Species differences in spatial memory performance on a three-dimensional task

Three species of seed-caching corvids were tested in a spatial, three-dimensional analog of the radial maze. The apparatus consisted of five artificial trees, each with six branches. A wooden feeder could be attached to each branch. Each feeder contained a hole that could hold a pine seed. During the first 40 trials of acquisition testing, all three species improved rapidly with nutcrackers and pinyon jays performing at higher levels than scrub jays. Testing was then interrupted for 31 d. After the interruption, the two species of jays continued to improve but the nutcrackers did not. This species performed with only modest accuracy through the remainder of the experiment. Mixed-interval testing was done at 10, 60, 180, and 300 min. All species declined in accuracy with increased retention interval. However, at 10 and 180 min, pinyon jays performed significantly better than scrub jays. This is the fourth spatial memory task in which pinyon jays have out-performed scrub jays. The difference in performance between these two species provides more evidence for divergence in spatial cognition as a function of dependence on cached food.