IR, Rat Strain

**Semantic type:** Mammal

**Definition:** Vigorous and healthy, but high incidence of physical abnormalities. Skulls of young fragile through weaning. High death rate from hemorrhage due to blood platelet disease (Harrington 1981). Long latency to emerge into familiar environment (12/12 males, 10/12 females) (Harrington 1971a). High open field exploration in females (3/12) (Harrington 1972). Low wheel activity (11/12 males10/12 females) (Harrington 1971b).