Relocate nests/eggs for artificial incubation: Tuatara

Overall effectiveness category Awaiting assessment
Number of studies: 2
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Background information and definitions

Relocating eggs to artificially incubate them may be used as a way to maximise hatching success as the eggs will no longer be vulnerable to natural threats such as predation. Consideration must be given to the potential impacts of incubation conditions (for example temperature and humidity) on the sex, size, shape, colour, behaviour, movement ability and post-hatching growth of reptile hatchlings (Warner & Andrews 2002, Booth et al. 2006).

This action includes studies where eggs are incubated in artificial conditions, which ranges from controlled laboratory settings to using polystyrene boxes to incubate eggs in buildings. Studies are also included where gravid females are brought into captivity to lay eggs, but eggs are taken away from the females for artificial incubation.

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.

For studies that discuss the effects of relocating and re-burying eggs in natural habitats to avoid threats, see Relocate nests/eggs to a hatchery and Relocate nests/eggs to a nearby natural setting (not including hatcheries).

^{Booth D.T. (2006) Influence of incubation temperature on hatchling phenotype in reptiles. Physiological and Biochemical Zoology, 79, 274–281.}

^{Warner D.A. & Andrews R.M. (2002) Laboratory and field experiments identify sources of variation in phenotypes and survival of hatchling lizards. Biological Journal of the Linnean Society, 76, 105–124.}

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.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (2 STUDIES)

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.

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

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
Referenced paper
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.
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
Referenced paper
Keall S.N., Nelson N.J. & Daugherty C.H. (2010) Securing the future of threatened tuatara populations with artificial incubation. Herpetological Conservation and Biology, 5, 555-562.

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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This Action forms part of the Action Synopsis:

Reptile Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Relocate nests/eggs to a hatchery: Tortoises, terrapins, side-necked & softshell turtles Action Link	Awaiting assessment	2	Synopsis Link
Relocate nests/eggs to a hatchery: Tuatara Action Link	No evidence found (no assessment)	0	Synopsis Link
Relocate nests/eggs for artificial incubation: Snakes Action Link	Awaiting assessment	4	Synopsis Link