Gamla Nature Reserve (GNR) used to host the largest colony of Eurasian griffon vultures (Gyps fulvus) in northern Israel. Since the early 2000s, the colony has suffered a drastic decline, which could lead to its extinction. In this descriptive study we present the population dynamics at GNR based on an analysis of data collected over 15 years (1999–2013). A monitoring scheme of monthly counts, developed at GNR, provided a database, facilitating a mathematical analysis of the population decline trends and their seasonal fluctuations. The analysis revealed a decline in the population size, which appears similar to an inverse-sigmoid and indicates a potential extinction of the colony by 2020. The analysis also indicates that, in addition to the overall pattern, the number of vultures fluctuates seasonally, with smaller numbers in spring and greater numbers in autumn and winter. Furthermore, this model suggests that latent factors might have influenced the decline; poisoning, thought to be a root cause, might not be the only factor influencing extinction. We demonstrate the importance of combining frequent data collection with modeling techniques for the analysis of raptor population trends.
Bibliographical noteFunding Information:
We thank the INPA for supplying the data and N. L. Richards for her review and contributions to this manuscript. We thank the editors of the Journal of Wildlife Management and 2 anonymous reviewers for their valuable comments that helped improve the manuscript. We also thank A. W. Gelman for assisting in the final draft. The Israeli Ministry of Science, Technology and Space partially funded this study (Grant No. 3-13578).
© The Wildlife Society, 2018
- Eurasian griffon vulture
- Gamla Nature Reserve
- logistic model
- monthly counts
- population dynamics
- time series analysis
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Nature and Landscape Conservation