Ecological Correlates of Roost Fidelity in the Tent-Making Bat Artibeus watsoni

Dinámica poblacional y fidelidad de refugio de Carollia brevicauda (Quiroptera: Phyllostomidae) en un refugio artificial, en los Andes nororientales de Colombia

Los refugios imponen presiones selectivas a los murciélagos. Los refugios proporcionan sitios de apareamiento, hibernación y crianza; promueven interacciones sociales, digestión de alimentos; y ofrecen protección contra el clima adverso y los depredadores. Por ende, tienen un papel importante en la ecología y evolución de estos mamíferos. En este trabajo se estudió la dinámica poblacional y fidelidad del murciélago Carollia brevicauda en un refugio artificial a lo largo de un año. Capturamos murciélagos con una trampa-arpa entre las 18:00 y 00:00 horas, con un esfuerzo de muestreo de 120 horastrampa y un total de 91 individuos marcados. Los resultados mostraron que la colonia permaneció con un número de individuos poco variable (15 ± 5) a lo largo del periodo de muestreo. La mayor fidelidad de las hembras (1.25 ± 0.17) en comparación con los machos (0.85 ± 0.12) sugiere que este refugio es usado como sitio de crianza. Análisis con el método de captura-recaptura, según el modelo de Cormack-Jolly-Seber, indican que la población es de 260 individuos. La tasa de recaptura fue baja indicando una alta movilidad de los individuos, que puede estar asociada a un comportamiento social fisión-fusión de grupo. Los datos sugieren que las hembras sincronizan la gestación para dar a luz en la época de lluvias cuando hay mayor disponibilidad de recursos alimenticios y que las construcciones humanas al tener características de refugios permanentes, ofrecen condiciones propicias para la reproducción y maternidad de esta especie.

Sociality influences thermoregulation and roost switching in a forest bat using ephemeral roosts

In summer, many temperate bat species use daytime torpor, but breeding females do so less to avoid interferences with reproduction. In forest-roosting bats, deep tree cavities buffer roost microclimate from abrupt temperature oscillations and facilitate thermoregulation. Forest bats also switch roosts frequently, so thermally suitable cavities may be limiting. We tested how barbastelle bats (Barbastella barbastellus), often roosting beneath flaking bark in snags, may thermoregulate successfully despite the unstable microclimate of their preferred cavities. We assessed thermoregulation patterns of bats roosting in trees in a beech forest of central Italy. Although all bats used torpor, females were more often normothermic. Cavities were poorly insulated, but social thermoregulation probably overcomes this problem. A model incorporating the presence of roost mates and group size explained thermoregulation patterns better than others based, respectively, on the location and structural characteristics of tree roosts and cavities, weather, or sex, reproductive or body condition. Homeothermy was recorded for all subjects, including nonreproductive females: This probably ensures availability of a warm roosting environment for nonvolant juveniles. Homeothermy may also represent a lifesaver for bats roosting beneath loose bark, very exposed to predators, because homeothermic bats may react quickly in case of emergency. We also found that barbastelle bats maintain group cohesion when switching roosts: This may accelerate roost occupation at the end of a night, quickly securing a stable microclimate in the newly occupied cavity. Overall, both thermoregulation and roost-switching patterns were satisfactorily explained as adaptations to a structurally and thermally labile roosting environment.

From resource to female defence: the impact of roosting ecology on a bat's mating strategy

With their extraordinary species richness and diversity in ecological traits and social systems, bats are a promising taxon for testing socio-ecological hypotheses in order to get new insights into the evolution of animal social systems. Regarding its roosting habits, proboscis bats form an extreme by occupying sites which are usually completely exposed to daylight (e.g. tree trunks, vines or rocks). This is accompanied by morphological and behavioural adaptations to remain cryptic in exposed day roosts. With long-term behavioural observations and genetic parentage analyses of individually marked proboscis bats, we assessed its social dispersion and male mating strategy during day and night. Our results reveal nocturnal male territoriality-a strategy which most closely resembles a resource-defence polygyny that is frequent also in other tropical bats. Its contrasting clumped social dispersion during the day is likely to be the result of strong selection for crypsis in exposed roosts and is accompanied by direct female defence in addition to male territoriality. To the best of our knowledge, such contrasting male mating strategies within a single day-night cycle have not been described in a vertebrate species so far and illustrate a possible evolutionary trajectory from resource-defence to female-defence strategy by small ecologically driven evolutionary steps.

Anthropogenic impacts on Costa Rican bat parasitism are sex specific

While anthropogenic impacts on parasitism of wildlife are receiving growing attention, whether these impacts vary in a sex-specific manner remains little explored. Differences between the sexes in the effect of parasites, linked to anthropogenic activity, could lead to uneven sex ratios and higher population endangerment. We sampled 1108 individual bats in 18 different sites across an agricultural mosaic landscape in southern Costa Rica to investigate the relationships between anthropogenic impacts (deforestation and reductions in host species richness) and bat fly ectoparasitism of 35 species of Neotropical bats. Although female and male bat assemblages were similar across the deforestation gradient, bat fly assemblages tracked their hosts closely only on female bats. We found that in female hosts, parasite abundance per bat decreased with increasing bat species richness, while in male hosts, parasite abundance increased. We hypothesize the differences in the parasite-disturbance relationship are due to differences in roosting behavior between the sexes. We report a sex-specific parasite-disturbance relationship and argue that sex differences in anthropogenic impacts on wildlife parasitism could impact long-term population health and survival.

Social calls produced within and near the roost in two species of tent-making bats, Dermanura watsoni and Ectophylla alba

Social animals regularly face the problem of relocating conspecifics when separated. Communication is one of the most important mechanisms facilitating group formation and cohesion. Known as contact calls, signals exchanged between conspecifics that permit group maintenance are widespread across many taxa. Foliage-roosting bats are an excellent model system for studying the evolution of contact calling, as there are opportunities to compare closely related species that exhibit major differences in ecology and behavior. Further, foliage-roosting bats rely on relatively ephemeral roosts, which leads to major challenges in maintaining group cohesion. Here, we report findings on the communication signals produced by two tent-making bats, Dermanura watsoni and Ectophylla alba. We found that both species produced calls in the early morning near the roost that were associated with roostmate recruitment. Calling often ended once other bats arrived at the tent, suggesting that calls may be involved in roostmate recruitment and group formation. The structure and function of these calls are described and future research directions are discussed.

Roost Selection by Male Indiana Myotis Following Forest Fires in Central Appalachian Hardwoods Forests

Despite the potential for prescribed fire and natural wildfire to increase snag abundance in hardwood forests, few studies have investigated effects of fire on bat roosting habitat, particularly that of the endangered Indiana myotis Myotis sodalis. From 2001 to 2009, we examined roost selection of Indiana myotis in burned and unburned forests in Tucker County, West Virginia. We radiotracked 15 male Indiana myotis to 50 roost trees; 16 in burned stands and 34 in unburned stands. Indiana myotis roosted in stands that had initially been burned 1–3 y prior to our observations. In burned stands, Indiana myotis roosted exclusively in fire-killed maples (Acer spp.). In unburned stands, they roosted in live trees, predominately hickories (Carya spp.), oaks (Quercus spp.), and maples. Roost trees in burned stands were surrounded by less basal area and by trees in advanced stages of decay, creating larger canopy gaps than at random trees in burned stands or actual roost trees located in unburned stands. Compared to random trees in unburned stands, roost trees in unburned stands were less decayed, had higher percent bark coverage, and were surrounded by less basal area, also resulting in larger canopy gaps. Roost-switching frequency and distances moved by Indiana myotis among roost trees were similar between burned and unburned stands. Our research indicates that use of fire for forest management purposes, at minimum provoked no response from Indiana myotis in terms of roost tree selection, and may create additional roost resources, depending on spatial context.