Shark Bay mouse (Pseudomys fieldi)

Also known as: Alice Springs mouse, Djoongari
Synonyms: Pseudomys praeconis
  
Spanish: Ratón Bastardo Peludo
KingdomAnimalia
PhylumChordata
ClassMammalia
OrderRodentia
FamilyMuridae
GenusPseudomys (1)
SizeHead-body length: 9.5 cm (2)
Tail length: 12 cm (2)
Weight30 – 50 g (3)

Classified as Vulnerable (VU) on the IUCN Red List 2007 (1), and listed on Appendix I of CITES (4).

The Shark Bay mouse is a robust, long-haired rodent often given the nickname ‘shaggy mouse’ for the shaggy fur that covers its body (2) (3). The fur is pale yellow-fawn mixed with grey on the back, giving a grizzled appearance, fading into buff on the sides and white below (2) (3). The tail is slightly longer than the head and body and is coloured grey on top and white underneath, with a dark tuft of hairs at the tip (2) (3).

Currently, the Shark Bay mouse is known only from Bernier Island in the Shark Bay region of Western Australia, and from two translocated populations on Faure Island and North West Island (3). Translocation attempts on Doole Island and Heirisson Prong were unfortunately unsuccessful (5).

On Bernier Island, this mouse is found in coastal sandy areas and dune vegetation, and also at lower densities in inland heath (3).

Outside of the breeding season, the Shark Bay mouse does not seem to use burrows as much as other Pseudomys species, but rather builds tunnels and runways amongst vegetation, which it uses as daytime refuges. The mice on Doole Island have been observed using hollows in mangrove trees, as well as sites among rocks for daytime refuges. Little is known about the diet of this nocturnal species, although it is believed to comprise flowers, leaves and insects, and individuals have been recorded eating spiders (3).

The Shark Bay mouse is apparently solitary (2), and most information on its reproductive behaviour has come from observations of captive animals (3). Breeding on Bernier Island primarily takes place between May and November and gestation lasts around 28 days (2) (3). Litters of up to five young have been recorded in captivity, although around three is thought to be more common (2) (3). Young are born hairless but are furred by 11 days, although the eyes remain closed for a further four (2) (3). Young are weaned by four weeks and obtain full adult size at around 100 days. Specimens on Bernier Island have lived for at least two years (3).

Before translocations to other locations began in 1993, the Shark Bay mouse was amongst the most threatened of all Australia’s mammals, being geographically restricted to just one small island, after having become extinct on the mainland. The precise reasons for the decline of this species are unknown, although a number of theories exist. One suggestion is that cats introduced to the mainland by 19th century may have been responsible for the decline and extinction of many native species on the mainland, but particularly rodents. Predation by foxes may also have had an impact. Another idea is that grazing and trampling by domestic stock brought over by European settlers has contributed to the extinction of Australian fauna on the mainland, possibly including the Shark bay mouse. Likewise, it has been proposed that the rabbit has degraded and competed for fertile habitat, a particularly scarce resource in arid zones of Australia, especially in those that experience successive periods of drought. Altered fire regimes have also been cited as a possible reason for the decline of native species. Sadly, the fact that the Shark Bay mouse does not construct substantial burrow systems underground, but rather build tunnels in vegetation, means that it is particularly exposed and vulnerable to these threats, more so than many other rodents (3).

Thankfully, the Shark Bay mouse population on Bernier Island is protected from the threats that have impacted those on the mainland, as this island is part of the Bernier and Dorre Islands Nature Reserve and lacks any exotic predators. Feral goats were eradicated in 1984, and public access is limited to day visits. Nevertheless, this restricted distribution left the species in a highly vulnerable position. Thus, a Recovery Plan was created for the mouse, which involved the translocation of populations to three other exotic predator-free island nature reserves, Doole Island (June 1993), North West Island (June 1999), and Faure Island (June 2003), and to Heirisson Prong, Shark Bay, on the mainland (November 1994), after intensive feral animal control had been undertaken (3) (5). The reintroduced populations have been monitored on an ongoing basis and restocking has occurred where necessary (3). However, the populations on Doole Island and Heirisson Prong have not persisted. It is believed that predation by Varanus lizards prevented the establishment of a viable population at these sites (5). To aid the translocation programs, a captive breeding programme was established in 1998 at Perth Zoo. It is vital that translocated populations become established and self-sustaining if this geographically restricted mouse is to be brought out of the danger zone, but so far these have had mixed success, and the future of this tiny mammal remains uncertain (3).

For more information on the Shark Bay mouse see:

Authenticated (21/11/07) by Keith Morris, Biodiversity Conservation Group, Department of Environment and Conservation, Government of Western Australia.

  1. IUCN Red List (January, 2007)
    http://www.iucnredlist.org
  2. AustralianFauna.com (January, 2007)
    http://www.australianfauna.com/sharkbaymouse.php
  3. Morris, K., Speldewinde, P. and Orell, P. (2000) The Recovery Plan for Djoongari or the Shark Bay Mouse (Pseudomys fieldi) 1992-2001. Department of the Environment, Water, Heritage and the Arts, Canberra, Australia. Available at:
    http://www.deh.gov.au/biodiversity/threatened/publications/recovery/djoongari/index.html
  4. CITES (January, 2007)
    http://www.cites.org
  5. Morris, K. (2007) Pers. comm.