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Pair bonding within the Bearded Vulture Captive-Breeding Network  

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In ancient mythology, Greeks would call him Eros, Romans would call him Cupid. But for the Bearded Vultures within the Captive-Breeding Network (Bearded Vulture EEP), our “God of love and attraction” is called Àlex Llopis. As our captive-breeding expert and coordinator of the Bearded Vulture EEP on behalf of EAZA, Àlex assumes the challenging responsibility of pairing the Bearded Vultures (Gypaetus barbatus) held in captivity in more than 40 Zoos and specialised Breeding centres inside the network.


Pair bonding within the Bearded Vulture EEP 

The Bearded Vulture EEP is a network composed of many different types of institutions, mainly zoos (35), specialised breeding centres (6), private partners (2) and recovery centres (2). All these institutions keep 184 birds as captive stock, owned mainly by the Vulture Conservation Foundation (VCF). The network aims to ensure the species’ long-term survival and genetic diversity (conservation ex-situ) and produce the maximum number of offspring (conservation in-situ), which is fundamental for restocking and restoring Bearded Vulture populations in the wild. 

Pair formation is a complex and risky task. Bearded vultures are monogamic species, meaning they keep their partners for life. They are very selective and don’t pair as easily as other species; some individuals within the network have been paired with 5 or 6 potential partners until they bred successfully! The pairs productively breeding in captivity is kept with the same partner until one dies, which is precisely how it happens in the wild.  

Unfortunately, as we lose some adult birds every year (such as Winnie, one of the founder birds of the EEP), experienced individuals can be paired again. Before the breeding season starts, Àlex does his magic by finding the right match between those experienced adults, individuals that did not pair successfully, the new juveniles born this year held in captivity, and irrecoverable birds from the wild that have eventually joined the network. 

How the Bearded Vulture EEP works 

Before disclosing the criteria that fundaments Bearded Vulture pair bonding, it is essential to understand that each institution within the network fulfils a different objective. For instance, the Vallcalent specialised breeding centre (Spain) managed by the VCF and the Richard-Faust Centre (RFZ, Austria), are responsible for taking in new founders (injured birds from the wild), adopting chicks and housing problematic birds. By hosting individuals from all genetic lineages within the EEP, they promote reproduction to maintain their genetic information in captive stock. 

Gualalentín specialised breeding centre in Cazorla, Spain, also managed by the VCF under an agreement with Junta de Andalusia, thrives on prodcuing as many offspring as possible, which are mainly released in the wild within the ongoing conservation efforts. Zoos and private centres house already established pairs and breed the maximum number of offspring under the guidance and supervision of Àlex.  

Bearded Vulture pair in Guadalentín Specialised Breeding Centre © Hansruedi Weyrich

Finding the “right match” 

One of the factors weighing in Àlex’s decision is the experience of the partner institution in breeding and rearing chicks. An individual holding an important genetic heritage will not be sent to a less experienced partner within the EEP. The decisions are difficult to make, and sometimes birds must be transferred to a different partner within the EEP.  

The age of each individual has a strong influence. Bearded Vultures are long-lived species that take 7-9 years to reach sexual maturity. Males, though, tend to be ready to mate before females, which sometimes poses a problem. If a pair is established and the male reaches sexual maturity before the female, she can become aggressive towards the male and cause him injuries. In these cases, the bonding is broken; usually, the birds must be paired with other individuals. Therefore, Àlex tries to guarantee that females are 1 or 2 years older than males. Juveniles will also be paired on their first winter; it is important that they start bonding at an early age.  

Ensuring genetic diversity within the Bearded Vulture EEP 

Genetics is another determinant factor for pair bonding. The Bearded Vulture EEP strives to ensure genetic diversity for the species’ long-term survival. The first efforts of breeding Bearded Vultures in captivity in Europe go back to 1978 when the existing autochthonous Bearded Vulture population was threatened, and the Alpine population was completely extinct. The Richard Faust Centre was the headquarters of a programme to breed Bearded Vultures in captivity and reintroduce their offspring in the wild, which brought the species back to the Alpine mountains. The current knowledge and experience on captive-breeding  within the Bearded Vulture EEP, stems from the RFZ, that pioneered in the area, ttogether with the support of many European Zoos that housed pairs 

Studies found that historically, the Alpine Bearded Vulture population had alleles from the Asian population, bridging the West (Pyrenean) and the Eastern (Asian) populations. Pyrenean birds would also hold alleles from Asian populations back then by breeding with Alpine individuals; however, due to their extinction in the Alps, the Asian heritage in the Pyrenees is now barely expressive. Thanks to genetic analyses, we hold the species’ studbook and family tree of each individual within the Bearded Vulture EEP, which allows us to preserve the lineages and promote intraspecific diversity. Lineages that are more threatened, such as the Creete and Corsican, have ongoing projects, such as the LIFE GypRescue in Corsica, to perpetuate their important genetic heritage.  

From genetics to behaviour 

Each Bearded Vulture individual has strong personal traits; some would be more dominant, some show aggressiveness, and others are calmer or submissive. When it comes to behaviour, no exact science or theory can work. They can be very aggressive with a potential partner and act differently when paired with another individual.

Apart from collecting information for the studbook and guaranteeing the safety and well-being of all birds, the technicians at our Breeding Centres attentively observe the birds’ behaviour. Each cage has a webcam that provides real-time insightful information. Every hatched Bearded Vulture is assigned an ID number and given a name, endowing each individual with distinct personality traits. 

“We are not working with Bearded Vultures; we are working with individuals. This is what makes the programme successful.” 

Àlex Llopis, Manager of VCF Captive-breeding centres and Coordinator of the Bearded Vulture EEP 

Àlex revealed a technique for enhancing pair bonding, which has proven to yield promising results. To encourage bonding between a pair that is not yet breeding, they are occasionally placed in a cage positioned between breeding pairs. According to the expert, they sense the other pairs and are stimulated by them, starting to defend their territory, often intensifying their bonding and, eventually, leading to breeding. 

Fifteen new pairs will be formed this year 

Considering each of these attributes, Àlex still adds to the equation the future release site of the offspring descending from that potential pair. After all, species conservation is a long-term commitment. It takes almost a decade for an individual to produce offspring, sometimes more. There are many potential problems between the pairs, such as diseases or infections that can jeopardise the efforts. Perseverance and determination are fundamental traits of human keepers.

As of today, two new pairs were already formed, and thirteen additional will be bonded in the coming weeks. An operation that involves transferring individuals between countries and institutions. New pairs will be tried out in the Guadalentín, Vallcalent, Richard Faust specialised Breeding and Parc Animalier des Pyrénées Centres, but also in the  Poznan Zoo, Green Balkans, Liberec Zoo, Montowl private collection, Frankfurt Zoo and Goldau.  

By mid-October, we expect the birds sexually mature to start playing with nesting materials provided, such as sticks and wool, building their nest. Engaging in mutual preening and exhibiting aggression towards neighbouring pairs is often observed, signalling the start of the breeding season.  

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