Protect nests and nesting sites from predation by camouflaging nests

Overall effectiveness category Awaiting assessment
Number of studies: 2
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Effectiveness

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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.

Study locations

Key messages

Two studies evaluated the effects of protecting nests and nesting sites from predation by camouflaging nests on reptile populations. One study was in the USA and one was in Costa Rica.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (2 STUDIES)

Reproductive success (2 studies): One replicated, controlled study in the USA found that Ouachita map turtle nests that were disguised by sweeping with a broom were predated at a similar rate as unswept nests. One before-and-after, site comparison study in Costa Rica found that camouflaged (details of method not provided) olive ridley turtle nests had similar hatching and emergence success compared to nests moved to a hatchery.

BEHAVIOUR (0 STUDIES)

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

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
Referenced paper
Geller G.A. (2015) A test of substrate sweeping as a strategy to reduce raccoon predation of freshwater turtle nests, with insights from supplemental artificial nests. Chelonian Conservation and Biology, 14, 64-72.
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
Referenced paper
James R. & Melero D. (2015) Nesting and conservation of the olive ridley sea turtle (Lepidochelys olivacea) in playa Drake, Osa Peninsula, Costa Rica (2006-2012). Revista de Biología Tropical, 63, 117-129.

Please cite as:

Sainsbury K.A., Morgan W.H., Watson M., Rotem G., Bouskila A., Smith R.K. & Sutherland W.J. (2021) Reptile Conservation: Global Evidence for the Effects of Interventions for reptiles. Conservation Evidence Series Synopsis. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

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This Action forms part of the Action Synopsis:

Reptile Conservation

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