Protect nests and nesting sites from predation by camouflaging nests
Overall effectiveness category Awaiting assessment
Number of studies: 2
Background information and definitions
Camouflaging nests, for example by sweeping the surface substrate to remove evidence of nest laying, removes visual cues that predators and humans may use to locate nests and so may reduce incidences of predation or poaching.
Supporting evidence from individual studies
A replicated, controlled study in 2013–2014 at two riverbank sites in Wisconsin, USA (Geller 2015) found that sweeping the surface of Ouachita map turtle Graptemys ouachitensis nests or artificial nests with a broom did not reduce nest predation by racoons Procyon lotor. Turtle nest predation by racoons was the same for swept (16 of 16, 100% nests predated) and unswept (19 of 20, 95% nests predated) nests. Almost all artificial nests that were swept or unswept were also dug up by racoons (swept: 18 of 19, 95%; unswept: 20 of 20, 100%). Two nesting sites (112 m2 and 157 m2) were divided into four adjacent, alternating areas of swept (total of 16 natural and 19 artificial nests) and unswept (total of 20 natural and 20 artificial nests) nests (2 swept and 2 unswept areas/site). A three-headed broom was dragged across the surface substrate of swept areas daily from the beginning of the monitoring period until ≥7 days after the last observed nesting event during May–July 2013–2014. In addition, artificial nests were constructed by hand and made to resemble natural nests (20 nests) or swept nests (19 nests). Predation of nests by racoons was monitored with four trail cameras at each site.Study and other actions tested
A before-and-after, site comparison study in 2005–2012 on a beach in Costa Rica (James & Melero 2015) found that camouflaging olive ridley Lepidochelys olivacea sea turtle nests in situ resulted in similar hatching rates to nests that were moved to an on-beach hatchery with 24-hour monitoring. Results were not statistically tested. Hatching success was similar for nests that were camouflaged (79%) or relocated to the hatchery (79%). The emergence rate of hatchlings from camouflaged nests was 71%, compared to 77% of hatchlings from fenced hatchery nests. Egg poaching reduced from 85% in 2005 to 10% of eggs in 2006–2012. Nesting activity was monitored by nightly beach patrols (4x 4 hours/night) in July/August-December in 2006–2012 (958 nests were laid, 98–177/year). In 2006–2012, nests were either relocated to a monitored on-beach hatchery (363 nests, 38%), or camouflaged (595 nests, 61%; details of camouflaging method not provided) to discourage illegal collecting. Relocated nests were randomly allocated a 1 m2 plot in the hatchery and dug into the sand. The hatchery was monitored 24 hours a day during the nesting season. Hatchlings from both treatments were monitored on emergence and nests were excavated after hatching due dates to check hatching success.Study and other actions tested