Urban rivers and creeks are often severely degraded. Not surprisingly, platypus and other aquatic species have struggled to survive as native vegetation has disappeared from stream and river banks, water has become polluted and drainage patterns altered to suit human requirements.
The platypus was first recorded by European colonists in 1797 near the Hawkesbury River, on the northwestern fringes of what is now the Sydney urban region. Around Sydney today, platypus appear to occur in nearby national parks (Ku-ring-gai Chase to the north and Royal and Heathcote to the south) and upstream of major water impoundments on the edges of the greater metropolitan area. Otherwise, recent platypus sightings are essentially lacking both for the Sydney and Wollongong regions.
Platypus are believed to survive in a few streams in the semi-rural western suburbs around Brisbane, and are still occasionally seen within a short distance of Hobart’s city centre. Around Adelaide, the animals have not been reported from the Torrens River catchment for many decades, although there is some evidence that the species was probably not very numerous in South Australia even before European settlement.
There is good
reason to believe that platypus were abundant around Melbourne at the time the
city was founded in the middle of the 19th century. In the 1870s, a "sportsman-cum-naturalist"
named Bob Stuart supported himself by selling platypus skins taken from Merri
and Darebin Creeks and adjoining sections of the Yarra River, in what are today
the city's inner suburbs. By the 1980s it was widely believed that platypus had
disappeared completely from the Melbourne metropolitan region because of
pollution and habitat destruction.
However, surveys undertaken by the Australian Platypus Conservancy in
collaboration with Melbourne Water since the mid-1990s have shown that platypus
still inhabit many urban waterways, although generally more patchily and at
lower densities than would have been the norm historically.
Case study - Melbourne Urban Platypus Program
The Urban Platypus Program began in 1995 as a joint initiative of Melbourne Water and Australian Platypus Conservancy. The program aimed in the first instance to map the distribution and status of platypus in the main rivers around the city. This has been achieved mainly through live-trapping surveys, although some valuable information has also been obtained by encouraging the public to report sightings of the animals.
Work initially focused on the Yarra River and its tributary streams, followed by the Maribyrnong River catchment and other rivers in Melbourne's western suburbs, the Dandenong Valley catchment in the city's southeast, and river systems flowing into Western Port. Surveys have now confirmed the presence of platypus along nearly half of the rivers and creeks where nets have been set in and around the Melbourne metropolitan region.
Over time, the survey effort has expanded to include studies providing the first real understanding of platypus habitat requirements in urban areas. As well, detailed radio-tracking studies have provided information on specific management issues (such as the effect of bank stabilisation and willow removal projects on platypus behaviour) to assist the development of "best practice" protocols for waterway improvement works.
Consequently, the APC/Melbourne Water Platypus Research Program has allowed Melbourne Water (and its partners at local council and community level) to undertake a wide variety of projects to improve conditions for the species. These works include:
1) willow-removal/riparian re-planting – especially Diamond Creek, Plenty River, Running Creek, Corhanwarrabul Creek, Werribee River.
2) bank stabilisation and in-stream rehabilitation (especially “riffle and pool” sequences) – e.g. Mullum Mullum Creek, Olinda Creek, Diamond Creek, Plenty River, Running Creek, Monbulk Creek, Tarago River.
3) development of major artificial “riffles” – e.g. Yarra River at Heidelberg.
4) fencing-off – e.g. joint MW/Knox Council/Salvation Army Farm Stream Frontage Management initiative along upper Dandenong/Dobsons Creek.
5) creation of “platypus-friendly” lakes/wetlands – e.g. Olinda Creek and Monbulk Creek.
6) platypus re-introduction project – Cardinia Creek.
7) water-supply closed catchment conservation zones – e.g. platypus population at Toorourrong Reservoir.
In the Yarra River catchment, platypus populations have been recorded along the Plenty River, Bruces Creek, Ruffey Creek, Diamond Creek, Running Creek, Arthurs Creek, Watsons Creek, Mullum Mullum Creek, Andersons Creek, Olinda Creek, Steels Creek, Sassafras Creek, Emerald Creek, Menzies Creek, Stringybark Creek, Watts River, Grace Burn Creek, Badger Creek, Woori Yallock Creek, Wandin Yallock Creek, Cockatoo Creek, Hoddles Creek, the Little Yarra River, Big Pat's Creek and the Yarra itself.
The APC/MW survey program has established that the breeding population in the Yarra River is now resident as far downstream as Heidelberg. In addition, in recent years, platypus have been increasingly observed in the Kew/Fairfield area - i.e. less than 10 kilometres from the city-centre - suggesting that re-colonisation is starting to occur along the most urbanised section of the river and its inner-city tributaries. (However, in this regard it is important to note that a December 2003 survey of the lower reaches of Darebin Creek did not find any platypus.)
In the meantime, platypus continue to be found in increased numbers along the middle suburban tributaries of the Yarra, especially Mullum Mullum Creek, Diamond Creek and the Plenty River. The combined platypus capture success rate for the lower sections (0-3 kilometres from the Yarra) of these three creeks over the second five year period of surveys (1999-2004) is 22% higher than the comparable rate for the first five years (1995-1999), suggesting strongly that platypus numbers have risen significantly in the Yarra’s urbanised reaches.
In addition, platypus are also being found along a greater length of these waterways. In particular, recolonisation of Mullum Mullum Creek has been marked. Platypus now can be found as far upstream as the northern outskirts of Ringwood. Platypus usage of the lower 10 kilometres of the creek nearly doubled in the 1999-2004 period compared to the first five years of surveys (1995-1999).
Likewise, recolonisation of Diamond Creek has also been pronounced. Platypus now can be found as far upstream as Wattle Glen. Platypus usage along the lowest reach of Diamond Creek (i.e. Yarra to Eltham) has more than doubled for the 1999-2004 period compared to 1995-1999. In the next section upstream (i.e. North Eltham-Diamond Creek township) the situation has gone from no platypus found at all in the early period to a resident breeding population in the 1999-2004 period.
Platypus usage of the lower Plenty River has more than doubled for the 1999-2004 period compared to 1995-1999. The population now extends upstream to the southern outskirts of Greensborough, whereas prior to1999 platypus were only found downstream of the Lower Plenty Road at Yallambie.
In the Maribyrnong River catchment, surveys have established that substantial resident platypus populations occur along the two main tributaries within the system - Jacksons Creek (including in and around Sunbury township) and Deep Creek (to at least as far upstream as Darraweit Guim). A few individual platypus are also found in the upper reaches of the Maribyrnong River itself (from the junction of Jacksons and Deep Creek at Sydenham to as far downstream as Keilor, about 10 kilometres from the CBD). However, conditions in the lower Maribyrnong remain somewhat problematic and there is no evidence yet of platypus re-colonisation of this section of river.
Elsewhere in the western Melbourne region, APC surveys have confirmed a strong platypus population in the lower reaches of the Werribee River but the species was not found along Kororoit Creek. Surveys have not been undertaken along the Little River but the absence of sightings reports suggests that platypus are not present.
Within the Dandenong Valley catchment, the platypus population occupying the Monbulk Creek/Corhanwarrabul Creek system appears to constitute the only substantial concentration of the species. The resident population appears to be in the order of 30 adult animals with the greatest density in the upper sections (i.e. near Belgrave Lake and in the Birds Land/Upwey Retarding Basins Reserve) steadily decreasing downstream towards Rowville and Scoresby. Consequently, this population is of major conservation importance. A large amount of work has been undertaken by Melbourne Water and other agencies in recent years to improve conditions, including development of “platypus-friendly” wetlands (Koolamara Waters at Ferntree Gully). It is anticipated that this will eventually lead to increased platypus numbers along this creek.
Elsewhere in the Dandenong Valley, surveys since 2001 have also confirmed the existence of a small, isolated population (which probably comprises only about 12 adult individuals) in upper Dandenong Creek/Dobsons Creek, near the Liverpool Road Retarding Basin. The long-term survival of this group is also of key conservation significance in this catchment. Accordingly, major efforts are now being undertaken to improve environmental conditions, especially through the Melbourne Water Stream Frontage Management program.
The only other evidence of platypus remaining in the Dandenong Valley occurred along Upper Ferny Creek when a single adult male (assessed to be a very old animal) was captured several times in 1996/97 surveys. However, he was not encountered in subsequent fieldwork, suggesting that platypus may now be locally extinct along this particular creek.
In the Westernport district, platypus have been recorded in the Bunyip River catchment (including Cannibal Creek, the Tarago River and Labertouche Creek, as well as the Bunyip itself) and the middle reaches of the Lang Lang River (downstream of Minnieburn Creek). However, platypus were not found in surveys along Toomuc Creek and Cardinia Creek, reflecting the fact that the species may have gone extinct in these streams as an outcome of the massive “Ash Wednesday” bush-fires in 1983.
In April 2004, the first phase of an APC/MW program to re-establish a population in upper Cardinia Creek (initially in the section between Cardinia Reservoir and Beaconsfield) commenced. Three juveniles from a neighbouring waterway were released into the creek in a trial translocation. This has proved very successful, so additional animals are be transferred to establish a core breeding population. established.
Surveys have not
been conducted along any rivers on the Mornington Peninsula. Anecdotal evidence suggests that platypus
disappeared from this area many decades ago.
However, there have been occasional purported sightings of platypus
along certain creeks in recent years, suggesting that some isolated groups may
still exist. Reports on past and
current sightings of platypus on the Peninsula would be greatly welcomed by the
APC/MW so that appropriate conservation action can be planned.
The Melbourne Urban
Platypus Program has been highly successful in linking the Conservancy's
experience in platypus research and Melbourne Water's expertise in waterway
assessment and management - exemplifying how research and management can be
directly and effectively integrated to their mutual advantage. This
co-operation reflects a climate of trust and sense of genuine shared
accomplishment between the two organisations.
The Urban Platypus Program has demonstrated unequivocally that platypus conservation is an important consideration when managing rivers across the Melbourne metropolitan region. Reflecting the enduring interest in platypus by both the news media and the local community, It has also been a remarkably effective vehicle for building community awareness of the need to use water resources in a sustainable manner.
Updates on the APC/Melbourne Water program are given from time to time in the APC newsletter Platypus News & Views.
Australian Platypus Conservancy
Phone: (03) 5157 5568 Email firstname.lastname@example.org