Relocate nests/eggs for artificial incubation: Tuatara

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

Study locations

Key messages

  • Two studies evaluated the effects of relocating nests/eggs for artificial incubation on tuatara populations. Both studies were in New Zealand.



  • Reproductive success (2 studies): One of two replicated studies (including one controlled study) in New Zealand reported that hatching success of tuatara eggs relocated for artificial incubation was 86–100%. The other study reported hatching success of 44%.
  • Condition (1 study): One replicated, controlled study in New Zealand found that 10 months after hatching, artificially incubated tuatara were larger that those from natural nests.


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 1998 in a captive setting and an island in Marlborough Sounds, New Zealand (Nelson et al. 2004) found that tuatara Sphenodon punctatus eggs relocated for artificial incubation had high hatching success and that 10 months after hatching, young were larger than those from naturally incubated nests. Hatching success for artificially incubated eggs was 86–100% (18°C: 105 of 120, 86%; 21°C: 80 of 80, 100%; 22°C: 113 of 120, 94%) and all but three hatchlings survived for at least 10 months. Just after hatching, artificially incubated tuatara were larger in two of five measures and similar in three of five measures compared to tuatara that were naturally incubated for 11 months, but 10 months after hatching, artificially incubated tuatara were larger in all five measures (see paper for details). In 1998, a total of 320 eggs were collected either from natural nests (154 eggs from 29 clutches) or by inducing females to lay eggs with oxytocin (166 eggs from 21 clutches). Eggs were incubated in moist vermiculite in plastic containers, with clutches divided equally for incubation at 18°C, 21°C or 22°C. In addition, eggs from 25 naturally laid nests were left in situ for 11 months and then eggs and hatchlings were brought into captivity (eggs were incubated at 22°C until hatching). Hatching success was monitored and all hatchlings were weighed and measured.

    Study and other actions tested
  2. A replicated study in 1990–2007 in artificial enclosures in North Island, New Zealand (Keall et al. 2010) found that less than half of relocated artificially incubated wild tuatara Sphenodon punctatus eggs hatched. Over 16 years, 44% of eggs (241 of 553 eggs) laid by wild tuatara in captivity and relocated for artificial incubation hatched successfully. The first clutches to hatch successfully were laid 2–8 years after tuatara were brought into captivity. Second-generation female hatchlings that had been artificially incubated went on to produce three clutches during the study. In 1990–1992 four entire tuatara populations from four islands (6–15 individuals/island) were placed in one of three captive facilities pending eradication of pacific rats Rattus exulans. Clutches laid by 15 females were moved to a separate facility for artificial incubation in dampened vermiculite at temperatures to ensure an even sex ratio (see original paper for details). Four clutches were induced and the remaining 27 were laid naturally. Eggs that perished shortly after being laid (5–16 eggs in 2 clutches) and eggs laid by artificially incubated females were excluded from the data.

    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.

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Reptile Conservation

This Action forms part of the Action Synopsis:

Reptile Conservation
Reptile Conservation

Reptile Conservation - Published 2021

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