Effects of hunting males on female cougar population growth and persistence

Dana Eleanor Morrison

Carnivore populations are often managed based on the density dependent, compensatory mortality hypothesis, which suggests that trophy hunting of males causes an increase in female reproductive success, survival, and population growth. Our previous research on cougars showed that increased mortality of males resulted in no net reduction in males due to increased immigration by males. Female reproduction and survival did not increase to compensate for male mortality. We suggested that female demographics are additive to male mortality and might even be depensatory (inversely compensatory), whereby increased male immigration and infanticide may be associated with decreased female reproductive success, survival, and population growth. In this paper we test the compensatory, additive, and depensatory mortality hypotheses by censoring incidental female hunting deaths and plausible kitten infanticides from two independent cougar populations. We then recalculated female reproduction, survival, and population growth. The previously observed lack of compensatory demographics allowed us to censor deaths in this manner. The lightly hunted population (hunting mortality of males = 0.16) had a female population growth rate of 1.05. With incidental female mortality from hunting removed the growth rate increased to 1.14. The heavily hunted population (hunting mortality of males = 0.35) had a female population growth rate of 0.78. With infanticide removed the growth rate increased to 0.89. With incidental hunting mortality of females removed, the growth rate increased to 0.98. With both incidental female mortalities and infanticide removed, the growth rate increased to 1.14. Light hunting of males (no net male immigration) decreased female population growth in an additive manner and heavy hunting of males (increased net male immigration) decreased female population growth in a depensatory manner. We reject the compensatory mortality hypothesis, and suggest that hunting of males has a negative additive or depensatory effect on female population growth depending on the intensity of male mortality. We encourage others to test our conclusions on a variety of hunted carnivores.

Effects of hunting males on female cougar population growth and persistence

Files and links (1)

Abstract

Metrics

Details