Before the prairies of the North American West were cultivated for farmland and turned into cattle pasture, ferrets would have been a common sight. The burrows that they and their prey made in the ground formed dangerous obstacles to grazing cattle and farm machinery, so the animals were methodically exterminated by pioneer farmers. Today the ferrets - the only species of ferret native to N. America - occur wild in just three places in Montana, S. Dakota and Wyoming (all reintroduced populations).

As well as having black feet, these ferrets have a black "mask " over their eyes. The underside of the body is covered in yellowish fur. Male black-footed ferrets are slightly larger than females.

The ferrets live on and under prairies that have short or medium-length grasses. Each ferret occupies about 40ha (100 acres) of prairie, in which it finds all its food, but a nursing mother needs two or three times this space. Black-footed ferrets take up residence in burrow systems abandoned by prairie dogs, their main food. In places where prairie dogs form large communal "towns", the ferrets may actually live among their prey.

The breeding season is in late spring. The young remain underground for a month after they are born. Mother and young forage together in late summer, generally at night, and by autumn the young begin to drift away. Males take no part in raising the young.

Distribution: Historically southern Canada to northern Mexico; today reintroduced populations exist in Montana, S. Dakota and Wyoming.

Habitat: Prairie.

Food: Mainly prairie dogs, along with some mice, ground squirrels and other small animals.

Size: 38 - 60 cm (15 - 23.5 in) 645 - 1.125g (22.75 - 39.75 oz).

Maturity: 1 year.

Breeding: Single litter of 1-6 young produced in early summer, after a gestation of 35 - 45 days.

Life span: 5 years.

Status: Endangered.