Gilbert’s Potoroo

Gilbert’s Potoroo (Potorous gilbertii) is a small marsupial endemic to Albany on the south coast of WA. They were thought to be extinct by the early 1900s, but a population on Mt Gardner in Two Peoples Bay was discovered in 1994 by a graduate student trapping for Quokkas (Setonix brachyurus). Trapping in suitable habitat along the south coast since that time has found no other populations of Gilbert’s potoroo and only 30 to 40 animals in the Mt Gardner population, meaning they are critically endangered [1].

quokka on Rottnest Island by Thomas Rutter

quokka on Rottnest Island by Thomas Rutter

Peter from the Albany Branch of The Wildflower Society of WA told me about Gilbert’s potoroo co-habiting with quokkas [2]. The vegetation on Mt Gardner is very thick because fire hasn’t burnt the area for many years. The potoroos are able to tunnel through this dense heathland and the quokkas make use of their tracks. Quokkas are found on Rottnest Island off the coast of Perth, which is famous for them, and Bald Island off the coast of Albany, with other populations throughout the south west [3].

Potoroos need dense ground vegetation to survive [4]. A fire on Mt Gardner, apart from being likely to kill the whole population, would mean any survivors could not live in the area until dense vegetation had regrown, many years after the fire. Fires in the vicinity of Mt Gardner are responded to immediately and contained very quickly. When the Mt Gardner potoroos were discovered a captive colony was established at Two Peoples Bay Nature Reserve to ensure against such a disaster, but breeding among this colony declined after 2001 [1]. Other options for population increase had to be found.

Excess young are produced by the Mt Gardner potoroos, but numbers do not increase because the area of suitable habitat is not large enough to support population growth [1]. Young independent potoroos have been successfully transferred to Bald Island, where dense sedges grow among melaleuca heaths, there is abundant underground fungi [5] and their friends the quokkas – all the things they like. DEC Principal Research Scientist Dr Tony Friend said,

The potoroos have resoundingly endorsed our choice of Bald Island as a translocation site. [6]

While this is slowly increasing potoroo numbers, another technique has been found. Kangaroos, wallabies and their relatives produce an undeveloped embryo while suckling a joey [1]. This adaptation evolved so that if a mother is in danger she can push her suckling joey out of her pouch for the predator chasing her and make her get-away while the predator is otherwise occupied. Females who do this live to raise their undeveloped embryo and pass on their DNA to the next generation, ensuring the replication of the trait.

During the 1960s it was discovered young joeys can be removed from their mother and placed with a foster mother to continue their development. The removal triggers the development of the waiting embryo and another joey is born within three to four weeks, increasing the birth rate for the donor mother. When the surrogate and donor mother are from different species this is called cross-fostering and was found to work with Gilbert’s potoroo and long-nosed potoroo foster mothers [1]. A cross-fostering facility was built near Two Peoples Bay (the land and financial support provided by an Albany resident) and a captive colony of long-nosed potoroos (Potorous tridactylus) from Warrawong Sanctuary in Adelaide moved to their new home.

Two Gilbert’s potoroos have survived to independence and were moved to the Gilbert’s potoroo captive colony at Two Peoples Bay. One of the other two did not survive and the other was still in her foster mother’s pouch at the time of publication [2008]…The cross-fostering trial so far indicates that there is promise in this technique for Gilbert’s potoroo. [1]

long-nosed potoroo by Kristian Golding

long-nosed potoroo by Kristian Golding

Find out more from the Gilbert’s Potoroo Action Group on Twitter or Facebook.

References

  1. Friend, Tony (2008) “Cross-fostering Gilbert’s Potoroo” Landscope, vol.23, no.3, p.6-8
  2. Peter (2008) President of the Albany Branch of The Wildflower Society of WA, personal communication
  3. Department of the Environment (2016) Setonix brachyurus — Quokka in Species Profile and Threats Database, Dept of the Environment, Canberra http://www.environment.gov.au/sprat
  4. Strahan, Ronald (Ed.) (1983) The Australian Museum Complete Book of Australian Mammals: The National Photographic Index of Australian Wildlife. Sydney: Angus & Robertson
  5. Friend, Tony & Bougher, Neale (2009) “Gilbert’s potoroo translocated to new areas find their fungi” Information Sheet 4, Dept of Environment & Conservation, WA
  6. WA Dept of Environment & Conservation (2007, 17 July) “Bald Island a successful breeding site

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