Island tameness: living on islands reduces flight initiation distance

Abstract

One of Darwin's most widely known conjectures is that prey are tame on remote islands, where mammalian predators are absent. Many species appear to permit close approach on such islands, but no comparative studies have demonstrated reduced wariness quantified as flight initiation distance (FID; i.e. predator-prey distance when the prey begins to flee) in comparison with mainland relatives. We used the phylogenetic comparative method to assess influence of distance from the mainland and island area on FID of 66 lizard species. Because body size and predator approach speed affect predation risk, we included these as independent variables. Multiple regression showed that FID decreases as distance from mainland increases and is shorter in island than mainland populations. Although FID increased as area increased in some models, collinearity made it difficult to separate effects of area from distance and island occupancy. FID increases as SVL increases and approach speed increases; these effects are statistically independent of effects of distance to mainland and island occupancy. Ordinary least-squares models fit the data better than phylogenetic regressions, indicating little or no phylogenetic signal in residual FID after accounting for the independent variables. Our results demonstrate that island tameness is a real phenomenon in lizards.

Exploring conservation discourses in the Galapagos Islands: A case study of the Galapagos giant tortoises

“…Unlike predators (e.g. wolves and tigers), which have been historically configured in terms of 'disgust/fear' (Emel 1995), giant tortoises and in general Galapagos' wildlife, has been historically and ecologically recognized as 'tame' and gentle (Cooper et al 2014). Although this could be similar for example with the recent case of the white rhino in South Africa (Brooks 2006), the difference is the time people had to develop a particular stance towards a specie (i.e.…”

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

“…This suggests that FID in horses, whether directly or indirectly through correlation with other risk aversion traits, could be influenced by predation risk. However, whether this pattern holds across populations, as seen in other species (Cooper et al 2014), remains to be determined.…”

“…This finding opens the door to a number of additional analyses in the study population, including testing for the presence of additive genetic variance for FID and genetic correlations with other traits (Wilson and Poissant 2016), as well as the presence of negative directional selection as predicted for populations inhabiting predator-free islands (Cooper et al 2014;Brock et al 2015). Although additional research will be necessary to confidently identify drivers and consequences of observed temporal and spatial variation in FID, results clearly indicate that foals in the east have greater FIDs than those in the west.…”

“…Recently, research on the evolution of personality traits has turned toward understanding the phenomenon of island tameness (Cooper et al 2014;Brock et al 2015). The concept is relatively old, however.…”

“…For example, Brock et al (2015) recently showed that for Aegean Wall Lizards (Podarcis erhardii (Bedriaga, 1882)) inhabiting island environments, antipredator behaviours like FID generally decline in tandem with predator diversity across an archipelago, but also increased duration of isolation from predators. Using a phylogenycontrolled analysis, Cooper et al (2014) showed that FID in 66 lizard species decreases as distance from mainland increases and is shorter in island than mainland populations, concluding that island tameness is a real phenomenon in lizards. Although the evolution of island tameness implies selection on personality traits, no study has yet quantified selection on FID (covariance with fitness components) in this context.…”