Integrating behavior and demography in vertebrate conservation: Does mating behavior improve estimates of population viability?

Individual differences in behavior and social status can determine the rate of population change and thus the threat that imperiled species face in the real world.  One way that behavior may be manifested in terms of an annualized population growth rate (l) is through the effects of sex ratio biases.  A population’s operational sex ratio (OSR) typically deviates from the actual sex ratio (ASR), leading to pronounced sexual dimorphism in fecundity.  I describe a developing  framework for integrating behavioral estimates of OSR into population models used for conservation.  As an example, I estimate male and female fertility for six island study sites for California sea lions using data from population censuses (ASR) and behavioral data (OSR).  I then use estimates of fertility to construct alternate demographic schedules to examine consequent impacts on l.  For all sites, including behavioral information on sex ratio in demographic models yields estimates of l that fall within the 95% confidence interval of l from estimates made from population trend data.  Inclusion of behavioral data in population models not only allows for explicit analysis of the effects of behaviors on viability, but may also help to identify behavioral attributes that one might use as an early indicator of population decline.