Territoriality and Social Organization
As predicted under the territory defense hypothesis (Burt 1943, Maher and Lott 1995) and confirming previous observations (Vaughan 1976, McWilliam 1987, Smarsh and Smotherman 2017), tracking Cardioderma cor revealed that males sing on small territories containing food sources, they return to these locations nightly, and there is minimal overlap between neighbors. This space use strategy is consistent with predictions for terrestrial gleaning species (Egert-Berg et al. 2018). Some of the ranges we calculated from our telemetry data were larger than those estimated from observation only (Vaughan 1976). While C. cor territory locations and boundaries can be reliably determined by observations of singing perches, this method may underestimate total space use, as demonstrated in Swainson’s warbler (Limnothlypis swainsonii ) (Anich et al. 2009). Scaling laws and diet can influence foraging range size (Haskell et al. 2002). C. cor night ranges were similar in size to the congeneric gleaning species Megaderma lyra , the greater false vampire bat, which is a bat of similar size and diet to C. cor(Audet et al. 1991).
The core areas of the night ranges are the focal spots for singing inC. cor males. As nights progressed and foraging activity decreased, bats spent more time on more concentrated areas as they increased singing output. The overlay of the singing ranges and overall use ranges (including foraging) further supports singing as a territorial behavior for resource defense foraging strategies inC. cor , rather than an exploded lek (Toth and Parsons 2013). Previous work found that song playbacks conducted within the outermost singing perches of heart-nosed bats evokes strong territorial response, but not beyond these perches, demonstrating boundary maintenance demarked by singing (Smarsh and Smotherman 2017). Our observations of antiphonal singing when a neighbor sang within the outer singing perches also supports this mechanism of spatial organization. During the summer rains singing ceases and males disperse (Vaughan 1976), but opportunistic recapture data from this paper and others suggests that territory fidelity of heart-nosed bats extends across years (Vaughan 1976, McWilliam 1987).
Similar to the multi-use territories in songbirds and gibbons, (Marshall and Marshall 1976, Mitani 1984, 1987, Raemaekers and Raemaekers 1985, Ham et al. 2016) McWilliam noted that male-female heart-nosed bat pairs hold territories, which was not observed in this study (McWilliam 1987). A sympatric species, Lavia frons , the yellow-winged bat, has multi-use territories in which male-female pairs roost in Acacia trees and forage on the territories (Wickler and Uhrig 1969, Vaughan and Vaughan 1986). For C. cor, our study suggests that females have fidelity to foraging areas that may overlap more with neighboring males, and do not sing. On several occasions we observed a non-singing adult producing contact calls and joining the tracked male for short time periods, possibly for courtship, although presumably mating would take place in the mixed-sex colonies in baobabs. A targeted tracking study of females along with courtship observation will determine whetherC. cor females may benefit from mating outside of the roost, such as additional access to resources, and where C. cor may fall on the resource defense polygyny- exploded lek continuum (Kotrschal and Taborsky 2010, Alonso et al. 2012, Toth and Parsons 2013).