Microgale gracilis

Geographic Range

Microgale gracilis (gracile shrew tenrec) is endemic only to the island nation of Madagascar. Individuals have been recorded over the length of the island from the mountains of Marojejy National Park and Anjanaharibe-Sud Reserve to the southern edge of the island, near Andohahela National Park. They're generally confined to the eastern portion of Madagascar, which includes Anjozorobe forest, Ankaratra forest, Ranomafana forest and Andringitra National Park.

• Biogeographic Regions
• ethiopian ethiopian
  • native native

• Other Geographic Terms
• island endemic island endemic

Habitat

Microgale gracilis prefers the eastern humid forests of Madagascar. Specimens have been recorded in valley bottoms with dense vegetation in moist, subtropical, montane areas from 1,200 m to 1,990 m elevation. Nearly all Microgale species live sympatrically in at some point in their geographic range (e.g., all species have been recorded in the Andringitra National Park), however, M. gracilis lives at a higher elevation than most Microgale .

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• rainforest rainforest

Physical Description

Like other members of its family, Microgale gracilis retains many primitive traits, including a low and seasonally variable body temperature, a cloaca (common opening for the urogenital, anal and reproductive tracts) and testes that are undescended in the male. Microgale gracilis is shrew-like in appearance and many of its morphological features suggest that it is semi-fossorial. This species is characterized by an elongate skull, long rostrum and rhinarium, dense, velvety pelage, reduced eyes and ears, short forelimbs with broadened forefeet, and enlarged claws with five digits. The tail is shorter than the head/body length. Individuals have dark-brown dorsal pelage with buff speckles, and dark grey ventral pelage with a "buff wash." The tail is bicoloured, dark brown dorsally and light brown ventrally. Juveniles appear less speckled than adults, particularly posteriorly. The dentition is much reduced in size with slender canines and incisors. The adult dental formula of M. gracilis is I3/3, C1/1, P3/3, M3/3.

Microgale gracilis may be confused with Microgale gymnoryncha , but the two can be differentiated by the posterior region of the rhinarium, which is reticulated in M. gracilis . Also, the braincase length is generally less than 8.5 mm in M. gracilis and greater than 8.5 mm in M. gymoryncha .

Basal metabolic rate of M. gracilis is unknown, but there is information on closely related species. The field metabolic rate (FMR) for nonreproducing Microgale dobsoni is 77.1 kJ/d (mean body mass 42.6 g), which is 3.8 times the resting metabolic rate (RMR) of the species. Also, the mean FMR for nonreproducing M. talazaci (mean body mass 42.8 g) is 66.5 kJ/d, which is 3.2 times RMR.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Reproduction

The mating system of Microgale gracilis has not been studied. However, other Microgale species are polygynandrous. Evidence suggests that some Microgale use sound to communicate with potential mates, but this has not been studied in M. gracilis .

Microgale gracilis becomes sexually mature after the formation of adult dentition, however, little else is know of the reproductive behavior of this species. All species of the family Tenrecidae that have been studied have relatively long gestation periods. Though Microgale are nearly the same size as a true shrew , their gestation period is almost twice as long (eight weeks versus three to four weeks in a shrew). Litter size of related Microgale species tend to be small, with a maximum of three. All Tenrecidae lack a fluid-filled cavity (antrum) that develops in the ovarian follicle. Before ovulation, spermatozoa contact and penetrate the developing follicles, fertilizing the egg before ovulation. The only other mammal in which this occurs is Blarina brevicauda (the short-tailed shrew). Microgale gracilis can have up to six mammae.

Size at birth of and the timing of ontogenetic events of Microgale gracilis young is unknown. However, Microgale dobsoni offspring weigh 3.95 g at birth, on average and are fully furred by 18 to 22 days after birth. Most M. dobsoni young are weaned by 28 to 30 days, become sexually mature by about 2 years old, and weigh an average of 37.8 g upon reaching independence.

• Key Reproductive Features
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• viviparous viviparous

No information is available regarding parental care in Microgale gracilis . As mammals, females likely invest much time and energy in their young until they are weaned. Evidence from closely related Microgale species ( M. talazaci and M. dobsoni ) suggests that offspring are weaned by 28 to 30 days, then followed the mother at night as she forages. Following behavior by young suggests that mothers may protect offspring prior to independence. There is no information on post-independence associations between mother and offspring.

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

Lifespan/Longevity

There is no information available regarding the lifespan of Microgale gracilis . However, closely related species ( Microgale dobsoni and M. talazaci ) live up to 6 years in captivity.

Behavior

Little is known of the general behavior of Microgale gracilis . This species is not arboreal or scansorial like many Microgale species. Morphological traits suggest a semi-fossorial behavior (e.g., small eyes, small ears, short, dense pelage). Microgale gracilis is terrestrial, nocturnal and forages alone, suggesting that it is solitary.

• Key Behaviors
• terricolous
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• solitary solitary

Home Range

There is no information available regarding home range in Microgale gracilis , or closely related species.

Communication and Perception

• Communication Channels
• tactile tactile
• chemical chemical

• Other Communication Modes
• pheromones pheromones
• scent marks scent marks

• Perception Channels
• tactile tactile
• chemical chemical

Food Habits

Like other Microgale species, Microgale gracilis is probably insectivorous, though there is no information on the feeding behavior of this species. It has been suggested that M. gracilis may also eat other small invertebrates and earthworms. The stomach contents of several closely related Microgale species ( M. taiva , M. principula , and M. drouhardi ) show predation on Coleoptera (beetles), Dermaptera (earwigs), Hymenoptera (ants, bees, wasps), Orthoptera (grasshoppers, crickets, locusts), Annelida (segmented worms), Arachnida (arachnids) and Amphipoda (crustaceans).

• Primary Diet
• carnivore carnivore
  • insectivore insectivore

• Animal Foods
• insects
• terrestrial non-insect arthropods
• terrestrial worms

Predation

No information is available concerning the major predators of Microgale gracilis . However, this species is probably prey for small carnivores , birds of prey , snakes and other Microgale . Remains of the closely related species ( M. melanorrhachis and M. talazaci have been found in the scat of fossas and in barn owl pellets, and both Microgale species occur sympatrically with M. gracilis . There is no information on anti-predator adaptions of Microgale gracilis or closely related species, however, its suggested fossorial and nocturnal lifestyle may help reduce risk of predation.

Ecosystem Roles

Economic Importance for Humans: Positive

There are no known positive effects of Microgale gracilis on humans.

Economic Importance for Humans: Negative

There are no known adverse effects of Microgale gracilis on humans.

Conservation Status

Microgale gracilis is classified asa species of "least concern" on the IUCN's Red List of Threatened Species. Despite this, however, its numbers are decreasing and deforestation of Madagascan rainforests may lead to further decline of this species. Many primary forests in Madagascar are being logged to provide land for agriculture, and the ability of M. gracilis to survive in second growth forests is unknown. More research is needed to gain a better understanding of the potential conservation needs of this species.

Other Comments

Microgale gracilis was discovered by Charles Immanuel Forsyth Major on an expedition in 1896.

Microgale , Oryzorictes hova , Oryzorictes tetradactylus and Limnogale are placed in their own subfamily of tenrecids , the Oryzorictinae (spineless tenrecs). This split and phylogenetic tree is based on analysis of the mitochondrial genes 12S rRNA, tRNA-Valine and ND2 and exon 28 of the nuclear von Willebrand Factor gene. According to this study, M. gracilis is most closely related to Microgale gymnohyncha .

Additional Links

Encyclopedia of Life

Contributors

Kayla Paulson (author), University of Michigan-Ann Arbor, Phil Myers (editor), University of Michigan-Ann Arbor, John Berini (editor), Animal Diversity Web Staff.

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