SOCIAL AND ENVIRONMENTAL-FACTORS INFLUENCE CATTLE DISTRIBUTION ON RANGELAND

We determined the cattle distribution patterns of dams (and foster dam s) and their offspring while grazing a 1030 ha (about 3 km by 5 km) al lotment during the summers of 1990-1993. Our primary objective in this 4-year field study was to determine whether yearling and adult offspr ing (and foster offspring) would return to the initial locations and a ssociated habitat types that they were exposed to by their dams (or fo ster dams) early in life. We observed the dams' offspring for four con secutive summers (1990-1993) and the foster-dams' offspring for 3 cons ecutive summers (1991-1993). Cross-fostering was conducted to learn th e relative importance of natural darns vs. foster dams as social model s in influencing distribution patterns of offspring. Offspring were oa red mostly in two different locations on the allotment by their dams o r foster dams. Centroid analyses indicated that offspring in all 4 gro ups remained near the general location where they were reared as calve s when they returned to the allotment as older animals (mean 0.5 to 1. 2 km from dams' or foster dams' centroid). Peers apparently attenuated the dams' (and foster dams') influence on location and habitat use wh en offspring were yearlings. The effect of peers was manifested by an increase in distance from dams' or foster dams' centroid, and by a hig her association index among yearlings, both of which reflected the col lective experiences of offspring in the peer groups. Drought weakened the darns' and foster dams' influence on location and habitat use as w ater became scarce near their centroids, but drought amplified the dam s' and foster dams' influence when water was not limited near their ce ntroids, By the final year of the study, offspring in 3 of the 4 group s monitored were within 0.7 km from the darns' or foster dams' centroi d (offspring in the fourth group were within 1.1 km from the foster da ms' centroid). Collectively, our results suggest that experiences earl y in life affected cattle distribution, and that distribution at any p oint in time was a 'snapshot' of ongoing behavioral changes that were developing according to each individual's antecedent experiences and c urrent environmental and social conditions. These results support the 'working hypotheses' that herding, selective culling, and water and sh ade development are important management techniques that can enhance d ispersion and decrease use of sensitive areas on rangelands (e.g., rip arian areas). (C) 1998 Elsevier Science B.V.