TREE SHREWS: Scandentia

PHYSICAL CHARACTERISTICS

In physical appearance, tree shrews resemble a squirrel with a long snout, nose. The scientific family name is from the Malay word tupai, which means squirrel. Animals in this family are commonly referred to as tree shrews, ever since they were first mistaken for shrews when they were first spotted in 1780. Shrews are small, insect eating mammals with pointy snouts.

Tree shrews are relatively small, with the head and body length ranging from about 5 to 9.5 inches (13 to 24 centimeters). These animals have a long tail, which is covered with long thick hair in all the species except the pen-tailed tree shrew. The tails of pen-tailed tree shrews are hairless except for a whitish feather-shaped arrangement of hairs near the end. In general, tree shrews have small ears similar to those of a squirrel, and their ears are covered with fur. An exception is the ears of the pen-tailed tree shrews, which are bare and larger than all the other species.

Fur colors of tree shrews range from gray to dark brown on the upper side of their body, and white, yellow-brown, or dark brown on their belly. Their fur is generally soft and thick. Some species have light shoulder stripes and others have facial markings. Their legs are short, with claws on their fingers and toes.

GEOGRAPHIC RANGE

Tree shrews are found in south and Southeast Asia, ranging from India and southwest China eastward through Malaysia, Indonesia, and the Philippines. Out of the nineteen tree shrew species, ten live on the island of Borneo.

HABITAT

Tree shrews live in shrub and forested areas, which are often mountainous. Many of the tree shrews are arboreal, meaning that they live in trees. Some species spend the majority of their time on the ground.

DIET

Tree shrews primarily eat a combination of insects and fruits. They also will occasionally feed on plant material, along with other small animals, including fish and mice. Different tree shrew species have their own feeding method, one species may collect black ants at night while another species digs up earthworms.

BEHAVIOR AND REPRODUCTION

In general, tree shrews are active during the day. The pen-tailed tree shrew is nocturnal, meaning that it is active at night. Researchers do not know a lot about the behavior of tree shrews. One reason is that they are difficult to observe because they are highly active animals that move quickly and constantly.

All tree shrews have the ability to climb trees. They use their sharp claws to dig into the trees and branches as they climb. Many species are arboreal, while others find their food and spend a great deal of time on the ground. Tree shrews commonly use the same paths along the ground or on branches to reach their favorite feeding or resting areas.

They have well-developed senses of vision, hearing, and smell. These animals typically catch food with their snout, and use their hands only when they cannot reach their food. They may grab hold of flying insects with their hands. They eat in a style similar to squirrels, hunching on their hind legs while holding the food in their arms and eating it.

Most species nest in holes in tree trunks or branches. These animals make a nest of dried leaves, twigs, and soft wood. Tree shrews are territorial, meaning they protect their own territory. They release droplets of urine and scent to mark their territory. Tree shrews have specialized glands, located on their chest and belly, which produce the chemical scent. Many of the scents are distinct to a particular animal. They deposit their scent in areas where other animals may smell it to let them know that the area is occupied.

Tree shrews live in monogamous (muh-NAH-guh-mus) pairs, meaning they have one mate. Gestation, or pregnancy, lasts between forty-three and fifty-six days. Females give birth to small litters (young born at the same time) of poorly developed, hairless offspring. The typical litter size ranges from one to three offspring. Baby tree shrews are often born in pairs.

In many of the species studied, researchers found an unusual mothering strategy unlike other mammals. Mother tree shrews visit their babies only once every two days for about two minutes each visit. When the mother visits her young in the nest, she immediately allows the babies to nurse, which they do quickly. Babies take in large amounts of milk and lie back with a bloated stomach. With no mother in the nest, the babies snuggle with each other to keep warm. The babies also groom each other, a task traditionally done by the mother.

Field studies have found that tree shrews breed when fruiting peaks occur in the forest.

TREE SHREWS AND PEOPLE

With their close relationship to primates, and a well-developed sense of vision and hearing, tree shrews are being used by researchers as animal models for human diseases. An animal model is an animal studied that mimics human biological or psychological disease. Research studies have included hepatitis (hep-uh-TIE-tuhs), a disease of the liver, vision disorders, and psychosocial stress.

A CASE OF MISTAKEN IDENTITY

For years, scientists debated about who was the tree shrews' closest relative. In the 1920s, a scientist proposed that tree shrews were related to primates based on studies of primate and shrew skulls. Many accepted these findings and said the tree shrew belonged in the primate order. Other researchers said it was more similar to animals in the insectivore order, because of its resemblance to animals such as the shrew. In 1984, researchers decided the tree shrew was unique enough to have its own order.

CONSERVATION STATUS

The majority of tree shrew species are common, however several are Endangered or Threatened. Long-footed tree shrews and Nicobar tree shrews are Endangered, facing a very high risk of extinction in the wild. Bornean smooth-tailed tree shrews, golden-bellied tree shrews, Palawan tree shrews, and Mindanao tree shrews are Vulnerable, facing a high risk of extinction in the wild. Mindanao tree shrews are listed as Near Threatened, not currently threatened, but could become so.

COMMON TREE SHREW (Tupaia glis): SPECIES ACCOUNT

Physical characteristics: Common tree shrews have a head and body length of about 7.5 inches (19.5 centimeters). They have a long, pointed snout. Their fur is darker on the upper side of their body than on their bellies. Upper side fur can be dark brown, pale brown, blackish gray or it can appear almost black. Their undersides are whitish, orange or rusty red, or a light or dark brown. Common tree shrews that live in northern areas with less rainfall are typically lighter than those in southern areas with greater rainfall.

They often have a pale stripe along their shoulder. Similar to a squirrel, common tree shrews have a long, bushy tail. It can be about as long as the length of the head and body. These animals have relatively small ears, with their lower lobe smaller than the upper one.

Geographic range: Common tree shrews are found in Thailand, the Malayan Peninsula, and in Sumatra, Java, and surrounding islands.

Habitat: Common tree shrews live in evergreen tropical rainforests.

Diet: Common tree shrews eat a varied diet that they collect primarily from the ground. Their food includes insects, particularly ants, as well as spiders, seeds, buds, leaves, and fruit. They can also eat lizards.

Behavior and reproduction: Active during the day, common tree shrews are extremely energetic. They spend a great deal of their time on the ground, yet they can also easily climb trees. They typically live alone or with a mate. Field studies in Malaysia have shown that breeding may occur at any time of year. Gestation periods last roughly forty-six to fifty days, and families produce one to three offspring. The newborn young are hairless, with closed eyes. The young are ready to leave the nest about thirty-three days after birth. The young are reared in a nest separated from that of the mother and are suckled every other day.

Common tree shrews and people: There is no known connection between common tree shrews and people.

Conservation status: Common tree shrews are not considered threatened. ∎

FOR MORE INFORMATION

Books:

Nowak, Ronald M. Walker's Mammals of the World Online. Baltimore: Johns Hopkins University Press, 1997 http://www.press.jhu.edu/books/walkers_mammals_of_the_world/scandentia/scandentia.html (accessed July 1, 2004).

Stone, David, and the IUCN/SSC Insectivore, Tree Shrew and Elephant Shrew Specialist Group. Eurasian Insectivores and Tree Shrews-Status Survey and Conservation Action Plan. Gland, Switzerland: IUCN, 1995.

Periodicals:

Bloch, Jonathan I., and Dough M. Boyer. "Grasping Primate Origins." Science (June 2001): 1606–1609.

Crosby, Olivia. "Wild Jobs with Wildlife: Jobs in Zoos and Aquariums." Occupational Outlook Quarterly (Spring 2001): 2–15.

Eckstrom, Christine. "What is a Tree Shrew?" International Wildlife (November/December 1996): 22–27.

Gore, Rick "The Rise of Mammals: Adapting, Evolving, Surviving." National Geographic (April 2003): 2–37.

"Tree Shrews Could Model a Number of Chronic and Infectious Human Diseases." Hepatitis Weekly (July 14, 2003): 8.

Web sites:

"Common Tree Shrew (Tupaia glis)." America Zoo. http://www.america.zoo.com/goto/index/mammals/83.htm (accessed on July 1, 2004).

Meyers Phil. "Order Scandentia." Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/information/Scandentia.html (accessed on July 1, 2004).

"Rainforest Animals: Common Tree Shrew." Missouri Botanical Garden. http://mbgnet.mobot.org/sets/rforest/animals/shrew.htm (accessed on July 1, 2004).