Contraception can Lead to Trophic Asynchrony between Birth Pulse and Resources
Figure 3
Birth phenology of feral horse (Equus caballus) untreated (○) and post-treated (• = first post-treatment birth, ▴ = birth subsequent to •) females.
Births are shown as a function of temperature at approximate conception date for populations at Little Book Cliffs Wild Horse Range, CO (A), 2005–2011, and Pryor Mountain Wild Horse Range, MT (B), 2005–2011, and McCullough Peaks Herd Management Area, WY (C), 2007–2011. Post-treated females were previously inoculated with the immunocontraceptive porcine zona pellucida (PZP). Mean Normalized Difference Vegetation Index (green) represents temporal availability of forage. Mean daily surface temperature is shown in red.