Consistent long-distance foraging flights across years and seasons at colony level in a neotropical bat

Abstract

All foraging animals face a trade-off: how much time should they invest in exploitation of known resources versus exploration to discover new resources? For group-living central place foragers, this balance is challenging. Due to the nature of their movement patterns, exploration and exploitation are often mutually exclusive, while the availability of social information may discourage individuals from exploring. To examine these trade-offs, we GPS-tracked groups of greater spear-nosed bats (Phyllostomus hastatus) from three colonies on Isla Colón, Panamá. During the dry season, when these omnivores forage on the nectar of unpredictable balsa flowers, bats consistently travelled long distances to remote, colony-specific foraging areas, bypassing flowering trees closer to their roosts. They continued using these areas in the wet season, when feeding on a diverse, presumably ubiquitous diet, but also visited other, similarly distant foraging areas. Foraging areas were shared within but not always between colonies. Our longitudinal dataset suggests that bats from each colony invest in long-distance commutes to socially learned shared foraging areas, bypassing other available food patches. Rather than exploring nearby resources, these bats exploit colony-specific foraging locations that appear to be culturally transmitted. These results give insight into how social animals might diverge from optimal foraging.

Keywords: central-place foraging; colony; exploitation; foraging fidelity; long-distance foraging.

Figure 1.

Consistent, colony-specific long-distance foraging flights across years and seasons. (a) Map of Panama, inset: study area. (b) Colony 1 (wet and dry seasons 2016–2023). (c) Colony 2, March 2022 (dry) and August 2023 (wet). (d) Colony 3, March 2022 (dry). Roosts (diamonds) colony 1: green, colony 2: purple and yellow: colony 3. Wet season: dotted lines, dry season: solid lines.

Figure 2.

(a) Mean and 95% credibility interval for model estimates on population means. Population mean, effective standard deviation and individual-level variability for distance (upper row) and angle from the cave (lower row) to foraging locations. Wet season: light grey, dry season: dark grey. (b) Spatial representation of model estimates of foraging locations beyond Isla Colón (dry season; left, wet season: right). Shown are the scaled product of the distance and angle probability density functions, clipped to the 95% contour and coastline. Colony 1: green, colony 2: purple/blue, colony 3: yellow and intensity of colour: relative density of the PDF product.

Figure 3.

Distribution of angles of outbound commute endpoints from each colony. Histogram: simulated angles of outbound commutes from the colonies based on the available landscape for each colony. Vertical lines (colored): observed angles of endpoints of outbound commutes for individual bats.