Get reliable science

With limited management (i.e., feral or wild) cattle tend to form stable subgroups based on matriarchal lines. However common livestock management practices may disrupt formation of matriarchal groups. Few studies have examined social interactions among cattle raised under typical ranch management practices while grazing rangelands. The objective of this study was to evaluate the strength of spatial associations among individual cows based on locations recorded by horseback observers and GPS tracking data in a variety of herd and pasture sizes within diverse regions of the western United States. Herds ranging from 27 to 114 cows were observed 10 to 15 times over a 30 to 45 d period during the summers of 2000 and 2001 in Montana and during the summer of 2011 in New Mexico. In Montana, mean association between cow dyads decreased as herd size increased. Mean association among cattle in small herds (27 cows) was 28.0 ± 4.0 % SD, but in larger herds (111 or 114 cows) mean association was only 3.0 ± 1.0 % SD. Permutation tests indicated that within 5 of 8 herds, associations among cattle did not differ (P >0.05) from random levels. However, previous management may influence how individual cattle associate. In New Mexico, cattle from 4 pastures were combined in a common pasture. Mean association among cattle previously managed in the same pasture was 2.4 times greater (P < 0.001) than the mean association among cattle from separate pastures, 17.0 ± 7.0 % SE and 7.0 ± 2.0 % SE, respectively. Additionally, GPS tracking data showed that cows that were previously in same pastures were closer together than cows from different pastures when evaluated in a common pasture. When managed together under typical ranch practices, cattle did not appear to form strong association among individuals while grazing extensive rangelands.