Relocate nests/eggs for artificial incubation: Snakes
Overall effectiveness category Awaiting assessment
Number of studies: 4
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.
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
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
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
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