The web-footed tenrec, Malagasy otter shrew, or aquatic tenrec (Microgale mergulus) is the only known semiaquatic 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 , and was once thought to be extinct. It feeds on crabs, aquatic insects, and crayfish. The population is considered vulnerable. It was formerly placed in the monotypic genus Limnogale, but has been moved to Microgale based on molecular data showing it to be deeply nested within the latter. Life history Microgale 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 M. mergulus is only known to inhabit stream habitats in eastern Madagascar. While it is no longer classified in the obsolete order of Insectivora, M. mergulus could very well be designated an insectivore. The bulk of its diet consists of aquatic insects and larvae, with crustaceans and small fish making up the rest. The larvae of insects in the orders Ephemeroptera, Odonata and Trichoptera are favored. Diets of individuals inhabiting zero-canopy steams appear to be the same as those living in forested streams. Phylogeny The aquatic or web-footed tenrec, Microgale mergulus, and other tenrecs are endemic to Madagascar. They are part of the monophyletic clade Afrotheria, which includes placental mammals of diverse anatomies including hyraxes, elephants and mammoths, manatees 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 one of 22 members of the genus Microgale. Molecular studies have led to its placement in the subfamily Oryzorictinae, along with two species each of the genera Nesogale and Oryzorictes. It is the largest member of this subfamily and likely evolved this increased size in response to its aquatic lifestyle. Ancestral tenrecs are thought to have rafted from mainland Africa to Madagascar in a single event. All tenrecs are thought to descend from a common ancestor that lived 29–37 million years (Ma)