Researchers examined four anatomical sites on each of 155 birds: the facial surface, oral cavity, trachea and cloaca. Species identity accounted for 18.1% of variation in bacterial composition, while the sampled region accounted for 8.9%. The interaction between species and body site was also statistically significant, meaning that differences between species depended on the site examined. The sites differ in their exposure to food, air and fecal material.
The study included four European vulture species: the bearded vulture (Gypaetus barbatus), griffon vulture (Gyps fulvus), Egyptian vulture (Neophron percnopterus) and cinereous vulture (Aegypius monachus). The fifth species was the red kite (Milvus milvus), a facultative scavenger.
The results appeared in Proceedings of the National Academy of Sciences (PNAS). Antoni Margalida of the Pyrenean Institute of Ecology (IPE-CSIC, Spain) led the international study, co-directed by Michael Wink of the University of Heidelberg in Germany. Antonio Castellano-Hinojosa of the University of Granada’s Department of Microbiology also took part.
The anatomical samples had distinct bacterial profiles, rather than one uniform vulture microbiome. The cloaca contained a greater representation of bacteria associated with the digestive system, while facial surfaces and the trachea had more environmental and respiratory-associated microorganisms. These compositional differences do not establish whether particular bacteria are beneficial, harmless or pathogenic. The researchers say the functions of these bacterial species still need to be investigated.
Age was another source of variation. Chicks of the bearded vulture and Egyptian vulture had bacterial communities that differed from those of older birds. The study found little influence from sex.
Vultures consume carcasses at different stages of decomposition and are continually exposed to diverse microorganisms, including potentially pathogenic bacteria. Their scavenging role also features in wider biodiversity reporting, including a Canary Islands programme. This research focused on how host species and body region relate to microbial communities.
The findings show the limits of exposure as an explanation for microbiome composition: contact with a microorganism does not by itself mean it will establish and persist in an animal. The researchers say the functional role of the identified bacteria will require further study.
