system are used for food storage. Typically solitary, B. brevicauda exhibits several aggressive displays and vocalizations to ward off other members of the species when encounters occur. Pairs of shrews which were introduced to a cage simultaneously coexisted for less than four months before one killed the other, and a new shrew placed in a cage containing an already established shrew will be killed within a few hours. Reproduction Mating occurs from March through September, though most births occur early or late in that period. Male shrews in captivity were observed to make clicking sounds while courting a female. During copulation, the male and female are locked together, and the female drags the male along with her. Gestation lasts 21–24 days, and after birth, the six to eight young are suckled for up to 25 days before the babies are weaned. Two litters per season are typical, though three are possible. The female strengthens the nest when the young are nursing, and is more active to support her increased nutritional needs. The young, which were born hairless and blind and weighing less than a gram, may become sexually mature in as soon as 2–3 months; those born in the spring mature more quickly than those born late in the season, and may themselves reproduce in the same year they were born. The juvenile pelage is pale and quite similar to the adults' summer fur, and is molted when the young reaches adult size. Predation The northern short-tailed shrew has a high mortality rate, though it attempts to escape predation by remaining hidden under vegetation, soil, leaf litter, or snow; only 6% of a marked group of shrews survived to the next year, and winter mortality of 90% has been recorded, probably due to cold stress. This shrew is consumed by many predators: trout, snakes, raptors, canids, cats, mustelids, skunks, raccoons, and opossums, though mammalian carnivores appear to be deterred by the musky odor produced by the shrew's scent glands. Conservation The northern short-tailed shrew is considered a species of least concern in the IUCN Red List, as it is widespread, abundant, and its population is not declining. Relationship with humans Northern short-tailed shrews cannot be domesticated. References Aminetzach, Yael T.; Srouji, John R.; Kong, Chung Yin & Hoekstra, Hopi E. (2009): Convergent Evolution of Novel Protein Function in Shrew and Lizard Venom. Current Biology Blarina Venomous mammals Shrew, Northern Short-tailed