380.

Arizona Myotis

Myotis occultus

French: Murin de Hollister / German: Arizona-Mausohr / Spanish: Ratonero de Arizona

Taxonomy. Myotis occultus Hollister, 1909,

“west side of Colorado River ten miles [= 16 km] above Needles, California,” USA.

Subgenus Pyzonix; lucifugus species group. See M. evotis . Myotis occultus was considered a subspecies of M. lucifugus, but morphology and molecular data support it as a distinct species. Monotypic.

Distribution. SE California, Arizona, S Colorado, New Mexico, and perhaps S Utah and W Texas; distributional limits in NC Mexico are uncertain, considering it has been recorded only in several localities in Chihuahua and a disjunct site near Texcoco, in the Distrito Federal.

Descriptive notes. Head-body 41-54 mm, tail 29-41 mm, ear 10-13 mm, hindfoot 7-11 mm, forearm 36-41- 8 mm; weight 7-9 g. The Arizona Myotis is morphologically similar to the Little Brown Myotis ( M. lucifugus), but distinguished by cranial features. Fur is long and silky. Dorsal hairs are bicolored, with blackish bases and prout’s brown to golden yellow tips and strong contrast between bases and tips. Ventral hairs are bicolored, with dark brown bases and pale yellow to whitish graytips. Ears are mediumsized, extending forward halfway from eye to nostril. Tragus is ¢.6- 5 mm long, with indented edges. Membranes, ears, and skin 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 large in size (greatest skull lengths 14-1-16- 4 mm); sagittal crest is well developed. There is only one premolar behind C! in most specimens; other Myotis species usually have two.Its teeth are larger than in most Myotis; maxillary tooth row is usually greater than 5- 5 mm.

Habitat. Variety temperate deserts and woodlands (e.g. ponderosa pine, Pinus ponderosa, Pinaceae and oak-pine forests), often near water without respect to vegetation type and most commonly pine forests at elevations 2000-3000 m.

Food and Feeding. Arizona Myotis forage in lower strata, such as over water bodies and orchards and under tree canopies. They detect prey at very short distances and are able to capture prey in rapid succession—up to 600 mosquitoes/hour. Diet consists of soft- and hard-bodied arthropods (e.g. coleopterans, dipterans, hymenopterans, hemipterans, lepidopterans, neuropterans, and arachnids). In New Mexico, it consumes mainly wasps, mosquitoes, and other soft-bodied insects. Diets in Colorado mainly contained hard-bodied insects (e.g. coleopterans). Lactating females eat larger prey than non-reproductive females and males.

Breeding. Breeding of Arizona Myotis occurs in autumn when there is more movement than usual and swarming occurs hibernacula and outside caves. Mating is polygynandrous. Females store sperm until spring. Gestation averages 50-60 days; young are usually born in June-August. Neonates barely have fur weighing 1-8 g and are completely furred when 6- 6 g and nearly readyto fly. Generally, only one young is born per pregnancy, with few records of twins. At c.21 days old, young are weaned, and at 30 days old, they can fly and feed by themselves. Females reach sexual maturity in their first year and can breed; males reach sexual maturity in their second year.

Activity patterns. Arizona Myotis generally emerging from roosts at dusk, with peak activity in the first two hours after dusk and before dawn. Arizona Myotis have separate roosts for day, night, hibernation, and maternity activities. Most day roosts are in buildings and hollow trees or under rocks or wood. Night roosts can be very similar to day roosts, perhaps even the same site, but are usually in more confined spaces and include bridges. Winter roosts include caves and abandoned buildings. Maternity roosts are periodically changed and are in hollow trees, buildings, house roofs, caves, mines, tunnels, crevices in bridges, and snags. Maternity roosts are warmer than regular roosts. Wing morphology and echolocation frequency are typical of aerial insectivorous bats. Echolocation calls have strongly FM initial component, terminating with short CF component. Arizona Myotis are part of the Myotis 40 kHz call group, which is characterized by frequencies of calls of 35-60 kHz. Mean call parameters are bandwidth of 45-3 kHz, characteristic frequency of 34-9 kHz, dominant slope of 14-1 kHz, maximum frequency of 81-7 kHz, minimum frequency of 33-7 kHz, peak frequency of 46 kHz, total slope of 16-6 kHz, and duration of 3 milliseconds.

Movements, Home range and Social organization. Arizona Myotis moves up to several kilometers between day roosts and feeding sites daily. There is no evidence ofterritoriality. Hibernation begins in September—-November and ends in March—-May. Young remain active later into autumn to build up fat reserves for hibernation. They can enter torpor daily outside of hibernating season. Aggregations of Arizona Myotis can have up to 300,000 individuals. In summer, females and males live separately, with maternity colonies of up to 800 females. A colony with ¢.2000 bats in horizontal timbers of a large bridge in the Lower Colorado River Valley contained Arizona Myotis (40% of total), Yuma Myotis (M. yumanensis), and Brazilian Free-tailed Bats (1adarida brasiliensis). Brazilian Free-tailed Bats roosted by themselves, and the two species roosted together.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Arizona Myotis is widespread, occurs in several protected areas, and is unlikely to be declining at nearly the rate to qualify forlisting in a threatened category.

Bibliography. Barbour & Davis (1969), Diamond et al. (2015), Geluso & Mink (2009), Harvey et al. (2011), Hayward (1963), Jenkins (2017), Ortega & Arita (2014b), Piaggio et al. (2002), Solari (20180), Stager (1943), Valdez & Bogan (2009), Valdez et al. (1999).