A state-dependent sex difference in spatial memory in pinyon jays, Gymnorhinus cyanocephalus: mated females forget as predicted by natural history

Based on differing roles during the breeding season, male pinyon jays are predicted to be more accurate than females in recovering cached seeds over long retention intervals. We additionally predicted that males should be able to accurately recover caches made by their mates over short and long retention intervals. We conducted four experiments to test these predictions. During experiment 1, we tested the accuracies of the jays' spatial memory at a short retention interval of 5–7 days. We tested their recovery of their own caches and caches made in their presence by their mate and a nonmate of the opposite sex. While females and males found their own caches with similar accuracy, males were more accurate in finding caches made by their mates. Experiment 2 used the same design for caching, but longer retention intervals of 1, 2 and 4 months. Males were more accurate than females in the longer month intervals. To test whether differences found indicated a broad difference in spatial cognition, in experiment 3 we tested nonmated male and female jays in an open-field analogue to the radial arm maze. There were no significant effects of sex for task acquisition, accuracies across retention intervals, or patterns of adjacent holes or errors chosen. In experiment 4, we compared nonmated males and females in cache recovery at long internals and found no sex difference in accuracy. In addition, neither sex was affected by opportunities for memory rehearsal. We conclude that spatial memory in pinyon jays may be a state-dependent trait: females tend to be less accurate after longer intervals when mated than when not mated.