Greater spear nosed bats commute long distances alone, rest together, but forage apart

Animals frequently forage in groups on ephemeral resources to profit from social information and increase efficiency. Greater spear-nosed bats (Phyllostomus hastatus) develop group-specific social calls, which are hypothesized to coordinate social foraging to feed on patchily-distributed balsa flowers. We tracked three social groups of P. hastatus on Isla Colón, Panamá, using high frequency GPS. We found commuting distances of 20-30 km to foraging sites, more than double of what has been previously reported. In contrast to our expectations, we found that individuals commuted alone. They then joined group members in small foraging patches with high densities of flowering balsas on the mainland. Close proximity to group members did not influence foraging efficiency or energy expenditure, but it positively influenced time outside of the cave, and increased the duration and synchrony of rest. These results show that stronger social proximity associations were more closely tied to resting behaviour, and indicate that factors other than increased feeding efficiency may structure social relationships of group members while foraging. It appears that depending on the local resource landscape these bats have an excellent map even of distant resources and may use social information only for current patch discovery. They then may no longer rely on social information during daily foraging.