Spatial cognition in western gorillas (Gorilla gorilla): an analysis of distance, linearity, and speed of travel routes.

ABSTRACT

Spatial memory allows animals to retain information regarding the location, distribution, and quality of feeding sites to optimize foraging decisions. Western gorillas inhabit a complex environment with spatiotemporal fluctuations of resource availability, prefer fruits when available, and travel long distances to reach them. Here, we examined movement patterns-such as linearity, distance, and speed of traveling-to assess whether gorillas optimize travel when reaching out-of-sight valued resources. Our results show that gorillas travel patterns are affected by the activity they perform next, the type of food they feed on, and their preference level to specific fruits, suggesting they are able to optimize foraging based on spatial knowledge of their resources. Additionally, gorillas left in the direction of the next resource as soon as they started traveling and decelerated before approaching food resources, as evidence that they have a representation of their exact locations. Moreover, home range familiarity did not influence gorillas' movement patterns, as travel linearity in the core and periphery did not differ, suggesting that they may not depend wholly on a network of paths to navigate their habitat. These results show some overlap with chimpanzees' spatial abilities. Differences between the two ape species exist, however, potentially reflecting more their differences in diet (degree of frugivory) rather than their cognitive abilities. Further studies should focus on determining whether gorillas are able to use shortcuts and/or approach the same goal from multiple directions to better identify the spatial abilities used by this species.