Effects of predator exclusion on nest and hatchling survival in the gopher tortoise

Published source details Smith L.L., Steen D.A., Conner L.M. & Rutledge J.C. (2013) Effects of predator exclusion on nest and hatchling survival in the gopher tortoise. Journal of Wildlife Management, 77, 352-358.
Share Tweet Email

Actions

This study is summarised as evidence for the following.

	Action	Category
	Remove or control predators by relocating them Action Link
	Remove or control predators using lethal controls: Tortoises, terrapins, side-necked & softshell turtles Action Link
	Remove or control predators using fencing and/or aerial nets Action Link

Remove or control predators by relocating them

A replicated, controlled study in 2002–2005 in a pine forest in Georgia, USA (Smith et al. 2013) found that removal of predators using relocations and lethal controls from fenced exclosures resulted in higher survival of gopher tortoise Gopherus polyphemus nests and hatchlings compared to areas with no fencing or predator removal. The effects of predator removal (both relocations and lethal controls) and fencing cannot be separated. Survival was higher inside fenced areas with predator removal compared to outside for both nests (Fenced: 52 of 78, 66% survived; Un-fenced: 26 of 73, 35%) and hatchlings (Fenced: 74% survived for 1 year; Un-fenced: 38%). In 2002–2003, four plots (40 ha) were randomly selected and enclosed in 1 m high mesh fence with electrical wires at the top and bottom. A further four plots were left un-fenced. In 2002–2003, all mammalian predators within the exclosures were live-trapped and removed, and in 2003–2005, further trapping of meso-predators was conducted. Predators that re-entered exclosures were euthanized. In May–June 2003–2005, all tortoise burrows were searched for nests, and all active nests were monitored 1–2 times/week up to 110 days. In 2004, forty hatchlings from 13 different nests were fitted with radio transmitters and monitored for up to a year.

(Summarised by: Maggie Watson, William Morgan)
Remove or control predators using lethal controls: Tortoises, terrapins, side-necked & softshell turtles

A replicated, controlled study in 2002–2005 in a pine forest in Georgia, USA (Smith et al. 2013) found that removing predators from fenced exclosures resulted in higher survival of gopher tortoise Gopherus polyphemus nests and hatchlings compared to areas with no fencing or predator removal. The effects of predator removal (lethal controls and relocations) and fencing cannot be separated. Survival was higher inside fenced areas with predator removal compared to outside for both nests (fenced: 52 of 78, 66% survived; unfenced: 26 of 73, 35%) and hatchlings (fenced: 74% survived for 1 year; unfenced: 38%). In 2002–2003, four plots (40 ha) were randomly selected and enclosed in 1.1m high mesh fence with electrical wires at the top and bottom. A further four plots were left unfenced. In 2002–2003, all mammalian predators within the exclosures were live-trapped and relocated, and in 2003–2005, further trapping of predators was conducted. Predators that re-entered exclosures were euthanized. In May–June 2003–2005, all tortoise burrows were searched for nests, and all active nests were monitored 1–2 times/week up to 110 days. In 2004, forty hatchlings from 13 different nests were fitted with radio transmitters and monitored for up to a year.

(Summarised by: Maggie Watson, William Morgan)
Remove or control predators using fencing and/or aerial nets

A replicated, randomized, controlled study in 2002–2005 in a pine forest in Georgia, USA (Smith et al. 2013) found that constructing fences to exclude predators along with predator removal resulted in higher survival of gopher tortoise Gopherus polyphemus nests and hatchlings compared to areas with no fencing or predator removal. Survival was higher inside fenced areas compared to outside for both nests (fenced: 52 of 78, 66% survived; unfenced: 26 of 73, 35%) and hatchlings (fenced: 74% survived for 1 year; unfenced: 38%). In 2002–2003, four plots (40 ha) were randomly selected and enclosed in 1.1m high mesh fence with electrical wires at the top and bottom. A further four plots were left unfenced. In 2002–2003, all mammalian predators within the exclosures were live-trapped and removed, and in 2003–2005, further trapping of predators was conducted. Predators that re-entered exclosures were euthanized. In May–June 2003–2005, all tortoise burrows were searched for nests, and active nests were monitored 1–2 times/week for up to 110 days. In 2004, forty hatchlings from 13 different nests were fitted with radio transmitters and monitored for up to a year.

(Summarised by: Maggie Watson, William Morgan)