Smithsonian National Museum of Natural History, North American Mammals
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  Chiroptera · Vespertilionidae · Myotis vivesi
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Myotis vivesi

Fish-eating Myotis

Order: Chiroptera
Family: Vespertilionidae

 

Conservation Status: Vulnerable.


The Fish-eating Myotis rakes its big feet through the water to catch its food. Its kidneys are able to concentrate salt in the urine, so the bats can eat marine crustaceans, which are about 75 percent sea water. An analysis of the bats’ droppings found crustacean exoskeletons, fish scales and bones, algae, and insect remains, clues to a varied diet.

Most Fish-eating Myotis live on islands in the Gulf of California. Smaller populations are found on the nearby mainland. The bats often share cave roosts with petrels, flying out to sea to hunt as the birds return in the evening. Some bats return to the roost several times during the night. Others may use night roosts, but all return to the day roost before dawn. Hawks, gulls, and ospreys are daytime predators to be avoided. The bats sometimes roost in crevices in rock slides, seeking out tiny spaces that rats, another serious predator, cannot enter.

This is the largest New World myotis, and is unique in having white fur on its belly. Its young are born after a gestation of 55 to 65 days, weighing about 6 grams, more than most other adults in the genus Myotis. The young bats can fly when they are about seven weeks old. By then they have doubled their length and quadrupled their weight. They begin to follow the adults as they hunt, but continue to have nothing but milk in their stomachs for a while longer.

Length:
Range: Total Length: 145, 140 mm; Tail: 70, 69 mm

Weight:
Range: few measurements, no adult Weights of 3 newborns: 5.9, 6.2, 6.6 g

References:

Menegaux, 1901. Bulletin du Museum D'Histoire Naturelle, Paris, 7:323.

Links:

Mammal Species of the World

Mammalian Species, American Society of Mammalogists' species account

Distribution of Myotis vivesi