Head-start wild-caught reptiles for release: Tuatara
Overall effectiveness category Awaiting assessment
Number of studies: 2
Background information and definitions
Head-starting is a specialized management technique that raises early-stage reptiles (eggs, hatchlings and/or juveniles) to later life stages (juvenile, sub-adult or adult) in captivity before releasing them into the wild. Rearing animals beyond their most vulnerable stages may increase the chance of survival following release, and as such improve the chances of reintroduction success.
Here we only include those studies where eggs or juveniles were collected from the wild; for those that were bred in captivity see Breed reptiles in captivity and Release captive-bred reptiles in to the wild. See also Release reptiles born/hatched in captivity from wild-collected eggs/wild-caught females without rearing.
Due to the number of studies found, this action has been split by species group, though no studies were found for amphisbaenians. See here for: Sea turtles; Tortoises, terrapins, side-necked & softshell turtles; Snakes & lizards or Crocodilians.
Supporting evidence from individual studies
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
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