
a series of conservation guidelines. For those persons who prefer the convenience of storing reference
materials in a printed and bound format, the guidelines are also included in
the booklet Living with Platypus, which can be purchased from the
APC for $6.50 per copy (including GST and postage).
The guidelines have been developed based mainly on findings from
research projects undertaken by the APC in the past decade to monitor the
effects of activities such as removing willows, stabilising banks, building a
golf course, and creating new wetlands.
Recommendations regarding how to go about helping platypus
populations in rural and urban environments are included, including advice on
issues such as catchment planning, retaining vegetation buffers, designing
stream improvement works, and the best time to implement work along waterways.
However, it’s
important to note that these guidelines have never been intended to serve as a
substitute for a proper EIR: commissioning an adequate assessment of the local
conservation status of platypus and their specific requirements to persist and
thrive should be a key requirement of the planning review process.
CASE STUDY: MONBULK CREEK WETLAND
When a new housing estate was proposed for a site near Monbulk
Creek in Melbourne’s southeastern suburbs, two key planning authorities (the
City of Knox and Melbourne Water) suggested that the developer (Wilbow
Corporation) consult the Australian Platypus Conservancy at an early stage of
the planning process to ensure that there was no adverse impact on the local
platypus population.
As part of this technical review, the design of the wetland
associated with this development was changed, making the new water body more
accessible to platypus from the creek in order to boost the number of platypus
that can live in the area.
The re-design of
the wetland also reduced the cost of the project very significantly by reducing
the need for major earthworks.
PLATYPUS EMERGENCY CARE
The late summer/autumn period is the time of the year when “lost”
platypus are most likely to be encountered.
Such animals are most typically
inexperienced or dispersing juveniles that end up in inappropriate
localities such as puddles in the middle of farm paddocks, suburban swimming
pools or (according to a report recently received by the APC) the brackish
margin of a sandy foreshore at a resort crowded with holidaymakers. However, adult platypus are also sometimes
found in unexpected places, especially if forced to migrate from their normal
haunts by natural catastrophes such as drought or bushfires.
The Conservancy’s leaflet Platypus Emergency Care provides
a series of recommendations on how best to deal with displaced or injured
animals until they can be released safely.
Copies of this publication can be obtained free of charge by contacting
the APC.
SPONSOR A PLATYPUS
Featured on the cover of the Platypus Emergency Care leaflet
is Double Trouble, who was rescued as a young juvenile from the jaws of a dog
in a public park. Unfortunately, the
rescuer then made a common error by placing the tiny animal in a tub of water
for the night. When finally picked up
by the APC, the young platypus was so cold and exhausted that she could barely
move. However, with some expert care,
she recovered completely and was eventually released back to the wild.
Double Trouble is one of four animals that can be sponsored to
assist the APC’s research and conservation programs. For each sponsored platypus you will receive:
A
certificate bearing your name (or the name of a person you designate),
A blank
platypus greetings card.
The cost of sponsorship (in Aus. $) is as follows:
1 platypus only: $10.00; 2 platypus: $18.00;
3 platypus: $25.00; All
four: $30.00.
Sponsorship
application forms can be obtained from the APC website or by contacting the
Conservancy directly.
Did You Know That….
An orphaned platypus will drink milk by sucking the liquid up
noisily from a human hand while sweeping its stubby bill back and forth against
the palm. In the wild, such pressure
probably stimulates the flow of milk, which oozes from pores on the mother’s
belly.
DRAWING
A FINE LINE
The line-drawings of platypus and water rats used in Ripples
and on the APC’s official website (www.platypus.asn.au) are the work of
Canberra-based wildlife artist, Peter Marsack.
Peter has won numerous wildlife art awards and has been the main
illustrator contributing to the most recent volume of Birds Australia’s
prestigious Handbook of Australian and New Zealand Birds (HANZAB).
In 1994, Peter also produced the image for the APC’s logo,
showing a platypus floating in its freshwater world to symbolise how platypus
conservation is integrally linked to preserving river, creek and lake habitats.
Further information on Peter and his art can be found by visiting www.marsack.com.au.