Bat guilds, a concept to classify the highly diverse foraging and echolocation behaviors of microchiropteran bats

Abstract

Throughout evolution the foraging and echolocation behaviors as well as the motor systems of bats have been adapted to the tasks they have to perform while searching and acquiring food. When bats exploit the same class of environmental resources in a similar way, they perform comparable tasks and thus share similar adaptations independent of their phylogeny. Species with similar adaptations are assigned to guilds or functional groups. Habitat type and foraging mode mainly determine the foraging tasks and thus the adaptations of bats. Therefore, we use habitat type and foraging mode to define seven guilds. The habitat types open, edge and narrow space are defined according to the bats' echolocation behavior in relation to the distance between bat and background or food item and background. Bats foraging in the aerial, trawling, flutter detecting, or active gleaning mode use only echolocation to acquire their food. When foraging in the passive gleaning mode bats do not use echolocation but rely on sensory cues from the food item to find it. Bat communities often comprise large numbers of species with a high diversity in foraging areas, foraging modes, and diets. The assignment of species living under similar constraints into guilds identifies patterns of community structure and helps to understand the factors that underlie the organization of highly diverse bat communities. Bat species from different guilds do not compete for food as they differ in their foraging behavior and in the environmental resources they use. However, sympatric living species belonging to the same guild often exploit the same class of resources. To avoid competition they should differ in their niche dimensions. The fine grain structure of bat communities below the rather coarse classification into guilds is determined by mechanisms that result in niche partitioning.

Does Thinning Homogenous and Dense Regrowth Benefit Bats? Radio-Tracking, Ultrasonic Detection and Trapping

“…In particular, one ensemble of bats, narrow-space bats [17], that possess specialised traits favouring slow, manoeuvrable flight within vegetation clutter, particularly in forests, is considered especially prone to extinction [18,19]. While these bats can sometimes also forage within open space [20,21], they are often forest-dependent and are predicted to be particularly sensitive to vegetation loss and potentially to altered vegetation structure, for instance due to thinning of dense forests.…”

Echolocation parameters of Australian humpback dolphins (Sousa sahulensis) and Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the wild

“…Moreover, bat biosonar is further shaped within the same guild. Sympatric bat species change biosonar parameters, such as frequency, duration, and bandwidth, allowing for niche partitioning and avoiding competition for the same limited resources (Siemers and Schnitzler, 2004;Denzinger and Schnitzler, 2013). In contrast, toothed whales are comparatively understudied, and it remains unclear whether such adaptations have similarly shaped odontocete biosonar source parameters given the general functional convergence in bat and toothed whale biosonars (Madsen and Surlykke, 2013).…”

“…This process has been studied in detail in bats where the primary determinants of their biosonar characteristics are considered to be habitat type and foraging mode. Bat species use different biosonar parameters depending on ranges to prey, background vegetation, and foraging behavior (Denzinger and Schnitzler, 2013). As a result, bats are assigned into guilds independent of phylogeny, but rather based on common adaptations to environmental resources.…”

Echolocation behaviour of the big brown bat (Eptesicus fuscus) in an obstacle avoidance task of increasing difficulty

“…Foraging bats have to perform many echolocation tasks in parallel: spatial orientation, biotope recognition and food finding (Denzinger and Schnitzler, 2013). When orienting in space along background contours, bats continuously determine their position in relation to the environment, a necessity for route following and obstacle avoidance.…”