178 Southeastern Naturalist Vol. 10, No. 1 178 Observations of Parturition in Rafinesque’s Big-eared Bats (Corynorhinus rafinesquii) Beneath a Concrete Bridge Monica S. Wolters1 and Chester O. Martin2,* Abstract - We report on observations of parturition and maternal behavior of Corynorhinus rafinesquii (Rafinesque’s Big-eared Bat) at a bridge in west-central Mississippi. Rafinesque’s Bigeared Bats formed a maternity colony beneath the bridge in March, and parturition occurred from late May to early June. On 28 May 2004, a female Rafinesque’s Big-eared Bat was observed giving birth in the breech position, which has not been previously reported for the species. On the same day, another adult female and her pup were found struggling on the ground due to entanglement of the umbilical cord around the mother’s wing, and a third female was observed biting her pup. While important data were obtained during our observations, we emphasize the necessity of using extreme care when conducting repeated surveys at maternity roost sites. Previous research has documented the use of concrete bridges as maternity roosts of Corynorhinus rafinesquii (Lesson) (Rafinesque’s Big-eared Bat) (Bennett et al. 2008; Ferrara and Leberg 2005a, b; Lance et al. 2001; Trousdale and Beckett 2004). However, there is limited information on parturition and mother/pup behavior. We located a maternity colony of approximately 30 Rafinesque’s Big-eared Bats beneath a concrete bridge in Claiborne County, west-central Mississippi, on 14 April 2000. The bridge is a T-beam pre-stressed girder bridge with parallel beams that span its entire length. There are three compartments and support beams intersected at right angles on each side. We monitored this bridge biweekly or monthly from April 2000–December 2004, and monthly during the spring and summer of 2005, 2006, and 2009. The maternity colony was established at the bridge during March of each year, with parturition occurring from late May to early June. The earliest dates that pups were observed were 23 May 2000, 28 May 2004, and 20 May 2009. These dates are slightly later than reported by Trousdale and Beckett (2004), who first observed pups on 12 May 2000, 15 May 2001, and 27 May 2002 at bridge roosts in southern Mississippi. Herein we describe observations on the parturition process and maternal behavior of Rafinesque’s Big-eared Bats at the Claiborne County bridge site. On 28 May 2004, we observed 11 females with pups beneath the bridge. Additionally, a solitary female was roosting in an outer compartment of the bridge in proximity to the cluster. This bat was captured to determine reproductive condition, and parturition was observed in progress in a breech presentation. Breech presentation is generally considered the norm for insectivorous bats (Bhatnagar 1978, Wimsatt 1960), but to our knowledge it has not been previously described for Rafinesque’s Big-eared Bats. Twelve adult females with 12 pups were observed on 29 May 2004. Because Rafinesque’s Big-eared Bats give birth to a single pup (Jones 1977), we assume that the female that we had observed giving birth and her pup had joined the cluster. Also on 28 May 2004, another adult female and her pup were found struggling on the ground beneath the roost with the umbilical cord wrapped around the female’s wing. We cut the cord to free the wing and the mother flew immediately (with her pup) to a separate site under the bridge. Concurrently we also observed a third female that appeared to be ¹Department of Education, Mississippi College, Clinton, MS 39056. 2Environmental Laboratory, US Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199. *Corresponding author - chester.o.martin@usace.army.mil. Notes of the Southeastern Nat u ral ist, Issue 10/1, 2011 2011 Southeastern Naturalist Notes 179 agitated and was biting her pup. On the following day (29 May), we observed a solitary male pup roosting where the female was seen biting her pup during the prior visit. All adult females in proximity to the pup were accompanied by a pup. We took the following measurements on the solitary pup: total length (27.31 mm), forearm length (21.24 mm), and weight (2.2 g.); the pup was then returned to its roost site. According to Lollar and Schmidt-French (1998), a solitary pup observed during daylight roosting hours may be an indication of abandonment, but we were unable to determine if this was the case since we did not make another visit until 12 June 2004. On this date, 19 bats (including adult females, volant pups, and 1 adult female with an attached pup) were observed. Although we visited the bridge roost monthly throughout the maternity season for five years, we limited close observations of mothers and pups to 28–29 May 2004 because we were concerned that our presence and monitoring activity might detrimentally affect the colony. Many authors warn that roost surveys must be conducted carefully because disturbance could alter patterns of roost use, and even cause disturbed bats to abandon traditional roosts (Hayes et al. 2009, Kunz 1982, Tuttle 1979). Jones and Suttkus (1975) and Trousdale and Beckett (2004) reported that Rafinesque’s Big-eared Bat maternity colonies were especially susceptible to human disturbance. While Ferrara and Leberg (2005b) found that frequent surveys of day-roosting bats had no negative effects on bat numbers or bridge use, they emphasized that disturbance should be minimized and caution used in surveys of maternity colonies. Lance et al. (2001) found that bridge roosts of Rafinesque’s Big-eared Bats were seldom abandoned after surveys that did not include the handling of bats. Because of their permanence and accessibility, bridges provide opportunities for monitoring roosting trends of bats in southern forests (Ferrara and Leberg 2005a, b; Lance et al. 2001). As there is concern about the status of breeding populations of Rafinesque’s Big-eared Bats throughout their range (Bayless 2009), we will continue our surveys of maternity roosts in central Mississippi. However, we will exercise extreme caution when conducting these surveys, and will avoid close contact during periods of parturition. Acknowledgments. The study was conducted as part of regional bat surveys of the Mississippi Bat Working Group using facilities and equipment provided by the Environmental Laboratory of the US Army Engineer Research and Development Center. We thank W.M. Ford, E.R. Britzke, and M.L. Bayless for reviewing an earlier draft and providing helpful comments. Literature Cited Bayless, M.L. 2009. Rafinesque’s Big-eared Bat(Corynorhinus rafinesquii) and Southeastern Myotis (Myotis austroriparius) conservation strategy. Draft Report, Bat Conservation International, Austin, TX. Bennett, F.M., S.C. Loeb, M.S. Bunch, and W.W. Bowerman. 2008. Use and selection of bridges as day roosts by Rafinesque’s Big-eared Bats. American Midland Naturalist 160:386–399. Bhatnagar, K.W. 1978. Breech presentation in the Hairy-legged Vampire, Diphylla ecaudata. 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