Browsing Journal of Range Management, Volume 51, Number 4 (July 1998) by Subjects
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Diet selection by sheep and goats on Mediterranean heath-woodland rangeThe study determined the species components of the diets of small ruminants grazing mountain ranges of the Montseny Biosphere Reserve (Catalunya, NE Spain). Three mixed flocks of sheep and goats, led by shepherds, were monitored for a year. Animals grazed a mountain rangeland composed of Quercus ilex woodland and Calluna-Erica heathland during the day and were returned to their corrals every night. Diet selection was estimated using fecal analysis. Of the 111 species that were identified, 71 were common to both sheep and goat. Of these, 23 were represented in proportions of more than 1% of the annual diet. Even though goats and sheep grazed together, their diets were significantly different (p < 0.0001), the animal factor accounting for 18% to 60% of the total variation among the main diet components. Variation between seasons was also a major (5% to 56%) highly significant factor, while differences between flocks accounted for a significant, but relatively small part (3 % to 10% ) of the total variation in diet. The outstanding difference was the avoidance of the tree, Quercus ilex, by the sheep while the goats selected it throughout the year. Sheep selected graminoids throughout the year while goats tended to avoid them. For the rest there was substantial overlap in species composition between the diet of sheep and goats, especially when analysed over an entire cycle.
Spatial memory and food searching mechanisms of cattleUneven 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.