By David Alvarado
Geographic Range
Idionycteris phyllotis is found in the mountainous regions of the southwestern United States through central Mexico.
Biogeographic Regions:
nearctic 
(native ); neotropical (native ).
Habitat
Idionycteris phyllotis primarily dwells in caves in mountainous pine and oak forests. The availability of water holes is a significant factor in habitat selection due to their high rate of evaporative water loss. Nearly all capture sites have been in the vicinity of rocks, such as cliffs or large boulders, their most probable roosting sites.
Terrestrial Biomes:
forest ; scrub forest ; mountains .
Physical Description
(0.28 to 0.56 oz; avg. 0.42 oz)
The defining characters of Idionycteris phyllotis, also known as Allen's Big-Eared Bat, are its large ears (34 to 43 mm) which possess lappets projecting from the base of the ears and extending over the forehead. Idionycteris phyllotis has a total length of 103 to 118mm, a tail length of 44 to 55mm, and a forearm length of 42 to 49 mm. The wing span of I. phyllotis ranges from 302 to 344mm. Dorsal and ventral pelage is long (10mm) and basally black with yellowish gray tips. A patch of white hair occurs at the base of the ears. Females are generally about 5% larger in head and body length, however, there is no difference in forearm length.
Some key physical features:
endothermic ; bilateral symmetry .
Reproduction
Females form maternity colonies during the summer months, from June to late July, where they give birth to and raise their young. Maternity colonies consist of an average of 30 females. Males live separately from the females during this time. Females give birth to a single young.
Key reproductive features:
seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous .
Behavior
Most I. phyllotis are observed two to three hours after sunset near water. Their flight is characterized by swift, direct movements during open flight and slow, highly maneuverable movements in close quarters. They are also capable of hovering. They emit an audible echolocation signal during open flight. Males and females live in colonies of from 5 to 28 individuals during the non-summer months. Males are solitary and females form maternity colonies during the summer months.
Key behaviors:
motile .
Food Habits
Idionycteris phyllotis is an insectivorous bat which feeds mostly by gleaning moths and stationary insects from surfaces.
Economic Importance for Humans: Negative
Bats are known to carry the causative virus of rabies
Economic Importance for Humans: Positive
Because Idionycteris phyllotis is an insectivorous bat it plays an important role in pest control. Bat guano is used as a source of fertilizer, and organisms housed in the guano are used for waste detoxifying.
Conservation Status
IUCN Red List: [link]:
Lower Risk - Least Concern.
US Federal List: [link]:
Threatened .
CITES: [link]:
No special status.
Roost disturbance is the greatest threat to I. phyllotis. Mining activities have caused the relocation or extermination of several bat roosts. Reproduction is shown to decrease after relocation, threatening the survival of the roost. Deforestation removes the feeding environment for the bats, as well as that of their insect prey.
For More Information
Find Idionycteris phyllotis information at
Contributors
David Alvarado (author), University of Michigan.
Phil Myers (editor), Museum of Zoology, University of Michigan.
