Ido Izhaki Previous Research Project

 

Land-use effect on the foraging and feeding of Eurasian griffon vultures (Gyps fulvus) in northern Israel

 

 

(with Dr. Dr. Yohay Carmel, Dr. Ofer Bahat and Lia Court)

 


        

 

The goal of this study was to Identify the effect of land use and other environmental factors on the foraging and feeding patterns of Griffon vultures

 

 

Griffon vulture (Gyps fulvus)

 

Project description (Lia's Court M.A.'s abstract):

 

Human activities frequently reduce wildlife food availability that may cause population decline and species extinction. Endangered species Management regimes often provide supplements when food availability or quality is a major limiting factor. This activity requires comprehensive understanding of foraging and feeding patterns of the referred species.

The population (ca. 350 individuals) of the locally endangered Eurasian Griffon vulture (Gyps fulvus) in Israel has declined significantly in recent decades, due to persecution and reduced habitats. Griffon vultures are gregarious obligatory scavengers, which feed mainly on carcasses of cattle and large wild ungulates. Extremely low nesting success rate of Griffon vultures has been observed in the Golan area, where most of Israels population exists (60-70% pre-fledged chicks mortality). Major causes for this phenomenon were found to be artifacts in food brought to nestlings and calcium deficiency. Management activities treat this situation by adding crushed bones to the carcasses vicinity in the open and at feeding stations. Vulture usage of feeding stations is very limited and there is no information about which amongst the abundant carcasses they might use. Hence, this activity is complex and requires many financial and human resources and much time.

The research was based on the hypothesis that the degree of usage of available food by Griffon vultures is simultaneously affected by various factors in its habitat. The main goal of this research was to identify the effect of land-use and other environmental factors, on the foraging and feeding patterns of Griffon vultures and exploitation rate of available food, spatially and temporally. An efficacious tool for food quality control can be devised, based on the results, which will optimize conservation policy of Griffon Vultures, and also can be used to predict impact of development, such as settlements and tourism, on the vulture population in Israel.

In order to identify the effect of land-use and selected environmental factors on foraging and feeding patterns of the Griffon vultures, 237 carcasses in the Golan area were characterized and quantified during 2002-2003. Data was analyzed by GIS (Geographic Information System) and multi-variables statistical tests. The results present models for predicting the temporal and spatial food exploitation patterns of vultures by the tested variables.

This research successfully identified food abundance and preferred feeding areas of the Griffon vultures in the Golan Heights. The exploitation predictive models show that the food characteristics (carcass condition, availability time and size) have a pivotal role in its use by vultures. This reduces the predictability since these variables can not be spatially mapped or forecasted. The preferred carcass by vultures was found to be partly pre-eaten by scavengers, fresh and large. Carcass usage by vultures was also recognized to be influenced by land use agents such as the carcass distances from electricity lines, orchards and built-up area (the further the carcass is from these elements, the usage increases), as well as the distance from nesting and roosting sites (vultures prefer to feed in the vicinity of their roosting colonies).

The Golan Heights forms an attractive area for vultures from all over Israel and its surroundings, since it comprises a unique combination of food abundance, suitable habitats for foraging and roosting and better nature conservation conditions, in comparison to the near by areas. According to these results it is highly recommended, to base future rural planning on enlarging existing settlements or orchards rather than establishing new ones. In addition, it is advisable to minimize disrupting factors (power lines, protective management against predators using dogs), in order to encourage the vultures to forage and feed in the Golan area. Treating available food in the open (bone adding and laceration), correspondingly with improving the locations and operation of feeding stations, as a quality food source backup, are essential management tools for conserving the species and can have significant implications for the survival of the Eurasian Griffon vulture in Israel.

 

 

This project was supported by The  Garelik Fund, The Golan Research Institute