Egg mass determines hatchling size, and incubation temperature influences post-hatching growth, of tuatara Sphenodon punctatus

Published source details Nelson N.J., Thompson M.B., Pledger S., Keall S.N. & Daugherty C.H. (2004) Egg mass determines hatchling size, and incubation temperature influences post-hatching growth, of tuatara Sphenodon punctatus. Journal of Zoology, 263, 77-87.
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This study is summarised as evidence for the following.

	Action	Category
	Relocate nests/eggs for artificial incubation: Tuatara Action Link
	Alter incubation temperatures to achieve optimal/desired sex ratio: Tuatara Action Link
	Use hormones and/or other drugs during captive-breeding programmes to induce reproduction/birth Action Link

Relocate nests/eggs for artificial incubation: Tuatara

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.

(Summarised by: William Morgan)
Alter incubation temperatures to achieve optimal/desired sex ratio: Tuatara

A replicated study in 1998 in a captive setting in New Zealand (Nelson et al. 2004) found that incubating tuatara Sphenodon punctatus eggs at higher temperatures resulted in more male hatchlings compared to cooler temperatures. Results were not statistically tested. More male hatchlings were produced at the highest incubation temperature (22°C: 100% of 113 hatchlings were male) compared to the intermediate temperature (21°C: 4% of 80 hatchlings were male) and lowest temperature (18°C: 0% of 105 hatchlings were male). 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. The sex of young tuatara was determined one year after hatchling using a surgical procedure.

(Summarised by: William Morgan)
Use hormones and/or other drugs during captive-breeding programmes to induce reproduction/birth

A study in 1998 in a captive setting in New Zealand (Nelson et al. 2004) found that female tuatara Sphenodon punctatus could be induced to lay eggs using oxytocin. A total of 166 eggs from 21 clutches were produced by inducing females with oxytocin (total number of injected females not provided). In 1998, females were induced to lay eggs with an injection of synthetic oxytocin (Oxytocin-s, 10IU/ml).

(Summarised by: William Morgan)