Allen’s big-eared bat
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Idionycteris phyllotis
NatureServe conservation status
Global (G-rank): G4
State (S-rank): S3
Utah Wildlife Action Plan status
- SGCN
External links
Species range
Allen’s big-eared bats (also known as lappet-browed bats) range from Central Mexico to the American Southwest including Arizona, California, Colorado, Nevada, New Mexico, and Utah. In Utah, the species has been observed in Grand, Wayne, San Juan, Garfield, Kane, and Washington counties.
Habitat
Black (1970), reporting the first specimen of this species taken in Utah, described the collection site as "an artificial reservoir in a pinyon-juniper woodland" at an elevation of 6,000 ft.
Armstrong (1974), documenting the second report of this species in Utah (the second and third specimens), wrote of the locality: "Squaw Spring is a perennial seep in the bed of Squaw Canyon, a generally sandy wash which carries an ephemeral affluent . . .. The vegetation about Squaw Spring is a well-established mesic-adapted assemblage including horsetail (Equisetum), cattail (Typha), bulrushes (Scirpus), rabbitfoot grass (Polypogon) and little bluestem (Andropogon scoparius), sweetclover ((Melilotis) and willows (Salix). This vegetation presents a marked contrast to that of immediately adjacent uplands, where open, silty flats are sparsely covered with ricegrass (Oryzopsis) and snakeweed (Gutierrezia) and rocky areas support an open woodland of pinyon pine (Pinus edulis) and juniper (Juniperus osteosperma). Well-developed woodland occurs within a mile of the spring."
Poche (1975) published the third report of this species in Utah and described the locality: "Vegetation in the wash includes Tamarix and Salix, and that on the adjacent upland is comprised [sic] primarily of blackbrush (Coleogyne ramosissima), and infrequent pinyon pine (Pinus edulis) and juniper (Juniperus osteosperma). Grass cover is predominantly Bromus and Hilaria. Average elevation for the area is 1,250 m with annual precipitation of less than 200 mm. The Hurricane Cliffs are located 5 km west of the collection area and descend over 500 m to Warner Valley, which is covered with creosotebush (Larrea tridentata), blackbrush, and snakeweed (Gutierrezia microcephala). The surrounding region consists of numerous steep rises and mesas, canyons, and cliffs."
Foster et al. (1996) captured this species at two Utah Localities and reported the habitat of one of them. The capture site was at 6,500 ft elevation, in "submontane tall shrubland" characterized by Tamarixramosissima, Salix sp., and Pinus edulis. "Tantalus Creek runs down the length of a long narrow canyon roughly 27m deep. The floor of the canyon is nearly flat, yielding a very shallow, slow stream. Stream dimensions are typically .5mX.2m. . . . The stream bed is very sandy . . .. The dominant vegetation in the canyon is willow (25%) and grass (35%). However there is some tamarisk (2%) and cottonwood (1%). The hillside is covered in sage (30%) and rabbitbrush (25%). . . . Cliffs, embankments, trees, and shrubs are all common and within 10 meters of the stream and its pools."
Ecology
This species is often found at mid-elevations (3,600 ft. - 8,200 ft.) and frequently occupies woodlands consisting of oak, juniper, or ponderosa with rocky and riparian components. Additionally, Utah capture records indicate the species also utilizes desert shrub habitats and riparian habitats consisting of cottonwood and willow. Maternity colonies have been found in rock piles, in loose bark on dead trees, and in mines. Hibernation sites are not well known, but have been documented in caves in mines. Allen’s big-eared bats are insectivores, eating moths and beetles in flight or by gleaning them from foliage.
Threats or limiting factors
The primary threat to Allen’s big-eared bat is the loss of roost and maternity colony sites. These bats are particularly sensitive to human disturbance and may abandon such sites if disturbed. Additionally, forest management practices that hinder the retention or recruitment of large trees and snags may result in the loss of current maternity colonies, or reduce the potential for future maternity colonies to develop. Given the presumed rarity of this species, and its low reproductive output, the loss of maternity colonies may result in serious declines. Similarly, the closure of abandoned mines, if not done properly, may result in the loss of important roost sites.
Taxonomy
Most authors writing of this species in Utah (e.g., Black 1970, Armstrong 1974, Poche 1975, Hasenyager 1980, Hall 1981) have referred to it by the name PLECOTUS PHYLLOTIS.