Feeding reptiles and amphibians

Transcription

1 Feeding reptiles and amphibians Find out more about feeding reptiles and amphibians by asking these questions: What does it eat? Does it need live food? Some reptiles and amphibians are very finicky eaters and will only eat live food of a certain type. Where will you get the food? Do you need to breed your own food to ensure continuity of supply? If so, then not only do you have to set up enclosure(s) for your animal you also need to set up a breeding area for its food. How often should it be fed? When should it not be fed? When should you start to worry if it is not feeding? How will you check if it is receiving enough food of the right sort? How will you make sure the live food does not attack the reptile? Have the animals feeding records been kept by the carer? Feeding behaviour The carnivorous reptiles and amphibians that eat live prey tend to be extremely quick once they strike at the intended victim. The animal is then either eaten alive (eg frogs will munch on a live mealworm without killing it first) or held until they suffocate (pythons), killed by a venom (snakes) or drowned (crocodiles). Prey can be located by sight, smell, body heat sensing and/or vibrations which are picked up through the reptile's body as the prey moves. Usually, the strike is so quick and the prey small enough that it can be eaten almost whole. As most reptiles and amphibians have poorly developed teeth and tongues, they do not tend to bite chunks or chew their food, swallowing is done using gulping motions to move the prey along inside the oral cavity. Snakes Venomous snakes use their sense of smell and their tongue pick up vibrations from their intended prey. Once it is located they will strike very quickly, catching and holding the animal in their mouth until the venom has 1

2 time to take effect. Pythons locate their prey by using these senses and the heat sensing 'pits' on their jaw. They, too, strike quickly holding their prey in their mouth then throwing coils around which they then tighten. This stops the animal from being able to expand its chest to breath and they suffocate. Snakes then swallow their prey whole and usually head first, although in the video on feeding a tiger snake the mouse is swallowed tail first, which is unusual. A snake's upper and lower jaws do not attach at the symphysis allowing them to have a very wide gape with which they can grasp large prey. They then swallow it by 'walking' along it with the four jaws working independently see the video of the death adder swallowing a mouse. If they have been handling carnivore food, reptile keepers need to be very careful to wash their hands thoroughly to remove all scent of the prey. Otherwise, these reptiles will strike at the keeper's hands, mistaking them for their prey. The vegetarian species tend to be clumsy eaters as they either have no teeth or only poorly developed teeth. Consequently, they have to bite chunks off the food item and then swallow it more or less whole, using the same gulping action as described above. Environmental considerations Captive reptiles will only feed if maintained in an environment with the correct temperature, humidity and photoperiod. If the temperature drops significantly after feeding, this will cause a drop in the metabolic rate and cessation of digestion. Consequently, the reptile may regurgitate the meal or the food will sit in the gut and decompose. Reptiles may also regurgitate their food if handled in the first few days after feeding. Natural sunlight and vitamin D3 Reptiles must be exposed to natural, unfiltered sunlight. Window glass will filter out most of the UV spectrum in sunlight, which is needed to synthesise vitamin D3 in their skin. Vitamin D3 is needed for absorption of calcium and phosphorus from the gastro-intestinal tract and contribute to growth of bones in young animals. Vitamin D can be added to a diet but beware, because chronic over supplementation can result in calcification of soft tissues and poor growth. Water Fresh drinking water must always be present. This can be provided in a shallow dish or bath that is cleaned and refreshed daily as many reptiles will use the dish to lie in on hot days. Some species will only lap water off vegetation so for these you must supply foliage and mist spray it twice a day. Gout can occur if reptiles do not have adequate access to water. 2

3 Selecting the correct diet Due to the large number of reptiles and amphibians that exist, this article will only deal with generalisations for the different groups. If you are intending to keep a particular animal you need to find out the dietary requirements of that animal before keeping it. Chelonians Australian freshwater tortoises are all carnivorous and should be fed a varied diet based on what they would access in the wild. This can include whole fish either dead or alive, whole mice, yabbies, shrimps, worms and insects. The fish and mice may need to be chopped into bite size pieces for feeding. Fresh fish are preferred to frozen because thiamine and vitamin E are depleted by freezing. Therefore, if frozen fish have to be used do not use them as a major constituent of the diet. Adult mice are preferred to newborns (pinkies) as they have a calcium:phosphorus ratio closer to that needed by the chelonian. Whole prey items are preferred because they are a 'complete' and 'balanced' diet. A diet of raw meat is unbalanced and will cause skeletal and shell problems. Substitutes canned dog food formed into pellets commercial products eg 'Wombaroo' reptile diet. Feeding Always offer the food to a Chelonian in the water or they will refuse to eat it. Feed daily for young chelonians and three times a week for adults. Approaching winter, the feeding should cease because once the animal goes into hibernation any food in the gut will decompose and cause death. Main nutritional problems in chelonians Vitamin A and calcium deficiencies are common, especially in young chelonians, mainly because owners feed a red meat diet. It is advisable, even with the provision of a correct diet, to provide calcium supplementation by placing a block of plaster of Paris in the tank/pond. Lizards Australian lizards have varied dietary requirements so research your animal thoroughly before starting to feed it. 3

4 Lizards Feeding issues Gecko chopped fruit soft yet firm vegetables green beans, carrots, alfalfa sprouts, parsley, watercress, Blue Tongue Lizard Dragons and geckos dried raisins, figs oranges and melons boiled egg mixed with canned dog food or dog biscuits soaked in water first a commercial reptile food supplement small flowers (dandelions) snails and insects (mealworms). Avoid cat food as it has too much protein, fat and vitamin D and dog biscuits should only form 5% of the diet because of its high Vitamin D content. Feeding frequency: three to four times a week for the larger specimens daily for smaller species and young. Problems associated with incorrect nutrition: periodontal disease if the food is too soft gout from excess protein soft tissue calcification caused by excess vitamin D. These are mostly insectivorous and should be offered live crickets, silkworms and mealworms. They can be supplemented with live 'pinkies' (baby hairless mice) and finely chopped raw meat. Feeding frequency: three to four times a week for the larger dragons. For those that are strictly insectivorous they need daily feeds. Problems with this diet Because of the high percentage of exoskeleton, these insects (especially mealworms), are very deficient in calcium. To overcome this, when you are raising these insects in their last week before being fed out, feed them a diet high in calcium so that their gut is full of it when being fed to the lizard. Alternatively, you can dust them with calcium carbonate powder but this tends to fall off if they are not eaten immediately. Another method is to inject them with calcium sandoz syrup until they are at leaking point just before feeding. If these measures are not undertaken then osteodystrophy will probably result, especially in young, growing lizards. Monitors These lizards are usually fed a varied diet of small 4

5 mammals, birds, fish, eggs and raw meat. Feeding frequency: Once a week for the large monitors and more frequently for younger and smaller species. Problems with this diet: Monitors will suffer from skeletal problems if fed a diet of pure meat. They must have the whole animal as their food to make sure they get the right amounts of calcium for correct bone development. Care when feeding monitors These lizards crush their prey's skull in their powerful jaws and then try to tenderise them by banging them on the ground and against the walls of their enclosure. This would not be much fun if it were your fingers or hand that they are trying to do this to. The best way to avoid this is to always use tongs or throw the food into the enclosure; never hand feed. Even when using tongs or haemostats, if you've been handling prey or other reptiles, as some reptiles eat others wash your hands with hot soapy water before feeding. Snakes All snakes are carnivorous and prefer to swallow their prey whole. Therefore, you should only offer whole prey that can be swallowed by the snake. Rodents, chicks and skinks can be used and should only be offered dead except to new arrivals which may not be used to eating dead prey or may need live prey to entice them to start eating in a new environment. If live rodents are used, take care not to leave them in with the snake if not eaten immediately as the rodent will commonly attack the snake. Feeding frequency Most snakes should be fed twice a week to once a fortnight, depending on their size. The diet varies from species to species; so check a reference book for each one. Individuals also show preferences and whenever possible, the snake's natural food should be offered. In winter, most will feed less often, if at all, unless their preferred body temperature is maintained in the enclosure. Even a healthy snake will fast for several weeks to months with no ill effects. It is important to monitor their body weights during these times to make sure they are not losing too much weight. 5

6 Amphibians Green tree frog Most amphibians are insectivorous and require live food. Foods such as crickets, cockroaches and mealworms, which are regularly available commercially or can be easily bred and raised at home, can be used. It is important to use insects that have been maintained on a balanced diet. Insects that have been fasted during transit should themselves be fed for 1-2 days before being offered to an amphibian. Other species that are used as prey items for amphibians include tubifex worms, earthworms, brine shrimp, fruit flies, and juvenile rodents (pinkies). While most amphibians require prey movement to stimulate feeding, some species will feed on commercially available fish food which comes in numerous sizes and either sinks or floats. Some species display a feeding frenzy that can lead to injury of their cage mates. This can be minimised by: not overcrowding housing similar sized individuals together feeding more frequently dispersing food evenly throughout the cage. Tadpoles are mostly herbivorous, requiring a diet different from that of the metamorphosed adults. Boiled spinach, fish flake food, and alfalfa pellets blended in water are commonly used foodstuffs for tadpoles. Producing your own food The live foods that can be produced easily by a reptile keeper are rodents, earthworms and insects like wood roaches, crickets, mealworms and maggots. 6

7 Wood roaches breed well in captivity. House them in a warm, dark, 'tight' environment with other roaches in 'tower blocks' made of egg cartons and wood shavings on the bottom. This can be housed in an old aquarium or plastic storage container with a well-fitting lid. Feeding is easy as wood roaches eat anything! Water must be supplied but use a water soaked sponge or dripper bottle as they will drown in a dish. They are harmless and can be caught by hand. Rodent colonies Rats and mice are easy to keep and breed in these commercial type 'houses'. Their gestation period is 21 days and they are weaned in 21 days. They should not be mated before ten weeks of age and their breeding peak is six months of age. A ratio of one male to two or three females per container is ideal. Pinkies In the above photos, a variety of ages of young mice showing the pinkies (unfurred) to the furred; all of which can be used as reptile food. The average litter size for both rats and mice is 6-8. Baby rats weigh 5-6 g and mice 2-3 g at birth. These can be euthanased by placing pinkies in the freezer and older animals can be hit swiftly on the back of the head on a hard edge, eg a table, while holding onto the tail firmly. Alternatively, you can use carbon dioxide gas. 7