Foraging in a complex naturalistic environment: capacity of spatial working memory in flower bats

Abstract

Memory systems have evolved under selection pressures, such as the need to remember the locations of resources or past events within spatiotemporally dynamic natural environments. The full repertoire of complex behaviours exhibited by animals in dynamic surroundings are, however, difficult to elicit within simply structured laboratory environments. We have developed a computercontrolled naturalistic environment with 64 feeders for simulating dynamic patterns of water or food resource availability (depletion and replenishment) within the laboratory. The combination of feeder and cage remote control permits the automated transfer of animals between cage and test arena and, therefore, high experimental throughput and minimal disturbance to the animals (bats and mice). In the present study, we investigated spatial working memory in nectar-feeding bats (Glossophaga soricina, Phyllostomidae) collecting food from a 64-feeder array. Feeders gave only single rewards within trials so that efficient foraging required bats to avoid depleted locations. Initially, bats tended to revisit feeders (win-stay), but within three trials changed towards a win-shift strategy. The significant avoidance of revisits could not be explained by algorithmic search guiding movement through the array nor by scent cues left by the bats themselves and, thus, the data suggest that bats remembered spatial locations depleted of food. An examination of the recency effect on spatial working memory after bats shifted to a win-shift strategy indicated that bats held more than 40 behaviour actions (feeder visits) in working memory without indication of decay. This result surpasses previous findings for other taxa.Supplementary material available online at

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

“…However, in general it appears that attempts to control for the possible effects of spatial memory are more important in studies using frugivorous and nectivorous species (e.g. Carter et al, 2010;Stich and Winter, 2006;Winter and Stich, 2005;Winter and von Helversen, 2001) than for the design of similar studies using predatory species (Ratcliffe and Dawson, 2003;ter Hofstede et al, 2008). In those studies using predatory bats, there was no evidence that bats relied on spatial memory over real-time sensory information (e.g.…”

Development of foraging strategies with age in a long-lived marine predator

“…Other young or naive animals have been shown to adjust search and foraging strategies quickly as they sample resources in the environment (e.g. Greggers & Menzel 1993, Sutherland & Gass 1995, Winter & Stich 2005. In this population, however, YOY are almost certainly not as proficient as adults at foraging, as evidenced by their need to make longer foraging trips.…”

Influence of Landmarks on Spatial Memory in Short-nosed Fruit Bat, <I>Cynopterus sphinx</I>

“…Short-term changes in their living space did not affect their choice of roosts. Bats can accurately remember the nest, or a fixed food source (like fruits, nectar) position, using spatial information rather than shape or color information of food and nests (Höller, 1995;Thiele & Winter, 2005;Winter & Stich, 2005). Similar results were confirmed in pigeons (Strasser & Bingman, 1996) and hummingbirds (Hurly & Healy, 1996).…”

“…Many animals are able to find the place where they went to before. The ability is generally called "spatial memory", but the underlying mechanism of them is different (Winter & Stich, 2005), mainly including echolocation (Ulf et al, 2008;Richard et al, 2005), vision (Strasser & Bingman, 1996) and olfaction (Richard et al, 2005). In the study mentioned above, G. soricina relys on echolocation to identify and remember the spatial location (Ulf et al, 2008), while the R. aegyptiacus is able to orient and navigate using both vision and echolocation (Richard et al, 2005), pigeons use vision to remember the spatial position of nests and returns to their nests accurately (Strasser & Bingman, 1996).…”

“…But Richard et al (2005) found that once the spatial location memory of Egyptian rousette bat (Rousettus aegyptiacus) was formed, moving the landmarks made no effect on their spatial memory. On the process of obtaining nectar, the nectar feeding bats of family Glossophaginae pay attention only to the location of the flowers in the space, instead of the shape and color (Winter & Stich, 2005;Thiele & Winter, 2005). The above studies have shown that landmarks or cues played different roles in the spatial memory of different animals when they were foraging.…”