Breeding New Zealand lizards in captivity can be very rewarding, but care must be taken to do this responsibly.
Unless you are part of an official breeding programme (endorsed by DOC), captive New Zealand lizards cannot be released into the wild for sound ecological (and legal) reasons.
As such, before you breed more lizards make sure you are prepared for the babies which may need separate housing, and also that:
- You have space / capacity to house the animals in the immediate and long-term (bearing in mind that not all lizards will co-exist amicably), OR
- You have made arrangements with another authorised holder who can keep the lizards that you breed.
Sexing New Zealand lizards
For geckos, telling the sexes apart is relatively easy for most species. Male geckos have a 'bulge' at the base of the tail which is a sac containing the hemipenes (the paired copulatory organs in male lizards). Males will also have prominent pre-cloacal and femoral pores, and cloacal spurs on their ventral side. Females, may have small spurs, but lack these other features.
Sexing skinks is more complicated. Males generally have a more ‘barrel’ shaped torso with the section of tail immediately behind the vent being relatively ‘square’ in cross section. Female skinks generally have a wider torso just in front of the back legs, with the section of tail immediately behind the vent being relatively round compared to males. In some species such as Otago and chevron skinks, males have larger / wider heads than females.
Breeding New Zealand lizards
Breeding New Zealand lizards involves having a compatible male and female of a given species together at the appropriate time of year.
Breeding seasons vary widely between species, the majority appear to mate in autumn or early spring and give birth the following summer or autumn respectively. Species held outside of their native range have been known to breed / give birth at different times of year to their wild counterparts. Some of the larger / rarer species may only breed once every two years.
Challenges can be encountered when breeding species which are particularly aggressive. Inter-sexual aggression (between males and females) may result in serious injury or death for aggressive species. In general, no more than one male of a given species should be housed together, as aggression between males during the breeding season is more common and often more serious.
Some species are difficult to breed when they are housed outside of their native range / climate. For example, some South Island and alpine species of geckos and skinks do not breed well in northern North Island climates.
Gravid (pregnant) females will show signs of increased swelling around the abdomen which becomes particularly prominent just prior to giving birth. Another sign that a female lizard may be gravid is increased basking behaviour, which assists with the development of her young. This is particularly obvious for species which are nocturnal / don't usually appear much during the day, as females will often spend extended times basking near refuge sites.
All New Zealand lizards apart from the Egg-laying skink (Oligosoma suteri) give birth to live young, and the juveniles appear as miniature versions of the adults. The number of offspring per litter depends on the species and size / age of the lizard. Geckos are physiologically restricted to a maximum of two offspring per litter, but younger females may give birth to only a single baby if it is their first time breeding. The number of offspring that skinks give birth to varies widely. For smaller or younger lizards it may be as few as one or two per litter, whereas for some of the larger species they can have up to nine offspring per litter. With skinks, larger / older females tend to have more young per litter than smaller / younger females.
Raising the young
There is increasing evidence that certain species of New Zealand Lizards show some form of parental care, or at least some tolerance of their young. For example, Duvaucel's geckos (Hoplodactylus duvaucelii) and Otago skinks (Oligosoma otagense) will often live in family groups in the wild. In some cases it may be safe to leave offspring in with their parents for the first couple of years (after which they would naturally disperse in the wild). However, maintaining offspring with their parents does carry some risks, and instances of competition or cannibalism by the parents have been reported by several keepers (even for the aforementioned species).
The majority of keepers prefer to remove the offspring from the parents enclosure and raise them in smaller 'juvenile rearing enclosures.' These enclosures are smaller versions of the enclosures used for the adults (usually around 30x30x50cm), and set-up in the same manner, but including appropriately smaller refuge sites for the juveniles to access.
Juvenile lizards are voracious feeders, and food items of an appropriate size should be offered from birth. A popular food item for neonates (newborns) of most geckos and smaller skinks are fruit flies (Drosophila spp.). A wingless form of these is available commercially and they can be easily cultured in jars with slices of fruit and a small mixture of active yeast added over the top. Alternatively, fruit flies can be attracted into the enclosure by adding a jar / container of sliced fruit (if using this method, take care to place the jar / container on its side so baby lizards do not climb in and become trapped / drown).
Once neonate lizards have grown they can gradually be offered larger food items (e.g. houseflies, blowflies, small crickets and locusts) until they are large enough to feed on the same food items as the adults.
The time for baby lizards to reach maturity / adult size varies between species. For some of the smaller species such as elegant geckos (Naultinus elegans) and Shore skinks (Oligosoma smithi) this can occur as quickly as two years from birth, whereas for larger species such as Duvaucel's geckos (Hoplodactylus duvaucelii) and robust skinks (Oligosoma alani) it may take as long as eight years for individuals to reach sexual maturity.