Behavioral Flexibility Positively Correlated with Relative Brain Volume in Predatory Bats

Abstract

We investigated the potential relationships between foraging strategies and relative brain and brain region volumes in predatory (animal-eating) echolocating bats. The species we considered represent the ancestral state for the order and approximately 70% of living bat species. The two dominant foraging strategies used by echolocating predatory bats are substrate-gleaning (taking prey from surfaces) and aerial hawking (taking airborne prey). We used species-specific behavioral, morphological, and ecological data to classify each of 59 predatory species as one of the following: (1) ground gleaning, (2) behaviorally flexible (i.e., known to both glean and hawk prey), (3) clutter tolerant aerial hawking, or (4) open-space aerial hawking. In analyses using both species level data and phylogenetically independent contrasts, relative brain size was larger in behaviorally flexible species. Further, relative neocortex volume was significantly reduced in bats that aerially hawk prey primarily in open spaces. Conversely, our foraging behavior index did not account for variability in hippocampus and inferior colliculus volume and we discuss these results in the context of past research.

Encephalization, Neuronal Excess, and Neuronal Index in Rodents

“…Of interest, much evidence suggests that larger EQs or relative brain size endow species with improved cognitive abilities (Lefebvre et al, 2004); with behavioral flexibility, such as the ability to respond successfully to novel environments (Sol et al, 2005) or to alternate between feeding strategies (Ratcliffe et al, 2006); and even correlate with intelligence (Jerison, 1985). These findings seem to agree with the fact that humans, dolphins, and chimpanzees have the largest known EQs (Marino, 1998).…”

Evolutionary escalation: the bat–moth arms race

“…Although many bat species take prey from water and terrestrial surfaces, most of these species also capture prey in flight (Ratcliffe et al, 2006;Ratcliffe, 2009). Over time, airborne insects, through the evolution of bat-detecting ears and auditory-evoked defensive flight behaviours and passive anti-bat behaviours (both discussed above), would in general have become more difficult to track and capture, providing selective pressure for bat biosonar systems to better track would-be prey.…”

Niche-specific cognitive strategies: object memory interferes with spatial memory in the predatory bat, Myotis nattereri

“…However, once an underestimated strategy, half or more of today's ca. 900 predatory bat species may glean some or all of their prey (Ratcliffe et al, 2006). For bats that glean from terrestrial surfaces or hawk prey close to vegetation, recognizing plant species by shape, rather than position, may be vital.…”

“…spiders and caterpillars), which vary in palatability, close to vegetation. Myotis nattereri is behaviourally flexible with respect to foraging strategy (Ratcliffe et al, 2006), aerially hawking prey close to vegetation and gleaning prey from substrate (Czech et al, 2008;Schnitzler and Kalko, 2001;Siemers and Schnitzler, 2000;Swift and Racey, 2002). It uses very short, broadband echolocation calls to resolve the echoes from suspended prey from those returning from clutter (Siemers and Schnitzler, 2000;Siemers and Schnitzler, 2004).…”