Including behavioral data in demographic models improves 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 (λ) 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. This paper provides a framework for integrating behavioral estimates of OSR into population models used for conservation. Male and female fertility is estimated at six island study sites for California sea lions (Zalophus californianus), using population census data (ASR) and behavioral data (OSR). These estimates are used to construct alternate projection matrices to examine the impacts on λ. 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 could be used as an early indicator of population decline.