Micropotamogale lamottei
Nimba otter shrew

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)

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)

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)

The lifespan of Micropotamogale lamottei is not known.

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)

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)

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)

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)

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.

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)

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

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)

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)