Shrews, often regarded as some of the most enigmatic and remarkable creatures in the animal kingdom, are small mammals that belong to the family Soricidae. These pint-sized predators may not be as well-known as their larger counterparts, but they possess a host of fascinating characteristics that make them stand out in the wild.
Despite their diminutive size, shrews are renowned for their voracious appetites and unrelenting energy, which has earned them a reputation as one of the most ravenous mammals on Earth. These remarkable creatures are among the oldest predators on the planet, with their origins dating back an astonishing 45 million years.
- Shrews are one of the most voracious mammals on Earth.
- The shrew is the smallest terrestrial mammal on Earth.
- Shrews are one of the world’s most ancient predators.
- The shrew is the smallest mammal in the family Soricidae.
- Shrews are classified as insectivores, not rodents.
- Shrews emerged approximately 45 million years ago and have remained nearly unchanged for at least 10 million years.
- The shrew is one of the smallest mammals.
- The shrew is one of the most wide-ranging mammals in all of North America.
- North American short-tailed shrews are about 4 inches long.
- Shrews have beady eyes and pointed noses.
- They have a dark grayish body with a stumpy tail.
Physical Characteristics and Behavior
- The North American Shrew has velvety, soft fur with a short tail and small eyes.
- They have a white belly and grayish to reddish-brown fur.
- Their summer fur is lighter than their winter fur.
- The North American short-tailed shrew is the most common mammal in the United States.
- Shrews move quickly with rapid, bouncy movements.
- They have the fastest heartbeat, recorded up to 1,200 beats per minute.
- The largest shrews in North America are about 4.3 to 5.5 inches in length.
- The shrew builds its home in burrows and thin runways under flat stones and fallen logs.
Reproduction and Metabolism
- The shrews mating season is March to November.
- Shrews usually produce two litters per season with three to six young per litter.
- North America Shrews have been recorded making 12 body movements per second.
- Shrews live life at a very fast pace.
- A shrew’s heartbeats rate generally beats 800 to 1000 times per minute.
- Shrews are in a stable motion, not often stopping to sleep.
- Shrews have a very high metabolism.
- A shrew’s life consists of constantly searching for prey.
- The shrew eats insects, from the corpses of dead animals, as well as seeds and fruit.
- If shrews do not find food within a two-hour period, they will attack and eat each other.
- A shrew will die if they do not eat within a few hours.
Senses and Venom
- Shrews have poor eyesight.
- Shrews move their whiskers continually. This movement is called ‘sufficient whisking’. They will do this until they brush against their prey.
- Shrews store enough venom to kill 200 mice.
- Shrews bite the heads off crickets and grasshoppers to eat their internal organs.
- The shrew lacks hollow fangs but has a gland that allows saliva to flow with venom.
- Shrew bites on humans are painful but not deadly.
- Many mammalian predators, including red foxes, raccoons, and cats, will attack shrews but hardly ever eat them.
- Shrews release an unpleasant smell when attacked.
- The shrew has been known to live inside beehives and shares food with other shrews before storing the waste.
Habitat and Diet
- Shrews like grassy open lands and are also found in open forests and marsh habitats.
- A shrew’s body is smooth with a unique pointed snout equipped with a highly movable and functional nose and very sharp teeth.
- The sharp teeth of the shrew help them for killing and tearing their prey to pieces.
- North American shrews have 32 teeth.
- The shrew has movable vibrissae around the nose and mouth which provide a very eager vibratory sense to detect movement, helping them greatly in locating insects.
- Half of a shrew’s diet consists of aquatic insects, the other half is terrestrial insects.
- Shrews are active at all hours of the day but more active at night.
Reproduction and Family Life
- Shrews are not sociable mammals.
- Shrews breed year-round and normally produce many litters per year.
- North American shrews mate from March through September.
- During mating, male shrews will make clicking sounds to invite females.
- After a gestation period of about 21 -22 days, litters of 4-7 young are born. Young babies are born naked with their eyes and ears closed.
- At birth, young shrews weigh only 0.11 ounces.
- Both parents care for the young and within a month are fully weaned and resembling adults.
- Shrews can become sexually mature at 2-3 months of age.
- Shrews have a very high metabolic rate and burn up large amounts of energy in a short duration of time.
- A shrew has an average life span of less than one year.
- Shrews never sleep for more than a few minutes at a time.
Unique Adaptations and Behavior
- Shrews have to eat three times their body weight daily, which means they capture prey every 15 to 30 minutes, day and night.
- The saliva of these little animals packs a strong punch to its prey in the form of a neurotoxin.
- Shrews are not deadly for humans.
- Shrews make ultrasonic noises, similar to bats.
- During the winter, shrews tend to eat 40% more food in order to maintain their body temperature.
- Like other mammals, shrews also possess brown adipose (fat) tissue that also aids them in maintaining body heat during the cold winter months.
- Shrews produce venom from their salivary glands which helps them overcome prey larger than themselves such as salamanders, frogs, snakes, mice, and birds.
- Shrews can stay underwater for 45 seconds or more at a time.
- Shrews are able to skitter across water surfaces supported by air bubbles trapped in the feet and toes.
- Shrews are very territorial and aggressive.
- Shrews are helpful for farmers because they reduce insects, slugs, and other vermin from their crops.
- Shrews have the fastest metabolic rate of all known animals.
- A shrew’s brains weigh 10% of their total body weight.
- Shrew venom is not conducted into the wound by fangs but by a groove in the teeth.
- Shrews are solitary animals.
- The Northern Shrew does not hibernate. Their winter death rate is as high as 90%.
- Shrews will aim for the legs in order to cripple an animal when confronted with a larger creature.
- Shrews cannot stay alive in temperatures higher than 77 degrees F.
Bryan Harding is a member of the American Society of Mammalogists and a member of the American Birding Association. Bryan is especially fond of mammals and has studied and worked with them around the world. Bryan serves as owner, writer, and publisher of North American Nature.