The importance of alert distance in flight initiation distance of alpine marmot (Marmota marmota): a cost/benefitapproach [Importance de la distance d'alerte sur la distance de fuite de la marmotte alpine (Marmota marmota): une analyse coûts / avantages].

Résumé

Following the economic model by Ydenberg et Dill (Adv. Stud. Behav. 16:229_249, 1986) the distance at which a prey initiates flight (flight initiation distance or FID) corresponds to the distance at which the risk of predation equals the cost of fleeing. This model predicts that a prey does not initiate flight as soon as it detects a predator. The risk of predation increases quickly when a prey is not aware, and this constrains the prey to monitor the predator’s behaviour. Then, the benefit of not fleeing drops to 0 at the alert distance (AD), the distance at which an animal detects an approaching threat and alters its behaviour. Although rarely mentioned in FID studies, AD should alter FID and be optimised. Here we verify the relationship between AD and FID in alpine marmot (Marmota marmota) in the Gran Paradiso National Park (Italy). We also test how AD and FID are affected by environmental variables potentially linked to risk of predation and to the cost of fleeing. Our tests revealed a strong relationship between FID and AD, suggesting that alpine marmot flee very little after being alerted of a threat. Our results suggest that the risk of predation increases rapidly right after the beginning of the threat. We conclude that the link between FID and AD can be explained by costs of vigilance.