Tenrecs are a group of placental mammals belonging to the family Tenrecidae that have exclusively colonized the island of Madagascar. They are characterized by pointed snouts and tiny yet distinct ears. Some species also bear hard spines and resemble hedgehogs, while others could be mistaken for shrews, mice, rats, or even opossums. Despite their superficial resemblance with these groups, tenrecs are phylogenetically more closely related to the otter shrews (family Potamogalidae) of Africa.
They are primarily nocturnal and forage at night, often locating food using ultrasonic soundwaves (echolocation). Though primarily terrestrial, some of these mammals also occupy arboreal, fossorial, and aquatic habitats.
As a broad group, tenrecs show variability in body size. While the largest species, the common or tailless tenrec, measures around 9.8 to 15.4 in ( 25 to 39 cm) and weighs over 2.2 lb (1 kg), the smaller species are barely 1.8 in (4.5 cm) long, weighing no more than 0.18 oz (5 gm).
The lesser hedgehog tenrec is about 7 in (18 cm) long and weighs about 8.8 oz (250 gm), whereas the long-eared tenrec is even smaller, measuring around 2.8 in (7 cm) and weighing only 0.2 to 0.3 oz (5 to 9 gm).
Tenrecs are characterized by pointed snouts, prominent ears, and short tails (if present). Their appearance varies across the different species.
Their skulls are distinguished by incomplete zygomatic arches and annular tympanic bones. However, they lack jugals.
Their upper molars are zalambodont, characterized by a V-shaped crest called an ectoloph. The dental formula for the group is 2-3.1.2-3.2-4/2-3.1.2-3.2-3 = 32-40.
The name tenrec is derived from the Malagasy word tandraka, which refers to the species common tenrec (Tenrec ecaudatus). This Malagasy word is thought to be related to the Malay word landak, which means a porcupine, hinting at the porcupine-like spines of some tenrecs.
Currently, 31 species of tenrecs are listed under 8 genera.
These mammals are believed to have evolved from a single species that colonized the island of Madagascar between 42 and 25 million years ago. This ancestor probably arrived from Southeast Africa by crossing the Mozambique channel on floating vegetation and eventually settled on the island.
With time, they attained features that they coincidentally shared with unrelated mammalian groups (convergent evolution). For example, the hedgehog tenrecs attained hard spines on their coats, just like hedgehogs, despite being unrelated to them.
Tenrecs have the highest species diversity on the island of Madagascar, though some species are native to the mainland (west-central part) of Africa. The common or tailless tenrec (Tenrec ecaudatus) also inhabits the Comoro Islands between Madagascar and Africa and has been introduced to the islands of Réunion, Mauritius, and Seychelles.
These mammals occupy a number of habitats, including terrestrial, arboreal, fossorial, and aquatic environments. Both greater and lesser hedgehog tenrecs are commonly found in Madagascar’s dry deciduous forests and xerophytic spiny forests in the western regions. In contrast, the web-footed tenrec (Microgale mergulus) inhabits the rainforests of eastern Madagascar, living near rivers and streams, and rice tenrecs are mostly found in rice fields.
These animals are omnivores and generally feed on invertebrates, like insects and their larvae. Some species, like Talazac’s shrew tenrec and the tailless tenrec, feed on small vertebrates, like amphibians, and even bird eggs.
The streaked tenrecs mostly consume soft-bodied invertebrates, like earthworms, while lesser hedgehog tenrecs occasionally consume fruits.
Tenrecs live up to 10 years in the wild, while in captivity (and under expert care), they may survive up to 13 years.
These mammals undergo a considerably long gestation period of about 50 to 64 days, following which they give birth to altricial or underdeveloped young. However, in species like the lowland streaked tenrec, the young are quite developed at birth (precocial) and attain sexual maturity in just 35 to 40 days.
Highland streaked tenrecs usually have between 1 to 5 young, while the tailless tenrec gives birth to as many as 32 offspring (second largest recorded mammalian litter size) and has around 29 teats to accommodate the same number of young.
Some species, such as large-eared tenrecs, exhibit post-partum estrus, allowing females to conceive a new litter shortly after giving birth, even while nursing their current offspring.
Tenrecs face predation from birds of prey, snakes, and cat-like mammals such as the fossa. They are also vulnerable to attacks by domestic cats and dogs, as well as larger members of their own species. In Mauritius and the Comoro Islands, some local communities hunt them for their meat.
All 31 extant species of tenrecs have been evaluated for the IUCN Red List. Among them, 24 species are classified as Least Concern (LC), while one species, the four-toed rice tenrec, is listed as Data Deficient (DD).
The Dryad shrew tenrec, Montane shrew tenrec, Web-footed tenrec, and Nasolo’s shrew tenrec are classified as Vulnerable (VU), while Jenkins’s shrew tenrec and Northern shrew tenrec are listed as Endangered (EN).
The major factors posing a threat to these animals are habitat loss and fragmentation (largely due to deforestation), hunting, incidental capture, and harmful practices like slash-and-burn agriculture, commercial logging, and mining activities.
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