Smithsonian National Museum of Natural History, North American Mammals
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Rheomys thomasi

Thomas’ Ichthyomyine

Order: Rodentia
Family: Cricetidae


Conservation Status: Near Threatened.

Thomas’ Ichthyomyine, a water mouse, is sometimes found in very small forest streams in the highlands of southern Mexico, Guatemala, and El Salvador. Its diet apparently includes insects, insect larvae, birds, salamanders, and even other mammals. Like other water mice, its nostrils open facing backward, towards its ears, behind flaplike valves. It has small eyes and ears and webbing between its hind toes, all adaptations to a semiaquatic life. Little is known about reproduction in this animal; however, a pregnant female was carrying just one embryo.

Also known as:
Thomas' Water Mouse

Range: Head and Body: 94-136 mm; Tail: 105-137 mm

Range: 25-29 g


Dickey, 1928. Proceedings of the Biological Society of Washington, 41:11.


Mammal Species of the World

Distribution of Rheomys thomasi