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Live Food Choices for Turtles

Andy C. Highfield

Some, mostly tropical, tortoises and most turtles are omnivorous. Many people accommodate the dietary requirements of these species by feeding small quantities of processed cat and dog foods. Such foods do tend to be high in fat compared to the natural food choices of these species, and a viable alternative does exist in the form of cultured live insect prey. The use of live prey items can also prove invaluable when rehabilitating wild specimens, or when trying to tempt sick animals to begin feeding. The visual stimuli offered by live prey is undoubtedly a major factor in this respect. I have seen even very sick box turtles and hinge-back tortoises suddenly begin to take an interest in life when a few crickets begin hopping in front of their faces…..

The common house cricket (Achetus domesticus) is an important and nutritious food for many lizards and amphibians. Crickets are also enjoyed by many omnivorous turtles, especially box turtles (both Asian and American) and by numerous other semi terrestrial species such as Pyxididea mouhotti or Cyclemys dentata.

Crickets may be kept very satisfactorily in a well-ventilated 18" x 18" x 24" (45 X 45 X 60 cm) aquarium tank fitted with a fine mesh top. A substrate of mixed dry peat moss and sand about 1" (25 mm) deep should also be provided if the colony is intended purely for maintenance - if it intended for breeding purposes, see below. Sheets of paper egg containers must also be provided for them to hide in. This is extremely important. Ensure that only paper egg boxes or containers are used. Styrofoam is not at all suitable. If inadequate hiding places are available, the incidence of cannibalism among the crickets will increase dramatically. Crickets should be kept quite warm :- 80-90 degrees F (26-32 C) is suggested for rapid development. For heat, an overhead reflector lamp may be used, balanced on top of the grill cover. Alternatively, an under tank heat pad may prove useful. Remember, however, that crickets do not do well in dark conditions and that if a heat pad is used, some additional lighting will also be necessary. Another important point to remember is that only metal screening and grill material should be used on cricket enclosures. Plastic or fibreglass grill will be chewed through in a matter of hours. Escaped crickets can become a major household pest, so do ensure all containers have secure, tightly fitting lids.

Breeding crickets
For ease of management, breeding groups are best kept without a substrate. Instead, pots or containers of substrate (into which the eggs will be laid) are located within the main tank. Plastic yoghurt pots or Styrofoam cups are ideal for this purpose. A good substrate is light peat moss mixed with sand. It is extremely important that this is kept moist. If it is allowed to dry out, the eggs will desiccate and die. Remove the pots containing eggs to a separate, warm tank, every 5-7 days for incubation. After a further 7-10 days, the incubation tank will be swarming with tiny crickets. If kept at temperatures between 28-32 C (80-90 F), and well fed, they will grow rapidly. Once the juvenile crickets have reached about 1/4" (6 mm) long, 75 or so should be returned to the breeding container. This is extremely important as the adults live for only a few weeks, and if the breeding colony is not replenished regularly it will die out.

Feeding crickets
Commercial cricket foods are available, but it is easy - and certainly much cheaper - to make your own. One typical recipe consists of; 10 parts by volume of skimmed milk powder to 1 part quality calcium supplement. Add a commercial dried cat food, roughly ground, and mix in well. Rolled oats, alfalfa, cornmeal, or poultry mash can also be added for variety. A quantity of fresh fruit and vegetables should also be provided at all times. Orange is especially favored. Crickets obtain most of their moisture requirements from this fresh produce, but it is advisable to provide additional water in the form of shallow jar lids and bottle caps equipped with cellulose sponge. The crickets will extract fluid from the sponge in safety - if 'open topped' water containers are provided drownings will occur all too easily. Alternatively, a small mammal or bird watering bottle can be used to provide a longer-term supply, over a weekend, for example. Again, if inadequate moisture is available in the environment crickets will engage in cannibalism. On the other hand, if the environment is too humid, bacterial and viral diseases will proliferate, so good ventilation is also important. It is generally best to keep the overall environment on the hot and dry side, with a few water dishes as described and a small, but regularly changed, quantity of fresh produce available at all times.

Mealworms - Tenebrio molitor
The mealworm larvae is a very common food item for reptiles, and is widely available in pet stores or by mail order. These larvae are typically about an inch (25mm) in length, and are a golden yellow colour - in fact, they are sometimes known as "golden grubs". Mealworms are the larvae of the grain, flout or 'hardback' beetle, once a major agricultural pest, and their life cycle runs from an egg, through larvae, pupae and beetle stages. As a larvae grows it sheds is exoskeleton several times. The beetle that eventually emerges is a light beige color, changing rapidly to red, brown, and finally to black after approximately 48 hours. It is best to feed larvae which have just shed their exoskeleton. These are pale in color and lack the darker rings seen on 'older' specimens. These softer larvae are preferred by many reptiles as they are easier to chew than 'harder' examples. Mealworms can be kept in a darkened glass, plastic or metal container fitted with a fine mesh lid, filled to a depth 1.5"or 2" (35 mm to 50 mm ) with a mixture of bran, oats, ground alfalfa, bread crumbs and a small quantity of fruit and vegetables such as apple, orange, potato peelings, carrot chunks or similar. Do not allow fruit or vegetables to become mouldy, but change regularly. This vegetable matter is very important, as it provides the creatures with a vital source of moisture. I place all vegetable matter on a small, very shallow paper dish on top of the bran and oats, and refresh it every 24 hours. Adult beetles lay their eggs in the bran and oats. These eggs are very difficult to detect, but as there is no need to change the bran layer, this is not a problem. Each female lays several hundred eggs. The time they take to develop into a useable mealworm is highly dependent upon the temperature at which they are maintained. At 18-20 C (65-68 F) they can take a year to 18 months to mature, whereas at 25 C (77 F) they can mature in 6-8 months. At these temperatures, however, the useful pupal stage lasts for only two to three weeks. The answer is to remove the pupae to a lower temperature environment, 45 F or 7 C, where they will remain in a useable state for a very extended period. During this time, they should, of course, be fed normally. If you wish to begin breeding them, simply raise the temperature.

Superworms or Zoophobas (Zophobus morio)
These fast moving, brown banded larvae are similar in appearance to ordinary mealworms but are very much larger. They are much also lower in chitin (the indigestible exoskeleton compound) than ordinary mealworms and are very high in protein. They can remain in the larval stage for three to five months or longer. Zoophobas or Superworms are widely available from reptile suppliers as they are a popular food item with many species. Their general care is as for regular mealworms, however, they cannot be refrigerated, and are more difficult to breed.

To breed Zoophobas, separate out a dozen healthy specimens and place in individual small containers, each with a supply of food/substrate as described above. Maintain at a constant 80-85 F (28-29 C) under dark conditions. After about 14 days, they should begin to metamorphose into pupae. Between the third and fourth weeks the pupae will develop into adult beetles. These beetles are white upon emergence but soon turn pink, reddish brown and black within 24-48 hours. Remove the beetles as they emerge to their own container with a bran and oat substrate, a quantity of fresh fruit and vegetables, and a piece of porous wood upon on which they will deposit their eggs. Maintain them in a warm29 C (80 F) room to encourage continued breeding and rapid development. One important point to bear in mind is that you should never feed live mealworms, especially large ones, to sick or weak animals. Mealworms can bite back and may injure their intended predator. Also, do not use injured or diseased mealworms as these can act as vectors for bacterial, fungal or even viral infections.

Feeding insect prey to turtles
Insects typically contain little or no calcium by themselves, therefore, if they are not specially treated, their use can lead to calcium deficiencies occurring in the diet. Such deficiencies can prove catastrophic. It is therefore extremely important that efforts are made to ensure that adequate levels of calcium are present in all live insect foods offered to reptiles. Insect prey is typically rich in phosphorus, so, where possible, a phosphorus-free calcium and D3 additive should be used to achieve a positive Ca:P ratio. Additives which themselves contain phosphorus will certainly provide calcium, but they will do little to improve the overall ratio.

There are two practical methods of enhancing the calcium content of live insect foods.

1. Gut loading
This method consists of feeding high calcium-content foods to the insects for 48 hours prior to use. Longer periods should not be employed, as it has been shown that excess dietary calcium has a negative effect upon the growth of some invertebrates. Provision of a high-calcium content food to crickets for 48 hours before use has definitely proven useful in enhancing their overall calcium content and their is good evidence that this additional calcium is utilised by the predator animal. Proprietary high-calcium cricket foods are marketed by several manufacturers for this purpose.

2. Dusting
This method consists of placing the prey animals in a closed container together with a quantity of mineral and vitamin supplement powder, and shaking to ensure they receive a thorough coating, or dusting, immediately prior to use. It is extremely important that this is done within a minute or two prior to use, as it has been shown that the quantity of powder which adheres to invertebrates begins to fall off very rapidly indeed. After only 25 minutes, the amount of extra calcium provided will be negligible. If applied immediately prior to consumption, however, dusting is a highly effective and efficient method of providing additional calcium, other trace elements and vitamins to captive reptiles.

The vitamin content of most invertebrates is impossible to quantify, therefore, a routine dusting before use is highly recommended in addition to use of the gut-loading technique. This combination of treatments should ensure that prey invertebrates are not grossly deficient in essential vitamins or trace elements. They key to excellent nutrition is variety. It is vitally important that captive reptiles are not permitted to become addicted to a narrow range of food items. Vary intake as much as possible, and ensure that all items offered are both safe and nutritious.

The 'staple' items of crickets, standard mealworms and zoophobas can be supplemented with earth worms (which are highly nutritious), snails (which come with their own calcium supplement built-in!) and Waxworm larvae (Galleria mellonella), although the latter should not be used in excess as they are rather high in fat compared to crickets and earthworms.