417.

Common Black Myotis

Myotis nigricans

French: Murin noiratre / German: Schwarzes Mausohr / Spanish: Ratonero hollinoso

Taxonomy. Vespertilio nigricans Schinz, 1821,

“Ostkiiste von Brasilien [= east coast of Brazil].” Based on neotype selection, restricted by R. K. LaVal in 1973 to “ 42 km S Rio de Janeiro [Seropédica Municipality, Rio de Janeiro State], Brazil.”

Subgenus Pizonyx; albescens species group. Based on morphology and molecular data, M. nigricans is a complex of undescribed cryptic species. Recent taxonomic revisions of population samples previously identified as M. nigricans have resulted in new species (e.g. M. lavali, M. clydejonesi, M. attenboroughi, M. handleyi, and M. diminutus) and raising subspecies to species level (e.g. M. caucensis). Nevertheless, thorough taxonomic revision of all populations currently referred to as M. nigricans is needed. Four subspecies recognized.

Subspecies and Distribution. M.n.nigricansSchinz,1821—SouthAmericaNof¢.26°S,includingTrinidadandTobagoIs.

M.n.carteriLaVal,1973—PacificcoastofMexico,fromNayaritandMichoacantoBalsasBasininSMexicoState.

M. n. extremus G. S. Miller & G. M. Allen, 1928 — Gulf coast of Mexico from S Tamaulipas S through Central America to Panama.

M. n. osculatii Cornalia, 1849 — throughout the Andes from c. 5° N to c. 15° S.

Descriptive notes. Head-body ¢. 39-52 mm, tail 28-39 mm, ear 10-14 mm, hindfoot 6-9 mm, forearm 31-2-36- 5 mm; weight 3-7 g. Fur is silky and moderately long (dorsal fur 6-9 mm; ventral fur 5—7 mm). Dorsal hairs are bicolored, with black bases (two-thirds the length) and blackish brown to medium brown tips (one-third). In some darker specimens, dorsal hairs are nearly unicolored. Ventral hairs are bicolored, with black bases and yellowish brown to ocherous buff tips. Ears are comparatively short (length), extending forward halfway from eye to nostril. Tragus is long and slender, tapering slightly at tip. Membranes are mummy brown or blackish. Plagiopatagium is attached to feet by a broad band of membrane;fringe of hairs along trailing edge of uropatagium is absent. Skull is medium-sized (greatest length of skull 12- 8-15 mm). Generally, parietals slope forward in lateral view, and occipital usually projects well behind posterior limit of occipital condyles; sagittal is normally absent, but if present,it is always low. P* usually is aligned in tooth row and visible in labial view, but in some individuals,it is displaced lingually and not clearly visible labially. Bacular sizes and proportions are extremely variable among localities; in Mexico, Central America, and South America, respectively, mean lengths are 0-67 mm, 0-68 mm, and 0-69 mm; mean depths are 0-28 mm, 0-27 mm, and 0-3 mm; and mean widths are 0-36 mm, 0-32 mm, and 0-31 mm. Chromosomal complement has 2n = 44 and FN = 50, with three large pairs and one small pair of metacentric and 17 pairs of medium to minute acrocentric autosomes. X-chromosome is medium submetacentric, and Y-chromosome is small submetacentric.

Habitat. Virtually every tropical and subtropical forest formation, savannas, wetlands, scrublands, agricultural landscapes, and peri-urban areas from sea level up to elevations of ¢. 2500 m (more common below 1000 m).

Food and Feeding. The Common Black Myotis is forages in forests and forest edges and over water. It catches insects in flight, and usually forages near the surface of water or a few meters aboveground. Its diet includes various insects, especially Lepidoptera, Coleoptera, and Diptera, and other arthropods such as spiders. Small seeds were found in feces of an individual from Brazilian Atlantic Forest. Plant remains were also found in the stomach of a specimen from Costa Rica. These observations suggest that the Common Black Myotis might be the only species of Myotis that eats plant parts, but rarity of these reports might suggest that plant consumption is incidental.

Breeding. In tropical climates, the Common Black Myotis seems to be polyestrous. Observations from Barro Colorado Island, Panama, show that mating and implantation occur in late December and earlyJanuary. Gestation lasts c.60 days, and first parturition peak occurs in February. Parturition is followed by postpartum estrus and repeat of the reproductive cycle resulting in second birth peak in April-May and third in August. After third birth peak, reproductive activity declines until late December when the new annual cycle begins. First birth peak results in a maximum number of young that are weaned in April, coinciding with onset of rainy season and increased insect availability. Decrease in reproductive activity from August seems to be correlated with seasonal insect supply, such that no young are weaned during dry season when insects are relatively scarce. Spermatogenic cycle of males is in synchrony with female cycle. Spermatogenesis slows or stops in September—-November, and no sperm storage occurs. Common Black Myotis from Mexico have a pattern of reproduction more similar to that of species in temperate zones, with one annual reproductive peak. Females give birth to one young that remain attached to them for the three first days oflife; then they are left in large nursery groups when mothers leave to feed at night. Males become reproductively active at 15-17 weeks old, and females can mate when they are ¢.8 weeks old.

Activity patterns. Common Black Myotis often emerge from diurnal roosts before sunset. Activity peaks occur immediately after dusk and just before dawn, periods that correspond to periods of greatest abundance of flying diurnal and nocturnal insects. In Brazilian Atlantic Forest, individuals returned to roosts ¢.b hours after sunset and leave again to forage c.1 hour before dawn. Roosts include hollow trees, under foliage, caves, rock crevices, buildings (e.g. roofs), bridges, and mines.

Movements, Home range and Social organization. On Barro Colorado Island, Panama, some Common Black Myotis could return to the roost from distances of up to 50 km. Common Black Myotis are colonial and form groups of hundreds of individuals. Small to large clusters of females, young of both sexes, and few adult males suggest a social hierarchy such as harem formation. Most of males in roosts are solitary. Common Black Myotis usually share roosts with other bat species, such as Pallas’s Mastiff Bat (Molossus molossus) and the Greater Spear-nosed Bat (Phyllostomus hastatus).

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

Bibliography. Bogan (1978), Larsen, Knapp et al. (2012), LaVal (1973b), Lopez-Gonzélez et al. (2001), Moratelli & Morielle-Versute (2007), Moratelli & Wilson (2011), Moratelli, Gardner et al. (2013), Moratelli, Peracchi et al. (2011), Moratelli, Wilson, Gardner et al. (2016), Moratelli, Wilson, Novaes et al. (2017), Novaes et al. (2015), Solari (2019j), Wied-Neuwied (1826), Wilson (1971, 2008b, 2014b), Wilson & LaVal (1974).