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Microgale gymnorhynchanaked-nosed shrew tenrec

By Louis Trojan

Geographic Range

Microgale gymnorhyncha, also known as the naked-nosed shrew tenrec, is endemic to the island of Madagascar. It is mostly limited to the eastern portion of the island with minimal occurrence throughout the west and central portion. Microgale gymnorhyncha has been found in Andringitra National Park, Andohahela National Park, Ranomafana National Park and Reserve Specialed'Anjanaharibe-Sud. (Rathbun and Hoffman, 2013)

Habitat

Microgale gymnorhyncha is found inland throughout humid montane forests with elevations varying from 970-1990 meters above sea level. They forage on forest floors with large amounts of vegetation providing many potential insects. Moist areas are of preference due to fossorial lifestyle that would favor softer soils. Habitat seems to overlap extensively between species of Microgale so interactions of Microgale gymnorhyncha with other shrew tenrecs is likely. (Eisenberg and Gould, 1970; Goodman, 1998; MacPHEE, 1987)

  • Range elevation
    970 to 1990 m
    3182.41 to 6528.87 ft

Physical Description

Variation across the genus Microgale is minimal and often requires several distinctions, both internal and external, to determine specific species. There are several universal characteristics within the genus Microgale. Microgale species have reduced eyes with abundant whiskers along a long narrow rostrum. They possess short limbs with five digits. The have dense fur covering a long, tapering body.

Microgale gymnorhyncha shares these traits as well as other features that are very similar to other members of Microgale. Total length of Microgale gymnorhyncha ranges from 138-176 mm. The weight ranges from 13.5 – 26 grams with a mean of about 16 grams. Dorsally, it is dark grey with dark brown guard hairs. The tail has different shades of grey with a darker tint to the dorsal surface whereas the ventral side of the tail is lighter.

Microgale gymnorhyncha is partly fossorial, resulting in reduced eyes and ears which are sometimes hidden within pelage. In addition to reduction of these features, claws are enlarged to enhance digging. The rostrum, like most members of Microgale, is elongated with proboscises that extend well beyond the mouth.

Species in the genus Microgale has a dental formula 3/3 1/1 3/3 3/3 = 40.

Testes in male naked-nosed shrew tenrecs are in the abdominal cavity and not present in an external scrotum. As a result, distinguishing female based on physical characteristics is very difficult. (Eisenberg and Gould, 1970; Garbutt, 2007; Goodman, 1998; MacPHEE, 1987; Olson, 2013; Racey, et al., 1994)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    13.5 to 26 g
    0.48 to 0.92 oz
  • Average mass
    16 g
    0.56 oz
  • Range length
    138 to 176 mm
    5.43 to 6.93 in

Reproduction

There is currently no information regarding the mating systems of Microgale gymnorhyncha. Studies of other species of Microgale have yielded a broad range of potential mating systems varying from monogamy to polygynous. (Eisenberg and Gould, 1970; Garbutt, 2007)

Little is known solely on Microgale gymonorhyncha but some information in regards to reproduction seems to be consistent across Microgale. Male have been shown to exhibit extensive mounts in which it is unknown how many times the male ejaculates during the mount. Some mounts have been timed at 7 minutes in some members of Microgale with durations up to 20 minutes in other genera of the Tenrecidae. Mounting by the male may even occur when the female is not completely receptive. Mounting occurs multiple times over a period of days, gradually ceasing. Births in Microgale species typically occur in November and December in relation to the onset of the rainy season, thought to be due to the abundance of invertebrates available for juvenile consumption and development. Gestation in other species of Microgale exhibit a consistent timetable of about 58-63 days, which likely results in a mating season occurring in the September-October months. Litter size found in other species have yielded about 3-8 young most often. Although, some members of the Tenrecidae have been shown to have litters of more than 15 individuals. Young in other Microgale species have produced young with weights about 10% of the adult weight. This would result in Microgale gymnorhyncha producing young weighing about about 2 grams. (Eisenberg and Gould, 1970; Eisenburg, 1975; Garbutt, 2007)

  • Breeding interval
    It is unknown as to whether or not mating occurs at another time of the year
  • Breeding season
    Mating typically occurs in September and October with birth occuring in November and December coinciding with the rainy season.
  • Range number of offspring
    1 to Potentially as much 8
  • Range gestation period
    58 to 63 days

The young observed in other Microgale species births are underdeveloped. However, members of the Tenrecidae were shown to provide extensive care to the young. The young were held in nests and only left unattended when the mother left for foraging. Otherwise, the mother was quick to retrieve any wondering young and nursed the young frequently. The young will nurse until able to walk along side the mother when she forages. Male parental involvement is not known. (Eisenberg and Gould, 1970; Eisenburg, 1975)

Lifespan/Longevity

There is no information on lifespan reported in the literature.

  • Range lifespan
    Status: wild
    Unknown (low) years
  • Range lifespan
    Status: captivity
    No extensive monitoring in captivity (low) years

Behavior

Microgale gymnorhyncha possess a tail that is less than the size of its head and body length. As a result, it has been suggested to be highly terrestrial and likely fossorial. Microgale gymnorhyncha remains on the forest floor and searches for insects and small vertebrates. With its large claws and elongate muzzle, it disturbs leaves and the soil and senses any prey with elongate whiskers along the muzzle. The naked-nosed shrew tenrec has sharp pointed teeth that is used to hold onto slippery prey such as worms. Small eyes and reduced ears suggest semi-fossoriality. Solidarity or group living is unknown in Microgale gymnorhyncha as it seems to vary across tenrecs.

Some species of Microgale have been known to exhibit fat storage in accordance with torpor however it is not known as to whether or not Microgale gymnorhyncha exhibits such behavior. (Eisenberg and Gould, 1970; Eisenburg, 1975; Eisenburg and Muckenhirn, 1968; Garbutt, 2007; Goodman, 1998; Olson, 2013; Racey, et al., 1994)

Home Range

No information regarding home range is currently available

Communication and Perception

Despite reduced eyes and ears, Microgale gymnorhyncha possess many whiskers along its elongated rostrum, indicating a likely use for perceiving the environment. With most other members of Microgale possessing reduced eyes, visual communication seems to be a minimal characteristic of Microgale species in general. Observations of nose touching has been observed in other species of Microgale as well as various types of rubbing along the body and anal/genital region. This could potentially be evidence for chemical communication though it is still unknown. Vocals observed vary from squeaks and squeals to an intense screech. It is not know when each vocalization in used though it is likely the screech is used when frightened. (Eisenberg and Gould, 1970; Garbutt, 2007; Olson, 2013)

Food Habits

Though Microgale gymnorhyncha is thought to be an insectivore, various studies have shown tenrecs to be opportunistic feeders. This includes feeding on small mammals, amphibians, vegetation, and potentially carrion. Some captive studies on other members of Microgale have yielded short lifespans and the belief is due to lack of information in regards to diet. As a result, Microgale species could exhibit a balance of carnivory with herbivory or is consuming an unknown item as a supplement to its known diet. (Eisenberg and Gould, 1970; Eisenburg, 1975; Eisenburg and Muckenhirn, 1968; Garbutt, 2007; Olson, 2013)

  • Animal Foods
  • carrion
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • fruit

Predation

Various predators include native snakes and members of the mammalian family Viverridae. There is a common belief that raptorial birds will also prey upon tenrecs in general but no direct occurence has been observed. Unlike other genera of the Tenrecidae, Microgale don't appear to possess the quill structures that provide a defense. As a result, Microgale seems especially vulnerable to larger carnivores. It is possible that Microgale gymnorhyncha utilizes its fossorial lifestyle as a method of escaping or avoiding prey entirely. (Eisenberg and Gould, 1970)

Ecosystem Roles

Microgale gymnorhyncha is a consumer of many insect prey types, but also is potentially a scavenger. Therefore, it could serve the purpose of consuming carrion. In addition, it is likely a prey item for many carnivores on the island of Madagascar. Because of their role as both predator and prey, they serve an important ecosystem role on the island of Madagascar. (Eisenberg and Gould, 1970; Olson, 2013)

Economic Importance for Humans: Positive

Some tenrecs have been harvested for food consumption and even as pets. However, Microgale gymnorhyncha specifically occurs at higher elevations and as a result has minimal contact with humans. (Eisenberg and Gould, 1970; Garbutt, 2007; Olson, 2013)

Economic Importance for Humans: Negative

There are no known negative effects on humans.

Conservation Status

Despite a declining population, Microgale gymnorhyncha is currently listed as a "least concern" species by the IUCN. Belief is that the potential for fragmentation and expanding human populations could have an impact in the near future. (Goodman, 1998; MacPHEE, 1987)

Contributors

Louis Trojan (author), University of Wisconsin - Stevens Point, Christopher Yahnke (editor), University of Wisconsin-Stevens Point, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Ethiopian

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

World Map

acoustic

uses sound to communicate

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

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

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.

female parental care

parental care is carried out by females

forest

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

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

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).

monogamous

Having one mate at a time.

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.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

polygynous

having more than one female as a mate at one time

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.

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

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

tactile

uses touch to communicate

vibrations

movements of a hard surface that are produced by animals as signals to others

viviparous

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

References

Eisenberg, J., E. Gould. 1970. The Tenrecs: A Study in Mammalian Behavior and Evolution. Smithsonian Contributions to Zoology, 27: 1-152. Accessed April 25, 2014 at http://www.sil.si.edu/smithsoniancontributions/zoology/pdf_hi/sctz-0027.pdf.

Eisenburg, J. 1975. Tenrecs and solenodons in captivity. International Zoo Yearbook, 15: 6-12.

Eisenburg, J., N. Muckenhirn. 1968. The reproduction and rearing of tenrecoid insectivores in captivity. International Zoo Yearbook, 8: 106-110.

Garbutt, N. 2007. Mammals of Madagascar. United States: Yale University Press.

Goodman, S. 1998. A Floral and Faunal Inventory of the Reserve Speciale d' Anjanaharibe-Sud, Madagascar: With Reference to Elevational Variation. Zoology, 90: 1-268.

MacPHEE, R. 1987. The Shrew Tenrecs of Madagascar: Systematic Revision and Holocene Distribution of Microgale (Tenrecidae, Insectivora). American Museum Novitates, 2889: 1-45.

Olson, L. 2013. Tenrecs. Current Biology, 23: 5-8. Accessed April 29, 2014 at http://linkolson.org/research/publications/My%20pubs/Olson%202013.pdf.

Racey, P., F. Rakotondraparany, P. Stephenson. 1994. Maintenance and reproduction of tenrecs (Tenrecidae) at Parc Tsimbazaza, Madagascar. International Zoo Yearbook, 33: 194-201.

Rathbun, G., M. Hoffman. 2013. "Microgale gymnorhyncha" (On-line). IUCN. Accessed April 25, 2014 at http://www.iucnredlist.org/details/62014/0.

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