391.

Golden Myous

Myotis midastactus

French: Murin midas / German: Goldgelbes Mausohr / Spanish: Ratonero dorado

Other common names: Midas Myotis

Taxonomy. Myotis midastactus Moratelli & Wilson, 2014,

“Cercado, Rio Mamoré, Beni, Bolivia, about 23 km W of San Javier (1434S, 64°B5"W).”

Subgenus Pyzonix; ruber species group. Myotis midastactus was recently described from 28 specimens originally identified as Myotis simus . Monotypic.

Distribution. Known only from Bolivia (Beni and Santa Cruz departments) and Paraguay (Presidente Hayes Departament).

Descriptive notes. Head—body ¢. 50-59 mm, tail 36-41 mm, ear 12-15 mm, hindfoot 8-11 mm, forearm 38-2—40- 7 mm; weight 6-11 g. The Golden Myotis is morphologically similar to the Velvety Myotis ( M. simus) but easily distinctive to other New World Myotis . It differs from all other South American myotine bats (except the Velvety Myotis) by having plagiopatagium attached at toes by narrow band of membrane (less than 1-5 mm). Pelage is woolly, extremely short (less than 5 mm), and bright golden yellow. Bolivian samples are ocherous orange dorsally, with slightly paler venter. A few specimens are slightly paler, with mixed blocks of grayish and golden fur. Ears are short, extending forward halfway from eye to nostril. Antitragal notch is barely evident; tragus is pointed, slightly curving outward above and convex below, with small triangular lobule at outer base. Ears and membranes are blackish. Skull is moderately long (greatest skull lengths 13-9-15- 1 mm), and occipital region is flattened. Sagittal and occipital crests are present and vary from low to moderately high. C' is large in length and basal cross section, and there is short distance between C' and P*, resulting in P* and P* being close or in actual contact, displacing P? lingually so that P? is usually not visible in labially. Chromosomal complement has 2n = 44 and FN = 50, with three large and one small metacentric and 17 medium to small acrocentric pairs of autosomes. X-chromosome is medium submetacentric, and Y-chromosome is small acrocentric.

Habitat. Semideciduous forest (Cerrado ecoregion, Bolivia) and savanna (Chaco ecoregion, Paraguay) at elevations of ¢. 150-250 m.

Food and Feeding. The Golden Myotis is an aerial insectivore. Its diet contains Orthoptera (Gryllidae), Hemiptera (Corixidae), Hemiptera ( Cicadellidae, Delphacidae), Coleoptera ( Carabidae, Dytiscidae, Staphylinidae, Scarabaeidae, Curculionidae), Lepidoptera (at least three families), and Diptera (Nematocera) . Nine of ten prey items in stomachs were less than 10 mm long. Dietary items indicate that it forages in forest interiors and near water bodies.

Breeding. Ten pregnant Golden Myotis, each with one embryo, were caught in September in Bolivia, and four pregnant females were caught in October in Paraguay.

Activity patterns. The Golden Myotis emerges just before sunset. It roosts in hollow trees and holes in the ground and under thatched roofs in Bolivia.

Movements, Home range and Social organization. The Golden Myotis roosts with the Argentine Serotine (Eptesicusfurinalis), the Lesser Bulldog Bat ( Noctilio albiventris), and Pallas’s Mastiff Bat (Molossus molossus). Golden Myotis and Lesser Bulldog Bats habiting the same roost had similarly colored fur, texture, and smell. Data from these roosts suggest that Golden Myotis are solitary or form very small groups.

Status and Conservation. Not assessed on The IUCN Red List.

Bibliography. Aguirre (1994), Aguirre, Lens & Matthysen (2003), Anderson (1997), Espinoza (2007), Moratelli & Wilson (2014a), Moratelli, Idarraga & Wilson (2015), Tarifa & Aguirre (2009).