Estimating survival of unmarked neonates with camera traps

Abstract

AbstractSurvival and recruitment of offspring are important drivers of population dynamics. Yet, studying wildlife shortly after parturition is logistically challenging and oftentimes cost‐prohibitive. As a result, our ecological understanding of neonate survival is limited for many species and management decisions are often made without an adequate understanding of their implications. We developed a model to estimate the overall survival rate of neonates and the timing of mortality (i.e., shape of the survival curve) based on changes in the ratio of neonates to adult females observed in camera trap photographs. We evaluated the model with simulations and provided an example application using North American elk (Cervus canadensis) in Idaho. Our simulations suggested that estimates of the overall neonate survival rate and the shape of the survival curve are accurate when researchers provide unbiased estimates of adult female survival, birth rate (offspring per adult female), and the distribution of birth dates. When researchers can provide a priori values for just adult female survival and birth rate, estimates of the overall survival rate were accurate, but early neonate mortality was underestimated. Our estimate of neonate elk survival in Idaho was consistent with values generated by capture‐based studies. Our ratio‐based model provides an alternative to traditional methods for estimating neonate survival and does not rely on invasive or expensive capture and monitoring techniques. We believe this method could apply to a wide variety of species due to the ease of data collection and the relatively small number of critical model assumptions. A major benefit of our model is the ability to simultaneously monitor other species in the community, which will facilitate a better understanding of drivers of variation in neonate survival.