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Yellowish Myotis

Myotis levis

French: Murin | éger / German: Gelbliches Mausohr / Spanish: Ratonero amarillento

Taxonomy. Vespertilio levis 1. Geoffroy Saint-Hilaire, 1824,

“ Brésil.”

Subgenus Pizonyx; albescens species group. See M. dinellii . Monotypic.

Distribution. Occurs in Atlantic Forest, from SE & S Brazil to NE Argentina and Uruguay.

Descriptive notes. Head-body ¢.38 52 mm, tail 42-48 mm, ear 14-19 mm, forearm 36-2-43.7 mm, hindfoot 8-12 mm; weight 5-10 g. Furis long (dorsal fur 5-9 mm; ventral fur 4-8 mm) and silky. Dorsal hairs are bicolored, with black or dark brown bases (two-thirds the total length) and yellowish brown or medium brown to light grayish brown tips; bases and tips contrast slightly. Ventral hairs are bicolored, with blackish brown bases (two-thirds the total length) and light-yellow, light-brown or grayish-brown tips, going white when approaching uropatagium; bases and tips in ventral fur contrast more than in dorsal fur. Some specimens have a frosted appearance. Ears are comparatively long, extending forward halfway from eye to nostril. Antitragal notch is barely evident. Tragus is long and pointed, slightly curving outward above and convex below, with small triangular lobule at outer base (length 6-10 mm). Membranes are dark brown, and plagiopatagium is broadly attached to foot at base of toes. Fringe of hairs along trailing edge of uropatagium is conspicuous. Skull is medium-sized to large (greatest length of skull 14-3-15- 8 mm); contour of skull in profile has gradual decay of parietal to frontal; posterior region of skull is formed by interparietal and supraoccipital bones, projected beyond posterior border of occipital condyles; rostrum is elongated and has narrow postorbital constriction (3-4—4- 2 mm); sagittal crest is generally absent, but when present,it is very low; lambdoidalcrests are usually present, ranging from low to medium; P? is generally aligned with P* and visible in profile view, but it is displaced to lingual side in a few specimens. Bacula are rather broad and stout; mean measurements were length 0-79 mm, depth 0-35 mm, and width 0-42 mm. Chromosomal complement has 2n = 44 and FN = 50, with three large pairs and one small pair of metacentric and 17 pairs of acrocentric autosomes. Large X-chromosome and small Y-chromosome are submetacentric.

Habitat. Upland rainforests, Araucaria forests, Pampa grasslands, savannas, and scrubsteppe at elevations of 300-1900 m.

Food and Feeding. The Yellowish Myotis forages in open areas and forests and over water, capturing prey in flight. Stomach contents from Brazilian Atlantic Forest contained Lepidoptera, Coleoptera, Hemiptera, and other unidentified arthropods.

Breeding. In Argentina, pregnant Yellowish Myotis were caught in October; lactating females in December—January; males with external testicles in April, June, August and November; and young in January, May, September, and November. In southern Brazil, lactating and post-lactating females were recorded in January. In Uruguay, reproductive activity seems to occur mainly in January-March. These data suggest year-round breeding but with greater concentration in summer. Sex ratio of adults in colony in southern Brazil suggested formation of seasonal multimale-multifemale polygynous group.

Activity patterns. Yellowish Myotis emerge just before sunset. Diurnal roosts include caves, tree hollows, under Eucalyptus (Myrtaceae) bark, and human constructions (e.g. house roofs). Wing morphology and echolocation frequency are typical of aerial insectivore that uses cluttered spaces. Echolocation calls have FM initial component, terminating with short CF component. Mean call parameters are peak frequency of 65-6 kHz, lowest frequency of 46 kHz, highest frequency of 80-8 kHz, bandwidth of 34-8 kHz, call duration of 1-5 milliseconds, and pulse interval of 77-2.

Movements, Home range and Social organization. In Uruguay, Yellowish Myotis form large colonies in caves, some with more than a thousand individuals. A grouping sheltered in the roof of a house in southern Brazil had c.15,000 individuals and was considered a nursery colony due presence of reproductive females, subadults, and young. It can also form small groups, sharing roost with Common Vampire Bats (Desmodus rotundus), Small Big-eared Brown Bat ( Histiotus montanus), and Brazilian Free-tailed Bats (Tadarida brasiliensis). It will move locally, particularly when shelters have marked thermal differences and become unusable.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Yellowish Myotis is widespread and presumably has a large population.

Bibliography. Arias-Aguilar et al. (2018), Barquez & Diaz (2016f), Barquez et al. (1999), Geoffroy Saint-Hilaire 1824), Gonzélez, E.M. (2001), Gonzalez, J.C. (1989), Loépez-Gonzalez et al. (2001), LaVal (1973b), Mares et al. (1995), Miranda, Kaku-Oliveira et al. (2010), Moratelli & Morielle-Versute (2007), Reis et al. (2002), Varela et al. (2004), Wilson (2008b).