(1997) Comparisons of Lethal and Nonlethal Techniques to Reduce Raccoon Depredation of Sea Turtle Nests. Referenced paper Ratnaswamy M.J., Warren R.J., Kramer M.T.

Turtle nests were monitored 2–4 times/month in 1993 and 2–3 times/week in 1994. Taste aversion involved provision of chicken eggs injected with 10 mg of oral oestrogen. Two-thirds of nests in the taste aversion area were also screened. Nests in the remainder of the block either received no treatment or were part of further tests of the effect of conditioned taste aversion or raccoon Procyon lotor removal. Screens were secured with steel rebar at each corner. In 1993–1994, a long stretch of barrier beach (37 km) was broken down into four experimental blocks, and around 2.5 km of each block was selected for a screening trial, with two-thirds of nests in the area receiving a screen (1.2 x 1.2 m wire screen, with 5.1 x 10.2 cm mesh). An additional group of nests that received both a screen and a conditioned taste aversion treatment had similar predation to both screened nests and non-screened nests (16% and 12% of 531 and 720 nests predated).

Predation of screened nests (9% and 7% of 499 and 737 nests predated) was lower than for nests with no screen (31% and 24% of 231 and 379 nests predated). 1997) found that covering sea turtle nests with a wire screen resulted in lower nest predation compared to when no screen was used. Supporting evidence from individual studiesĪ replicated, randomized, controlled study in 1993–1994 on a long sandy beach in Florida, USA (Ratnaswamy et al. One replicated, controlled study in Greece found that covering loggerhead turtle nests had mixed effects on hatching success compared to nests with no covers. One study also found that loggerhead turtle nests with artificial covers had similar hatching and emergence success compared to nests with no covers. Three studies also found that sea turtle and loggerhead turtle nests with artificial covers had higher hatching success than nests with no covers. The other study found that predation attempts of green and hawksbill turtle nests with artificial covers were similar compared to nests with no cover, but that predation success was affected by the cover design. One study found that olive ridley turtle nests with and without artificial covers were all predated. One study found that loggerhead turtle nests with artificial covers were predated more frequently than nests with no covers. Three studies found that covering sea turtle nests had mixed effects on predation, depending on predator species or year.

Reproductive success (15 studies): Eight of 14 studies (including 10 replicated, controlled studies) in the USA, Turkey, Qatar, Indonesia, Cape Verde, Australia and Costa Rica found that sea turtle, loggerhead, hawksbill and artificial sea turtle nests with artificial covers were predated less frequently than nests with no covers.

Six studies were in the USA, two were in each of Turkey and Australia, and one was in each of Greece, Qatar, Indonesia, Cape Verde and Costa Rica.

Fifteen studies evaluated the effects of protecting nests and nesting sites from predation using artificial nest covers on sea turtle populations.

Hawksbill sea turtle predators