Effect of nest location on gopher tortoise nest survival

摘要

Gopher tortoise (Gopherus polyphemus) populations are declining range-wide primarily because of habitat loss, fragmentation, and degradation, but low recruitment due to nest predation also may be contributing to this decline. The relationship of nest location and nest survival is unknown. Therefore, our objective was to determine whether nest location influenced depredation risk and potential recruitment success. Between 30 May 2013 and 3 September 2014, we constructed and monitored 105 artificial gopher tortoise nests (45 in 2013 and 60 in 2014) with 35 nests at each of 3 classifications of nest sites: within active burrow aprons (i.e., the mound of sand at the burrow entrance), inactive burrow aprons, and open sandy sites. Using the artificial nests, we investigated the influence of nest site classification, distance to road, and prescribed fire frequency (<1 year and 1 year since burn) on gopher tortoise nest survival. Additionally, we monitored 21 natural nests at burrow aprons to assess predation patterns as compared to artificial nests. Seventy-two (57%) of 126 nests were fully depredated during the study, and predation rates at artificial and natural nests were similar. We identified predators at 48 nests using trail cameras; the nine-banded armadillo (Dasypus novemcinctus) was the primary nest predator (69%). Nests in open sandy areas away from burrows exhibited greater daily survival rates (DSR; 0.991 +/- 0.005 SE) compared to nests in burrow aprons (active burrow aprons: 0.967 +/- 0.018; inactive burrow aprons: 0.949 +/- 0.027). Additionally, nests at locations burned the year of the study had a lower chance of survival (DSR: 0.959 +/- 0.022) than nests at locations burned the previous year (DSR: 0.991 +/- 0.005). Management practices that maintain open sandy areas (e.g., prescribed fire) away from burrows may increase tortoise nest survival. Fire return intervals of >1 year that are implemented frequently enough to maintain open sandy areas would be beneficial to nesting tortoises. (c) 2016 The Wildlife Society.