Shrews shrink their own skulls to get through the winter
Rather than hibernate, many shrews cope with winter by getting smaller, losing 30 to 50 percent of their body weight as bones, skull and organs shrink. August Dehnel documented the skull shrinkage in the common shrew in 1949. It is one of several odd tricks in a family that also includes venomous and echolocating species.
Shrews look like long-nosed mice but are not rodents; their closest relatives are hedgehogs and moles. With 385 species in 26 genera, the family ranks fourth among mammals for diversity, behind two rodent families and the vesper bats. They live almost everywhere except New Guinea, Australia and New Zealand; South America had none until the Great American Interchange brought a population into the northern Andes. The Asian house shrew reaches about 15 centimetres and 100 grams, while the Etruscan shrew, at 1.8 grams, is the smallest land mammal known.
Their metabolism runs hotter than that of other mammals their size, so they must eat almost constantly, and captive shrews get through half to twice their body weight in food each day. That diet grinds down their teeth, and shrews shed their milk teeth before birth, leaving one set for life. In the red-toothed species, iron in the enamel strengthens the surfaces that take the most wear. Females can raise up to 10 litters a year, often conceiving again within a day of giving birth, and shrews live 12 to 30 months.
Some species are venomous, delivering it through grooves in their teeth rather than fangs. The venom glands of one American short-tailed shrew hold enough to kill 200 mice by injection, and soricidin, a peptide from northern short-tailed shrew saliva, has been studied as an ovarian cancer treatment.
Two shrew genera, Sorex and Blarina, echolocate, joining bats, tenrecs and solenodons as the few mammals on land that do. Their soft ultrasonic squeaks seem to reveal the general character of a habitat rather than locate prey, somewhat as a person can hear the difference between shouting into a forest and into a cellar. Young of many species travel in a caravan, each gripping the fur at the base of the tail in front.
Source: Shrew
