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Smithsonian National Museum of Natural History, North American Mammals

  Chiroptera · Vespertilionidae · Idionycteris phyllotis

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Idionycteris phyllotis

Allen's Big-eared Bat

Order: Chiroptera
Family: Vespertilionidae

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Credit: New Mexico Bat Call Library, W. L. Gannon
Image of Idionycteris phyllotis
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Conservation Status: Least Concern.

As with other big-eared bats, the huge ears of Allen's big-eared bat can be curled back along the sides of the neck so they resemble the horns of a ram. When its ears are tucked out of the way in this manner, one of the cartilage folds of the ear (the tragus) remains erect and may actually look like a small ear, which can make it hard to identify a roosting bat. Few have been observed in their roosts; most information about them comes from bats that were netted while they were flying. These versatile bats adapt their flight patterns and sound emissions (echolocation calls) to varying terrains. They are capable of straight, direct flight, but can also fly slowly, maneuver well, and even hover, so they can forage in and among tree branches. They mostly eat small moths but also take other insects.

Also known as:

Mexican Big-eared Bat, Lappet-browed Bat

Sexual Dimorphism:

Females may be about 5% longer than males.


Average: 110 mm
Range: 103-135 mm


Range: 8-16 g


Allen, G.M., 1916.  Bats of the genus Corynorhinus.  Bulletin of the Museum of Comparative Zoology, 60:331-356.


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Distribution of Idionycteris phyllotis

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