382.

Flat-headed Myotis

Myotis planiceps

French: Murin a téte plate / German: Flachkopf-Mausohr / Spanish: Ratonero de cabeza plana

Taxonomy. Myotis planiceps R. H. Baker, 1955,

“ 7 mi. [= 11 km] Sand 4 mi. [= 6 km] E Bella Unién, 7200 fi. [= 2195 m], Coahuila,” Mexico.

Subgenus Pyzonix; lucifugus species group. Monotypic.

Distribution. Endemic to Mexico, restricted to a very small area in Coahuila, Nuevo Ledn, and Zacatecas.

Descriptive notes. Head-body ¢.30 51 mm, tail 21-25 mm, ear ¢. 10 mm, hindfoot 7-8 mm, forearm 26-5-27- 5 mm; weight 5-7 g. The Flat-headed Myotis is morphologically distinct from its New World congeners. Fur is long and silky. Dorsal hairs are 8-10 mm, with blackish bases and cinnamon-brown tips. Ventral hairs are bicolored, with dark brown bases and buff tips and strong contrast between bases and tips. Ears are proportionally long, extending forward halfway from eye to nostril. Membranes are dark brown; plagiopatagium is broadly attached to foot at bases of toes. Upper and lower surfaces of uropatagium are barely covered with hairs. Skull is moderate in size (greatest skull lengths 13-5-14- 5 mm) and flattened, more than in any other New World Myotis, sagittal crest is absent, and lambdoidal crests are present but very low; and rostrum narrows anteriorly. Teeth are small relative to palatal surface; occlusal surfaces of premolars are subequal in size, not crowded, and well-spaced; and P* and P* are very similar.

Habitat. Coniferous and mixed forests in the northern parts of Sierra Madre Oriental and surrounding habitats, at elevations of 1000-3200 m.

Food and Feeding. Limited captures suggest that the Flat-headed Myotis is an aerial insectivore that forages in forested areas and near water bodies. Stomach contents of one specimen had dipterans ( Tachinidae and Therevidae) and fragments of some lepidopteran.

Breeding. A male Flat-headed Myotis with scrotal testes was captured in mid-September. Seven females appeared to be lactating with no embryos when captured in June.

Activity patterns. The flattened skull of the Flat-headed Myotis is possibly an adaptation for roosting in crevices. Echolocation calls of indoor flying individuals were short (2-3 milliseconds), broadband (40-45 kHz), and steep FM. They swept from 80-90 kHz at the beginning of the call to 40-42 kHz at the end. Pulse interval was ¢.60-70 milliseconds. In open space, terminal frequency tended to decrease slightly (c.1 kHz); call duration and pulse interval increased from 2-3 milliseconds to 4 milliseconds and from ¢.60-70 milliseconds to 90 milliseconds, respectively, compared with indoor recordings. Bandwidth was similar (40-45 kHz).

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Endangered on The IUCN Red List. The Flatheaded Myotis has an extremely restricted distribution, there are less than 250 mature individuals, and the population is probably declining because of wood exploitation and other disturbances in land use. Discovery of a new population near the known distribution in 2005 indicates it is not extinct, as it was once supposed to be.

Bibliography. Arroyo-Cabrales & Ospina-Garces (2016d), Arroyo-Cabrales etal. (2005), Baker (1955), Jimenez-Guzman (1968, 2014), Matson (1975).