Tenrecs

(Tenrecidae)

Class Mammalia

Order Insectivora

Family Tenrecidae

Thumbnail description
Very small to small mammals showing a considerable range in external morphology with regards to, for example, tail length (very short to three times body length), fur color and texture, and foot structure; some species have dorsal fur modified into spines and others with elongated trunk-like bodies; four to five fingers and five toes; tooth count ranges from 32 to 40, depending on genus

Size
Head and body length 2–14 in (5.5–35.7 cm); weight 0.1–70 oz (3.5 g–2 kg)

Number of genera, species
10 genera; 27 species

Habitat
Forest, pseudosteppe, scrublands, and spiny bush

Conservation status
Critically Endangered: 1 species; Endangered: 6 species; Vulnerable: 3 species

Distribution
Most restricted to Madagascar; otter shrews, mainland Africa

Evolution and systematics

Four subfamilies and 10 genera of Tenrecidae are generally recognized: the Tenrecinae or spiny tenrecs (Tenrec, Echinops, Setifer, and Hemicentetes); the Oryzorictinae or shrew tenrecs (Microgale and Limnogale) and the rice tenrecs (Oryzorictes); the Geogalinae or large-eared tenrec (Geogale); and the Potamogalinae or otter shrews (Micropotamogale and Potamogale).

Recent studies indicate that the tenrecids form a monophyletic group, with the Potamogalinae or African otter shrews as the sister group. This indicates that the Tenrecidae are the result of a single colonization event and subsequently speciated into one of the most extraordinary adaptive radiations of mammals in the world. When and how this event took place is an open question. The mammalian fossil record on Madagascar is rather fragmentary and no deposits are known from the Late Cretaceous to the Late Pleistocene, a span of about 65 million years. This is presumably the period tenrecids colonized and radiated on Madagascar. Their arrival on the island is probably the result of the proto-Tenrecidae rafting on vegetation across the Mozambique Channel from Africa. Fossils from the African continent from the Miocene have been attributed by certain paleontologists to the Tenrecidae, but these designations are in need of reevaluation.

Recent field inventories and a reevaluation of existing museum specimens have resulted in considerable taxonomic changes to the Tenrecidae, most notably amongst Microgale. Several new species to science have been named in recent years and numerous others remain to be described. Further, molecular studies are uncovering several previously unrecognized cryptic species. It is certain that the next decade will see a considerable augmentation in the number of recognized species and refinement of the evolutionary history of Tenrecidae.

Physical characteristics

Tenrecidae show an assortment of morphological characters. They maintain certain characteristics that have been considered primitive among living mammals. These include, for

example, small body size, common urogenital opening, and abdominal testes in reproductive males. Tenrecidae range from small- to medium-sized mammals and span a remarkable morphological gamut from the large (up to 44 lb; 2 kg) spiny tenrec, the hedgehog-like Echinops and Setifer, the desman-like Limnogale, the mouse-like Geogale, the molelike Oryzorictes, and the shrew-like Microgale (with adults of some species weighing less than 0.14 oz; 4 g). The tails of Tenrecinae are very short or at least not discernable, while among most other species in the other two subfamilies, the tail varies in length and is covered with short fine fur. Members of this family, particularly Setifer and Echinops, can roll themselves

into tight balls when disturbed. No species, with the exception of Tenrec ecaudatus, display any measurement or phenotypic feature that differs between the sexes.

Even within the genus Microgale there is considerable variation in body morphology. For example, M. gymnorhyncha and M. gracilis are probably semi-fossorial and have dense velvety pelage, well developed forelimbs and associated digging claws, and reduced ears and eyes, while the partially arboreal or scan-sorial M. principula and M. longicaudata have notably long hind limbs and prehensile tails measuring more than twice as long as their body length.

Otter shrews in the genus Micropotamogale are small, brownish gray animals with unwebbed feet and a round tail. The giant otter shrew (Potamogale velox), as its name implies, is considerably larger (about twice as long and much heavier) and has glossy chocolate-brown fur and a thick, rudderlike tail.

Distribution

The family is confined to Madagascar with the exception of the otter shrews, which are found in Africa. Tenrec ecaudatus has been introduced to the western Indian Ocean islands of the Comoros, Seychelles, and Mascarenes as a food resource.

Habitat

Most Tenrecidae are forest dwelling animals, particularly in the humid forests of eastern Madagascar. The major exceptions are the genera Tenrec, Setifer, Hemicentetes, and Echinops that can also be found in human-created grasslands or pseudosteppe covering significant portions of the island, and the first three genera also occur in agricultural areas and

near human habitations. Further, Tenrec and Setifer occur in all of the natural forest formations on the island. Most Tenrecidae species are terrestrial, although certain Microgale are best considered scansorial and two genera of spiny tenrecs (Echinops and Setifer) climb in vegetation several meters off the ground.

Microgale, with its currently recognized 18 species, is largely confined to the humid forest formations of the island. One member of this genus, Microgale brevicaudata, also occurs in the dry deciduous forests and spiny bush of the western and southern portion of the island. Two genera (Echinops and Geogale), each with a single species, are also confined to these drier native vegetal formations. Limnogale is confined to streams within native forest within the eastern humid forests and is the only largely aquatic mammal on the island. Micro-gale pusilla and Oryzorictes hova can be found in forested areas with wet soils or in marshlands, including those converted to rice paddy, outside of forest formations. Micropotamogale are found in upland forest streams of western and central Africa, while Potamogale velox occurs in rivers, streams, and swamps in the rainforests of tropical Africa.

At certain sites in the eastern humid forest, the density and diversity of Tenrecidae are notably high. For example at one forested site near the village of Tsinjoarivo in the eastern central portion of the island, 17 species of Lipotyphla (including 16 tenrecids) were found in sympatry. This high density in a relatively small block of forest is perhaps without parallel anywhere else in the world.

Behavior

Given that most species of Tenrecidae are small nocturnal and forest-dwelling animals it is not surprising that few details are available about their life history.

Two genera of Tenrecidae have a dense grouping of spiny hairs on their back that have been modified into quill-like structures and form a stridulating organ. In young Tenrec, this organ is well developed and is used for communication within family groups, and with increasing age the quill-like structures

are replaced with standard spines and the organ no longer functions. In Hemicentetes adults possess a mid-dorsal stridulating organ, also formed of modified spines. These quills, when vibrated by muscle action, produce an ultrasonic sound that can be detected by nearby conspecifics.

The spines of Tenrecinae are used in a defensive fashion against predators. In Hemicentetes, the easily detachable spines

of the back with their very fine fishhook tips are raised when a potential predator approaches. If the predator makes direct contact, it can receive a face full of spines. Although this must be a formidable deterrent, spiny tenrecs are frequent prey for native predators.

During the austral winter, several species of Tenrecidae show a shift in activity patterns behavior, ranging from a reduction in daily movements to complete hibernation. These shifts are correlated with changes in ambient temperature, photoperiod, and food availability. In certain species, such as Hemicentetes nigriceps or Tenrec ecaudatus, animals enter a profound torpor during the period from approximately May to October. A further variation within the family is found in Geogale, which is heterothermic and body temperature follows the ambient temperature. This species has a notably low resting metabolic rate, even for a Tenrecidae.

Feeding ecology and diet

Most Tenrecidae feed on insects and a variety of other soil invertebrates—few quantitative studies are available. In the western dry deciduous forests, Tenrec feed extensively on soildwelling beetle (Coleoptera) larvae of the families Scarabaeidae and Alleculidae, and to a lesser extent on ants (Hymenoptera), scolopenders (Chilopoda), and butterfly (Lepidoptera) larvae. They are known to also feed on fruits and vertebrates.

A study conducted in the humid forests of eastern Madagascar on the diets of Microgale spp., based on stomach contents, found that various types of Orthoptera were the most frequently consumed prey, followed by Hymenoptera and Coleoptera. Remains of other animals were also identified, including Dermaptera, Annelida, Arachnida, and Amphipoda. At the level of determination, no clear dietary differences were found between sympatrically occurring Microgale subspecies.

The most common prey of Limnogale, an aquatic tenrec with a flattened tail and webbed feet that hunts while swimming,

is Ephemeroptera nymphs, followed by larvae of Odonata, Trichoptera, and Coleoptera. A few other types of aquatic invertebrates (crabs and crayfish) and vertebrates (frogs) are also taken. In addition to worms and insects, otter shrews also prey upon crabs, fishes, frogs, and mollusks found in their aquatic habitat.

It is assumed that most terrestrial Tenrecidae actively hunt their prey amongst leaf and rotten wood litter, fallen branches, and root tangles of standing trees or scansorial species on vegetation in the forest understory to mid-canopy. In some cases, particularly for genera with well developed digging claws, prey is excavated from the ground and may be detected by scent and acoustic signals. For most Tenrecidae prey are pinned down with the forelimbs and then seized with the mouth.

Reproductive biology

The reproductive biology of most Tenrecidae is poorly known—a few species have been studied in the wild or in captivity and certain details are available. Some species build nests out of vegetation that are placed in concealed places or excavate

burrows ending in a nest chamber. The majority of species have three to five pairs of mammae.

Among Microgale living in humid forests, reproduction starts in September to October, coinciding with the start of the rainy season. Litters, generally varying from one to four, are born in November and early December. Neonates are naked with non-functional ears and eyes. Young start to make foraging bouts away from the nest after their eyes open at 22 to 27 days old. Most females probably have one or maximum two litters per year. Among certain species, there is evidence that they are reproductively mature before they have their full adult dentition. In captivity, certain species seem to form male-female pairs.

Tenrec has one of the highest breeding potentials of any mammal species in the world. Litters of up to 32 individuals have been documented, and more than 20 individuals is not uncommon. Females often have 32 to 36 mammae. After being born in late November to January, young emerge from the burrow at between 18–20 days old and commence actively foraging with their mother, and become independent at about 35 days.

Within the genus Geogale, there is a post-partum estrus and females are able to nurse one litter while another is developing in the uterus. This reproductive strategy is unknown in any other Tenrecidae, and may be an adaptation to the extremely dry conditions where this animal lives, allowing it to maximize reproductive output when optimal conditions prevail.

Conservation status

The main threat to members of the Tenrecidae, as with all forest-dwelling organisms on Madagascar, is the continued destruction of forest habitat for slash-and-burn agriculture, charcoal, and cattle pasture. The IUCN Red List indicates that several species are threatened with extinction. However, the information used to compile this list is out of date, as is the taxonomy. A meeting held in Madagascar in 2001 and attended by numerous specialists proposed new conservation status designations for Malagasy vertebrates. Among the Tenrecidae one species is classified as Endangered, one as Vulnerable, none as Near Threatened, 22 as Least Concern, and three as Data Deficient.

The African otter shrews face similar threats as the members of the Tenrecidae inhabiting Madagascar. Habitat destruction and degradation is the primary concern. The IUCN Red List classifies all three species of otter shrews as Endangered.

Significance to humans

Throughout much of Madagascar, spiny tenrecs, most notably Tenrec and to a lesser extent Echinops and Setifer, are widely hunted by people as a supplementary source of meat. In fact, in some areas, these animals are sufficiently relished that their flesh is more expensive per unit weight than beef. In certain regions, the consumption of Tenrecinae meat is considered taboo (fady) and these animals are not hunted locally.

Species accounts

List of Species

Common tenrec

Tenrec ecaudatus

subfamily

Tenrecinae

taxonomy

Erinaceus ecaudatus (Schreber, 1777), Madagascar.

other common names

None known.

physical characteristics

Head and body length 10.5–15.3 in (26–39 cm); weight 42–70 oz (1.2–2 kg). Fur is grey-brown or red-brown and has long stiff hairs along the back. Front legs are longer than hind legs.

distribution

Across much of Madagascar. It has been introduced to the western Indian Ocean islands of Comoros, Seychelles, and the Mascarenes.

habitat

Occurs in a wide variety of habitats from humid forests, to deciduous forest, gallery forest, and spiny bush. It also is found in human modified habitats including savanna, pseudosteppe, agricultural zones, and near habitations.

behavior

Usually seen singly and generally nocturnal, although sometimes crepuscular. During the breeding season females can be seen accompanied by a bevy of young even during daylight hours.

feeding ecology and diet

Terrestrial. The diet includes mostly invertebrates, but fruits and small vertebrates have also been recorded.

reproductive biology

Very high reproductive potential with litters of up to 32 young. Females often have 32 to 36 mammae. May be polygamous or promiscuous.

conservation status

Not threatened. Widely distributed on the island and even in zones with considerable human hunting pressure this species seems to be maintaining viable populations. Its ability to live in human-modified habitats is an important factor in this regard.

significance to humans

Widely relished for its meat.

Large-eared tenrec

Geogale aurita

subfamily

Geogalinae

taxonomy

Geogale aurita Milne-Edwards and Grandidier, 1872, Moron-dava, Madagascar. G. a. orientalis is known from one specimen collected along the east coast.

other common names

None known.

physical characteristics

Head and body length about 2.8 in (7 cm); weight 0.2–0.3 oz (5–8.5 g). Fur is red-brown, yellow on underside. Tail has fine hair covering.

distribution

Restricted to western and southwestern portion of Madagascar, except for the specimen noted above.

habitat

Occurs in dry deciduous, gallery, and spiny bush forest. Unknown outside of forested zones. Often associated with fallen and rotten tree trunks.

behavior

Few details available about this nocturnal species. Usually seen singly, although apparent male-female pairs can be found in close proximity to one another. Heterothermic with body temperature corresponding to the ambient temperature; enters a daily state of torpor.

feeding ecology and diet

Terrestrial. The diet includes mostly invertebrates, particularly termites.

reproductive biology

May be monogamous. Mating in late September to March. Gestation 54–69 days. Litter size 1–5 and neonates naked with nonfunctional ears and eyes. Eyes open between 21 and 33 days old and the young are soon thereafter weaned.

conservation status

Within its range this species can be notably common. Its continued existence depends on the maintenance of natural forest.

significance to humans

None known.

Nasolo's shrew tenrec

Microgale nasoloi

subfamily

Oryzorictinae

taxonomy

Microgale nasoloi Jenkins and Goodman, 1999, Vohibasia Forest, Madagascar.

other common names

None known.

physical characteristics

Head and body length about 3 in (8 cm); weight 0.5 oz (7 g).

distribution

Only known from southwestern Madagascar.

habitat

Occurs in transitional dry and spiny bush forest. Unknown to occur outside of forested zones.

behavior

Nothing is known.

feeding ecology and diet

Scansorial. The diet is presumably mostly invertebrates.

reproductive biology

Nothing is known.

conservation status

Only recently described from two specimens taken at two nearby sites—one in a national park and the other in a forest protected by local traditions. This species probably has a very limited distribution.

significance to humans

None known.

Dobson's shrew tenrec

Microgale dobsoni

subfamily

Oryzorictinae

taxonomy

Microgale dobsoni Thomas, 1884, Fianarantsoa, Madagascar.

other common names

None known.

physical characteristics

Head and body length 3.9–4.5 in (10–11.5 cm); weight 0.6–0.9 oz (18.0–25.5 g). Fur is gray-brown with gray belly. Tail is long, usually length of body.

distribution

Across much of eastern and northern Madagascar.

habitat

Found in lowland and montane humid forests. Occurs in some secondary forest or other human-modified habitats.

behavior

Nocturnal and generally terrestrial. Towards the end of the rainy season this species accumulates body fat, particularly in the tail, and is known to aestivate.

feeding ecology and diet

Largely terrestrial, but occasionally scansorial. Well developed canines and molariform teeth indicate that it is a formidable predator. Prey located by visual, olfactory, and visual means, and then subdued with forelimbs or seized directly with the mouth. The diet consists mostly of invertebrates, however it is known to predate on small land vertebrates.

reproductive biology

In captivity mating in September to October. Gestation 62 days. Litter size one to five and neonates naked with non-functional ears and eyes. Eyes open between 22 to 27 days old. One litter per year. Presumably polygynous.

conservation status

A widely distributed species and known to occur in several protected areas. As with other forest-dwelling organisms on Madagascar, the continued existence of this species depends on the maintenance of forest habitat.

significance to humans

None known.

Resources

Books

Eisenberg, J. F., and E. Gould. "The Insectivores." In Madagascar. Edited by A. Jolly, P. Oberlé, and R. Albignac. Oxford: Pergamon, 1984.

Garbutt, N. Mammals of Madagascar. New Haven: Yale University Press, 1999.

Goodman, S. M., and J. P. Benstead, eds. The Natural History of Madagascar. Chicago: The University of Chicago Press, 2003.

Genest, H., and F. Petter. Part 1.1. "Family Tenrecidae." The Mammals of Africa: An Identification Manual. Edited by J. Meester and H. W. Setzer. Washington, DC: Smithsonian Institution Press, 1975.

Heim de Balsac, H. "Insectivores." In Biogeography and Ecology in Madagascar, edited by R. Battisitini and G. Richard-Vindard. The Hague: W. Junk, 1972.

Nicoll, M. E., and G. B. Rathbun. "African Insectivora and Elephant-shrews: An Action Plan for their Conservation." IUCN/SSC Insectivore, Tree-Shrew and Elephant-Shrew Specialist Group. Gland, Switzerland: IUCN, 1990.

Racey, P. A., and P. J. Stephenson. "Reproductive and Energetic Differentiation of the Tenrecidae of Madagascar." Biogéographie de Madagascar, edited by W. R. Lourenço. Paris: ORSTOM, 1996.

Periodicals

Benstead, J. P., K. H. Barnes, and C. M. Pringle. "Diet, activity patterns, foraging movement and responses to deforestation of the aquatic tenrec Limnogale mergulus (Lipotyphla: Tenrecidae) in eastern Madagascar." Journal of Zoology 254 (2001): 119–129.

Butler, P. M., and A. T. Hopwood. "Insectivora and Chiroptera from the Miocene rocks of Kenya Colony." Fossil Mammals of Africa 13 (1957): 1–35.

Eisenberg, J. F., and E. Gould. "The tenrecs: A study in mammalian behavior and evolution." Smithsonian Contributions to Zoology 27 (1970): 1–137.

Ganzhorn, J. U., A. W. Ganzhorn, J. P. Abraham, Andriamanarivo, and A. Ramananjatovo. "The impact of selective logging on forest structure and tenrec populations in western Madagascar." Oecologia 84 (1990): 126–33.

Goodman, S. M., and D. Rakotondravony. "The effects of forest fragmentation and isolation on insectivorous small mammals (Lipotyphla) on the Central High Plateau of Madagascar." Journal of Zoology 250 (2000): 193–200.

Goodman, S. M., et al. "Inventaire biologique de la forêt de Tsinjoarivo, Ambatolampy." Akon'ny Ala 27 (2000): 18–35.

Gould, E. "Evidence for echolocation in the Tenrecidae of Madagascar." Proceedings of the American Philosophical Society 109 (1965): 352–60.

Gould, E., and J. F. Eisenberg. "Notes on the biology of the Tenrecidae." Journal of Mammalogy 47 (1966): 660–86.

Jacobs, L. J., W. Anyonge, and J. C. Barry. "A giant tenrecid from the Miocene of Kenya." Journal of Mammalogy 68 (1987): 10–16.

MacPhee, R. D. E. "The shrew tenrecs of Madagascar: Systematic revision and Holocene distribution of Microgale (Tenrecidae, Insectivora)." American Museum Novitates 2889 (1987): 1–45.

Nicoll, M. E. "Mechanisms and consequences of large litter production in Tenrec ecaudatus (Insectivora: Tenrecidae)." Annales de la Musée Royale de l'Afrique Centrale, Sciences Zoologiques 237 (1983): 219–26.

Nicoll, M. E. "Responses to Seychelles tropical forest seasons by a litter-foraging mammalian insectivore, Tenrec ecaudatus, native to Madagascar." Journal of Animal Ecology 54 (1985): 71–88.

Olson, L. "Phylogeny of the Tenrecidae (Mammalia, Lipotyphla): morphological support for a single invasion of Madagascar." Zoological Journal of the Linnean Society (2003) in press.

Petter, J. J., and A. Petter-Rousseaux. "Notes biologiques sur les Centetinae." La Terre et la Vie 1963 (1963): 66–80.

Poduschka, W., and C. Poduschka. "Zur Frage des Gattungsnamens von "Geogale aletris" Butler und Hopwood, 1957 (Mammalia: Insectivora) aus dem Miozän Ostafrikas." Zeitschrift für Säugetierkunde 50 (1985): 129–40.

Stephenson, P. J. "Reproductive biology of the large-eared tenrec, Geogale aurita (Insectivora: Tenrecidae)." Mammalia 57 (1993): 553–63.

Stephenson, P. J. "Notes on the biology of the fossorial tenrec, Oryzorictes hova (Insectivora: Tenrecidae)." Mammalia 58 (1994): 312–15.

Stephenson, P. J. "Taxonomy of shrew-tenrecs (Microgale spp.) from eastern and central Madagascar." Journal of Zoology 235 (1995): 339–50.

Steven Goodman, PhD