A variety of foods should be made available to grand and Otago skinks throughout the year, to ensure their dietary needs are being met. It is important not to rely on just one or two types of food. Grand and Otago skinks rely heavily on berry fruits in the wild, however in captivity Otago skinks have bred successfully on a diet containing very little fruit.
In captivity, grand and Otago skinks have been observed eating and can be offered the following:
- Crickets (wild or cultured) –not too many at a time
- Huhu beetles and grubs and other similar large beetles
- Grass grub (Costelytra zealandica) adults/larvae and porina moth larvae or similar
- Wetas (up to 5cm)
- Spiders (a wide variety)
- Flies (wild or cultured) - larvae and pupae readily taken by grand skinks
- Slaters/woodlice (not favoured but occasionally taken, useful if other live foods are not available)
- Locusts (cultured)
- Slugs and snails (shell removed from large snails) - snails are hard and rubbery, so chopping them up or mincing is recommended.
- Mealworms (cultured) - beetles and larvae should be regarded as stop gap only as they are reputedly difficult to digest – best to use larvae that have recently moulted (white) or pupae.
- Mediterranean flourmoth (cultured) - to juvenile skinks
- Large species of Drosophila (vinegar fly) (to juvenile skinks)
- Earthworms – skinks find long worms difficult to swallow and may give up. Worms that have been chopped are accepted. Worms from compost heaps (usually tiger worms) should not be used as food (as a conservative measure).
- Praying mantis
- Walking stick insects
- Caterpillars, of most moths
Houseflies, European greenbottle flies, crickets, waxmoths, locusts, mealworms, and Mediterranean flourmoths, can be cultured or purchased from insect supply companies. See Appendix 2 for supplier. A large variety of insects can be captured in light traps.
With any large, hard beetles, the skinks may be more likely to eat them if the hard wing cases are removed before feeding out. If feeding locusts or crickets, the hind legs should be removed before feeding them out as a precaution – the hind legs have barbs on them which could potentially harm the skinks.
Cultured insects are generally less nutritious than wild insects, and in captivity the lizards have much less choice about what they choose to eat. Captive reptiles fed a majority of live food without supplements may suffer from deficiency of a range of nutrients including (but not limited to) calcium and many vitamins. It is therefore recommended that a good nutritional supplement, such as Wombaroo Reptile supplement or insectivore mix, or Herpetevit be used regularly. Use a supplement that caters for insectivorous reptiles (many US supplements are made for herbivorous iguanas and may not be suitable), and follow the manufacturer’s directions with regard to how much and how often to use it. Insects can either be dusted with the supplement and immediately fed, or with larval stages the insects can be gut-loaded by placing them in a container of the supplement overnight before feeding them out (Finke 2003). Some animals will accept supplements in fruit purees. Note that over-supplementation can cause problems such as tissue calcification (if fed abundant amounts of calcium and vitamin D [greater than 3-4 times recommended dosage]) (Fledelius et al. 2005). When using a good reptile supplement, do not use any additional calcium powders or liquids unless prescribed by a veterinarian.
Skinks will take many non-living animal foods, but such foods should be kept to a minimum. It should be noted however, that feeding skinks even moderate quantities of foods not natural to them in the wild may pose a risk of nutrient disorders (Alison Cree; Proceedings of the giant skink workshop 1991). They should be treated as a stopgap only in case of a shortage of live foods. Non-living animal foods known to be accepted by Otago skinks in captivity (not all these foods have been tried with grand skinks):
- Snails – can be frozen. Thaw, remove from shell and slice or mince.
- Sliced or blended liver or kidney – low fat (Otago skinks rather than grand skinks)
- Crickets – frozen for storage, then thawed
- Shrimp (or other crustaceans) – minced, raw or cooked
- Fish (fresh)
- Raw egg
See also section 3.4 – Feeding behaviour, for a list of native fruits used by wild grand and Otago skinks. Ideally some of these natural fruits should be offered if possible. The following fruits can be fed:
- Small Coprosma spp. berries e.g. mingimingi
- Pear (fresh or canned, mashed with fork or stewed).
- Pear baby puree.
- Overripe mashed banana.
- Any small or soft minced fruit would be beneficial and no doubt accepted by Otago skinks. Include some of the skin of the fruit where practicable.
During spring, summer, and autumn, feed fruits once every 2 - 4 weeks. Remove leftovers from the enclosure after 2 days. Offer as much as the skinks will want, which is likely to be ½ - 1 teaspoon each.
If native fruit berries are available, feed them out more often – once per week, or ad lib while in season. Any native berries known to be edible and of the correct size can be offered.
Juvenile skinks require smaller insects than the adults. They can be fed Mediterranean flourmoth, grass moths, small flies, maggots (cultured or cleaned), caterpillars, and any small insects caught in a moth trap. Neonates are less likely than adults to take non-living food in the first few months, so adequate supplies of live food are essential. Juveniles do not usually take much fruit, but this should still be provided regularly. Growing juveniles should have food available most of the time, and the diet should be as varied as possible.
Place fruit puree in a small shallow plastic dish or metal jar lid. If the dish is large and shallow it is less likely to roll over or be tipped up. Alternatively, the food container can be wedged between rocks.
Release the live insects into the enclosure for the skinks to find and hunt themselves. To maximise the skinks chances of catching prey, feed out when the skinks are most active. Any non-live animal food goes into a dish as for the fruit puree. The quantity of food and the frequency of feeding will be determined by temperature. During summer, live food should be offered to adults every 3 - 4 days. If a healthy animal ignores food, feeding should be cut back. If the base of the tail becomes wider than the area directly below the vent, the animal is probably overweight. Adult Otago skinks have a tendency to become obese (Bernard Goetz; Proceedings from giant skink workshop 1991). Obesity can reduce fertility, so overweight animals should be of concern (refer to sections 3.3 – Natural weights and measurements; and 4.2.2 – General health indicators and health monitoring). Growing juveniles should always have live food available.
Skinks will take some food in winter if temperatures rise for several days, but can go for several weeks without food in cold conditions. Body condition should be monitored regularly throughout the winter by observation when the lizards come out to bask rather than disturbing them in their refuges. See also 4.2.2 – General health indicators and health monitoring.
A study of the diet of grand and Otago skinks by Tocher (2003) indicated that fruit was a major component of the diet of both species, especially during autumn. There were seasonal changes in grand and Otago skink diet that could not be entirely explained by seasonal changes in availability of invertebrates or fruit. During November, both species consumed less fruit, even though fruits were available at that time and readily consumed in later months. Likewise, during May, both species concentrated on fruit, even though invertebrates were still available. Otago skinks also specialised on just a couple of the fruit species available. Invertebrate consumption increased significantly in November, presumably coinciding with the increased natural availability of insects during spring and summer.
The purposes/effects of seasonal discrimination in diet are poorly understood, and there has been no detailed research undertaken on energy allocation surrounding vitellogenesis (yolking of the egg) and ovulation in these species. However, the discriminatory nature of grand and Otago skink diet in November and May is possibly associated with reproduction (Tocher 2003). Key times are vitellogenesis (March-October) and ovulation (October-November) (Cree 1994). Female condition prior to copulation is known to be critical in determining the quality and quantity of young in captive colonies (Mike Kean pers. comm. 2002 – taken from Tocher 2003).
Experience so far has shown a higher reproductive rate in captivity than in the wild for Otago skinks, so further dietary refinements may not be necessary. However, techniques for the breeding of grand skinks are still being developed, and with this in mind, it is prudent to offer natural fruits where possible ad lib, and ideally monitor and note consumption as they may be related to breeding success.