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Estimating individual survival using territory occupancy data on unmarked animals
 

Summary: Estimating individual survival using territory
occupancy data on unmarked animals
Tobias Roth* and Valentin Amrhein
Research Station Petite Camargue Alsacienne, 68300 Saint-Louis, France, & University of Basel, Zoological Institute,
4051 Basel, Switzerland
Summary
1. Survival estimation forms the basis of much ecological research, and usually requires data on
marked animals. In population studies of territorial animals, however, data are often collected on
animal territory occupancy without identification of individuals. Previously, these data could not
be used to estimate demographic parameters such as survival.
2. We developed a hierarchical site-occupancy model for estimating survival from territory occu-
pancy data without individual identification. We defined survival as the probability that an individ-
ual occupying a territory survives until the next reproductive period and settles in the same territory
again. To evaluate our model, we used simulated data as well as real data from a long-term study on
nightingales Luscinia megarhynchos, from which mark-recapture data and territory occupancy data
were available.
3. When applied to simulated data sets on territory occupancy, with parameter settings that are
typical for different monitoring programmes (i.e. 10 years duration, three or eight visits per season,
and 55 or 200 territories surveyed), our model yielded unbiased estimates of survival if the probabil-
ity of detecting an occupied territory during a single visit was p = 0∆5 or p = 0∆7.

  

Source: Amrhein, Valentin - Zoologisches Institut, Universitšt Basel

 

Collections: Environmental Sciences and Ecology