Fig 1.
Map of aerial survey areas of feral horse (Equus caballus) populations in the United States.
Location and topography of four U.S. Bureau of Land Management Herd Management Areas (HMA) surveyed: (A) Little Owyhee-Snowstorm Mountain HMAs, NV; (B) Cedar Mountain HMA, Utah; (C) McCullough Peaks HMA, Wyoming; and (D) Sand Wash HMA, Colorado, USA.
Table 1.
Definitions of covariates considered in sighting probability models for feral horses (Equus caballus) in western USA.
Table 2.
Abundance or removal estimates from aerial surveys and known population or removal sizes of feral horses (Equus caballus) in western USA.
U.S. Bureau of Land Management Herd Management Area (HMA) surveys: McCullough HMA, Wyoming (MCP), 3 replicates; Sand Wash HMA, Colorado (SW), two replicates; Cedar Mountain HMA, Utah (CM); and change due to removal at Little Owyhee-Snowstorm Mountains HMAs, Nevada (LO-SM), USA. Aircraft types: airplane (AP) and helicopter (HELO).
Fig 2.
Comparison of estimates to known abundance for aerial surveys of feral horse (Equus caballus) populations.
Abundance estimates or change in abundance (black dots) and 95% confidence intervals for aerial surveys of feral horse (Equus caballus) populations in the western USA, using a hybrid double-observer method. Ranges of known population sizes are shown in green. Surveyed U.S. Bureau of Land Management Herd Management Areas (HMA): McCullough Peaks HMA, Wyoming (MCP); Sand Wash HMA, Colorado (SW); Cedar Mountain HMA, Utah (CM); and Little Owyhee-Snowstorm Mountains HMAs, Nevada (LO-SM).
Table 3.
Sample size, AICc model support, and parameter estimates for models of feral horse (Equus caballus) abundance.
U.S. Bureau of Land Management Herd Management Areas (HMA) Surveyed: McCullough Peaks HMA, Wyoming (MCP), Sand Wash HMA, Colorado (SW), Cedar Mountain HMA, Utah (CM), and removal at Little Owyhee-Snowstorm Mountains HMAs, Nevada (LO-SM), USA. Sample unit is horse groups, not individual horses.