Notomys alexis (*)
Notomys alexis Thomas, 1922
Type locality: Australia, Northern Territory, 35 miles (56.3 km) SW of Alroy, 800 ft (244 m); see Mahoney and Richardson (1988:166).
Holotype: BMNH 22.214.171.124
* Notomys alexis everardensis Finlayson, 1940
* Thomas, O. 1922. Two new jerboa-rats (Notomys). Annals and Magazine of Natural History, Series 9, 9: 316.
The Spinifex Hopping Mouse (Notomys alexis), also known as the Tarkawara or Tarrkawarra, occurs throughout the central and western Australian arid zones, occupying both spinifex-covered sand flats and stabilised sand dunes, and loamy mulga and melaleuca flats.
The population fluctuates greatly: in normal years it is sparsely distributed and probably confined to sandy country; after rain the population explodes and spreads to other types of habitat for a time.
They are mostly seen at night, bounding across open ground on their large hind feet, with tails extended and the body almost horizontal.
The apperarance is very similar to the Northern Hopping Mouse: a little larger than a common House Mouse at 95 to 115 mm (3.7 to 4.5 in) head-body length and an average weight of 35 g (1.2 oz). As with all hopping mice, the hind legs are greatly elongated, the fore limbs small, and the brush-tipped tail very long—about 140 mm (5.5 in). The fur is chestnut or fawn above, pale below, with a grey wash about the muzzle and between the eye and ear, and longer, coarse black guard hairs on the back. The tail is sparsely furred and pink, darker above than below.
Spinifex Hopping-mice live in small family groups of up to 10 in (250 mm) deep, humid burrow systems. Typically, there is a large nest chamber lined with small sticks and other plant material about a metre below the surface, from which several vertical shafts lead upwards. Shaft entrances do not have spoil heaps.
Adults emerge at dusk and spread out individually for some hundreds of metres, on all fours when moving slowly, on the hind legs alone at speed, foraging for seeds, roots, green shoots, and invertebrates. Seed is the primary diet item, other food is taken when available.
Breeding can be at any time of year depending on conditions, with spring being favoured. Pregnancy usually takes 38-41 days but can be extended significantly if the mother is still breastfeeding the previous brood. Litters of 3 or 4 are typical, 6 being the maximum. The young remain in the nest while the female forages; if they wander both male and female adults retrieve them. They reach sexual maturity in about two and a half months.
The Spinifex Hopping Mouse is widespread and although the population fluctuates considerably, is not considered at risk.
The spinifex hopping mouse is part of the Muridae family, the family Muridae gave rise to the rats, house mice, hamsters, voles, and gerbils that are found today first appeared around 34 million years ago. Rodents first appeared in the fossil record about 54 million years ago. These original rodents were themselves descended from rodent-like ancestors called anagalids; these anagalids gave rise to the rabbit group.
Homologous feature: An animal that shares a homologous feature with the spinifex hopping mouse is the Lepus capensis (brown hare), because they both have the same structured bones in their legs which allow them to bound across the ground at a fast pace. The spinifex hopping mouse and the lepus capensis share the same common ancestor. Spinifex hopping mice and Hares are in danger from the first day of their existence from a number of predators, including raptors and foxes and other mammalian carnivores. Their greatly elongated hind limbs have allowed them to adopt a bounding gait and occupy areas with limited shelter. So, instead of taking cover when danger approaches, they depend on their running ability for escape.
Analogous feature: An analogous feature of the spinifex hopping mouse is their eyes, compared to the eyes of a cat, even though they are both used to see in the dark and be able to detect predators they are not as closely related, like the spinifex hopping mouse and the hare. We know that these two species are not related because the spinifex hopping mouse is from the family Muridae whereas the common cat is felidae.
* Baillie (1996). Notomys alexis. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 12 May 2006.
Source: Wikispecies, Wikipedia: All text is available under the terms of the GNU Free Documentation License