Micropotamogale lamotteiNimba otter shrew

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Geographic Range

The Nimba otter shrew, Micropotamogale lamottei, is endemic to the Nimba mountains shared between Liberia, Guinea and Cote d’Ivoire. Populations are also known to exist in the Putu mountain range of Liberia less than 400 km south of the Nimba mountains. The Nimba otter shrew is limited to an absolute range of less than 5,000 km2, and likely a realized range of less than 1,500 km2. (Nicoll and Rathbun, 1990; Vogel, 2008)

Habitat

Micropotamogale lamottei requires the riparian montane forests (primary or secondary) of Liberia, Guinea, and Cote d’Ivoire directly associated with small rivers, mountain streams or swampy marshes. Based on dietary information, M. lamottei prefers forests associated with crustacean-rich bodies of freshwater. Records indicate M. lamottei also occurs in the waterways associated with densely vegetated plantations as well as rice fields. (Nicoll and Rathbun, 1990; Vogel, 1983; Vogel, 2008)

  • Aquatic Biomes
  • rivers and streams

Physical Description

Of the three extant members of the subfamily Potamogalinae, Micropotamogale lamottei bears the least resemblance to the otters from which their common names originate (otter-shrew). Instead it resembles muskrats and other aquatic rodents (at least superficially) with uniform brown pelage, rounded body, relatively short legs, a long, muscular tail, and overall small size. Lacking the partially webbed feet of Micropotamogale ruwenzori and the laterally compressed tail of Potamogale velox, M. lamottei is arguably the least adapted to a semi-aquatic lifestyle of the Potamogalinae. However, the enlarged upper lip and robust specialized vibrissae are characteristic of semi-aquatic foraging. It is thought that the relatively reduced level of aquatic specialization allows M. lamottei to exploit a broader ecological niche than M. ruwenzori or P. velox. M. lamottei appears to be sexually dimorphic, with males being up to 10% larger than females. The male M. lamottei skull is much more robust and dense than that of the female. Males possess a more pronounced nuchal crest than females, as well as a sagittal crest not present in females. (Kuhn, 1971; Nicoll and Rathbun, 1990; Stephan and Kuhn, 1982; Vogel, 1983; Vogel, 2008; Kuhn, 1971; Nicoll and Rathbun, 1990; Stephan and Kuhn, 1982; Vogel, 1983; Vogel, 2008; Kuhn, 1971; Nicoll and Rathbun, 1990; Stephan and Kuhn, 1982; Vogel, 1983; Vogel, 2008)

  • Sexual Dimorphism
  • male larger
  • Range mass
    53 to 70.6 g
    1.87 to 2.49 oz
  • Average mass
    64.2 g
    2.26 oz
  • Range length
    244 to 258 mm
    9.61 to 10.16 in

Reproduction

Gestation: at least 50 days

Average litter size: 2.6 (range 1–4)

Lactation: at least 40 days

Female otter shrews have mammae on the lower abdomen, central abdomen, and on their pectoral muscles. (Kuhn, 1971; Vogel, 2008)

Little is known about the breeding behavior of any of the African otter shrews, though it is believed that males of this subfamily undergo a rut and may cover large distances in search of mates. (Nicoll, 1985)

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual

Though there are few observations from the wild and no successful attempts at captive breeding, it is believed that the female Nimba otter shrews have a relatively high parental investment compared to similarly sized mammals, with at least 40 days of lactation. Young are born naked and blind with vibrissae already present. Body fur emerges approximately 11 days after birth, and eyes open 23 days after birth. (Vogel, 2008)

  • 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 Micropotamogale lamottei is not known.

Behavior

Semi-aquatic and nocturnal, the Nimba otter shrew is a solitary hunter/forager that gleans riverbanks and stream beds for crabs, crustaceans, mud-dwelling fishes and invertebrates. It is proficient at swimming and diving, using lateral motion of the tail in addition to foot-peddling for surface and underwater locomotion. Micropotamogale lamottei uses nerve-filled vibrissae and an enlarged upper lip to locate and grasp prey underwater. This otter shrew is able to dive for up to 15 minutes when stressed, temporarily slowing its metabolic rate to withstand oxygen deprivation. Upon leaving the water, M. lamottei grooms its pelage thoroughly and methodically with its hind feet at the water’s edge. (Vogel, 1983; Vogel, 2008)

Home Range

The Nimba otter shrew is solitary and territorial, though the extent of an individual’s home range is not well understood. However, data from fish-trap mortality captures indicate that in 1970 approximately one otter shrew per 10 square kilometer range would be captured accidentally each year. This does not necessarily represent an accurate measure of home range. (Vogel, 2008)

Communication and Perception

Olfactory perception in M. lamottei has been greatly reduced in comparison with other tenrecids, but relatively less reduced than Micropotamogale ruwenzori and Potamogale velox. This reduction in olfactory structures is observed in many water-adapted mammals and is correlated with an enlarged medulla oblongata, a presumed consequence of the increased development of the trigeminal tracts in the nervous system. In M. lamottei, vibrissae are innervated by thick trigeminal nerves, rendering the vibrissae capable of acting as vibration receptors under water. It is thought that this trigeminal system has evolved to replace the olfactory sensory system in M. lamottei. Modes of communication in Nimba otter shrews are not reported. (Stephan and Kuhn, 1982)

Food Habits

When hunting on land, M. lamottei gleans creek beds and vegetated riverbanks for soft-shelled crabs and other invertebrates. Crabs are hunted both underwater and on land. M. lamottei attacks the crab from behind so as to avoid the pincers and quickly kills it by striking the articulation of the abdomen and the cephalothorax. When hunting in water, M. lamottei begins by using the specialized trigeminal nerves of its vibrissae to detect underwater prey. In one observation, before diving, and M. lamottei individual held its head just over the surface of the water with its vibrissae contacting the water’s surface, perhaps detecting underwater vibrations of potential prey. After a successful dive, M. lamottei returns to land to kill and eat its prey. (Vogel, 1983; Vogel, 2008)

  • Animal Foods
  • fish
  • insects
  • mollusks
  • aquatic crustaceans

Predation

Little is known about the interactions between the Nimba otter shrew and its predators in the mountains of west Africa, although some speculative anti-predator adaptations have been described. The nocturnal lifestyle of M. lamottei is likely an adaptation in response to the presence of diurnal predators. However, it is also possible that a nocturnal lifestyle benefited the Nimba otter shrew by increasing the success rate of hunting and foraging, rather than being a response to diurnal predation. Micropotamogale lamottei can stay submerged for up to 15 minutes (average 10 minutes) when threatened. They are able to do this by lowering their metabolic rate. (Vogel, 1983)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Little is known about the ecological function and roles that M. lamottei play in the communities of the Nimba mountains. However, it is likely that the Nimba otter shrew has an impact on aquatic community structure resulting from predation on crabs, crustaceans, and small fish.

Economic Importance for Humans: Positive

There is little to no evidence for a positive economic importance for humans from Micropotamogale lamottei.

Economic Importance for Humans: Negative

Though there is little indication of a significant negative economic impact on humans, Nimba otter shrews often become entangled in local fish traps, nets, and pots. (Vogel, 1983)

Conservation Status

The Nimba otter shrew is classified as Endangered by the IUCN based on the criteria that its geographic extent of occurrence is less than 5,000 km2 and is characterized as being severely fragmented and in a state of continuing decline in extent and habitat quality.

Micropotamogale lamottei was discovered and described in 1954, with only a handful of records known into the 1970’s. Since then, limited efforts to assess the size and health of the population have been initiated, but a complete assessment has proven difficult to accomplish due to the presumed small population size and elusiveness of the species. The IUCN first classified M. lamottei as Endangered in 1990 (the first conservation status assessment of the species) based on the criterion that their entire range was limited to less than 5,000 km2 and subject to continuous habitat loss and degradation as agriculture and industry encroach on the forests of the Nimba and Putu mountains. (Vogel, 2008)

Other Comments

The name "otter shrew" is a double misnomer; African otter shrews are among the most distantly related eutherian mammals to both otters and shrews. Instead, the three members of Potamogalinae share common recent ancestors with the tenrecs of Madagascar and the golden moles of southern Africa. This group is now recognized as Afrosoricida. (Wilson and Reeder, 2005)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Kyle Campbell (author), University of Alaska Fairbanks, Link Olson (editor, instructor), University of Alaska Fairbanks.

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

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

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.

forest

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

freshwater

mainly lives in water that is not salty.

marsh

marshes are wetland areas often dominated by grasses and reeds.

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

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

nocturnal

active during the night

piscivore

an animal that mainly eats fish

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

sedentary

remains in the same area

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.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

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

vibrations

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

visual

uses sight to communicate

References

Kuhn, H. 1971. An Adult Female Micropotamogale lamottei. Journal of Mammalogy, 52: 477.

Nicoll, M. 1985. The biology of the giant otter shrew Potamogale velox. National Geographic Society Research Reports, 21: 331-337.

Nicoll, M., M. Rathbun. 1990. African insectivora and elephant-shrews. An action plan for their conservation.. IUCN/SCC Action Plans for the Conservation of Biological Diversity, 16: 18-19.

Stephan, H., H. Kuhn. 1982. The Brain of Micropotamogale lamottei Heim de Balsac, 1954. Z Saugetierkde, 47: 129-142.

Vogel, P. 1983. Contribution a l'Ecologie et a la Zoogeographie de Micropotamogale lamottei. Revue d'Ecologie, 38: 37-49.

Vogel, P. 2008. Micropotamogale lamottei. In: IUCN 2008. 2008 IUCN Red List of Threatened Species: 1.

Wilson, D., D. Reeder. 2005. Mammal Species of the World, 3rd edition. Baltimore: Johns Hopkins University Press. Accessed February 09, 2009 at http://www.bucknell.edu/msw3/.