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Rottnest Island - Quokka Country
In the early 1900's, an abundance of quokkas could be found throughout the south-west of Western Australia and this was believed to have been the case for as long as 33,000 years (1).
Around the 1930's, the quokka population was severely disrupted on the mainland, possibly as a result of predators, diseases, the loss of habitat (1) and a lack of quality sustaining nutrition.
It was largely believed they were limited to Bald Island near Albany and Rottnest Island ever since but during the mid-1980's, quokkas were found to still be residing in areas on the mainland, although within severely reduced habitat.
This included Two People's Bay Nature Reserve, Torndirrup National Park, Mt Manypeaks National Park and the Stirling Range National Park, the first three located in or in close proximity to Albany and the latter being a bit further north.
A full grown adult's body measures up to 55cm long with a tail up to approximately 30cm. They can weigh as much as 5kg.
Habitat
Quokkas are marsupials that feed on plants and are essentially nocturnal but it's quite common to see them throughout the day on Rottnest Island, particularly close to the settlement areas.
Whilst they are largely sedentary, long-distance movements tend to be limited to places where they can obtain drinking water or food, particularly as this is crucial to their survival (2).
Feeding and Diet
During the mid-1980's, it was found that quokkas tended to starve more during the summer and warmer periods, as a result of a decline in their preferred plant food (3). This was partially blamed in an increase of unpalatable and exotic vegetation that was introduced to the island, both accidentally and intentionally.
On 6 February 1955, a major scrub fire burnt a large area of Rottnest Island and this was also thought to have affected the vegetation favoured by quokkas, as well as the slow regrowth period subsequently resulting from over-grazing (4).
Quicker regeneration of plants in the winter meant quokkas were generally able to regain their lost weight.
Quokkas tend to supplement their diet from rubbish facilities and eating areas in the settlement, which is hardly surprising when tourists see the quokkas as an integral part of their Rottnest experience, whether it's taking a selfie with one, physical touch and quite often, feeding their foods scraps to them.
Rottnest Island Regulations 1988
There are many rules on Rottnest Island that are in place for a reason.
One is to not touch any wildlife, although quokkas tend to come up to people in search of food or out of curiosity and this can at times, be hard to avoid. Touching and petting the quokkas can "make them sick, spread disease and even cause mothers to abandon their young if they carry an unfamiliar scent".
Anyone who is seen to deliberately interfere with any of the wildlife on the island, including feeding a quokka, can be fined $150 on the spot or $750 in court under Rottnest Island Regulations 1988.
Earlier this year, a man staying on the island posted a photo of himself holding a quokka. Rangers tracked him down and whilst they didn't evict him from the island, they issued him a $200 infringement. Interestingly, the PerthNow article stated that authorities could issue fines of up to $300.
Salmonella
Quokkas are known to be infected with Salmonella. During the mid-1980's, 54 strains were identified in the quokkas confined to the island (4).
It was found that during the winter periods, infections tended to be low and was attributed to a good nutritional diet whilst the summer periods brought on an increase of infections due to the poor quality of the island's vegetation.
Quokkas, consuming food scraps or being fed by visitors, had a lower chance of carrying a strain of the virus, due to their susceptibility being reduced as a result of eating supplementary food during the warmer months (4).
The potential health risk posed to people can result from being in close proximity to the quokkas or when the marsupials access water catchment areas and contaminate the water supply with their faeces.
At the same time, an increase in visitors, particularly international tourists, could see exotic salmonella strains being introduced and transferred to quokkas (4).
References
(1) Lundelius, E.L. (1960) Report of International Geology Congress XXI, Session Part IV. Chronology and Climatology of the Quaternary, 142-153.
(2) Dunnet, G.M., (1962) A Population Study of the Quokka, Setonix brachyurus (Quoy and Gaimard) (Marsupiala) II Habitat, Movements, Breeding and Growth C.S.I.R.O. Wildl.Res. 7: 13-32
(3) Wake, J., (1980) The Field Nutrition of the Rottnest Island Quokka. Ph.D. Thesis, Zoology Department, University of W.A.
(4) Rottnest Island Management Plan – Volume 1: The Plan (August 1985)
