Insectivores (Insectivora) are a group of mammals that include hedgehogs, moonrats, shrews, and moles. Insectivores are generally small mammals with nocturnal habits. There are about 365 species of insectivores alive today.
Most insectivores have small eyes and ears and a long snout. Some do not have visible ear flaps but have a keen sense of hearing. They have clawed toes on each foot, and the pattern and number of their teeth are rather primitive. Some insectivores such as otter-shrews and moonrats have a long body. Moles have a more cylindrical body, and hedgehogs have a round body. Some insectivores such as tree moles and shrews are adept tree climbers.
Insectivores rely more on their sense of smell, hearing, and touch than their vision and some species of shrews can navigate their environment using echolocation. The bones in the inner ear of insectivores are different than other mammals. They lack an ossified temporal bone, and the tympanic membrane is attached to a bony tympanic ring while their middle ear is closed off by surrounding bones.
Insectivores live in terrestrial habitats around the world. Additionally, some species of insectivores inhabit aquatic environments while others burrow.
Moles spend most of their time below ground in their tunnels they excavate. Shrews generally live above ground and build burrows for shelter and sleeping. Some species live in boggy areas where rotting vegetation, rocks, and rotting logs are common. Other species inhabit arid regions including deserts. Moles and shrews are usually active throughout the year.
Hedgehogs are easily recognized by their rotund shape and spines. Their spines consist of tough keratin and serve as a defense mechanism. When threatened, hedgehogs roll into a tight ball so their spines are exposed and their face and belly are protected. Hedgehogs are mostly nocturnal.
As their name implies, insectivores feed on insects and other small invertebrates such as spiders and worms. The diet of insectivores is not restricted to invertebrates and also includes a wide variety of plants and animals. Water shrews feed on small fish, amphibians, and crustaceans while hedgehogs feed on birds' eggs and small vertebrates.
Many species of insectivores locate their prey using their keen sense of smell or by using their sense of touch. The star-nosed mole, for example, not only has a sharp sense of smell, but it also has a nose with many small and touch-sensitive tentacles that enable it to find and capture their prey.
- Animals > Chordates > Mammals > Insectivores
There are four living subgroups of insectivores. These include the hedgehogs, moonrats, and gymnures (Erinaceidae); the shrews (Soricidae); the moles, tree moles and desmans (Talpidae); and the solenodons (Solenodontidae). Insectivores are thought to be most closely related to bats, hoofed mammals, and carnivores.
The classification of insectivores is not well understood. Insectivores have a primitive mammalian body plan and are in many ways generic in their appearance. For this reason, insectivores have been classified in several other mammal groups in the past such as the tree shrews or elephant shrews. Additionally, some adaptations insectivores exhibit are convergent with the adaptations of other groups-a fact that further confuses the proper placement of insectivores within the mammals.
Previous classification schemes once placed tree shrews and elephant shrews in the insectivores, but today they are classified in their own separate orders. It is possible that other animal groups such as golden moles may be removed from the insectivores as new information comes to light.
Insectivores are considered to be among the most primitive groups of mammals. Some primitive traits insectivores still exhibit include a small brain and testes that do not descend into a scrotum.