The Mexican long-tongued bat (Choeronycteris mexicana, CHME) is a nectarivorous bat that occurs in southernmost portions of the American southwest (California to Texas) extending south throughout large portions of Central America. Individuals range in size from 81 to 103 mm and weigh from 10 to 25 g. CHME tend to roost in small colonies (< 10 bats) and individuals do not cluster tightly while roosting. Most documented roosts in southeast Arizona occur near water and riparian vegetation located more broadly within desert grassland or Madrean evergreen woodland plant communities. Females and males roost separately, and evidence suggests that only the females migrate north into southern Arizona and southwestern New Mexico to form maternity colonies, while adult males do not range into the United States. Consequently, most roosts documented being used by this species in Pima County between May and July are likely to be maternity roosts. CHME will often roost within portions of mines or caves where there is some penetration of light either because the feature itself is shallow, or due to roosting closer to the entrance of a mine or cave. CHME is considered a species of concern by Bureau of Land Management and the U.S. Forest Service.
This species produces a single pup between June to July, and in southern Arizona typically migrates south into Mexico between October and November, returning in early May, following the flowering cycles of their preferred food sources, agave, yucca, and columnar cacti. In eastern Pima County, the majority of pollen in bat guano samples collected between May and early September was from saguaro cactus and Schott’s agave, while October samples yielded primarily Palmer’s agave pollen. This work also documented pollen from Mexican bird-of-paradise and century plant in CHME guano, both common landscape plants in the Tucson area.. A population study in the foothills of the Rincon Mountains indicated that no CHME were noted in any of the monitored roosts later than November 13.
CHME readily feeds from hummingbird feeders, and the Arizona Game and Fish Department conduct citizen science-based monitoring of this species and the lesser long-nosed bat by recording the seasonal timing of hummingbird feeder use in both species (https://www.azgfd.com/wildlife/backyard-bats/). CHME have been found in roost sites located on County open space lands in the Santa Catalina Mountains, Rincon Mountains, and Cienega Valley.
Pima County’s bat monitoring objective is to monitor the occupancy, site condition, and associated management needs of a subset of roosts used by the Mexican long-tongued, Lesser long-nosed, California leaf-nosed, and Pale Townsend’s big-eared bats on Pima County open space lands. Monitored roosts will be those roosts that have particular importance to the local population of these four bat species. The County will also work towards documenting all of the known roosts sites for these species that are located on County lands, though not all will be chosen for additional monitoring efforts. Where possible and relevant, results from these inventory and monitoring efforts will be used to guide the management (i.e., gating) and/or restoration of key features that will benefit these and other bat species.
