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Geogale auritalarge-eared tenrec

By Thomas Nielsen

Geographic Range

Large-eared tenrecs are endemic to the island of Madagascar and are found in the south and southwest regions of the island. (Stephenson, 2003)

Habitat

Geogale aurita is found widely distributed in dry, deciduous forest, gallery forests, and spiny bush in southern and southwestern Madagascar. The species has also been observed in the rainforest of the southeast. These are environments with large annual variations in rainfall. (Stephenson, 2003)

Physical Description

Large-eared tenrecs are small, shrew-like tenrecs with very short, soft pelage, hair-covered tails, and large pinnae. Dorsal coloration is variable, ranging from light gray to light reddish-brown. Ventrally, these animals are buffy white. Large-eared tenrecs are among the smallest living tenrecs, with wild-caught animals ranging in body mass from 5.0 to 8.5 g. The length of the head and body is 60 to 75 mm, and the total body length including the tail can be between 90 and 105 mm.

Certain characters distinguish G. aurita from other tenrecs. The dental formula is 2/2 1/1 3/2 3/3 = 34, whereas most tenrecs have 36 teeth. Furthermore, large-eared tenrecs are the only member of the family Tenrecidae that exibit postpartum oestrus, which allows females to suckle a first litter while a second litter is developing in utero.

Geogale aurita is heterothermic, and body temperatures parallel the surrounding temperature at all times of year, although body temperatures higher than ambient temperature are observed in pregnant and lactating females. Low metabolic rate is correlated with this relatively low body temperature.

Testes are abdominal in G. aurita, as they are in all other tenrecs. Members of the family Tenrecidae have a cloaca into which both the intestinal and genitourinary tracts empty. (Stephenson, 2003)

  • Range mass
    5.0 to 8.5 g
    0.18 to 0.30 oz
  • Average mass
    6.0 g
    0.21 oz
  • Range length
    90 to 105 mm
    3.54 to 4.13 in
  • Average basal metabolic rate
    0.043 W
    AnAge

Reproduction

Information on the mating systems of these tenrecs was not available in the literature reviewed. Mating systems of tenrecs in general are poorly known. Most tenrecs are solitary, although some species appear to form stable long-term bonds between males and females, indicating that they may mate monogamously. It is not known at this time what mating system is employed by G. aurita. (Nowak, 1999)

Mating takes place from late September to March. Because these animals have a post-partum estrus, they can produce multiple litters during that time. Coital lock occurs during copulation and can last for more than 20 minutes. Large-eared tenrecs are capable of arresting the development of litters, thus the gestation period varies between 54 and 69 days. Litter size varies from 1 to 5 individuals, and the weights of the neonates range from 0.5 to 0.8 g. The offspring are altricial, and are born with closed eyes and ears. Young are weaned soon after the opening of eyes, which takes place after 21 to 33 days of age. (Stephenson, 2003)

  • Breeding interval
    It is not known how often these animals breed in the wild.
  • Breeding season
    Breeding occurs in late September to March.
  • Range number of offspring
    1 to 5
  • Average number of offspring
    3.9
    AnAge
  • Range gestation period
    54 to 69 days
  • Range weaning age
    21 to 33 days

Parental care in this species has not been described. However, because G. aurita is a mammal, we know that females provide extensive maternal care. Young are altricial, so it is likely that mothers provide not just food to their young, but also protection, grooming, and shelter, until the time that the young are weaned and can care for themselves. Male parental care is varied in mammals, and lacking specific information for these tenrecs, it is impossible to speculate upon. (Nowak, 1999; Stephenson, 2003)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

The lifespan of long-eared tenrecs living in the wild is unknown but in captivity they have been observed to live for more than two and a half years. (Stephenson, 2003)

  • Range lifespan
    Status: captivity
    more than two and a half (high) years
  • Typical lifespan
    Status: captivity
    2.5 (high) years

Behavior

Large-eared tenrecs are nocturnal, poor-sighted animals that depend on auditory and olfactory senses. They are mostly solitary animals, but male-female pairs are occasionally found living in proximity to each other. These animals are heterothermic and enter daily torpor. They can often be found torpid inside fallen logs and cavities of sand. (Stephenson, 2003)

Home Range

The size of home range for these animals has not been reported, but given their small size, territories and home ranges are not likely to be very large.

Communication and Perception

Large-eared tenrecs use sound to locate their termite prey. Being a nocturnal animal with poor eyesight, G. aurita depends on auditory and olfactory senses. As in all mammals, tactile communication is important between mates as well as between mothers and their offspring. Accoustic communication between members of this species has not been reported, but may occur. (Nowak, 1999; Peveling, et al., 2003; Stephenson, 2003)

Food Habits

Large-eared tenrecs are specialized insectivores showing a clear preference for termites. Their diet consists exclusively of arthropods, which they locate by using sound. They may also show a significant preference for certain species. (Peveling, et al., 2003)

  • Animal Foods
  • insects

Predation

Geogale aurita is preyed upon by various groups of animals. Remains of large-eared tenrecs have been found in pellets from two species of owls: barn owls and Madagascar long-eared owls. Other species expected to be predators of large-eared tenrecs are snakes, including Malagasy cat-eye snakes, which are associated with the habitat where Geogale is found, and carnivores such as Malagasy narrow-striped mongooses. (Goodman, et al., 1993a; Goodman, et al., 1993b)

Ecosystem Roles

Large-eared tenrecs are specialized termites feeders and thus act as secondary consumers in an ecosystem. The species also provides feeding opportunities for consumers at higher trophic levels. (Goodman, et al., 1993a; Peveling, et al., 2003)

Economic Importance for Humans: Positive

Habitats populated by large-eared tenrecs are not densely populated by humans, thus no known specific economic influence on human societies is known. (Stephenson, 2003)

Economic Importance for Humans: Negative

Large-eared tenrecs have no known specific economic influence on human societies.

Conservation Status

Large-eared tenrecs do not appear to be threatened, but as they are dependent on forest habitats, their distribution may decrease with increasing loss of suitable habitats. Other threats are indirect effects due to increased use of pesticides. Geogale aurita is a specialized termite feeder and termites are affected by pesticides. Thus, the potential effect on G. aurita appears high. (Stephenson, 2003; Tingle, et al., 2000)

Other Comments

Geogale has traditionally been placed in the monotypic subfamily Geogalinae. An African origin of tenrecs is widely accepted. Some authorities suggest that Geogale and the other tenrecs of Madagascar share a common ancestor, and have diverged from one another after a single colonization of the island. However, there is some evidence that Geogale may not have arizen from the same colonization event that links the other tenrecs of Madagascar.

Currently G. aurita is considered the sistergroup of the remaining tenrecs, and it is the only living descendent along its branch; the remaining Malagasy species are descendents of the other branch.

Due to dental similarities to Geogale in a fossil found in Miocene deposits of Kenya, this fossil was originally placed in Geogale. These dental similarities were considered too specialized to give rise to the remaining tenrecs, thus the ancestor of Geogale must have had colonized Madagascar independently.

The identification of this fossil has since been disputed, and is now taxonomically placed as Parageogale. The phylogenetic relationship to other members of the family Tenrecidae remains uncertain, but molecular and morphological evidence suggests a sister relationship, thus supporting a two colonizations hypothesis. (Olson and Goodman, 2003; Poduschka and Poduschka, 1985)

Contributors

Thomas Nielsen (author), University of Alaska Fairbanks, Link E. Olson (editor, instructor), University of Alaska Fairbanks.

Nancy Shefferly (editor), Animal Diversity Web.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

embryonic diapause

At about the time a female gives birth (e.g. in most kangaroo species), she also becomes receptive and mates. Embryos produced at this mating develop only as far as a hollow ball of cells (the blastocyst) and then become quiescent, entering a state of suspended animation or embryonic diapause. The hormonal signal (prolactin) which blocks further development of the blastocyst is produced in response to the sucking stimulus from the young in the pouch. When sucking decreases as the young begins to eat other food and to leave the pouch, or if the young is lost from the pouch, the quiescent blastocyst resumes development, the embryo is born, and the cycle begins again. (Macdonald 1984)

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

insectivore

An animal that eats mainly insects or spiders.

island endemic

animals that live only on an island or set of islands.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Goodman, S., O. Langrand, C. Raxworthy. 1993. Food habits of the Madagascar long-eared owl Asio madagascariensis in two habitats in southern Madagascar. Ostritch, 64: 79-85.

Goodman, S., O. Langrand, C. Raxworthy. 1993. The food habits of the barn owl Tyto alba at three sites on Madagascar. Ostritch, 64: 160-171.

Nowak, R. 1999. Walker's Mammals of the World, Sixth Edition. Baltimore and London: The Johns Hopkins University Press.

Olson, L., S. Goodman. 2003. Phylogeny and biogeography of tenrecs. Pp. 1235-1242 in S Goodman, J Benstead, eds. The Natural History of Madagascar. Chicago and London: The University of Chicago Press.

Peveling, R., A. McWilliam, P. Nagel, H. Rasolomanana, Raholijaona, L. Rakotomianina, A. Ravoninjatovo, C. Dewhurst, G. Gibson, S. Rafanomezana, C. Tingle. 2003. Impact on locust control on harvester termites and endemic vertebrate predators in Madagascar. Journal of Applied Ecology, 40: 729-741.

Poduschka, W., C. Poduschka. 1985. Zur frage des gattungsnamens von "<<Geogale" aletris>> Butler und Hopwood 1957 *<<Mammalia>>: <<Insectivora>>) aus dem Miozän Ostafrikas. Zeitschrift fur Säugertierkunde, 50: 129-140.

Stephenson, P. 2003. Lipotyphla (Insectivora): Geogale aurita, Large-eared Tenrec. Pp. 1265-1267 in S Goodman, J Benstead, eds. The Natural History of Madagascar. Chicago and London: The University of Chicago Press.

Tingle, C., J. Rother, C. Dewhurst, S. Lauer, W. King. 2000. "Pesticide Action Network" (On-line pdf). Accessed December 02, 2004 at http://www.pan-uk.org/briefing/fipronil.pdf.

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