247.

Mexican Big-eared Bat

Corynorhinus mexicanus

French: Oreillard du Mexique / German: Mexikanisches Langohr / Spanish: Orejudo de México

Taxonomy. Corynorhinus megalotis mexicanus G. M. Allen, 1916,

“ Mexico: Chihuahua, near Pacheco.”

Originally described as a race of C. megalotis [= rafinesquit], but morphological data supportits separation as a distinct species. Monotypic.

Distribution. Mexico, from Sonora and Chihuahua S along Sierra Madre Occidental and Sierra Madre del Sur, and from Coahuila S along Sierra Madre Oriental to Veracruz; isolated records from Yucatan Pemnsula and Cozumel 1, but these are uncertain.

Descriptive notes. Head-body c¢. 49- 52 mm, tail 41-51 mm, ear 29-36 mm, hindfoot 9-13 mm, forearm 39-3- 45- 2 mm; weight 5-12 g. Males larger than females. Furis long; dorsal hairs bicolored, with blackish bases and tips ranging from dark brown to cinnamon brown, without marked contrast between bases and tips (hairs at posterior base of large pinnae paler than on rest of dorsum); ventral hairs bicolored, with strongly contrasting dark brown bases and grayish or pale brown tips. Ears large and joined basally across forehead; tragus long (11-15 mm). Two large glandular lumps are present on dorsal surface of rostrum; external nares, viewed from above, relatively small and angular in posterior outline; nostrils elongated posteriorly; accessory basal lobe of auricle is absent. Ears, face, and membranes dark brown. Plagiopatagium broadly attached to foot at level of base of toes. Skull moderate in size (greatest skull length 14-7-15- 9 mm); deep wide braincase slopes upward abruptly above short depressed rostrum; lacrimal region smoothly rounded; supraorbital region not ridged; temporal ridges normally coalesced to form sagittal crest; median post-palatal process ranges from styliform to triangular; auditory bullae are relatively small. Maxillary tooth row relatively shorter, weaker, and more depressed, and P? is more consistently bilobed. Chromosomal complement has 2n = 32 and FN = 52, with nine metacentric pairs of chromosomes, one submetacentric pair, and the other six acrocentric pairs, including the sex chromosomes.

Habitat. Higher and more humid parts of Sierra Madre and the transverse volcanic belt of central Mexico, at 1460-3200 m. Found from dry lowlands to highland pineoak forest.

Food and Feeding. Probably eats small flying insects, such as Lepidoptera and Diptera .

Breeding. Copulation begins in late October and runs through January. Pregnant and lactating females inJanuary-April. Gestation lasts ¢.90 days; females give birth to single young. Females reach sexual maturity at about one year, males at two years old.

Activity patterns. Nocturnal, with emergence from roost after sunset. The species roosts in caves, basaltic lava tubes, mine tunnels, and abandoned houses. Wing morphology and echolocation frequency are typical of gleaning insectivorous bats. Call parameters (mean) are: minimum frequency 21-9 kHz, maximum frequency 44-6 kHz, peak frequency 30-9 kHz, bandwidth 21-4 kHz, and call duration 3-4 milliseconds.

Movements, Home range and Social organization. No long-distance movements. In roosts, individuals hang well apart from one another. Numbers present in caves may vary throughoutthe year, and hibernating groups have been found in deep caves. Most southern and lowland records were obtained in winter and may indicate seasonal migrations from cold, highland regions. Females form maternity colonies in the breeding season, while males form small groups. Colony size varies from a few individuals during summer to over 500 in winter. Sometimes roosts with other bat species, including the Common Vampire Bat (Desmodus rotundus), the Cave Myotis ( Myotis velifer), and the Tricolored Bat ( Perimyotis subflavus).

Status and Conservation. Classified as Near Threatened on The IUCN Red List. Even though it is widespread with an expected sizeable population, and occurs in a number of protected areas,its population is thought to be declining; the species may qualify for listing as threatened in the near future.

Bibliography. Barbour & Davis (1969), Bogdanowicz et al. (1998), Hall (1981), Handley (1955b, 1959), Lépez-Wilchis (2001), Lépez-Wilchis et al. (1995), Piaggio & Perkins (2005), Reid (2009), Simmons (2005), Tumlison (1992), Wilson & Ruff (1999).