Using GPS location data to assess red fox responses to predator exclosure setup and hatching at shorebird nests

Abstract

Wire cages (i.e., predator exclosures) are frequently used to protect shorebird nests from predation. While exclosed nests often have higher survival than unexclosed nests, concerns exist over whether the conspicuous structures might draw attention of predators, potentially increasing risks to adults and newly-hatched chicks. We present a new approach to investigating predator responses to exclosures and other stimuli at shorebird nests. We used location data from GPScollared red foxes (Vulpes vulpes) to examine short-term spatial responses of foxes to exclosure setup and hatching at piping plover (Charadrius melodus) nests on Fire Island, New York. We compared mean distances between fox locations and piping plover nests, and the proportions of fox locations within a 100-m buffer of nests, before and after exclosure setup and before, during, and after hatching. Mean distances from fox locations to nests were similar before versus after exclosure setup (x̄= 641 m before, 675 m after; permutation test for matched pairs, [PTMP], T = 0.28, P = 0.56, n = 9 foxes), before versus during hatching (x̄= 417 m before, 340 m during; PTMP, T = −0.93, P = 0.18, n = 5 foxes) and during versus after hatching (x̄= 340 m during, 330 m after; PTMP, T = 1.00, P = 0.84, n = 5 foxes). The proportions of fox locations within