Fish-eating myotis  (Myotis vivesi)

The fish-eating myotis is classified as Vulnerable (VU) on the IUCN Red List (1).

The fish-eating myotis (Myotis vivesi), the largest species of Myotis in the New World (2), is remarkable for feeding primarily on fish, and has a number of adaptations for this diet. Its robust legs allow the fish-eating myotis to carry heavy loads, while the long, thin claws and feet reduce drag through the water while hunting (2) (3), and the long, narrow wings are characteristic of bats that fly in uncluttered environments (2). The fur of the fish-eating myotis is dark buff through to pale tan on the back and white on the underparts (2). The scientific name Myotis stems from two Greek words, ‘Mus’ meaning mouse and ‘Otos’ meaning ear, and refers to the mouse-like ears of this bat (2).

Restricted to a few areas of specialised habitat (4), the fish-eating myotis is found only in Mexico where it occurs on the coast of Sonora and Baja California, primarily on the array of small islands that occur just off this coastline in the Gulf of California (1) (5).

The fish-eating myotis inhabits rocky coastline that provides suitable foraging areas and places to roost (1). Like many bats the fish-eating myotis will roost in caves but is also found under rocks in areas created by landslides. The fish-eating myotis prefers crevices which are not accessible to predators and it will usually roost alone, but has been known to share roosts with petrels (2).

The majority of the fish-eating myotis’s diet comprises oceanic species (6), primarily fish (7). The fish-eating myotis hunts at night, when it flies over the ocean searching for ripples in the water that indicate a fish swimming near the surface (8). The fish-eating myotis snatches the fish using its long feet, large toes and sharp, curved claws, and transfers the fish to its mouth (7) (8). The fish is then consumed during flight or when the bat has settled at a nearby roost (7). The fish-eating myotis is able to catch and eat around 30 fish each night (8). The fish-eating myotis also feeds on small crustaceans and some flying insects, both of which are believed to be caught in the mouth (7). Remarkably, the fish-eating myotis is able to drink seawater (9).

The gestation period in the fish-eating myotis is about 55 days, with females generally giving birth to a single pup in late May or early June (2). In early June females may be seen carrying the young on one of the teats (7). The young bat may remain on the mother for up to three weeks, after which it will not leave the roost until able to fly, at about seven weeks old (2).

The fish-eating myotis is preyed on by a number of seabirds, and predatory gulls have been observed inspecting rock crevices in search of this bat (2).

The fish-eating myotis is threatened by habitat loss and introduced species such as rats (Rattus species) and cats (Felis catus), which prey on this species (10). This has devastated some populations of fish-eating myotis in the Gulf of California (10).

Conservation efforts have focused on eradicating introduced cats and rats from a number of islands within the Gulf of California (10). The fish-eating myotis is also likely to be benefitting from other efforts to conserve the Gulf of California environment, for which a conservation and sustainable development action plan exists (11). Populations of the fish-eating myotis also occur in Las Islas del Golfo de California Biosphere Reserve and Isla Rasa Reserve, which hopefully offers its habitat some level of protection (1). 

To learn more about bat conservation see:

• Organization for Bat Conservation:
  http://www.batconservation.org/
• Bat Conservation International:
  http://www.batcon.org/