COS 140-2 - Early-life and acquired experience interact in shaping migratory behavior of Egyptian vultures (Neophron percnopterus)

Abstract: Two types of experience have been shown to affect animals' proficiencies and eventually their fitness: early life experience, i.e., the environment to which the animal is exposed to during its early development, and acquired experience, i.e., repeatedly practicing a specific task. One such task is the completion of long-range migratory journeys. For migratory animals, migration poses a major challenge as it is a period in which the animal is required to move very long distances, often encountering unfamiliar environments, while expending a lot of energy for long stretches of time. Indeed, migration has been shown to be a major cause of mortality in many migratory species, compared with other periods in their annual cycle. We used data collected by satellite transmitters to study the migratory proficiencies of two sympatric populations of Egyptian vultures (Neophron percnopterus) during multiple migratory journeys. The two groups differed greatly in their early life experience, one group being captive-bred and the other wild-hatched. Furthermore, captive-bred vultures were released to the wild after the annual period for the outset of their first migration has already passed, and thus migrated for the first time at an older age than wild-hatched vultures. We found that both early life (captive or wild origins) and acquired (number of times migrated) experiences affected the vultures’ migration proficiencies. Captive-bred vultures during their first migration were the least efficient group, showing longer migration times, shorter daily progress, and less efficient soaring-gliding behavior. However, these differences disappeared almost completely during their second migration, with no observed effect of mortality. Differences among other groups were less prominent, but where found, these differences always supported the hypothesis that flight and migratory proficiencies improved with acquired experience. Our results present important, and so far overlooked, consequences of captive-breeding and reintroduction and thus have important conservation implications. Furthermore, our findings highlight how the interactions between early-life and acquired experiences may shape animals' proficiencies, and thus directly impact their fitness.