Multi-scale straightness index analysis of goat behavior

TitleMulti-scale straightness index analysis of goat behavior
Publication TypeWeb Article
Year of Publication2015
AuthorsGipson, TA, Andries, KM, Hutchens, T, Evans, ME
Series TitleJournal of Animal Science
Type of Medium(Supplement s3)

Multi-scale straightness index (MSSI) has been proposed for determining behavioral states such as resting, grazing, or commuting in wildlife but its suitability in livestock is not known. Therefore, the objective of this study was to apply MSSI to a herd of grazing goats. On a random sample of 13 mature Boer-cross females from a herd of 120, GPS collars that recorded a fix every 5 min were fitted for 3 consecutive days in August, 2012. The study area was a 40-hectare unimproved hill pasture. The fix records were post-processed and imported into ArcMap. Boundaries of the pasture, including a 7-m external buffer, were constructed as shapefiles. Only fixes (average of 804 ± 15.2 fixes/goat) within the boundary and buffer shape-files were exported to a spreadsheet for the calculation of MSSI using granularity (g) from 1 to 12 and window (w) from 1 to 36 with the constraint that w/g must be an integer, yielding a total of 110 g-w combinations. Within daytime (D) and nighttime (N) periods, MSSI were calculated for each g-w combination yielding 868,707 MSSI for D and 541,599 MSSI for N. LSmeans for each g-w combination were estimated using mixed model analysis with collar as random effect and day (1, 2, or 3) as repeated measure. A linear-linear-linear grafted polynomial analysis was conducted to ascertain ridge points for g-w combinations (between two break points). The first linear segment before the first break point for both D and N was always when g = w for a g/w ratio of 1 and accounted for 11% of the MSSI. The last linear segment after the second break point represented highly tortuous travel indicating most probably grazing or resting. This segment was 81% and 85% of the MSSI with an average MSSI of 0.17 ± 0.083 and 0.08 ± 0.050 for D and N, respectively. The middle linear segment represented targeted travel and accounted for 8% and 4% of the MSSI with an average MSSI of 0.53 ± 0.108 and 0.41 ± 0.119 for D and N, respectively. For the targeted travel segment, g averaged 1 for both D and N and w averaged 5 and 3 for D and N, respectively. Even in a herd of goats familiar with the terrain, targeted travel account for a small percentage of behavior and was only for a short duration.