Island tameness and the repeatability of flight initiation distance in a large herbivore

Abstract

Antipredator behaviours can be lost relatively quickly in populations that are relieved of predation, as is known for several species inhabiting islands. Flight initiation distance (FID) is often studied in the context of island tameness; however, little is known about the factors that influence and maintain FID variation in predation-free populations. Here, we studied FID in foals of an isolated predator-free population of feral horses (Equus caballus L., 1758) on Sable Island, Canada, to determine if FID could be used for research on consistent individual differences in risk aversion and island tameness. In addition to testing for temporal, spatial, and sex effects on FID, we compared repeatability estimates at two temporal scales (within and among days). Similar FID for measurements obtained on the same day and for males and females indicated an absence of short-term desensitization and sex effects. In contrast, FID decreased for measurements made on subsequent days and from east to west, which could reflect habituation to human presence and (or) other temporal and spatial processes. Repeatability was high (0.42 ± 0.06), but tended to decrease with increasing time intervals. This study highlights the potential of FID for individual-based research on the ecology and evolutionary dynamics of risk aversion in predation-free populations.Key words: boldness, Equus caballus, fear, horse, personality, risk aversion, temperament.Résumé : Les comportements anti-prédateurs peuvent disparaître assez rapidement dans les populations ne faisant plus l'objet de prédation, comme cela est le cas pour plusieurs espèces habitant des îles. La distance de fuite (DF) est souvent étudiée dans le contexte de la docilité insulaire; cependant, les connaissances sur les facteurs qui influencent et maintiennent les variations de la DF dans les populations sans prédateurs sont toutefois limitées. Nous avons étudié la DF chez des poulains d'une population de chevaux feraux (Equus caballus L., 1758) isolée et sans prédateurs à l'île de Sable (Canada) pour déterminer si la DF peut être utilisée pour étudier les différences individuelles sur le plan de l'aversion au risque et de la docilité insulaire. En plus de vérifier la présence d'effets temporels, spatiaux et du sexe sur la DF, nous avons comparé des estimations de la répétabilité à deux échelles temporelles (durant une même journée et sur plusieurs jours). Des DF semblables pour des mesures obtenues le même jour et pour les mâles et les femelles indiquent l'absence de désensibilisation à court terme et d'effets du sexe. Par contre, la DF diminuait pour des mesures prises sur plusieurs jours et de l'est vers l'ouest, ce qui pourrait refléter une habituation à la présence d'humains ou d'autres processus temporels ou spatiaux. La répétabilité était élevée (0,42 ± 0,06), mais tendait à diminuer pour des intervalles de temps plus grands. L'étude fait ressortir le potentiel que présente la DF pour l'étude reposant sur les individus de l'écologie et la dynamique de l'évolution de l'...

Drivers of within- and among-individual variation in risk-taking behaviour during reproduction in a long-lived bird

“…The moderate within-individual repeatability of FID (r = 0.400) leaves room for differential selective disappearance of individuals depending on risk-taking propensity, but also for individually flexible adjustments of anti-predator behaviours according to internal state and environmental conditions. The repeatability of FID is at the lower end of published estimates, typically ranging from 0.34 to 0.88 [22][23][24][25][26], and lower than the one previously reported for eiders over a shorter portion of the species' lifespan [50], probably reflecting the fact that repeatability tends to decline with time between samplings [75].…”

Fear in urban landscapes: conspecific flock size drives escape decisions in tropical birds

“…longer FID) could also result from other life-history traits that we did not consider or the personality of the focal individual. Personality can affect FID in several ways [ 58 – 61 ], thus it is possible that within cities, birds that inhabit less human-intervened sites are less bold than the ones that live in fully urban zones and exhibited larger escape responses [ 62 ]. Moreover, birds in parks exhibited a similar response to the birds found in residential areas.…”

The effects of habituation on boldness of urban and rural song sparrows (Melospiza melodia)

“…It has been suggested that individuals might habituate to a behavioral assay when measured successively, which could enable the individual to become desensitized to the approach or, in contrast, become more responsive to the assay (Martin & Reale, 2008). A study on Sable Island horses (Equus caballus), found that repeatability of FID was high among individuals when tested on the same day, but decreased along trial days (Cabrera et al, 2017). I did not measure repeatability within days, but habituation across days could explain our results of low repeatability of FID.…”