On 6 March at 10:15 Kunter Tätte will defend his doctoral thesis „Towards an integrated view of escape decisions in birds under variable levels of predation risk”.
Professor Raivo Mänd (TÜ ÖMI)
Anders Pape Møller (Université Paris-Sud, CNRS, Prantsusmaa, Beijing Normal University, Hiina).
Guy Beauchamp, PhD (Kanada).
Animals with higher levels of fearfulness will spend more time being vigilant and will escape earlier after having spotted a potential threat. Human-caused disturbances can involuntarily increase fearfulness in animals, which can result in inaccurate behavioural decisions that can lead to population declines. The most common measures of fearfulness in animals are vigilance and flight initiation distance. Present thesis examined whether the use of a single behavioural indicator is enough to assess fearfulness and costs related to escape. The thesis also investigated whether birds continue to monitor predators during escape, and which other factors should be considered when studying escape behaviour. Tens of bird species were studied across Europe in a standardized way to find general patterns in the behaviour of birds. Urban birds were characterized by a more relaxed escape behaviour than rural birds. In addition, birds took longer to become alert to threats as latitude increased. Surprisingly, urban birds were more vigilant than rural birds, and, contrary to the prevalent theory, vigilant birds delayed escape more. These results raise doubt whether vigilance should be used as an indicator of fearfulness in birds. The thesis also highlighted that in addition to measuring flight initiation distance, it is important to measure subsequent behavioural decisions. Doing so provides a more complete view of the energetic and opportunity costs of escape, which helps to understand escape-related decisions. For example, it was found that escape duration depends on how the perceived risk of predation changes while fleeing. That is the first experimental evidence that birds continue to monitor predators after initiating escape. Last, the evidence from the thesis complements previous research that, for example, has found body mass, distance to refuge, and group size to influence escape decisions in animals. The knowledge gained from the thesis improves predictions about the impact of human-caused disturbances on fearfulness in birds, which in turn benefits decision making in wildlife management.