Action

Relocate nests/eggs to a nearby natural setting (not including hatcheries): Tortoises, terrapins, side-necked & softshell turtles

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Study locations

Key messages

  • Four studies evaluated the effects of relocating nests/eggs to a nearby natural setting on tortoise, terrapin, side-necked & softshell turtle One study was in each of Venezuela, Columbia, Canada and the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (4 STUDIES)

  • Reproductive success (4 studies): Two of four replicated, controlled studies in Venezuela, Columbia, Canada and the USA found that relocated Arrau turtle and Magdalena river turtle nests had similar hatching success compared to natural nests. One of the studies found that painted turtle and snapping turtle nests relocated to artificial nest mounds had higher hatching success than natural nests. The other study found that relocating diamondback terrapin nests to artificial nest mounds had mixed effects on hatching success compared to natural nests.
  • Survival (1 study): One replicated, controlled study in Venezuela found that Arrau turtle hatchlings from relocated nests had lower survival during their first year compared to hatchlings from natural nests.
  • Condition (2 studies): One replicated, controlled study in Venezuela found that Arrau turtle hatchlings from relocated nests had more physical abnormalities compared to hatchlings from natural nests. One replicated, controlled study in Columbia found that a similar number of eggs were infested by invertebrates and fungi in relocated and natural nests.

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

  1. A replicated, controlled study in 2003 on one river in Venezuela (Jaffé et al. 2008) found that relocating Arrau turtle Podocnemis expansa nests led to no difference in hatching success, but higher mortality during a year in captivity compared to turtles from naturally incubated nests. There was no significant difference in hatching success between relocated and natural nests (54–98%), but mortality during the first year was higher for turtles from relocated nests (relocated: 13 of 108, 12%; natural: 1 of 112, <1%). At two location on the shell, relocated turtles had more physical abnormalities than naturally incubated turtles (relocated: 74% and 77%; naturally incubated: 19% and 33%), whereas at a third location the number of physical abnormalities was similar (relocated: 4%; naturally incubated: 5%). In February 2003, six nests were excavated and reburied 1.5 km further up the riverbank. In April 2003, hatchlings from the relocated nests, as well as hatchlings from four naturally incubated nests were collected and moved to captivity. A total of 230 turtles (up to 28 turtles/nest) were included in the study and kept in captivity for up to a year.

    Study and other actions tested
  2. A replicated, controlled study in 2005–2006 in one wetland and two riverbank sites in northern Columbia (Correa-H et al. 2010) found that hatching success of Magdalena river turtle Podocnemis lewyana eggs was similar in relocated, artificial and natural nests. Hatching success was statistically similar in relocated nests (58%), artificial nests (21%) and natural nests (41%). The number of eggs infested by invertebrates and fungi was statistically similar for relocated and artificial nests (34%) and natural nests (35%). In 2005–2006, twenty-four nests were relocated higher up the beach away from rising river levels, and seven artificial nests were dug for eggs recovered from turtles that had been harvested by people. A further 22 nests were left in place. All nests were covered with wire mesh cylinders (1 x 1 cm) that were 40 cm wide and 50 cm high, with a 3 x 3 cm plastic mesh on top. In February–May 2005–2006, beaches were searched daily, with the aid of dogs Canis lupus familiaris, to locate turtle nests. All nests were inspected daily and excavated after hatching, or after 74 days of incubation.

    Study and other actions tested
  3. A replicated, controlled study in 2009–2010 in a mosaic of wetlands, rivers and lakes in Ontario, Canada (Paterson et al. 2013) found that relocating painted turtle Chrysemys picta and snapping turtle Chelydra serpentina eggs to artificial mounds resulted in higher hatching success than for eggs left in natural nests. Eggs transplanted to artificial nests had higher hatching success than those left in natural nests for nine painted turtle nests (artificial: 98%; natural 71%) and 12 snapping turtle nests (artificial: 88%; natural 56%). Four artificial nesting mounds (60% gravel and 40% sand) 6m diameter and 0.5 high were installed in April 2009 on top of a layer of geotextile cloth. Each mound was within 100 m of water, 50 m of a known nesting site and sited to prevent nesting turtles from having to cross a road. Nests were excavated and split evenly between the closest artificial mound and the original nest. Hatching events were monitored from August, and nests were excavated in October to assess hatching success.

    Study and other actions tested
  4. A replicated, controlled study in 2006–2007 on an island on salt marsh grasses in New Jersey, USA (Wnek et al. 2013) found that relocating diamondback terrapin Malaciemys terrapin nests to artificial nest mounds resulted in lower hatching success compared to natural nests in three of 12 comparisons. Hatching success for relocated nests ranged from 0–85%, and for natural nests it was 54% and 70%. Hatching success was lower in dredge soil (0%) and shaded sand (0%) compared to natural nests (54%) in the first year, but all other comparisons found no significant differences. Three experimental plots (2.25 m2) were filled with 45 cm of sand/soil:  sand from a beach; loamy sand from a natural nesting area or dredge soil from a nearby channel which had been dried for two months. One half of each plot was shaded by shade cloth 15 cm above the soil with the other half in full sun and each nest had a predator excluder made of wire mesh. Natural nests were in full sun with nearby vegetation cover. Clutches were relocated to treatment plots from areas with high human activity (2006: 5 nests/treatment, 5 natural nests; 2007: 6 nests/treatment, 8 natural nests). Nests were excavated after 60 days to assess hatching success.

    Study and other actions tested
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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Reptile Conservation

This Action forms part of the Action Synopsis:

Reptile Conservation
Reptile Conservation

Reptile Conservation - Published 2021

Reptile synopsis

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