SOCIAL INTERACTIONS AND VOCAL COMMUNICATION IN THE EURASIAN GRIFFON VULTURE
A bioacoustic approach
The genus Gyps, to which the vulture species commonly known as griffons belong, is an exception to all the other genera in the Accipitridae family as they form very numerous colonies, in which cooperation is essential for their survival, unlike their closest relatives. Until now, it has been a commonly thought that calls such as croaking, hissing, and screeching produced by these large birds of prey were almost exclusively linked to competition for trophic resources. Curiously, despite the many studies carried out on Gyps vultures, little was known about the vocalisations related to social interactions and communication between individuals.
Our bioacoustic study concerning the Eurasian griffon vulture has the aim of deepening the knowledge and the meaning of the sounds emitted, discovering when and why they are produced and finally to demonstrate that the complexity of vocal language in birds is not a prerogative of passerines, but can be linked to the evolutionary and social history of the species.
Considering the ‘Social Intelligence Hypothesis’, we hypothesised that griffon vultures’ communication system is more complex than what past observations suggested and, since no studies have been already carried out on this subject, we provided a working protocol to explore as much as possible the ecological contexts in which the species is more easily recorded and observed, such as feeding sites and roosting-nesting cliffs.
In the first step of our study we explored these two aspects: (i), the analytical and quantitative description of the vocal repertoire of the species, including adults, sub-adults, juveniles and chicks, with the population of the central Apennines as our model; (ii), the association of the identified vocalisation categories with specific behavioural and ecological contexts.
The next steps of this research project will focus on individual recognition mechanisms and the interactions with other species sharing part of the same ecological niche.
Gyps fulvus Hablizl, 1783
IUCN Red List status: Least Concern
The Eurasian griffon vulture is a large colonial bird of prey found mainly in Europe. Females can reach 12 kg in weight and a wingspan of more than 2.5 meters. Like all large raptors it takes advantage of thermal currents to cover great distances. This allows them to find the carcasses of wild ungulates and/or domestic livestock on which they feed. Pairs are monogamous for their entire lives, breed between January and February on towering cliffs, and the young fledge in August. They lay a single egg and both parents provide parental care.
After a dangerous population decline due to the gradual abandonment of pastoralism, voluntary and involuntary poisoning, electrocution accidents and the increasing administration of anti-inflammatory drugs for veterinary use, today the European population of this extraordinary bird species is estimated to be between 32,000 and 35,000 pairs. From 2014 to the present the population in Italy has increased by 40-60%, with 800-900 individuals and 213 territorial pairs estimated.