Unique Insights into Dispersion Distances Among Calling Males of Wahlberg’s Epauletted Fruit Bat in Kruger National Park, South Africa

Abstract

Abstract:In June 2009, we used a novel technique to quantify dispersion patterns among a large group of calling male Epomophorus wahlbergi congregated around five neighboring and synchronously fruiting sycamore fig trees (Ficus sycomorus) in Kruger National Park, South Africa by using the physics of sound attenuation over distance to monitor and map positions of calling males without disturbing their mating behavior. The lack of fruiting sycamore fig trees across the area concentrated males among five fruiting trees along a 10 km stretch of riverine corridor that paralleled the river road. We hypothesized that the patterns of dispersion among calling males would be clumped in relation to fruiting fig trees that attract foraging females. Results show that the distribution of calling perches were clumped (R = 0.75) as opposed to randomly or equally dispersed. In addition, we found that a 2 km section of the corridor contained the majority of calling males and in this area calling males were more tightly clumped (R = 0.58) than across the other 6 kms of corridor. In addition, distances among calling males and their nearest neighbor were significantly less on average (25m) in the higherdensity area, than in the lower density areas (315m)(P < 0.001). Although most males were near fruiting figs, they maintained a minimum dispersion and never were observed calling from the same tree. In addition, some males appeared dominant over others and consistently positioned themselves closest to ripe fig trees where females were foraging. Our data give previously unobserved insights into how male Wahlberg's epauletted fruit bats position their calling roosts in relation to one another and fruiting fig trees under conditions of extreme drought and limited local food availability.

Social communication in bats

“…An additional example of multimodal displays comes from male epauletted fruit bats (Epomops spp., Epomophorus spp. and Hypsignathus monstrosus), which emit 'honks' comprising simple, monotone, audible emissions (Wickler & Seibt, 1976;Adams & Snode, 2013). Sound is intensified using unique and sexually dimorphic cheek pouches, so it can cover long distances to attract females to leks (Adams & Snode, 2013).…”

“…and Hypsignathus monstrosus), which emit 'honks' comprising simple, monotone, audible emissions (Wickler & Seibt, 1976;Adams & Snode, 2013). Sound is intensified using unique and sexually dimorphic cheek pouches, so it can cover long distances to attract females to leks (Adams & Snode, 2013). Acoustic signals are coupled with visual displays such as intense wing flapping or exposing retractile tufts of white fur on the shoulders (Wickler & Seibt, 1976;Bradbury, 1977;Adams & Snode, 2013).…”

“…Carollia perspicillata wing‐shakes and extends its tongue in such situations (Fleming, ), or in courtship, when males may exhibit advertisement flights, wing shaking or hovering to attract females' attention (Vaughan & Vaughan, ; McWilliam, ). Visual displays are also common among epauletted fruit bats ( Epomophorus wahlbergi ) during courtship, when retractile tufts of white hair are erected by wing‐flapping males (Adams & Snode, ). Although one of their likely roles is to convey visual messages, such movements may also help spread pheromones or, as in pipistrelle song flights (Barlow & Jones, ), to broadcast social calls over defended territories.…”

Differences in the male mating calls of co-occurring epauletted fruit bat species (Chiroptera, Pteropodidae, Epomophorus wahlbergi and Epomophorus crypturus) in Kruger National Park, South Africa

“…As mentioned, the mating call of male epauletted bats appears to serve both the function of attracting females to their perch because male call rates increase as females approach, but secondly, male calls appear to act as a deterrent to other conspecific males attempting to call from perches too close to other calling males (Wickler and Seibt 1976;Adams and Snode 2013). Although one could argue that because we could not definitively identify individuals to species from which calls were recorded, we could not make this determination.…”

“…The mating call of male E. wahlbergi is described as a loud, audible, repetitive, monotone call (Wickler and Seibt 1976;Acharya 1992;Fenton et al 1985) and appears to serve two functions: a) to attract females and b) to space out male conspecifics calling in the same area (Kingdon 1974;Wickler and Seibt 1976;Adams and Snode 2013). Although the mating call of E. wahlbergi has been described, herein, we provide the first quantification of the male mating call of E. crypturus.…”