The relationship between urine-marking and caching was studied in two captive groups of wolves (Canis lupus). It was found that urine-marking never occurred when a cache was stocked, rarely occurred during later investigations if some food was still present, but usually occurred soon after the cache was emptied. The animal marking an empty cache was often not the one which had exploited it. Once an empty cache was marked it received little further attention, as opposed to caches that were empty but not urine-marked. These results suggest that urine-marking may enhance foraging efficiency in wolves by signalling that a site contains no more edible food despite the presence of lingering food odors.