Sexual size dimorphism and geographic variation in forearm length of Rafinesque’s Big-eared Bat (Corynorhinus rafinesquii) and Southeastern Myotis (Myotis austroriparius)

Sexual size dimorphism is common in many taxa and results from various pressures, including competition, reproductive requirements, functional differences, and sexual recognition. For mammals, males are typically the larger sex; however, for vespertilionid bats, females are more often the larger sex. Forearm length, a feature that influences overall wing and body size and is often sexually dimorphic, is a standard morphological measurement taken from bats. Forearm length was measured in two vesper bat species (Corynorhinus rafinesquii and Myotis austroriparius) that co-occur across much of the southeastern United States. Forearm length was greater in females of both species, and females of both species also exhibited regional variation in forearm length. By having a longer forearm and therefore being larger in size, females may be more maneuverable and better equipped to carry young. While this study did not directly investigate the mechanisms behind regional variation in forearm length, it is possible this is the result of variability in habitat types, resources, or thermodynamic constraints. Knowledge of sexually dimorphic characteristics is important for obtaining a general understanding of a species and its morphology.

Holocene vertebrates from a dry cave on Eleuthera Island, Commonwealth of The Bahamas

We report a mid- to late-Holocene, non-cultural vertebrate assemblage from Garden Cave (site EL-229), Eleuthera Island, The Bahamas, with 2450 fossils representing 26 species. The chronology is based on accelerator mass spectrometer (AMS) radiocarbon (14C) dates determined directly on individual bones of the hutia ( Geocapromys ingrahami), an extirpated species of rodent that dominates the bone assemblage at Garden Cave. Four AMS 14C dates from our excavation range from 1340 to 1280 cal. BP (surface of the site) to 4860 to 4830 cal. BP with depth. A hutia bone lying on the surface from elsewhere in the cave dated to 450 to 290 cal. BP, which is roughly the time of European and African contact on Eleuthera. Other extirpated species from Garden Cave are tortoise ( Chelonoidis sp.), rock iguana ( Cyclura sp.), skink ( Mabuya sp.), parrot ( Amazona leucocephala), crow ( Corvus nasicus), and southeastern myotis ( Myotis austroriparius). Each of these species may have survived on Eleuthera until sometime after the initial human occupation of the island (~1000 cal. BP), although we have direct AMS 14C dates for only the hutia. During the time of fossil deposition in Garden Cave, sea levels were approaching that of today, yet land areas were considerably larger than now, connecting Eleuthera to New Providence, and potentially to Exuma as well. Such relatively recent connections are important in explaining past and present distributions of terrestrial plants and animals.

Structure and Reproductive Patterns in the Summertime Forest-Bat Community of Southeastern Texas

Forests of eastern Texas represent the westernmost extent of the southern pine forests and part of the pine belt of the forested Gulf coastal plain. Bat community assemblages in similar forests throughout southeastern United States have been documented in various studies, but only scant data are available for Texas. The purpose of this study was to characterize the assemblage and investigate reproductive patterns of the summer bat community in the austroriparian forest of eastern Texas. Using mist nets, we captured bats during summers 2009–2011 and recorded species, gender, age and reproductive condition. We captured 382 bats of eight species: Seminole Lasiurus seminolus (n = 163), evening Nycticeius humeralis (n = 86), big brown Eptesicus fuscus (n = 57), eastern red Lasiurus borealis (n = 31), southeastern myotis Myotis austroriparius (n = 21), tri-colored Perimyotis subflavus (n = 19), Mexican free-tailed Tadarida brasiliensis (n = 4), and hoary Lasiurus cinereus (n = 1) bats. Analysis of reproductive data suggests that three of these species (big brown, evening, and Seminole bats) may be following a reproductive strategy—extended seasonal monoestry (births of single litters spanning a particular season)—different than their previously reported pattern of synchronous monoestry.