O’SHEA, CRYAN & BOGAN: UNITED STATES BAT SPECIES OF CONCERN 
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variable from light brown to 
almost blackish, and lighter ven- 
trally. The bases of the hairs are 
black, with tips various degrees 
lighter, often yellowish gray; a 
tuft of white hair is visible near 
the posterior base of each ear 
(Barbour and Davis, 1969; 
Czaplewski, 1983). 
Distribution and System- 
atics.— Allen’s big-eared bat 
occurs in the southwestern Unit¬ 
ed States and Mexico south to 
Oaxaca (Fig. 18; Czaplewski, 
1983; Bonilla et al., 1992). In the 
United States, it is mostly report¬ 
ed from middle-elevation forest¬ 
ed habitats in southern Utah and 
Nevada, Arizona, western New 
Mexico, southwestern California 
(Czaplewski, 1983), and western 
Colorado (Hayes et ah, 2009; Figure 17. Allen’s big-eared bat, Idionycterisphyllotis (photo by J. Scott 
Adams and Lambeth, 2015), Altenbach). 
although it also has been taken somewhat less frequently at both higher and lower elevations in 
some of these states (Hoffmeister, 1986). They are probably quite localized in distribution. The first 
U.S. specimen was taken in 1955 in the Chiricahua Mountains of southeastern Arizona at an ele¬ 
vation of 1,646 m, and prior to the Arizona record the species was only known based on two spec¬ 
imens taken in Mexico in 1878 and 1922 (Cockrum, 1956). 
The placement of Allen’s big-eared bat within the genus Idionycteris is a result of reliable tax¬ 
onomic research during the past 25 years. Handley (1959) considered Idionycteris to be a subgenus 
of Plecotus. Tumlinson and Douglas (1992) and Bogdanowicz et ah (1998) subsequently provided 
strong evidence that the generic name Plecotus was valid only for certain species of Old World 
bats. Based on their work and suggestions of previous authors (for example, Williams et ah, 1970, 
based on karyotypes), Idionycteris was elevated as the generic name for these bats, formerly known 
as Plecotus phyllotis based on Handley’s (1959) analysis and originally named Corynorhinus phyl¬ 
lotis by Allen (1916). Czaplewski (1983) provided a complete taxonomic synonymy of past scien¬ 
tific names applied to this species. Two subspecies have been described based on morphology, size, 
and distribution. Idionycteris phyllotis hualapaiensis is smaller in size and found in the northern 
part of the species range in Nevada, Utah, and northern Arizona, and Idionycteris phyllotis phyllo¬ 
tis is larger in size and found in the central part of the species range, which includes the remainder 
of Arizona and New Mexico (Tumlinson, 1993). 
The generic name Idionycteris is based on the Greek for “distinct” and “bat”. The specific epi¬ 
thet originates from Greek words meaning “long” and “ear”. The common name acknowledges 
Glover Morrill Allen, the early 20 th century mammalogist and bat specialist who first described the 
species. Other English common names include Mexican big-eared bat, lappet-browed bat, Allen’s 
lappet-eared bat, and Allen’s lappet-browed bat. 
Habitats and Relative Abundance.— Allen’s big-eared bat was discovered in the United 
