Spatial Memory and Food Searching Mechanisms of Cattle

Abstract

Uneven distribution of grazing negatively impacts rangelands through over- and under utilization of resources. The goal of this study was to quantify the role of experience on search pattern and foraging efficiency of cattle. Steers (Bos taurus x B. indicus) were exposed once daily during 15-20 min. sessions to 3 food-distribution treatments: VR (variable-random, food locations were changed randomly and daily), CR (constant-random, food locations were randomly set at the beginning and remained the same throughout the experiment), and CC (constant-clumped, food locations were constant and clumped in groups of 5). Pelleted feed was available in 20 out of 64 feeders arranged in 8 rows and 8 columns, with neighboring locations 5 m apart. Encounter rate of food locations was partitioned into search speed, total number of visits per unit distance walked, ratio of different (not previously visited within the session) locations to total visits (including revisits), and ratio of food locations to different locations visited. Intake rate increased (P < 0.01) as animals gained experience, but more slowly in variable-random than constant-clumped and constant-random. Residence time at food locations declined (P < 0.01) with increasing experience. Intake rate was negatively affected (P < 0.01) by search time per food location, which in turn was determined by the steers' ability to remember food locations. Steers in constant random and constant clumped used long-term spatial memory to return to food locations, and ignored areas where no food was found (P < 0.01). Conversely, steers in variable random used a strategy based on avoidance of locations already visited within sessions. Thus, in constant random and constant clumped food search was more efficient (P < 0.01) and concentrated in certain areas, whereas in variable random it was less efficient and more evenly distributed over the whole area. The results of this study suggest that impeding spatial memory could improve grazing patterns.