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Observations on the Roosting and Foraging Behavior of Woolly False Vampire Bats, Chrotopterus auritus, in Belize
R. Mark Brigham, Hugh G. Broders, Cory A. Toth, Jesika P. Reimer, and Robert M.R. Barclay

Caribbean Naturalist, No. 47

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Caribbean Naturalist 1 R.M. Brigham, H.G. Broders, C.A. Toth, J.P. Reimer, and R.M.R. Barclay 22001188 CARIBBEAN NATURALIST No. 4N7o:1. –477 Observations on the Roosting and Foraging Behavior of Woolly False Vampire Bats, Chrotopterus auritus, in Belize R. Mark Brigham1,*, Hugh G. Broders2, Cory A. Toth3, Jesika P. Reimer4, and Robert M.R. Barclay4 Abstract - We report on roost use and foraging by Chrotopterus auritus (Woolly False Vampire Bat) based on data collected in April and May from 2012 to 2014. We found that bats were loyal to a single day-roost in a Maya temple located in a 30-ha block of intact native forest at Ka’Kabish in Orange Walk District of northern Belize. Further, bats spent most of their time searching for prey in the forest block around the roost site. Over 12 nights of tracking, we did record 2 individuals moving across a gravel road into the adjacent forest block, and an individual was tracked once to a location about 3 km east of Ka’Kabish. Consistent with our expectations, the 6 bats we followed were loyal to their day roost, but, unexpectedly, they rarely moved long distances to forage despite their large size and carnivorous habits. Our results suggest that when roosting opportunities are available, groups of Chrotopterus could be found in small blocks of intact forest. Introduction Carnivorous bats in the Neotropics are all members of the Phyllostomidae. Compared to other terrestrial mammalian carnivores (Ripple et al. 2014), the relative densities of carnivorous bats are likely low and thus, for the most part, they are poorly studied. The purpose of our project was to add to the information available on the roosting and foraging behavior of Chrotopterus auritus Peters (Woolly False Vampire Bat), for which there are currently mostly anecdotal reports (e.g., Medellín 1989, Noqueira et al. 2006, Peraccchi and Albuqueque 1976, Sazima 1978). Chrotopterus auritus is the only member of its genus. Individuals are large, weighing 75–96 g (Medellín 1989), with a wingspan of ~75 cm. These bats are thought to form complex social groups that tend to stay together for several years. Group size varies from 1 to 7 (Medellín 1988) but most commonly includes 3–5 indiviudals (Sazima 1978), usually consisting of a male–female adult pair and pup(s). Despite being widespread throughout its range in Central America and northern South America, limited data suggest that the species is not found in large numbers because it is a high trophic-level carnivore (Kalko et al. 1996). Prey items typically vary from 10 to 35 g but can be as large as 70 g (Medellín 1989) and include birds, bats, and large insects (Bonato et al. 2004, Giannini and Kalko 2005, Nogueira et al. 2006, Sazima 1978). 1Department of Biology, University of Regina, Regina, SK S4S 0A2, Canada. 2Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada. 3Department of Biological Sciences, Boise State University, Boise, ID 83725, USA. 4Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada. *Corresponding author - Manuscript Editor: Angelo Soto-Centeno Caribbean Naturalist R.M. Brigham, H.G. Broders, C.A. Toth, J.P. Reimer, and R.M.R. Barclay 2018 No. 47 2 Individual C. auritus roost in caves, mines, and hollow trees (summarized in Medellín 1989) and have also been reported using Maya ruins as roosts (Peracchi and Albuquerque 1976). Based on 3 nights of radio-tracking, Medellín (1989) reported a single bat roosting in a hollow tree and foraging in a 4-ha area of mature forest. The echolocation calls of C. auritus are similar to those of foliage-gleaning Phyllostomids (i.e., short duration, high frequency, and low amplitude; Belwood 1989), suggesting that they forage in cluttered environments. It has also been proposed that they use prey-generated sounds to find food (Medellín 1988). We captured and radio-tracked 2 C. auritus in each of 3 consecutive years at a single location in Orange Walk District of northern Belize. Individuals were tracked for ~1 week at the end of April or early May. Based on previous studies, we predicted that individuals would roost in the same location and forage mostly in intact woodland. We expected, based on their large size and carnivorous habit, that individuals would travel relatively long distances and forage over large areas. We chose this location for our study due to the species being captured there in previous years (Fenton et al. 2001). Material and Methods Field-site description Our study was conducted in a forested area around the Maya ruin known as Ka’Kabish in northern Belize (17°48'56"N, 88°43'49"W; Haines 2011, McLellan and Haines 2013) about 10 km west of the extensive Lamanai Maya site. The forest was separated into 2 blocks (North and South) by a gravel road (Fig. 1). The south Figure 1. Aerial view of Ka’Kabish in May 2014 showing the more southern block of forest where Chrotopterus roosted, the northern block where some foraging took place, and the road bisecting the 2 blocks. Photograph © Helen Haines. Caribbean Naturalist 3 R.M. Brigham, H.G. Broders, C.A. Toth, J.P. Reimer, and R.M.R. Barclay 2018 No. 47 block (with the temple ruin where the bats roosted), was ~30 ha in area, and the north block was ~19 ha. We tracked bats for ~1 week near the end of April or early May in each of 2012, 2013, and 2014. Telemetry We caught bats in mist nets set within the south block of forest or at the exit of the tunnel they used to access the temple roost. We used a natural rubber-based glue to affix a 1.5-g radio transmitter (BD-2; Holohil Systems Inc., Carp ON, Canada), which represented less than 2% of body mass, to 2 individual bats during each year of the study (total of 4 males and 2 females). Transmitters were affixed between the shoulder blades after we trimmed fur using scissors. Each day we tracked bats using a hand-held R-1000 telemetry receiver (Communications Specialists Inc., Orange, CA, USA) to locate their day roosts, and on some evenings, we tracked individuals (usually for 60–90 minutes after they emerged) to make inferences about foraging behavior. Nightly bat locations were determined via triangulation of bearings collected simultaneously by 3–4 observers from high points in the forest block where the bats roosted. We used LOAS Radio Telemetry Software 4.0 (Sallee 2004) to calculate bearing intersections. Some locations were determined on foot by homing in on bats carrying transmitters. This research was conducted under permit from the Belizean Forest Department’s Ministry of Forestry, Fisheries, and Sustainable Development and following protocol 12˗03 of the University of Regina President’s Committee on Animal Care. Results In 2012, we tagged a male (78 g) and female (106 g) caught at 1925 hr in a net set on a trail near the main temple. In 2013, we caught a male (81.5 g) on 30 April in a net set outside the tunnel used by both bats in 2012. The next night, we caught another male (76.5 g) at ca. 2000 hr in the same location. In 2014, we affixed tags to a male (83 g) and a female (94 g) caught in one net on 29 April at 2012 hr outside the same tunnel. All radio-tagged individuals roosted during the day in what appeared to be a single tunnel (with 2 exits) in the largest temple in the Ka’Kabish southern site (Fig. 1). The bats used both exits from the tunnel (one on each side of the temple) over the 3 years but appeared to prefer the one where we netted (more western side, nearer to the road; Fig. 2). The tunnel was also used by Desmodus rotundus Geoffroy (Common Vampire Bat) and is known to be used by Trachops cirrhosus Spiox (Fringe-lipped Bat) and Carollia sowellii Baker, Solari, and Hoffmann (Sowell’s Short-tailed Bat) (M.B. Fenton, Western University, London, ON, Canada, 2017 unpubl. data). We ascertained early in 2012 that disturbance at the primary exit tunnel (trying to net for other species) caused the tagged bats to use the second exit (more easterly). We located the signals of roosting bats on 25 batdays over the 3 years, and they were always located in the same tunnel. On 29 April 2016, a colleague (W.F. Frick, Bat Conservation International, Austin, TX, USA) entered the tunnel and observed at least 5 Chrotopterus auritus and handCaribbean Naturalist R.M. Brigham, H.G. Broders, C.A. Toth, J.P. Reimer, and R.M.R. Barclay 2018 No. 47 4 Figure 2. Aerial view of Ka’Kabish showing the triangulated telemetry fixes for 4 individual Chrotopterus auritus while they were out of the roost (indicted by white star), presumably foraging. Code numbers starting with M and F indicate males and females, respectively. Caribbean Naturalist 5 R.M. Brigham, H.G. Broders, C.A. Toth, J.P. Reimer, and R.M.R. Barclay 2018 No. 47 netted 2 of them. During April 2017, a C. auritus was captured using a hand net as it exited the tunnel. On 12 nights (when there was no disturbance at the tunnel entrance), we tracked bats as they left the tunnel roost. The mean exit time was 1911 hr (earliest–latest: 1842–1928 hr), and none of the bats ever left prior to complete darkness. Sunset in the study area was at 1816 hr ± 2 mins between 25 April and 5 May. The bats we tracked spent most of their time in the south block of forest around the temple after leaving the tunnel at night (Fig. 2). During one brief (~30 min) evening of tracking at dusk in 2012, neither bat left the forest block. We tracked the 4 bats tagged in 2013 and 2014 over 10 nights. Overall, we registered 65 triangulated telemetry fixes (not necessarily independent) in these 2 years, and 56 of these were within the south block containing the temple where the bats roosted (Fig. 2). A male was triangulated once to the more northern block of intact forest and the other male was triangulated once to a location ~50 m SE of the south block. One female was tracked to locations ~400 m NE of the north block on 1 night, and the other female was tracked to a location ~3 km SE of the south block once. While we were unable to pinpoint exactly where this bat went, our suspicion based on signal strength was that it was foraging in a remnant block of forest ~3 km east and 1 km south of the road. In summary, individuals left the intact forest blocks on at most 3 occasions over the 10 nights of tracking (i.e., 20 bat-nights) in 2013 and 2014. On 2 occasions (different bats), we were able to approach individuals closely (to within ~25 m) and ascertain that they had hung up in a tree. We could not tell if they had been successful at capturing prey. Our impression from radio-tracking individuals was that foraging bats moved short distances (25–50 m) within the forest and then remained still for periods of 3–27 minutes, but mostly 5–10 minutes. On one occasion when we had a male in range for 40 consecutive minutes, the signal suggested that during that time it had periods of being stationary at 6 different sites totaling 33 minutes. One further impression of their foraging behavior was that bats did not emerge from the roost (n = 1 night, both individuals) or return to it (n = 1 night, both individuals) during periods of rain. Discussion In each year of our study, radio-tagged individual C. auritus roosted during the day in a tunnel in the largest Maya temple at Ka’Kabish, despite the disturbance caused by our catching bats at the entrance. Subsequent records suggest that the same tunnel was still in use in 2015 and 2017. As we predicted, groups of individuals were loyal to their specific roost. Several Chrotopterus as well as a single Vampyrum spectrum (L.) (Spectral Bat) have also been caught within the reserve at Lamanai, ~10 km from the study site (Fenton et al. 2001; M.B. Fenton, 2017 unpubl. data). Although the precise roost sites of these individuals are unknown, the location suggests that Maya structures may also be used as roost sites there. Unfortunately, we could not determine whether any of the bats we captured at Ka’Kabish were the same individuals over multiple years, or if they were relatives. Based on previous data (Medellín 1989), we suspect that we tracked the same individuals Caribbean Naturalist R.M. Brigham, H.G. Broders, C.A. Toth, J.P. Reimer, and R.M.R. Barclay 2018 No. 47 6 multiple times and that the group likely involved related individuals; however, further research on genetic relatedness and population size would be insightful. Bats spent most of their time foraging in the 30 ha of intact forest around the temple. Over 12 total nights of tracking, we found individuals occasionally traveled across the road into the northern forest block, and on 1 occasion, an individual was tracked to a location ~3 km east of Ka’Kabish, likely in a remnant block of forest. Thus, unexpectedly, bats rarely moved long distances to forage, at least at the time of year when we worked, despite this species’ large size and carnivorous habits. However, other studies on large carnivorous and insectivorous bats have yielded similar results. Veherencamp et al. (1977) tracked the largest neotropical carnivorous bat, Vampyrum spectrum, over only 3.2 ha during the course of a night. Likewise, Kalko et al. (1999) found the foraging range for 2 smaller (25–35 g) gleaning bats (Lophostoma silvicolum D’Orbigny ] [= Tonatia silvicola] [Whitethroated Round-eared Bat, which eats insects, and Trachops cirrhosus which catches insects and frogs) to be 3–12 ha. In addition, both V. spectrum and L. silvicolum, like the Chrotopterus we studied, moved short distances to feeding areas (>500 m). Audet at al. (1991) reported that another gleaning carnivore, Megaderma lyra E. Geoffroy (Greater False Vampire Bat; 40–60 g) used a 10-ha area for foraging. Finally, Vaughn (1976) found that the carnivorous Cardioderma cor (Peters) (African False Vampire or Heart-nosed Bat; 21–35 g) usually travelled 1 km or less to foraging areas of 1 ha or less. Taken together, these studies strongly suggest that carnivorous bat species have relatively small foraging ranges and often travel only short distances to them. In conclusion, based on our data from a specific time of the year, given the availability of roosting opportunities, groups of Chrotopterus use relatively small blocks of intact forest. Whether populations of this species, and other relatively large carnivorous bats, can persist in such small areas deserves further research. Acknowledgments We are grateful to the many people from the Lamanai Bat working group who helped us over the course of the study and the Lamanai Outpost Lodge for logistical support. We thank Fred Frick for bravely entering the tunnel in search of bats and Zen Czenze for commenting on an earlier draft of the manuscript. Our project was supported by Discovery Grants from the Natural Sciences and Engineering Research Council (Canada) to R.M. Brigham, H.G. Broders, and R.M.R. Barclay. We thank Brock Fenton and an anonymous reviewer for their comments, which improved the manuscript. Literature Cited Audet, D., D. Krull, G. Marimuthu, S. Sumithran, and J. Bala Singh 1991 Foraging behavior of the Indian False Vampire Bat, Megaderma lyra (Chiroptera: Megadermatidae). Biotropica 23:63–67. Belwood, J.J. 1989. Foraging behaviour, prey selection, and echolocation in phyllostomine bats. Pp. 601–605, In P.E. Nachtigall (Ed.). Animal Sonar: Processes and Performance. Plenum Press, New York, NY, USA. Caribbean Naturalist 7 R.M. Brigham, H.G. Broders, C.A. Toth, J.P. Reimer, and R.M.R. Barclay 2018 No. 47 Bonato V., K.G. Facure, and W. Uieda. 2004. 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Elmhagen, M.Letnic, M.P. Nelson, O.J. Schmitz, D.W. Smith, A.D. Wallach, and A.J. Wirsing. 2014. Status and ecological effects of the world’s largest carnivores. Science 343:1241484. Sallee K.L. 2004. LOAS. Ecological Software Solutions, Urnasch, Switzerland. Sazima I. 1978. Vertebrates as food items of the Woolly False Vampire, Chrotopterus auritus. Journal of Mammalogy 59:617–618. Vaughn, T.A. 1976. Nocturnal behavior of the African False Vampire Bat (Cardioderma cor). Journal of Mammalogy 57:227–248. Vehrencamp, S.L., F.G. Stiles, and J.W. Bradbury. 1977. Observation on the foraging behavior and avian prey of the neotropical carnivorous bat Vampyrum spectrum. Journal of Mammalogy 58:469–478.