| Locating food and refuge is essential for an animal's survival. However, little is known concerning how mammals navigate under natural conditions and cope with environmental constraints. To address these questions I investigated landmark-based navigation in free-ranging Columbian ground squirrels ( Spermophilus columbianus).;The first series of experiments investigated the importance of local (e.g., vegetation pattern, logs) and global (e.g., forest edge, mountains) landmarks for navigation during a foraging task. Squirrels were trained to find a baited platform within an array of nine platforms set up on their territories. After training, the position of the baited platform with respect to local and global landmarks was manipulated. The ability of squirrels to find the baited platform was affected by the manipulation of global but not local information, suggesting that when global landmarks were present, squirrels disregarded local landmarks.;A second set of experiments tested the ability of ground squirrels to locate escape burrows when local, global or both types of landmarks were obstructed. Squirrel escape times increased in each of these conditions suggesting that they need both local and global landmarks for successful navigation. The comparison of escape times between age groups revealed that young animals attended equally to local and global landmarks, while older individuals preferentially used global landmarks.;The last series of experiments investigated whether ground squirrels form a map-like representation of their environment that would allow them to establish relationships among different landmarks. To address this, I tested the ability of squirrels to perform simple detours that required traveling aboveground and also integrated detours that required traveling both aboveground and underground. The majority of the animals performed simple detours, while only some squirrels performed integrated detours suggesting that animals formed some type of map-like representation, but the process of integrating information from above- and underground spaces was challenging.;This study provides insights into landmark use by a wild mammal and demonstrates novel approaches for studying navigation in the natural settings. |
