Grazing animals are often confronted with spatially heterogeneous food resources in which preferred food types are distributed in patches. In this study the hypothesis that spatial memory is used less as the resource density increases was tested. Individual sheep foraged for 20 minutes in an arena containing a grid of 100 bowls of which 10, 20, 30, 40 or 50 contained 25 g of concentrate food. Amount eaten increased linearly over days indicating that learning occurred. There was an increase in the amount eaten per full bowl visited, an increase in the cumulative number of different bowls visited by the sheep and a reduction in the path length needed to find a given number of bowls leading to improved encounter rate with full bowls. Therefore, intake improved during the trial due to, at least in part, the use of spatial memory to learn full bowl locations and optimize the route taken to those locations. Length of the shortest possible path required to find five full bowls and expected path length from a random walk on the grid decreased exponentially as resource density increased. Actual path length to find five full bowls also decreased exponentially as the number of full bowls increased. Number of full bowls visited by the sheep (excluding revisits) within a day did not differ significantly between treatments. However, number of days on which any individual food bowl was visited (including 0 visits) decreased linearly as resource density increased. The proportion of full bowls visited that were revisited on the same day was significantly higher for the 10 bowl treatments. In summary, the results of this study suggest that sheep used spatial memory to optimize their route to food bowls more effectively at lower resource density.