Bats use caves for one reason — shelter. However, shelter provided by caves can serve many different purposes. Bats seek shelter in caves to establish maternity roosts, bachelor roosts, night roosts and hibernacula. Maternity, or nursery, roosts are where females congregate to give birth and raise their pups. Some maternity 

roosts may support millions of bats (Above: a large Mexican free-tailed bat maternity roost, western New Mexico; right: a Townsend's big-earted bat maternity roost, south rim Grand Canyon). A visitor to a cave can usually distinguish a maternity roost based upon how the bats are tightly clustered together. Another obvious way to tell a nursery roost is by the presence of small hairless, pink pups. However, if you encounter a maternity roost, please leave the cave immediately. Your presence may cause harm to the bat pups. Refer to Threats page for more information.

Bachelor roosts generally contain only male bats. These roosts generally form after the breeding season. Males tend to roost in a more diffuse pattern across the cave walls and ceiling. Night roosts may be used throughout the night by different bats. Individuals will go to certain caves to either eat their captured prey or to rest between foraging outings. Hibernacula roosts contain hibernating bats. These roosts are occupied during the colder winter months.

Bats can be vitally important for cave ecosystems — especially large roosts. Cave ecosystems rely almost entirely on the surface for nutrients. As a result, bats deposit considerable amounts of surface nutrients into caves via guano (or poop). Because of this, the presence of bats may support an entire ecosystem. Consequently, cave-roosting bats are often considered keystone species. If bats abandon a cave, for what ever reason, this may cause significant damage to the ecosystem.

Eighteen bat species are known to regularly use caves in the American Southwest (Table 1 below). Arizona is home to all cave-roosting bats occurring in the southwest; New Mexico supports 14 of these species. Colorado has 13 species, while Utah and Nevada support 11 and 12 species, respectively.

These bat species serve various ecological roles. Two of them are pollinators and seed dispersers. The lesser long-nosed bat (Leptonycteris yerbabuenae) and Mexican Long-Tongued Bat (Choeronycteris mexicana) both feed on the nectar and fruit of saguaro cacti and agave. These bats are also considered important pollinators of these plants and also assist in seed dispersal. They are migratory species, spending the summer months in southeastern Arizona and southwestern New Mexico and the winter months in southern Mexico. In general, nectar-feeding bat roosts are characterized by slick floors covered with a yellowish, sweet-odored, semi-liquid droppings.

Long-eared Myotis in cave Grand canyon North Rim, AZ - Courtesy Kyle Voyles / NPS

All other cave-roosting bat species are insectivorous. The pallid bat (Antrozous pallidus) is the kamikaze hunter of southwestern bats. Often times, bat scientists will note their wings are riddled with holes and tears. They believe this is due to the manner in which they crash through brush to capture their prey. Among other ground-dwelling arthropods, pallid bats hunt scorpions and centipedes. Another species that frequently captures prey on the ground (but also hunts within the foliage) is the California leaf-nosed bat (Macrotus californicus). This bat tends to hunt non-venomous arthropods including crickets, grasshoppers, and beetles.

Fringed Myotis in researcher's hand captured at cave entrance, Grand Canyon-Parashant National Monument, AZ - Courtesy Kyle Voyles / NPS

Seven Myotis bats call the American Southwest home. These are the long-eared myotis (Myotis evotis), western small-footed myotis (M. ciliolabrum), little brown myotis (M. lucifugus), long-legged myotis (Myotis volans), fringed Myotis (M. thysanodes), cave myotis (M. velifer), and Yuma myotis (M. yumanensis). Also, the western pipistrelle (Parastrellus hesperus) is known to use caves throughout the southwestern U.S. These bats are open-air foragers and prey upon tiny flying arthropods. Many of these species prey upon mosquitoes, which are not only an insect pest to humans, but also vectors for disease.

Other insectivorous cave-dwelling bats including the Mexican free-tailed bat (Tadarida brasiliensis) and big brown bat (Eptesicus fuscus) consume many agricultural pests. These bat species have been documented to forage on boll weevils, cucumber beetles (i.e., corn rootworms), leafhoppers, and corn earworm moths.

Bat Cave Use by State

Myotis sp. hibernating in cave, Cathedral Caves Preserve, AZ

Arizona — At Kartchner Caverns State Park in southern Arizona, nine bat species were captured in mist nets on the surface near the entrance. Of these, the cave myotis, Townsend's big-eared bat, and Mexican long-tongued bat were documented within the cave. Kartchner Caverns is predominantly used by the cave myotis as a maternity roost, and supports between one to two thousand bats. Because this is an important roost for this species, the Park closes the cave to tours during the spring and summer.  In Grand Canyon-Pararshant National Monument, four presumed maternity roosts have been identified.  These include two pallid bat, one fringed myotis (Above: one in hand after being identified, south rim Grand Canyon) and one unidentified myotis maternity colonies.  Also, two hibernacula have been confirmed on this monument, which consist primiarly of Townsend's big-eared bats (Left: a cluster of hibernating Townsend's big-eared bats, south rim Grand Canyon).

The endangered lesser long-nosed bat feeds almost exclusively on the pollen, nectar and fruit of columnar cacti (e.g., saguaro) and agave. Roosts are often located at proximity to these plants. This species resides in the state from late-April/ early May through late-September/ early October. Roosts are described as large multiple-roomed caves, but this species also uses lava tubes, mine tunnels and even abandoned buildings. This bat is highly gregarious forming large colonies ranging from several thousand to over 100,000 individuals.

This species is one of two long-distance cave-roosting migrants that spend the summer months in Arizona and New Mexico. This species arrives in Arizona in mid to early spring, and feeds on columnar cacti through late-July to early-August. Females often arrive gravid and rear their young in southeastern most Arizona. Once the young are weaned, these roosts begin to disband (between July and August), but some may remain until October. Although males are also known to roost with females and young, bachelor roosts have been identified in Chiricahua Mountains.

The Mexican long-tongued bat also occurs in Arizona. This species roosts in caves and abandoned mines, as well as rock fissures and rock shelters. It is often found roosting within the twilight zone of caves. This species feeds on the nectar and pollen from agave, yucca, cacti and other desert plants. It is also known to occasionally use hummingbird feeders in southeastern Arizona.

In Grand Canyon National Park, the Mexican free-tailed bat has been identified using one cave as a maternity roost. Townsend's big-eared bat has been identified using at least two caves. This does not imply these bats are rare in the Grand Canyon, rather this is a result of limited studies conducted on cave-roosting bats there.

New Mexico — Carlsbad Caverns supports a maternity roost of approximately one million Mexican free-tailed bats. However, roost counts conducted during the mid-1930s estimated the population at approximately nine million individuals. In central New Mexico, about 100 km northeast of Capitan, several species of bats were documented hibernating in a large dolomite and gypsum cave. This hibernacula consisted primarily of the cave myotis, Townsend's big-eared bat and western small-footed myotis.

Lesser-long nosed bats occur in southwestern New Mexico. It arrives in mid to late July season once the availability of saguaro fruit in southeastern Arizona has dwindled. At which time, this bat shifts to agave pollen, nectar and fruit. It feeds on this plant until late September-early October, and then it migrates south to Mexico. This bat is known to roost in caves on the New Mexican “sky islands” (including the Animas and Peloncillo Mountains) at proximity to the agave bloom.

The Mexican long-tongued bat is also known to roost in caves in Animas and Peloncillo Mountains, Hidalgo County, New Mexico.

Colorado — From a study conducted by the Colorado Division of Wildlife in 2002, 19 of 99 caves surveyed contained roosting bats. Species identified roosting in caves included Townsend's big-eared bat, big brown bat, silver-haired bat, western small-footed myotis, long-eared myotis, little brown myotis, long-legged myotis and Yuma myotis.

Utah — A study in northern Utah revealed 33 of 39 caves surveyed were used by Townsend's big-eared bats. Of these caves, there were eight maternity roosts, 29 hibernacula, and 25 bachelor roosts.

Nevada — In eastern Nevada, Townsend's big-eared bats and pallid bats were identified as requiring cliff sites, natural caves, and mine shafts for maternity, day roosts and hibernacula. Townsend's big-eared bats were also identified using caves in the Inyo Mountains, Esmeralda County along the California border. Also, in the Inyo Mountains, spotted bats (Euderma maculatum) were documented roosting in lava tube caves.

This is a brief overview of cave roosting bats in the Southwest. This page will be revised as more information on cave-roosting bats becomes available. If you have information to contribute on this topic, please contact us.

Table 1. Cave-roosting bat occurrence by state. Species profile information is provided by Bat Conservation International and predicted distribution maps of each species were developed by the USGS Southwest Regional Gap Program (SWReGAP). See http://fws-nmcfwru.nmsu.edu/swregap/habitatreview/RangeCoding.htm for distributional range codes. For more information on SWReGAP, see http://fws-nmcfwru.nmsu.edu/swregap/

Common Name Species Name AZ CO NM UT NV Profile Info SW Distribution Map
California leaf-nose bat Macrotus californicus *       * Profile Distribution Map
Lesser long-nosed bat Leptonycteris yerbabuenae *   *     Profile Distribution Map
Mexican Long-Tongued Bag Choeronycteris mexicana *   *     Profile Distribution Map
Pallid bat Antrozous pallidus * * * * * Profile Distribution Map
Townsend'sbig-eared bat Corynorhinus townsendii * * * * * Profile Distribution Map
Spotted bat Euderma maculatum * * * * * Profile Distribution Map
Big brown bat Eptesicus fuscus * * * * * Profile Distribution Map
Allen's big-eared bat Idionycteris phyllotis *   * * * Profile Distribution Map
Silver-haired bat Lasionycteris noctivagans   *       Profile Distribution Map
Long-eared myotis Myotis evotis   *       Profile Distribution Map
Western small-footed myotis Myotis ciliolabrum * * * * * Profile Distribution Map
Little brown myotis Myotis lucifugus * * * * * Profile Distribution Map
Long-legged myotis Myotis volans   *       Profile Distribution Map
Fringed myotis Myotis thysanodes * * * * * Profile Distribution Map
Cave myotis Myotis velifer *   *     Profile Distrubtion Map
Yuma myotis Myotis yumanensis * * * * * Profile Distribution Map
Western pipstrelle Parastrellus hesperus * * * * * Profile Distribution Map
Mexican free-tailed bat Tadarida brasiliensis * * * * * Profile Distribution Map