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178 Southeastern Naturalist Vol. 10, No. 1
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 - firstname.lastname@example.org.
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
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