|Scientific Name:||Pipistrellus hesperus|
|Species Authority:||H. Allen, 1864|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Arroyo-Cabrales, J. & Ticul Alvarez Castaneda, S.|
|Reviewer(s):||Medellín, R. (Chiroptera Red List Authority) & Schipper, J. (Global Mammal Assessment Team)|
This species is listed as Least Concern in because of its wide distribution, presumed large population, occurrence in a number of protected areas and because it is unlikely to be declining at nearly the rate required to qualify for listing in a threatened category.
|Range Description:||Washington to Southwestern Oklahoma (USA), and Baja California, south to Hidalgo and Guerrero (Mexico) (Simmons 2005).|
Native:Mexico; United States (Arizona, California, Colorado, Idaho, Nevada, New Mexico, Oklahoma, Oregon, Texas, Utah, Washington)
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Western pipistrelles begin their foraging flights very early in the evening hours, making them one of the most diurnal of North American bats. They may also be encountered later in the evening (4 hrs after sunset), or closer to the morning. Occasionally, individual bats have been observed on wing during mid-day, during which time they seek out water to alleviate stress caused by the arid environment they inhabit. Because these bats fly slowly, they are restricted to small foraging circuits. They have a very slow, fluttery flight that can often be observed along cliff faces, among pinyon trees, or other desert shrubs. They are often mistaken for large moths (Peters 2003).|
|Habitat and Ecology:||
Western pipistrelles inhabit a variety of habitats, ranging from rocky canyons, cliffs, and outcroppings to creosote bush flats. They are the most abundant of North American bats that are found in deserts, but are found at higher elevations in arid brush lands, grasslands, and even some forests. Western pipistrelles spend their days roosting in rock crevices, beneath rocks, in burrows, mines, and buildings. It has been suggested that western pipistrelles use burrows made by kangaroo rats (Dipodomys spp.) and other rodents (Barbour and Davis, 1969).
Western pipistrelles spend their winter hibernating in mines, caves, and rock crevices. Water is a very important resource determining the distribution of this bat. Because of the high proportion of protein in their diet, the arid environment that they inhabit, and the subsequent high levels of evaporative water loss, western pipistrelles generally roost close to a water source. Availability of maternity roost sites is an extremely important factor in successful bat reproduction (Cockrum and Cross, 1964).
|Major Threat(s):||Since reopening abandoned or inactive mines can negatively affect bat colonies, it has been recommended that multi-seasonal surveys be conducted prior to allowing any renewed mining. Human disturbance can be extremely detrimental to bat colonies, especially to non-volant young and hibernating adults, depending on the season and severity of the disturbance. Mines that are in close proximity to roads, towns, hiking trails or camp grounds are more susceptible to disturbance then those in remote areas with difficult access. There is a need for greater assurance that roosts will remain undisturbed and that future (potential) roost sites will be left when managing for bats in pinyon-juniper habitat. Ideally, management should aim to sustain adequate food, water, and roost sites in close proximity to one another (Klingel, 2000).|
|Conservation Actions:||Avoid habitat loss and human disturbance. Destruction of rocky areas due to renewed mining or other development activities can kill roosting bats and remove roosting habitat.|
|Citation:||Arroyo-Cabrales, J. & Ticul Alvarez Castaneda, S. 2008. Pipistrellus hesperus. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 29 July 2015.|
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