Platypus in Country Areas
Courtesy of:
The Australian Platypus Conservancy
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Platypus live-trapping surveys are physically quite demanding
and require specialised knowledge and equipment to carry out properly. In
consequence, our understanding of the distribution of platypus in most country
areas is very sketchy, derived mainly from anecdotal information gleaned from
reports of platypus sightings.
In New South Wales, platypus are believed to survive in all
of the rivers flowing east from the Great Dividing Range, and at least in the
upper reaches of 13 of the state's 16 west-flowing rivers.
In Queensland, the species has recently been reported in many
of the east-flowing rivers between Cooktown and the New South Wales border, and
the headwaters of three of the five river systems draining into the
Murray-Darling Basin. While the animals are still common in parts of the
Atherton Tablelands, they do not appear to occupy any of the waterways flowing
into the Gulf of Carpentaria.
Platypus are believed to be widespread in Tasmanian
waterways, including some streams passing through cave systems. The animals are
also found on King Island, though they appear to be absent from the islands of
the Furneaux group.
In South Australia, platypus are reported only rarely from
the Riverland area of the Murray River and have not been encountered in the
lower reaches of the Murray since 1960. They are believed to be extinct in the
Mount Lofty Ranges. A population descended from introduced animals (originating
in Victoria and possibly Tasmania) survives on Kangaroo Island.
In Victoria, platypus are thought to occupy at least 26 of
the state's 31 river systems. The species still seems to be common in many
places, especially parts of the Goulburn and Ovens River catchments and
waterways in the Otway Ranges and East Gippsland. Along the Murray River, there
are few recent reports of platypus downstream of Echuca. The species may have
disappeared from Tidal River on Wilson's Promontory and rivers along the
Portland Coast.
Because so little is known about the status of platypus, it
is impossible to say in most cases whether local populations are secure or
declining. However, based on the results of the Australian Platypus
Conservancy's studies along the Wimmera River, platypus are probably facing
severe problems in some rural catchments.
Factors which can have a serious impact on platypus numbers
include:
* Reduced or seasonally altered river and stream flows.
* Declining water quality.
* Loss of native vegetation along waterways.
* Increased erosion along banks and channels.
As well, predation by foxes and feral cats, deaths caused by
illegal fishing nets and traps, and injuries due to rubbish may all hurt
platypus numbers, while misuse of chemicals (such as pesticides, herbicides,
surfactants and fertilizers) near waterways can disrupt the aquatic food chain,
greatly reducing the platypus food supply.
Case study - Platypus in the Wimmera
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In 1997, the Australian Platypus Conservancy began a major
study in the upper catchment of the Wimmera River in western Victoria. The
research was designed to provide baseline information to a coalition of eleven
local Landcare groups, banded together under the title Rio
Tinto Project Platypus, which was working to
address environmental problems, including severe erosion and increasing dryland
salinity. In particular, it was considered important to determine precisely where
platypus still occurred in the catchment, and what
actions would contribute most effectively to
improving their habitat. Given the dearth of information on the factors which
primarily limit platypus populations in farming areas, it was expected that the
program's outcomes would also be of value in helping to shape waterway
management programs in other catchments supporting agricultural activities.
The ongoing research program includes four main elements:
* Wimmera Platypus Watch.
Creating a database of local platypus sightings has been useful in helping to
map the animals' distribution in the catchment. Associated publicity has also
helped to improve community awareness of platypus conservation issues.
* Platypus surveys.
Live-trapping surveys are providing reliable information on the status of
platypus populations in different parts of the catchment, and establishing the
basis for longer-term monitoring.
* Landholder interviews. Interviews
with landholders on properties along the main river channel and selected
tributary streams in the study area are being undertaken to help define the
animals' former distribution, establish when they disappeared from specific
areas, and canvass local opinion as to the factors which have been primarily
responsible for the species' decline.
* Studies of platypus ecology
and behaviour. By tracking the movements of
radio-tagged platypus and describing their burrows and feeding sites, key
habitat attributes of the channel and bank in relation to the animals are being
identified across different seasons.
In the period September 1997 to November 1999 the Conservancy
conducted ten major fieldwork expeditions to the Wimmera. Over 125 sites were
surveyed along more than 140 kilometres of the main river channel and all its
major tributaries in the upper catchment. Platypus were found to occur in
moderately high numbers in the uppermost part of the catchment near the Pyrenees
Range, with more than 90 individuals found near the townships of Elmhurst and
Warrak. Elsewhere, very few platypus were encountered - in all, over 80% of the
platypus caught were found in only 25% of the area surveyed - confirming
observations by local landowners that the species had declined over much of its
traditional range.
The animals generally appeared to be healthy, although a high
rate of scarring was observed on the bill, head, front feet and tail, probably
due to encounters with barbed wire fencing in the water. Unfortunately, very few
platypus were encountered elsewhere in the catchment. These results were
supported by local anecdotal accounts that platypus have declined in the region
over the past two or three decades in response to accelerating land and water
degradation. The results of the first phase of radio-tracking studies along the
Wimmera showed that in winter the animals significantly prefer using parts of
the waterway shaded by trees and having substantial amounts of woody debris
(logs and branches) in the water.
Because the platypus is such a popular "flagship"
for freshwater conservation, this research project continues to have an
important role in motivating landowners to improve the environmental quality of
their local waterways. Community interest in the outcome of the platypus survey
program has been very keen from the outset, with many landholders joining
researchers at dawn to see animals being released back to the wild. These
occasions have provided an ideal forum for researchers to answer questions about
platypus and also provide feedback on how best to manage riparian habitats with
respect to wildlife.
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