The influence of harvest timing on greater sage-grouse survival: A cautionary perspective

Abstract

Understanding the influence of harvest regulations on wildlife populations is crucial for successful population management and species conservation. This is true of greater sage-grouse (Centrocercus urophasianus), a species of great conservation concern in western North America that is a candidate for protection under the United States Endangered Species Act and is hunted in nine states within the United States. Recent recommendations have proposed shifting hunting seasons to later in the year, with a goal of reducing harvest of adult female and juvenile sage-grouse. Foundational principles of harvest theory, however, suggest that such changes to harvest timing could have unintentional and adverse effects on greater sage-grouse populations. I used published estimates of seasonal survival to reconstruct weekly mortality curves for adult female and juvenile greater sage-grouse in Nevada, USA. Under a hypothesis of compensatory mortality, I then calculated the maximum harvest occurring during any 1-week interval that could be compensated by non-harvest mortality that occurs after the hunting season. This value universally declines as harvest is held later in the season. Under a hypothesis of additive mortality, I calculated the realized reductions in both survival and subsequent reproductive success that would be expected for a given level of harvest. Both of these values increase if harvest is conducted later in the season, resulting in a larger additive effect than if harvest had occurred earlier. If reduced mortality of specific age or sex classes is desired, I suggest managers employ reduced bag limits, shortened season lengths, or permit systems to meet this objective. Holding hunting seasons later in the year than is presently custom (i.e., beginning sometime during Sep) should be avoided unless specific information exists to predict the change in harvest rate that would occur following changes to harvest timing. © 2015 The Wildlife Society.