Towards an integrated view of escape decisions in birds under variable levels of predation risk
Kuupäev
2020-02-03
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Abstrakt
Suurema hirmutunde korral panustavad loomad enam aega valvsusele ja ohtu silmates põgenevad varem. Inimene võib oma tegevustega tahtmatult loomade hirmutunnet suurendada, põhjustades halbu käitumisotsuseid ja populatsiooni arvukuse langust. Loomade hirmutunde hindamiseks mõõdetakse enamasti kas nende valvsust või põgenemiskaugust. Doktoritöös uuriti, kas üheainsa käitumispõhise indikaatori mõõtmisest siiski piisab, et lindude hirmutunnet ja põgenemisega seotud kulutusi veenvalt hinnata. Lisaks selgitati, kas linnud jätkavad kiskja jälgimist veel ka põgenemise ajal ja milliseid lisategureid tuleks põgenemiskäitumise uurimisel arvesse võtta. Doktoritöö raames uuriti standardiseeritud viisil kümnete linnuliikide põgenemiskäitumist mitmel pool üle Euroopa, et tuvastada üldisi trende lindude käitumismustrites. Põgenemiskäitumise poolest olid linnalinnud mitmes mõttes julgemad kui maalinnud ning laiuskraadi kasvades muutusid linnud vähem ettevaatlikuks. Üllatuslikult olid linnalinnud valvsamad kui maalinnud ning vastupidiselt varem eeldatule viivitasid valvsamad linnud mõlemas elupaigas põgenemisega kauem. Need tulemused seavad valvsuse tavapärase kasutatavuse lindude hirmutunde kirjeldamiseks kahtluse alla. Tööst ilmnes veel, et lisaks enamasti uuritavale põgenemiskaugusele tuleks mõõta ka põgenemishetkele järgnevaid käitumismustreid. Need täiendavad mõõtmised annavad terviklikuma ülevaate põgenemisega seotud ajalistest ja energeetilistest kulutustest, mis omakorda aitab kaasa põgenemisotsuste mõistmisele. Näiteks leiti, et põgenemisele kulutatud aeg sõltub hirmutunde dünaamikast põgenemise ajal. See on esimene eksperimentaalne tõend, et linnud jätkavad kiskja jälgimist ka pärast põgenemise alustamist. Doktoritöö tulemused toetasid ka varasemaid uuringuid, mis on leidnud, et põgenemisotsuseid mõjutavad ka näiteks liigiomane kehamass, peidupaiga lähedus ja seltsingu suurus. Doktoritööst saadud teadmised aitavad paremini ennustada, kuidas lindude hirmutunne võib inimtekkeliste häiringutega seoses muutuda, mis omakorda aitab kaasa looduskaitseliste meetmete planeerimisele.
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.
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.
Kirjeldus
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Märksõnad
birds, predatory animals, animal behavior, escaping