The ability of ungulates to discriminate among vegetation patches depends largely on the senses of vision, olfaction, tactility, and gustation. However, little is known about how ungulates rely on the respective senses in response to varying patch characteristics. This study aimed to evaluate how relative importance of senses in patch discrimination by cattle is affected by the sensory contrast between the discrimination targets. Five Japanese Black cows were allowed to choose between two forage patches from a distance of about 1 m. Two combinations of forage patches were used: one was a pair of green and dead forages of bahiagrass (BG) with clear mutual contrast in appearance and odor, and the other was a pair of green forages of BG and cogongrass (CG) with visual and olfactory resemblance. Cows preferably located and ate the green BG as the first choice (Type 1), or as the second choice after touching (Type 2) or further biting (Type 3) the alternative in error. Overall, Type 1 accounted for a high above-chance proportion of 0.94 in the green BG vs. dead BG discrimination, indicating the primary importance of vision and olfaction. By contrast, in the green BG vs. green CG discrimination, Type 1 remained at the chance level of 0.55 with proportions of 0.17 for Type 2 and 0.28 for Type 3, indicating the primary importance of tactility on the muzzle and in the mouth. The context-specific importance of the four senses in patch discrimination represents an adaptive mechanism of animals foraging in grasslands.
Keywords: Cattle; Dead forage; Forage discrimination; Green forage; Senses; Sensory contrast.