A multi‐event model to study stage‐dependent dispersal in radio‐collared hares: when hunting promotes costly transience

Abstract

Behavioral ecologists have often assumed that dispersal is costly mainly because of unfamiliarity with traversed habitats during dispersal and energy costs of the movement per se; thus, dispersers that have successfully settled should experience survival rates comparable to those of philopatric individuals. In this paper, we tested that hypothesis using 152 radio-collared European hares in a harvested population. We developed a multi-event capture recapture model, combining telemetry data and recoveries and separately modeling the foray probability, the settlement probability, and the permanent dispersal probability. The parameterization introduced here raises the possibility of separately testing effects on survival and dispersal probabilities at each stage of dispersal (departure, transience, and settlement). In accordance with our expectations, we reveal that dispersers incur higher mortality risks during transience and the early settlement period than philopatric individuals or settled dispersers. We also found that dispersers suffer from higher risks of being shot. Those results illustrate that unfamiliarity with the habitat during transience makes dispersal costly and that settled dispersers may enjoy survival rates comparable to those of philopatric individuals. Surprisingly, we also found that individuals have a higher probability of foraying during the hunting season. We suggest that hunting and related disturbances increase dispersal costs both by increasing mortality risk during transience and (perhaps) by increasing movement rates. We emphasize the need to take human pressures into account as factors that may drive the demographics of movements in populations.

Exploration forays in juvenile European hares (Lepus europaeus): dispersal preludes or hunting-induced troubles?

“…Given that natal dispersal in hares is male biased and occurs preferentially in immature individuals (< 180 days old) [17,18], we expected under the first prediction that the propensity for making explorations would be male-biased and occur preferentially in juveniles and during the period when most natal dispersal events are recorded, i.e. from July to November [17,18]. However, we did not find strong support for a male-bias in the propensity for undertaking explorations.…”

“…We chose a 588 m threshold distance because it was the usual home-range radius estimated using the locations of adults monitored in our population during the three years study (details about birth site estimates, and home-ranges are given in [17,18]).…”

“…Dispersal in European hares occurs predominantly in juveniles, from the end of summer until the end of autumn, overlapping with the beginning of hare hunting (autumn) [16,17]. The close overlap between dispersal and hunting periods has been shown to reduce survival of dispersing hares relative to philopatric individuals, with dispersers suffering a higher risk of being shot during the transient stage [18], in addition to the risk of being killed by natural predators (mainly red fox, Vulpes vulpes ) [19]. In contrast, non-lethal and indirect effects of hunting on hare movement and dispersal are still poorly documented and controversial.…”

“…Temporary forays outside the usual home-range have been observed in hares. In juveniles, most forays have been recorded during autumn, at the beginning of the hare hunting season [18,20], and may or may not followed by permanent dispersal. Given that these extra home-range movements were recorded together with dispersal events, we might expect them to be movements performed by potential dispersers searching for settlement places, but failing to find suitable ones and returning back to their site of origin.…”

Long-term decline in a salt marsh hare population largely driven by bottom-up factors

“…Intensification of agricultural practices has resulted in loss of crop and landscape diversity, and as such is thought to be the main cause behind the decline of hares in agricultural landscapes (Edwards et al 2000;Smith et al 2005). Other factors may have contributed to the decline but have probably not influenced the long-term population trends (Haerer et al 2001;Frölich et al 2007), and these include increased predator densities (Lindstrom et al 1994;Schmidt et al 2004), intensive hunting (Avril et al 2012(Avril et al , 2014 and diseases (Flux et al 1990;Mitchell-Jones et al 1999;Newey et al 2007). Moreover, these factors probably do not operate in isolation but strongly interact with each other.…”