Behavioral Thermoregulation: Sheep Moderation of Core Temperature through Shade Utilization.

Shade for livestock often is considered a beneficial attribute of silvopasture systems, in which trees are managed concurrently with livestock in a pasture. Although animals can utilize natural shade in silvopasture systems, direct connections between animal behavior and temperature regulation remain to be documented. In this study, sheep were assigned to black walnut- or honey locust-based silvopastures or to open pastures. Systems (r=3) were arranged as complete randomized block design, and stocked with three ewes and two or one wethers, depending on treatment. Temperature logging devices were constructed by inserting miniature temperature loggers into blank CIDRs. Three ewes in each experimental unit within a replicate were equipped with a GPS logger and a vaginally-inserted temperature logging device for two days every three weeks. Loggers were rotated consecutively through the three replicates after each week. To determine animal position relative to trees and shade, shade maps were modeled relative to the tree canopy when the sun was highest in elevation. Ewes were categorized as utilizing the shade if their GPS location was within the modeled shade region during those hours of high-intensity sunlight. Vaginal temperatures of ewes utilizing shade were compared to vaginal temperatures of ewes in treeless pastures and to ambient temperature provided from a local weather station. It is expected that the ewes with access to tree shade will spend the majority of the afternoon in the modeled shade. When they are in the shade, their core temperatures will be lower than the core temperature of sheep not provided with shade, resulting in overall lower mean core temperatures for ewes in the silvopastures compared to sheep in the open pastures. Such a connection between behavior and physiological changes will inform potential silvopasture implementation of an actual benefit to the livestock imparted by the presence of the trees.