Relocate nests/eggs for artificial incubation: Snakes

Overall effectiveness category Awaiting assessment
Number of studies: 4
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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; Lizards; Crocodilians or Tuatara.

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 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

Four studies evaluated the effects of relocating nests/eggs for artificial incubation on snake populations. Two studies were in Australia and one was in each of Japan and China.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (4 STUDIES)

Reproductive success (4 studies): Two studies in Australia reported that 87% of carpet python eggs and 83% of brown tree snake eggs hatched successfully following artificial incubation. One study also reported that zero of 10 artificially incubated Oenpelli python eggs hatched. One study in Japan reported that 265 habu eggs hatched successfully following artificial incubation. One replicated, randomized study in China found that hatching success of artificially incubated stripe-tailed ratsnake eggs was lowest at the coolest and warmest temperatures tested.

BEHAVIOUR (0 STUDIES)

OTHER (1 STUDY)

Offspring sex ratio (1 study): One study in Japan reported that artificially incubated habu eggs produced offspring with an even sex ratio.

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 study in 1982–1985 in Queensland, Australia (Charles et al. 1985) found that after bringing brooding female carpet pythons Morelia spilota and an Oenpelli python Morelia oenpelliensis and/or their egg clutches into captivity and incubating (artificially or with the female) the eggs, some carpet python eggs hatched successfully. From five female carpet pythons that were discovered with clutches of 7–23 eggs (clutch size for one snake not given), 21 of 23 and 5 of 7 eggs hatched successfully (one egg opened artificially), and some eggs from three other females also hatched successfully (number not given). None of the 10 eggs produced by an Oenpelli python hatched successfully. Brooding females that were discovered were brought into captivity along with their clutches, or in one case just the clutch was collected. Some eggs from one clutch were removed surgically. Eggs were incubated either in vermiculite or were left to incubate in the female’s coils (see paper for details).
Study and other actions tested
Referenced paper
Charles N., Field R. & Shine R. (1985) Notes on the reproductive biology of Australian pythons, genera Aspidites, Liasis and Morelia. Herpetological Review, 16, 45-48.
A study in 1981–1992 in the Okinawa Islands, Japan (Kamura & Nishimura 1993) found that artificially incubating habu Trimeresurus flavoviridis eggs resulted in some eggs hatching successfully. A total of 265 eggs hatched successfully (total number of eggs not given). When both hatchlings and un-hatched embryos were included, the ratio of females to males was equal (217:234). In 1981–1992, eggs from 62 female snakes were collected. They were incubated at 25–30°C in individual containers containing cotton or sphagnum moss Sphagnum sp., saturated with water.
Study and other actions tested
Referenced paper
Kamura T. & Nishimura M. (1993) Sex ratio and body size among hatchlings of habu, Trimeresurus flavoviridis, from the Okinawa Islands, Japan. Amphibia-Reptilia, 14, 275-283.
A replicated, randomized study in 1998 in a laboratory in Zhejiang, China (Du & Ji 2008) found that hatching success of artificially incubated stripe-tailed ratsnake Elaphe taeniura eggs was lowest at the coolest and warmest temperatures tested, and that incubation periods and hatchling morphology were also affected by incubation temperature. Hatching success was lower for eggs incubated at the coolest or warmest temperatures (22°C: 6 of 12, 50%; 32°C: 7 of 17, 41%) compared to eggs incubated at intermediate temperatures (24°C: 25 of 32, 78%; 27°C: 19 of 24, 79%; 30°C: 23 of 29, 79%). Incubation period decreased with increased temperatures from 102 days at 22°C to 51 days at 32°C. Five of seven morphological features were also affected by incubation temperature (see paper for more details). In 1998, thirteen captive-born gravid females were acquired and housed in a wire cage (200 x 80 x 80 cm) at 30°C. Eggs were incubated at 22, 24, 27, 30 or 32°C, with eggs from each clutch split evenly between temperatures. Eggs were incubated individually in covered plastic jars in vermiculite and water at a ratio of 1:2. Hatchlings were euthanized by freezing to -15°C to measure a 0range of morphological features.
Study and other actions tested
Referenced paper
Du W.G. & Ji X. (2008) The effects of incubation temperature on hatching success, embryonic use of energy and hatchling morphology in the stripe-tailed ratsnake Elaphe taeniura. Asiatic Herpetological Research, 11, 24-30.
A study in 1984–1985 at Taronga Zoo, Sydney, Australia (McFadden & Boylan 2014) found that a wild-caught female brown tree snake Boiga irregularis laid eggs in captivity that following artificial incubation hatched successfully. Five of six eggs hatched successfully after an incubation period of 82 days. A gravid female was acquired in 1984 and laid a clutch of eggs soon after arrival. The clutch was incubated artificially but details on incubation conditions are not available.
Study and other actions tested
Referenced paper
McFadden M. & Boylan T. (2014) Boiga irregularis (brown tree snake). Captive reproduction and longevity. Herpetological Review, 45, 60-61.

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?

List of journals searched by synopsis

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This Action forms part of the Action Synopsis:

Reptile Conservation

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Relocate nests/eggs for artificial incubation: Tuatara Action Link	Awaiting assessment	2	Synopsis Link
Relocate nests/eggs for artificial incubation: Crocodilians Action Link	Awaiting assessment	6	Synopsis Link