With so many varieties of shrews there are many different types of behavior with respect to their activities. Some shrews are active day and night and some are more active in the dark. None of the varieties of shrews hibernate during the winter months. Not even the ones living in northern Canada!
Their vision is poor and those little eyes do not do much good in showing the animals their neighborhood so they have come up with other ways to get around. Many scientists believe that shrews use echolocation to view their world. This is the same thing that bats do. Basically, the animals send out high pitched sounds, often clicking noises, into their environment. The speed at which the sound returns to the animal allows them to determine what and where objects are such as insects, plants, rocks, animals and people.
The Short-tailed Shrews have an interesting trait not seen in many mammals: a poisonous bite! It has been determined that they have glands in their teeth that secrete a poison toxic to small mammals such as mice and even other shrews which renders them paralyzed and helpless. This is what allows these animals to prey on mammals larger than themselves.
Family life is very utilitarian for all shrew species and shrew populations can reach high numbers fast. Mating occurs anytime between March and September with females giving birth two (2) to three (3) times per year. Litters can range from three (3) to upwards of eight (8) babies at one setting born only three (3) weeks after conception. The babies stay with mom for about 25 days before they leave the nest and are off on their own. With female shrews reaching sexual maturity at six (6) weeks old and ready to mate again almost immediately after giving birth, it is no wonder that shrew populations can get out of hand quickly!
Shrews have a very high metabolic rate which includes and very fast heart beat. Some shrews have had their heartbeats measured at 1200 beats per minute! To maintain themselves they must eat their weight in food every day. This is accomplished by eating every few minutes. With a heart beating so fast the animals are easily startled and with deadly consequences. They have been known to die of fright after a loud burst of thunder!
Predators of the shrew include mainly owls, weasels and foxes. Shrews have a defense mechanism much like the skunk. They excrete a musky smell from scent glands located on their bottom and sides. The smell is so foul that while shrews are often killed, they are rarely eaten.