Tenrec
Diverse Madagascar mammals that evolved via adaptive radiation.
Tenrecs are a family of mammals called Tenrecidae, found only on Madagascar. They belong to the Afrotheria group, which also includes golden moles and elephant shrews. The family is remarkably varied because of adaptive radiation—different species evolved to fill many different roles. Some look like hedgehogs, shrews, opossums, rats, or mice, even though they aren’t closely related to those animals. This is a clear example of convergent evolution. Tenrecs live in water, in trees, on the ground, and underground. Some, like the greater hedgehog tenrec, live in Madagascar’s dry deciduous forests, but new species have appeared more often in humid forests.
All tenrecs are thought to come from a single ancestor that reached Madagascar between 29 and 37 million years ago, likely by rafting on floating vegetation from Africa. Their closest relatives are African otter shrews, and the two groups split apart about 47 to 53 million years ago.
The word “tenrec” comes from the Malagasy word *tandraka* (or *trandraka*), which refers to the tailless tenrec. That Malagasy word may be related to the Malay word for porcupine.
Tenrecs are small mammals, but their size varies a lot. The smallest are shrew-sized, about 4.5 cm long and weighing just 5 grams. The largest, the tailless tenrec, can be 25 to 39 cm long and weigh over a kilogram. They have low body temperatures, and unlike most other placental mammals, they have a cloaca—a single opening for the rectum and urogenital tracts. They are among the few land mammals that use echolocation. Most species are nocturnal with poor eyesight but well-developed senses, especially their whiskers. Their teeth vary widely: different species have between 32 and 42 teeth. Unusually for mammals, their permanent teeth don’t fully come in until after they’ve reached adult size. This trait is shared with elephants, hyraxes, sengis, and golden moles, supporting their common ancestry.
All tenrecs eat at least some plants and animals, but invertebrates make up most of their diet. One species, *Microgale mergulus*, is semiaquatic, like its otter shrew relatives. Gestation lasts 50 to 64 days, and young are born relatively undeveloped. Litter size varies hugely: otter shrews have just two young, while the tailless tenrec can have up to 32. Female tailless tenrecs have up to 29 teats, more than any other mammal. Some tenrecs are social, living
- Scientific classification
- Family Tenrecidae
- Endemic region
- Madagascar
- Number of extant species
- 31
- Body size range
- 4.5 cm to 39 cm; 5 g to over 1 kg
- Gestation period
- 50 to 64 days
- Litter size
- Up to 32 young (tailless tenrec)
- Closest relatives
- African otter shrews
Lore & Background
Tenrecs are believed to have evolved from a single species that colonized Madagascar between 42 and 25 million years ago, likely by rafting on floating vegetation across the Mozambique Channel. The Tenrecidae family is one of only four extant terrestrial mammal lineages to have colonized and diversified on Madagascar. Once established, tenrecs diversified to occupy various niches, evolving resemblances to unrelated mammals not found on Madagascar, such as hedgehog tenrecs with hardened spines and the ability to roll into a ball, demonstrating convergent evolution.
Reader's Guide
Tenrecs are significant as a prime example of adaptive radiation on an island, having diversified into forms resembling hedgehogs, shrews, opossums, rats, and mice while occupying aquatic, arboreal, terrestrial, and fossorial environments. Their convergent evolution with unrelated mammals provides evolutionary biologists with opportunities to study adaptation over evolutionary timescales. Among the few terrestrial mammals that echolocate, tenrecs also possess a cloaca, a low body temperature, and up to 29 teats in some species. Their conservation is of concern due to habitat loss from deforestation, slash-and-burn agriculture, commercial logging, and mining, with five of six threatened species dependent on forest habitats. The lesser hedgehog tenrec is increasingly popular in the pet trade and may serve as an important model organism in biomedicine.
Did You Know?
- Tenrecs are among the few terrestrial mammals that echolocate.
- The tailless tenrec can have as many as 32 young per litter, and females possess up to 29 teats, more than any other mammal.
- Unusual among placental mammals, tenrecs have a cloaca, a feature more commonly seen in birds, reptiles, and amphibians.
- The word 'tenrec' is borrowed, via French, from the Malagasy word 'tandraka', which may be related to the Malay word for 'porcupine'.
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