The web-footed tenrec, otter shrew, or aquatic tenrec (Limnogale mergulus) is the only known semiaquatic|aquatic Malagasy tenrec (the related African otter shrews have similar habits), and is found in eastern Madagascar, especially in and around Ranomafana National Park. It grows to between 25 and 39 cm, and was once thought to be extinct. It feeds on crabs, water insects, and crayfish. It weighs between 40 and 60 grams, and the population is considered vulnerable. It is the only species in the genus Limnogale.
Life History[]
Limnogale mergulus is strictly nocturnal, spending the day in stream side burrows, only emerging at night to hunt. Nocturnal movements appear to be restricted to waterways but include movements away from burrows and diving. Radio collar tracking has shown that some individuals are known to utilize stream channels as much as 1160 meters in length, while others may only patrol 500 meters. In one night a web-footed tenrec may travel 1550 meters along channels in search of food.
Diet[]
L. mergulus is only known to inhabit stream habitats in Eastern Madagascar. Lypotyphlan is a term which has been used to group small, insectivorous mammals. While this term is no longer used in phylogenetics, it can still be used to accurately signify the diet of L. mergulus. The bulk of its diet consists of aquatic insects and larvae, with crustaceans like crayfish and small fish making up the rest. The larvae of insects in the orders Ephemeroptera, Odonata and Trichoptera being favorites. Diets of individuals inhabiting zero-canopy steams appears to be the same as those living in forested streams.
Phylogeny[]
The aquatic or web-footed tenrec, Limnogale mergulus, and other Malagasy Tenrecs are placed in a monophyletic clade called Afrotheria, which includes placental mammals of diverse anatomies including hyraxes, elephants and mammoths, manatee and dugong, tenrecs, golden moles, elephant shrews, and aardvarks. Genetic sequencing and other methods have confirmed the accuracy and relatedness of this grouping.
The Web-footed Tenrec is currently the only recognized member of its genus, Limnogale. Genomic sequencing has led to its placement into the subfamily Oryzorictinae, with the two Malagasy species of genus, Microgale.[5] It is the largest member of this family and likely evolved this increased size in response to its aquatic lifestyle.[3] Ancestral tenrecs are thought to have rafted from mainland Africa to Madagascar between 42 and 25 million years ago. Due to this time of independent evolution, Malagasy Tenrecs are often studied as a unique group, though still placed within the family Tenrecidae. Malagasy Tenrecs include members of subfamilies Tenrecinae and Geogalinae, and Oryzorictinae. While its habits are similar to the related otter shrews of Mainland East Africa, family Potamogalinae, their aquatic lifestyles evolved independently from one another.
Conservation[]
The Aquatic Tenrec, Limnogale mergulus, is currently ranked by the IUCN as Vulnerable on the Red List. Due to their specialized habitat requirements and restriction to the island of Madagascar, it is estimated that less than 2,000 km2 of suitable habitat remains. Degradation of riparian ecosystems and siltation of streams are the leading threat to the species’. Deforestation is also recognized as a potential cause of decline. However, recent studies have shown healthy populations of L. mergulus in streams where forest has been cleared or otherwise degraded, as well as non-native plantations. Areas of its habitat which are currently protected include Ranomafana National Park and the Andringitra National Park (1989) and it is also reported in the new Nosy Volo Reserve in the east (2014).
Within afrotherian mammals, Limnogale mergulus is typically considered for highest priority conservation priority along with Giant Otter Shrew, Giant Golden Mole, Northern Shrew Tenrec, Nimba Otter Shrew, as well as some better-known conservation symbols like Dugong, Asian Elephant, and Manatee (including three species). This priority has been analyzed using two different methods, including Phylogenetic Diversity (PD) and Evolutionary Distinctiveness (ED).