Association patterns reveal dispersalaggregation dynamics among cattle in a South Texas Rangeland,USA

Introduction:The spatial association dynamics of free-ranging cattle herds are not fully understood;however,they can have a direct influence on the spatial patterns of resource utilization.The aim of our study was to examine new analytical methods of identifying the spatio-temporal patterns of behavioral dynamics that determine cattle herd dispersal in the semi-arid rangelands of South Texas.We fitted 10 free-ranging cows with global positioning system collars and obtained positions every 5 min for each animal for 21-day trials,twice during the summer and winter period.We used an association pattern recognition software(ASSOC1)and the herd center of gravity to identify the spatial and temporal thresholds that defined dispersion-aggregation patterns and individual position to determine their relation to social dominance.Results:The association pattern defining herd membership was that animals spent 70%of their time within 200 m of each other.Dominance ranking did not appear to influence association membership or position within the herd.The cattle showed a more dispersed distribution during summer,but in winter,herd members behaved in a more aggregated pattern.This distribution is contrary to patterns described in more northerly and mountainous regions.Conclusions:The spatial thresholds of the cattle herd and the overall distance of all members to the center of the herd were smaller during winter and larger during summer,indicating that this study herd congregated during the winter and dispersed during the summer.Although this study uses a herd of 10 individuals in a 100 ha pasture to evaluate spatio-temporal dynamics,our results provide evidence of the ability of current tracking and spatial association tools to detect and quantify seasonal changes in cattle herd dispersion-aggregation patterns.The use of these data collection and analysis methods could prove useful in larger cattle herds,increase our understanding of herd spatiotemporal behavior,and subsequently help in the development of improved management practices.

Environmental and landscape influences on the spatial and temporal distribution of a cattle herd in a South Texas rangeland

The multiple spatial and temporal parameters affecting cattle herd distribution and activity dynamics can significantly affect resource utilization but are not fully understood.The aim of this study was to determine whether current animal tracking technology and spatio-temporal analysis tools can be used to integrate multi-scale information on herd distribution patterns as a function of seasonal forage production,periods of the day,animal activity,and landscape features.Positional and activity information of 11 free-ranging cows within a 31-member herd was obtained at 5-min intervals by using GPS collars for 1 year within a 457-ha ranch in the semi-arid rangelands of South Texas.Forage biomass was calculated with satellite imagery.Spatial analysis of cattle distribution and landscape features was conducted with GIS.Herd spread was greatest during the growing season.Throughout the year,during midday,the herd showed smaller spread and greater use of shade patches than any other time of day.Cattle also aggregated under trees in winter,particularly during the night.There was no statistically significant overall pattern of seasonal changes in the use of water and supplemental feeding areas,but a trend toward highest use during the winter.However,significantly different diurnal patterns in the use of supplemental feed and water were observed within each season.This study found a strong influence of shade patches relative to the influence of water and supplemental feeding areas on the diurnal and seasonal movement patterns of cattle in shrub-dominated rangeland.Although this study used only 11 tracked cows in a 31-member herd,the results indicated that techniques such as seasonal and diurnal GPS tracking,GIS,and remote sensing data enable evaluation of multiple spatial and temporal dynamics of cattle distribution and activity patterns.The smaller spread during the dry winter season associated with the observed aggregation of individuals in water and supplemental feeding areas,may aid in determining the most critical times for providing supplemental resources and guide the allocation of those resources to areas not frequently used by cattle,thus stimulating the animals to visit unused sites during the non-growing season.

Integrating space and time: a case for phenological context in grazing studies and management

In water-limited landscapes, patterns in primary production are highly variable across space and time.Livestock grazing is a common agricultural practice worldwide and a concern is localized overuse of specific pasture resources that can exacerbate grass losses and soil erosion. On a research ranch in New Mexico with average annual rainfall of 217 mm, we demonstrate with a quantitative approach that annual seasons vary greatly and examine foraging patterns in Angus-Hereford(Bos taurus) cows. We define five seasonal stages based on MODIS NDVI: pre-greenup, greenup, peak green, drydown and dormant, and examine livestock movements in 2008. Daily distance traveled by cows was greater and foraging area expanded during periods with higher precipitation. A regression model including minimum NDVI, rainfall and their interaction explained 81% of the seasonal variation in distance traveled by cows(P < 0.01).Cows explored about 81 ha·d^(–1) while foraging, but tended to explore smaller areas as the pasture became greener(greenup and peak green stages). Cows foraged an average of 9.7 h daily and spent more time foraging with more concentrated search patterns as pastures became greener.Our findings suggest that phenological context can expand the capacity to compare and integrate findings, and facilitate meta-analyses of grazing studies conducted at different locations and times of year.