Notomys alexis
spinifex hopping mouse

Notomys alexis is found in the sandy soils of Central Australia to Western Australia. Found abundantly in the Great Victoria Desert of Western Australia, N. alexis is the most abundant of all hopping mice in Australia (Watts and Aslin, 1981).

Notomys alexis lives in sandy soils in areas of plains and dunes. They have been found in eucalypt woods, acacia shrubland, and tussock grassland. Notomys alexis characteristically live in areas with hummocks of spiky spinifex. This vegetation gives N. alexis the common name of Spinifex Hopping Mouse. These hopping mice live in deep, simple burrows in the sand (Watts and Aslin, 1981).

Notomys alexis are light brown to chestnut dorsally and gray to white ventrally. They are relatively large for a mouse species. The tail is relatively long and colored brown on the top and lighter on the bottom. The tip of the tail has a brush on it but the brush is smaller than in related species. A throat pouch is present in both sexes and may vary in appearance as the sexual state of the animal changes (Watts and Aslin, 1981). Adults weigh 20 to 50 grams. Body and head length ranges from 91 to 177 mm, average tail length is from 125 to 225 mm (Verberne, 2002).

Although females can mate with multiple partners, no obvious intermale competition occurs. In captivity, females have been observed mating with more than one male during a single estrous cycle. When the paternity of the litter was tested, all the young were found to be from the same male (Hyde and Elgar, 1992).

Notomys alexis are opportunistic breeders. Although they can breed when conditions are not perfect, reproduction increases after periods of rain. Females can start breeding at 85 days old and have an estrous cycle of seven to eight days. Gestation ranges from 32 to 34 days if the female is not lactating. If a female is lactating, the gestation period can increase to about 40 days. Estrus continues during lactation and finding a female that is pregnant and lactating is not uncommon. Breeding can be inhibited by a high population density of N. alexis (Watts and Aslin, 1981).

Pink and sparsely furred, the young weigh about 3 grams when they are born. It takes about 15 days for the ears to open and 20 days for the eyes to open. They are cared for and nursed in the nest by their mother until they are weaned, at about 28 days (Watts and Aslin, 1981).

Spinifex hopping mice live as long as 3 years in captivity but probably much less in the wild. Most may live less than a year.

Notomys alexis are social animals and live in groups of up to 10 individuals. These groups live in single deep burrows but often these burrows are clustered into a system connecting many groups. Although these groups may communicate, the immediate family grouping is the strongest. When groups exceed the normal number, cooperative behavior ceases. In captivity, large group size may result in the killing of young. Notomys alexis are very abundant and very active creatures. Quadrupedal and bipedal hopping are only two of the seven modes of locomotion recorded (Watts and Aslin, 1981). Water loss is limited in many ways. Urination and defecation is minimized and the urine is the most concentrated of any mammal. Living in burrows also reduces water lost to heat because the environment stays close to one temperature. Notomys alexis sleep in one nest chamber huddled close together to reduce water loss due to evaporation. They are active after dark to decrease water loss also (Watts and Aslin, 1981).

Notomys alexis individuals eat mainly seeds, but also consume green plants and insects when available. They are not completely granivorous. A study has shown that they eat about 50% seeds and 50% invertebrates and supplement their diet with green plants (Murray and Dickman, 1994). These hopping mice can survive without free water by utilizing water in their food and efficiently using metabolic water.

Being active after dark and hopping quickly, in varying directions, helps N. alexis to avoid predators (Watts and Aslin, 1981). Most small to medium-sized predators in the regions where they live probably prey on spinifex hopping mice.

Notomys alexis serve as seed dispersers for many different plants. They occupy a unique niche and coexist with 10 to 12 other small mammal species. Most of these species are other rodents, but some are dasyurid marsupials (Murray and Dickman, 1994).

These small mice are sometimes kept as pets (Verberne, 2002). They are also used extensively in laboratories in Australia (Murray and Dickman, 1994).

Population explosions have been recorded for N. alexis. In 1975, a plague of N. alexis occurred. At this time, several hundred were reported being seen by spotlight by observers. It was also reported that they would enter campsites and steal scraps of food (Watts and Aslin, 1981).

Spinifex hopping mice are abundant and widespread, they are not threatened.