The effect on model identifiability of allowing different relocation rates for live and dead animals in the combined analysis of telemetry and recapture data

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Abstract

Models are described for the joint analysis of live-trapping and radio telemetry data from a study on black bears (Ursus americanus) in which all animals received ear tags and a subset also received radio tags. Concerns about bias in survival estimates led to investigation of identifiability and estimator precision for a series of models that allowed differenttelemetry relocation rates for living and dead animals, in addition to emigration and seasonal variation in survival. Identifiability was determined by showing that the expected information matrix was nonsingular. Models with fidelity constant across time, and with the same degree of time specificity for survival rates and relocation rates for dead animals, were determined to be nonidentifiable. More general models, with a greater degree of time specificity for survival rates, were near-singular, and estimators under these near-singular models had poor precision. Analysis of data from the study on black bears illustrated that estimates of survival have poor precision when relocation rates are estimated separately for live and dead animals. It is recommended that the effort expended to relocate both living and dead animals be consistently high in each telemetry survey, so that relocation rates will be high and constant across time and mortality status.