This project focuses on developing individual level hierarchical models to assess trade offs between demographic rates for a range of vertebrate and invertebrate species. This project is part of a long term initiative aiming at understanding the evolutionary mechanisms that shape age trajectories of mortality, fecundity and growth/maintenance along the tree of life.
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Estimating age-specific survival for long-lived species such as seabirds entails important challenges in that most capture-recapture datasets include large numbers of individuals with unknown times of birth and or death. The aim of this project is to develop a hierarchical Bayesian model that uses the information from those few censored and uncensored records to not only estimate survival function parameters but the individual times of birth and death for those for which the information is absent. After developing the model, I compared the results with traditional methods such those based on the Cormack-Jolly-Seber framework.
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From 1959 to 1980, The United States Park Service performed a sooty tern (Sterna fuscata) mass banding program on the Dry Tortugas National Park. During 22 years, over 300,000 juvenile and adult sooty terns were banded. This became one of the most extensive capture-recapture dataset for the species. Today, in collaboration with Biologist Oron "Sonny" Bass, Supervisory Wildlife Biologist for the Everglades and Dry Tortugas National Parks, and Dr. Clark, I am developing hierarchical Bayesian models that explore the influence of environmental variables such as sea surface temperature (SST) and surface air temperature (SAT) on juvenile and adult mortality as well as on the terns breeding phenology.
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In 1975, the Mexican Government, in collaboration with the New Mexico Game and Fish Department, introduced 20 desert bighorn sheep (Ovis canadensis mexicana) to Tiburon Island, Gulf of California, Mexico. Since 1995, Unidos Para la Conservacion, A. C. (UPC), under the direction of Carlos Manterola and Patricio Robles Gil, together with Dr. Rodrigo Medellin from the Ecology Institute of the National Autonomous University of Mexico (UNAM) and the General Direction of Wildlife of the National Institute of Ecology (INE) initiated a research and conservation program with the population. These efforts were coordinated with the Seri (Kun Kaak) government, an ethnic group who historically has inhabited the Island and the territories on the Sonoran mainland. Our role was to use the aerial survey data to determine the effect of extractions on the population, and its interactions with environmental stochastic processes, particularly droughts, and density dependent processes. I developed a Bayesian state space model that evaluated the effect of these variables on the population (including extractions) and predicted the fate of the population under different climate change scenarios. The resulting paper has been accepted in the Journal of Animal Ecology (go to PUBLICATIONS).
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