Head-start wild-caught reptiles for release: 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 head-starting wild-caught tuatara for release. Both studies were in New Zealand.



  • Survival (2 studies): One study in New Zealand reported that 67–70% of head-started tuatara survived over monitoring periods of 9–11 months. One study in New Zealand found that 56% of head-started tuatara were recaptured over six years following release.
  • Condition (1 studies): One study in New Zealand reported that head-started tuatara increased in weight by around 100 g during the five years following release.


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 study in 1995–2000 on an island in New Zealand (Nelson et al. 2002) found that most head-started tuatara Sphenodon punctatus survived at least five years following release. Twenty-eight of 50 head-started juveniles (56%) were recaptured over six years following release, as well as 11 of 18 translocated adults (61%). Juvenile weights increased by approximately 100 g (up to 106% increase) in the five years after release. No successful breeding was observed during the six-year period, though tuatara take 10–15 years to reach maturity. In November 1995, fifty head-started juveniles were released on Titi island (a rodent-free island), along with 18 adults translocated from North Brother Island. Juveniles were selected from those hatched and reared from eggs harvested from the wild population on North Brother Island in 1989–1991. Tuatara were released into artificial burrows at night (2100–2230 h). Six post-release monitoring trips were conducted between November 2995 and November 2000, when a team of 3–4 people spent up to seven nights on the island searching for tuatara.

    Study and other actions tested
  2. A study in 2012–2013 in regenerating temperate forest in South Island, New Zealand (Jarvie et al. 2015) found that most head-started tuatara Sphenodon punctatus survived at least 9 months after being released into a predator-free fenced enclosure with artificial burrows. Results were not statistically tested. After 3–5 months, 100% of tuatara captive-reared locally (13 of 13 individuals) and 96% of tuatara captive-reared to the north of the release site (27 of 28 individuals) had survived. After 9–11 months, 70% of tuatara reared north of the release site (9 of 13 individuals) and 67% of locally-reared and released tuatara had survived (19 of 28 individuals). Juvenile tuatara originating from the same wild population were released into a fenced predator-free reserve in November–December 2012: captive-reared locally to the release site (13 individuals), and captive-reared 480 km north of the release site in a warmer climate (28 individuals). Captive-reared tuatara were hatched from artificially incubated eggs and head started until 4–6 years old. Artificial burrows were buried in the release area. Tuatara were monitored by radio-tracking for 5 months (6 locally-reared, 10 north-reared individuals) and recapture surveys (all tuatara were PIT tagged) for up to 27 months after release.

    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
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Reptile Conservation - Published 2021

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