Print PageKnowledge of scale-dependent factors that affect the distribution of ungulate herds, such as cattle, is essential for the development of more accurate predictive models of animal movement and the management of sustainable agriculture. Our objectives were to (1) evaluate the seasonal and diurnal patterns of herd spread and (2) evaluate the influence of shade, water and supplemental feed areas on cattle distribution. Positional information of eleven free-ranging Bonsmara, Bos taurus, cows were obtained at five minute intervals using Global Positioning System collars. We conducted a total of 8 trials each of three weeks from September 2007 to August 2008 in a 457ha shrub-dominated savanna in South Texas. Spread was obtained by calculating the average Euclidean distance of individuals to the center of the herd. Number of GPS fixes was used as an indicator of animal use of shade patches and water and supplemental feeding areas.
Results/Conclusions
In this semi-arid environment, herd spread was greatest during summer when forage biomass was high. Herd spread was the least and shade patches were used more during winter when forage biomass was low. This is in contrast to patterns seen in more northerly rangelands. Throughout the year spread was smallest and use of shade patches highest during the midday period compared to other periods of the day. There was no significant overall pattern of seasonal changes in cattle use of water and supplemental feeding areas. Forage availability and shade patches seem to have a greater influence on herd dispersion patterns than the influence of water and supplemental feed areas. Herd distribution is likely related to changes in seasonal forage biomass and diurnal temperature fluctuations which drive compensatory night-time feeding and thermoregulatory actions. Accurate ethological studies of herds depend on our ability to understand herd dynamics at multiple scales that affect and are relevant to animal’s response to the landscape.
