Geographic Range
Mole tenrecs,
Oryzorictes hova
, are endemic to the island of Madagascar, the result of a spectacular radiation from
the single colonizing ancestor of all Malagasy tenrecs.
- Other Geographic Terms
- island endemic
Habitat
Mole tenrecs inhabit the forested regions of Madagascar, from lowland humid forests
to high elevation localities near tree line. Although semifossorial in nature,
O. hova
is also broadly distributed throughout wet bottomlands including agricultural sites
(converted rice paddies) and natural marshes.
- Habitat Regions
- tropical
- terrestrial
- Terrestrial Biomes
- forest
- Wetlands
- marsh
- Other Habitat Features
- agricultural
Physical Description
Members of the genus Oryzorictes measure between 99 and 124 mm in length, and are between 28 g and 40 g. They share several of the morphological characters that typify semifossorial insectivores. Well developed forelimbs and elongated claws are accompanied by small eyes and ears. Albinism is expressed in some populations of O. hova , although more frequently a brown-tan bicoloration of the dorsal and ventral pelage is seen.
The principle morphological character that has defined both species of
Oryzorictes
is the relative number of toes on the forearm. As the name implies,
Oryzorictes tetradactylus
has only four toes. Other members of the genus have five toes. The relative length
of the tail has also been used to distinguish
O. hova
and
O. tetradactylus
, the latter possessing a distinctly shorter tail. However significant overlap in
observed tail lengths has been noted.
- Other Physical Features
- endothermic
- homoiothermic
- bilateral symmetry
- Sexual Dimorphism
- sexes alike
Reproduction
Nothing is currently known on the mating systems of
Oryzorictes
in the wild. It is difficult to infer any pattern of mating because the family
Tenrecidae
shows considerable variation in their reproductive strategies.
Data from specimens collected provide a limited view of this animal's reproductive
life history. Embryo counts place a maximum of four in a litter, although they posses
six sets of mammae. Nowak (1999) reports an average of 3 young per litter. Testes
remain abdominal throughout the year as in other members of Tenrecidae.
- Key Reproductive Features
- iteroparous
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- viviparous
As with other aspects of the biology of this genus, almost nothing is known about
the parental investment of
Oryzorictes
. However, because they are mammals, we can infer that females provide a great deal
of parental care to their offspring. Females nurse their young, and provide them
with protection, grooming, and other care until they are weaned. It is not known
whether there is further association between offspring and their parents after independence.
The role of males in parental care is not known.
- Parental Investment
-
pre-fertilization
- provisioning
-
protecting
- female
-
pre-hatching/birth
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-weaning/fledging
-
provisioning
- female
-
protecting
- female
-
provisioning
Lifespan/Longevity
Specimens of
Oryzorictes
have been successfully kept in captivity, but full lifespan data have never been
published. Lifespan data for wild specimens have never been collected. Long-tailed
tenrecs, in the genus
Microgale
have been reported to live between 5 and 6 years. Because they are similar in size
to
Oryzorictes
, lifespans may be similar.
Behavior
Oryzorictes hova is a semifossorial species with locomotary adaptations similar to those of the true moles in the family Talpidae . Populations have never been noted in significant densities other than in anecdotal accounts by local farmers in rice paddies.
Daily torpor has been noted in many of the tenrecs, but has never been directly observed in Oryzorictes .
On the whole, little is known about semifossorial tenrecs. Trapping success of this
species and the other semifossorial Oryzorictinae (
Microgale gracilis
,
Microgale gymnohyncha
) is very low, and often correlates with rains that flood their natural burrows. Trends
in relative seasonal populations and estimated densities are unknown as a result,
as
O. hova
handily avoids most current trapping techniques.
Nowak (1999) reports that members of the genus
Oryzorictes
are thought to be mainly nocturnal.
Oryzorichtes hova
is thought to sometimes forage above ground, using its muzzel to probe beneath ground
cover. However, because these animals are active underground also, it is difficult
to know for certain whether they move about at other times of day.
Home Range
Because of low trapping success of this species, the size of home ranges is not known.
Communication and Perception
Oryzorictes
has relatively underdeveloped eyes and ears, presumably relying on its tactile senses
to navigate underground. Both species possesses a long, ennervated rostrum for touch
perception, and probably rely on their sense of smell to direct them to areas of high
prey density. However, little is known about aspects of social communication or environmental
perception beyond these morphological observations.
Food Habits
Nothing is known of the feeding habits of
Oryzorictes
other than data obtained through stomach content analyses. A high proportion of insects,
earthworms, and some vegetable matter have been reported, but no further research
has been conducted.
- Primary Diet
- carnivore
- Animal Foods
- insects
- terrestrial worms
- Plant Foods
- roots and tubers
Predation
The semifossorial nature of this species protects it from many of the natural predators
of Madagascar. However, remains have been observed in owl pellets and the intestinal
tract of at least one fossorial snake.
Ecosystem Roles
The role of
Oryzorictes
in ecosystem function is poorly understood, as data on their natural history are
almost nonexistent. Despite this, this genus of tenrecs represents a unique example
of adaptation to fill an available niche. The lack an extensive predator base as found
on other continents suggests Madagascar's semifossorial species do not play as critical
a role as the moles and gophers of North America's varied ecosystems in sustaining
predator populations. Beyond this, we can speculate that
O. hova
plays some role in controlling insect and earthworm populations, and may help to
aerate the soil. Further speculation is not possible with the scant information known
about the island's complex ecosystems.
- Ecosystem Impact
- soil aeration
Economic Importance for Humans: Positive
Other than its inherent value as a representative species of Madagascar's endemic biota, this species has little economic importance.
Economic Importance for Humans: Negative
Oryzorictes hova
has been known to inhabit rice paddies in considerable densities, causing damage
to young plants by uprooting shoots while burrowing.
- Negative Impacts
- crop pest
Conservation Status
The conservation status of these animals has not been evaluated.
Other Comments
An extensive review of the taxonomic history of
Oryzorictes
synonymized a previously recognized species,
Oryzorictes talpoides
with
Oryzorictes hova
after an extensive review of cranial and dental synapomorphies.
Additional Links
Contributors
Jonathan Fiely (author), University of Alaska Fairbanks, Link E. Olson (editor, instructor), University of Alaska Fairbanks, Nancy Shefferly (editor), Animal Diversity Web.
- Ethiopian
-
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- island endemic
-
animals that live only on an island or set of islands.
- tropical
-
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
- terrestrial
-
Living on the ground.
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- marsh
-
marshes are wetland areas often dominated by grasses and reeds.
- agricultural
-
living in landscapes dominated by human agriculture.
- 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.
- 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.
- 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).
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- viviparous
-
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
- fossorial
-
Referring to a burrowing life-style or behavior, specialized for digging or burrowing.
- nocturnal
-
active during the night
- motile
-
having the capacity to move from one place to another.
- tactile
-
uses touch to communicate
- chemical
-
uses smells or other chemicals to communicate
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- soil aeration
-
digs and breaks up soil so air and water can get in
- carnivore
-
an animal that mainly eats meat
- insectivore
-
An animal that eats mainly insects or spiders.
References
Eisenberg, J., N. Muckenhirn. 1968. The reproduction and rearing of tenrecoid insectivores in captivity. Internation Zoo Yearbook , 14: 108-110.
Goodman, S., D. Rakotondravony. 2000. The effects of forest fragmentation and isolation on insectivorous small mammals (Lipotyphla) on the Central High Plataeu of Madagascar. Journal of Zoology. , 250: 193-200.
Goodman, S., J. Ganzhorn, L. Olson, M. Pidgeon, V. Soarimalala. 1997. Annual variation in species diversity and relative density of rodents and insectivores in the Parc National de la Montagne D'Ambre, Madagascar. Ecotropica , 3: 109-118.
Goodman, S. 2003. Oryzorictes , Mole Tenrec or Rice Tenrec. Pp. 1278-1281 in The Natural History of Madagascar . Chicago: University of Chicago Press.
Gould, E., J. Eisenberg. 1966. Notes on the Biology of the Tenrecidae. Journal of Mammalogy , 47:4: 660-686.
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. 1235-1240 in The Natural History of Madagascar . Chicago: University of Chicago Press.