Micronycteris microtis G. S. Miller 1898
Creators: name: Wilson, Don E.
name: Mittermeier, Russell A.
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Chiroptera
Phyllostomidae
Micronycteris
Micronycteris microtis

description: 13. Common Big-eared Bat <i>Micronycteris microtis</i> <b>French:</b> Micronyctére modeste / <b>German:</b> Gewohnliche GroRohrblattnase / <b>Spanish:</b> Micronicterio comun de Miller <b>Taxonomy.</b> Micronycteris microtis G. S. Miller, 1898, “Greytown [= San Juan del Norte],” Rio San Juan, Nicaragua. G. S. Miller in 1898 described the subspecies M. megalotis mexicanus with type locality from Platinar, Jalisco, Mexico, based on its similarity to M. megalotis but with longer wings. Taxonomic revision by K. Andersen in 1906 questioned the species status of M. mucrotis due to vague diagnostic characteristics of the holotype. C. C. Sanborn in 1949 regarded M. microtis as a subspecies of M. megalotis, but C. O. Handley, Jr. in 1976 listed it as a valid species. A. Brosset and P. Charles-Dominique in 1991 corroborated this distinction based on ear length, craniodental differences, and ventral fur variations compared with M. megalotis. Finally, N. B. Simmons in 1996 agreed that these are distinct species based on examination of a larger sample size and also considered that mexicana is actually a subspecies of M. microtis. C. A. Porter and collaborators in 2007 found no support to separate them (again) based on their phylogenetic analysis of genetic sequences, concluding that morphological characteristics used to characterize them might represent intraspecific polymorphism of M. megalotis. Later studies (see previous account) agreed with that suggestion but refrained from making any definitive changes to the taxonomy. Here M. microtis is considered as valid. Two subspecies recognized. <b>Subspecies and Distribution.</b> M.m.microtisG.S.Miller,1898—AtlanticcoastofNicaraguaStoColombia,Venezuela,theGuianas,Brazil,andEBolivia(SantaCruzDepartment);alsoanisolatedrecordfromNWArgentina(SaltaProvince). M. m. mexicana G. S. Miller, 1898 — WC &amp; NE Mexico from Jalisco and Tamaulipas S to the Pacific coast of Costa Rica. <b>Descriptive notes.</b> Head-body 44-48 mm, tail 8:4-17 mm, ear 13-23 mm, hindfoot 8-11 mm, forearm 30-3-37-4 mm; weight 5-5-10 g. All studies before 1990 about the Little Big-eared Bat (M. megalotis) in Central America actually refer to what is now considered the Common Big-eared Bat. Greatest lengths of skulls are 16-4-19-4 mm. Pelage is wood-brown dorsally and a bit paler ventrally. Hairs on anterior part of back have white bases that comprise one-quarter to one-half of their lengths; fur color on posterior part of body can be variable. Pelage pattern of the Common Big-eared Bat is similar to that of the Little Big-eared Bat, exceptthat it differs consistently in length of fur on outside of medial one-third of ear pinna that is shorter (less than or equal to 3 mm) and denser on external basal one-half. The Common Big-eared Bat has large rounded ears, connected by transverse band that extends overhead with shallow notch at middle of upper margin of band. Uropatagium and base oftail are naked. Calcar 1s longer than hindfoot. Skull is small and slender, rostrum is narrow, and braincase is large, swollen, and elevated immediately behind orbits. Mastoid breadth is less than zygomatic breadth. P, is often slightly larger than P, and P,, although there is some intraspecific variation resulting in all three lower premolars being subequal in some individuals. Lower incisors are mostly bifid, although they are trifid in some South American specimens. Chromosomal complement has 2n = 40 and FN = 68. <b>Habitat.</b> Mostly well-drained primary forests, swampy primary forests, semideciduous lowland forests, edges of small forest fragments, pastures, and areas near human settlements. In Argentina, the Common Big-eared Bat was recorded in montane Yungas forests. In Brazil, it is mostly found in Amazonian rainforests in the north and transitional areas between the Cerrado and the Atlantic Forests ecoregions. In general,it has persisted in rather small habitat patches. <b>Food and Feeding.</b> The Common Big-eared Batis a gleaning insectivore (mostly), with an unusually broad diet. Most studies related to the feeding habits have shown that Lepidoptera and Coleoptera are consistently the most frequent orders of arthropods consumed. A detailed study in Panama concluded that the most frequent diet item was Lepidoptera, mostly caterpillars and then nocturnal moths and diurnal butterflies. Coleoptera (predominantly small soft-body beetles from Scarabaeidae) and Orthoptera (Tettigoniidae, Gryllidae, and Acrididae) followed in frequency of occurrence in diets. Cockroaches (Blattidae) and dragonflies (Odonata: Anisoptera) are also common food items. Less than 5% of prey is composed of cicadas (Homoptera, mostly Cicadidae), flies (Diptera, mostly Asilidae), spiders (Arachnida), ants and wasps (Hymenoptera, Apoidea and Formicidae), and stick insects (Phasmidae). Prey items varied in size by at least an order of magnitude. Common Big-eared Bats eat arthropods by repeatedly biting and crushing their heads or cephalothorax before consuming them;then,biting and discarding wings, antennae, and occasionally legs; and finally, consuming thorax and abdomen by repeatedly chewing them with their molars and premolars and rotating prey from one side ofthejaw to the other. In the case of phytophagous and detritivorous insects (caterpillars, beetles, crickets, katydids, phasmids, and cockroaches), abdominal regions are separated and discarded. This behavior probably avoids consumption of the insect’s intestine that contains plant material that is relatively less nutritious, difficult to digest, and might be toxic. Findings revealed that almost 70% of insects consumed are herbivores, which could be higher in wet seasons when herbivorous bugs thrive in response to new leaf production. Feeding habits of most insectivorous bats, such as the Common Big-eared Bat, are probably opportunist, varying with local conditions and abundance of preferred prey. A study on Barro Colorado Island, Panama, recorded for the first ime consumption of small anole lizards by Common Big-eared Bats. Observations revealed that they eat lizards in a similar fashion as they eat arthropods, but legs are also eaten. Analyses of bite forces and cranial morphology of the Common Big-eared Bat showed that it predominantly usesits molars and premolars to process food items and also has an increased ability to modify its bite performance behaviorally. The Common Big-eared Bat has the strongest bite force of any phyllostomids, including frugivores, omnivores, and other insectivores. Behavioral experiments have also demonstrated that it has a unique sensory strategy to locate prey with echolocation alone. It is slow flying, highly maneuverable, and capable of hovering, so it searches for prey up and down understory vegetation to detect silent and motionless insects that are usually found resting on vegetation rather than in flight. Several groups of insects consumed are noisy, especially when calling, so Common Big-eared Bats might be attracted by sounds produced by prey. Itis thought that such plasticity in foraging behavior of the Common Big-eared Bat has allowed its niche to expand, providing access to prey with wider ranges ofsizes and texture, including vertebrates, unique among coexisting phyllostomids. <b>Breeding.</b> The Common Big-eared Bat has a unimodal breeding phenology in its northern distribution, with a single peak in pregnancy in the middle to late dry season, followed by a peak in lactation during early wet season. Males are reproductively active for several months before peak pregnancy, showing descended testes at end of dry and wet seasons. In contrast, bimodal reproduction occurs more commonly in Mesoamerica and South America, with peak pregnancy in late dry season and another during most of wet season, coinciding with explosion of food resources (arthropods). Pregnant females have been found in February—April, June-August, and November throughout their distribution. Lactation records are from May-June, August, and November. In its southernmost distribution, pregnant females were found in September (Argentina) and a pregnant female and a lactating female in November (Bolivia). Males with descended testes have been recorded in June-August in Nicaragua and November, March, and April in Guyana. A behavioral study in Barro Colorado, Panama, found that mothers feed their young solid food for at least five months after weaning. Amount of prey fed by the mother declined over time as young mature and became capable of finding prey alone. This behavior might train young in prey-handling skills. Young recognize their mothers when they return to night roosts and display behaviors such as lifting their heads and orienting their ears toward their returning mothers significantly more often than toward other returning conspecifics. <b>Activity patterns.</b> During hovering flights, Common Big-eared Bats continuously emit broadband 83-4 kHz FM, multiharmonic echolocation calls of 68:6-143-3 kHz. Based on video recording and radio-tracking at a feeding roost in Barro Colorado, Common Big-eared Bats are active throughout the entire night and have no distinctive activity peaks. Nightly activity of individuals from first arrival (mean 16 minutes after sunset) at the feeding roost until last departure (mean 6 minutes before sunrise) encompassed 10-5 hours. Foraging flights lasted 15 seconds to 51 minutes; ¢.50% offlights was shorter than five minutes, 23% was 5—10 minutes, 17-5% was 10-20 minutes, and 10-5% exceeded 20 minutes. Individuals spent an average of 14-1 minutes/hour searching for prey, and six of ten times, they returned to the roost with something to eat. In Bolivia, emergence of Common Big-eared Bats from shelters occurred around local sunset, at 18:10 h on average. On repeated occasions, exits of individuals out of roosts could be observed for 10-15 seconds, in what appeared to be reconnaissance flights. Individuals returned to the roost between 03:40 h and 05:50 h,just before local sunrise. <b>Movements, Home range and Social organization.</b> Flight of the Common Big-eared Bat is not rapid, butit is highly maneuverable. Individuals forage in forest understories searching for prey on vegetation, briefly hovering in front of leaves. When prey is detected, stereotypic flight behavior is characterized by flight covering three-dimensional space in a radius of less than 15 cm in front and around the prey, and then hovering and going downward, moving quickly and repeatedly up and down in front of the target, in what seems to be scanning behavior. The individual then abruptly approaches the insect from a slightly higher position, lands on it, and grabs it. These hunting behaviors show that Common Big-eared Bats can detect, localize, precisely identify, and classify silent and motionless prey in vegetation. A radio-tracking study in Panama revealed average home ranges of c.1-2 ha. Another radio-tracking study in Panama in dry season found an average home range of 3-8 ha, and marked individuals did not cross open areas like lakes. These same studies found foraging areas averaging 2-1 ha; males used only one foraging area, and females used two foraging areas that were ¢. 200 m apart. Mean core area of use only encompassed 0-2 ha. Small area requirements of the Common Big-eared Bat might be explained by its particular foraging behaviors. It has been suggested that it might be less affected by habitat fragmentation because it appears to be less mobile, does not require extensive movement to find prey, and shows high fidelity to roosts. Unlike most other gleaning insectivorous bats, it shows high site fidelity to night roosts where prey is eaten. The Common Big-eared Bat commonly roosts in hollow trees and logs, small caves, crevices of rocky outcrops, buildings, ruins, and houses and under bridges and tunnels. It also uses metal culverts under roads through forested areas, underground drains, and cisterns. In caves, it prefers small, well-lit areas or near entrances of larger and deeper caves. In trees,it prefers to roost low down near the opening. It lives in social groups of 3-10 individuals, rarely exceeding twelve individuals and very rarely 25 individuals. Groups include adults and juveniles of both sexes. Common Big-eared Bats have been found roosting in association with Seba’s Short-tailed Bats (Carolia perspicillata), Tailed Tailless Bats (Anoura caudifer), Pallas’s Long-tongued Bats (Glossophaga soricina), and Common Vampire Bats (Desmodus rotundus). <b>Status and Conservation.</b> Classified as Least Concern on The IUCN Red List. <b>Bibliography.</b> Acosta et al. (2011), Albrecht et al. (2007), Alonso-Mejia &amp; Medellin (1991), Andersen (1906a), Bloedel (1955), Brosset &amp; Charles-Dominique (1991), Dias (2007), Diaz &amp; Barquez (2009), Durant et al. (2013), Geipel, Jung &amp; Kalko (2013), Geipel, Kalko et al. (2013), Goodwin (1946), Handley (1976), Humphrey et al. (1983), Jones, Smith &amp; Turner (1971), Kalka &amp; Kalko (2006), Larsen et al. (2011), Lim, B.K. et al. (1999), Louzada et al. (2015), Miller (1898a), Morales-Martinez (2017), Moras et al. (2015), Porter et al. (2007), Sanborn (1949a), Santana, Geipel et al. (2011), Simmons (1996), Simmons &amp; Voss (1998), Williams &amp; Genoways (2008).
description: Published as part of <i>Don E. Wilson &amp; Russell A. Mittermeier, 2019, Phyllostomidae, pp. 444-583 in Handbook of the Mammals of the World – Volume 9 Bats, Barcelona :Lynx Edicions</i> on pages 494-495, DOI: 10.5281/zenodo.6458594