Feeding Insectivorous Reptiles

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Many commonly kept species of reptiles and amphibians make insects and other invertebrate prey a large portion of their natural diet. In fact, they may feed upon as many as a dozen different species within a single day, each one containing different levels vitamins and minerals that are vital to health and growth. As with all aspects of captive husbandry, it is our goal as keepers to try and provide our animals with the most natural and beneficial care. Food is certainly no exception.

For years, commercially bred crickets have made up the diets of many captive reptiles. And until recently, these food items were the only ones readily available to most hobbyists. Field research, as well as observations in captivity have shown us that feeding reptiles a monotonous diet of only crickets can quickly prove detrimental to their health. Instead we have found that a wide variety or prey items offers reptiles a larger variety of nutrients, as well as being mentally stimulating.

As the main streaming of herps continues, it is becoming easier to find these other feeder insects to feed to your pets. Below, I will briefly discuss the importance of supplementing insects, the concept of gutloading, and outline a variety of the more common (and less common) feeder insects now being produced commercially to cater to pet feeding needs.

THE IMPORTANCE OF SUPPLEMENTATION Many reptiles are purchased as babies, and raised as pets in captivity. Under these conditions, many insect eating reptiles will grow very quickly. Rapid growth requires the presence of large amounts of specific nutrients in the diet.

The most commonly occurring nutritional disorders that occur in rapidly growing reptiles are related to insufficient amounts of calcium (Ca) in the diet. In order for a reptiles skeleton to properly develop, favorable amounts of calcium must be present in the food. This calcium is then absorbed in the GI tract, and with the help of vitamin D3, metabolized and converted to bone.

So it becomes obvious that the use of a quality calcium supplement is vital to reptilian health. However there is another mineral, phosphorus, that occurs naturally in all feeder insects. In order for proper calcium absorption to occur, it must be present in equal or larger quantities than that of phosphorus (P). The widely accepted range of ratios for calcium to phosphorus in the reptilian diet are as follows: Between 1.5:1 and 2:1.

Therein lies the problem. Take for example, the common cricket. It has a calcium to phosphorus ratio of .33:1. That is, they contain nearly 3 times as much phosphorus as calcium. Fed a diet of these un-supplemented crickets, most reptiles would quickly exhibit signs of calcium deficiency. The simple addition of a light coating of calcium would correct (or at least improve) these numbers.

If this seems confusing it is because it is. This is only a very basic description of the process, and there are a lot of other factors at work, and even some that we still do not understand. What is important to remember is that the majority of feeder insects are deficient in calcium, and contain excess amounts of phosphorus. Therefore it is vital that this ratio is corrected via the use of supplements to ensure the long term health of your pets.

GUTLOADING Gutloading is the process of feeding insects a diet high in calcium and other vital nutrients immediately prior to becoming dinner themselves. Most pet shops keep their feeder insects well fed to begin with, but it only takes a few hours for these animals (especially crickets) to empty their systems and become little more than an empty vessel.

If you are not feeding off your prey items right away, or if you keep feeders on hand in your home, you have to ensure that they are being well fed. It's much like the old saying, "you are what you eat." This applies here. If your feeder insects are chock full of good vitamins and minerals, your reptiles will be too.

There are a number of excellent gutload diets manufactured specifically for this purpose. Some are dry, and must be offered with a source of water. Other are so-called "moist" bites, and these include water as well as all of the vital nutrients in one product. These foods should be your first choice for gutloading feeder insects as they are specially formulated with the reptiles well-being in mind.

In a pinch, a variety of fresh fruits and vegetables coupled with a source of grains (bread) may be used. Keep in mind that while this will keep your feeders alive, and is certainly better than nothing, it is not quite as good as the products made specifically for this purpose.

Ideally you should allow the feeders access to the gutload for at least 24 hours. This will ensure that they have ample time to consume the foods you have provided for them. However, it is really what they eat within hours of being consumed themselves that is most important.

CRICKETS - Acheta domesticus Crickets are the most common and readily available feeder insect in the United States. They are available in any size, from newborn or "pinheads" to fully grown. Crickets are fast growing, and reach their adult size of just over an inch in length in about 6 weeks.

These insects are a great staple diet for many species of reptiles. However, a monotonous diet is not only boring for your pet, but may also rob them of important nutrients that a single food source may not provide.

Crickets have an average protein content of 17% and contain about 5.5% fat. As mentioned above, they contain calcium and phosphorus in a .33:1 ratio.

MEALWORMS - Tenibrio molitar Second to crickets, mealworms are the most widely recognized feeder insect. Actually a beetle larvae, mealworms are kept refrigerated to stunt the growth process and prevent them from metamorphosing into mature beetles. Even at temperatures below 40 degrees, mealworms can survive for up to a month in your fridge.

Mealworms are slightly higher in protein (19%) and much higher in fat (14%) than crickets. As a result, they will promote more rapid growth than a diet of only crickets. Although numbers vary from study to study, Ca:P ratios for mealworms range from .07:1 to .33:1.

Keep in mind that mealworms have a hard shell made a material call chitin. Some animals produce an enzyme that quickly breaks down these shells, but nonetheless, mealworms can be difficult for baby or weakened reptiles to digest.

GIANT MEALWORMS - Tenibrio molitar Although nearly five times as big as regular mealworms, giants are the exact same species as regular mealworms. The only difference is size, and a slight increase in protein and fat content (19% protein, 14% fat). Calcium to Phosphorus ratios are assumed to be the same.

SUPERWORMS (KING WORMS) - Zophobus morio Superworms are much larger than even giant mealworms (around 2 inches) and much more active. They are ideal foods for monitors, chameleons, and other reptiles that are attracted to moving prey. Superworms contain 22% protein and 17% fat. Accurate figures regarding calcium and phosphorus levels are lacking, but it can be safely assumed that they are deficient in calcium.

Superworms should be kept at room temperature, and will die if refrigerated.

WAXWORMS - Galleria mellonella Waxworms are small (about one inch) and pudgy, resembling grubs. In fact they are the larvae of the wax moth, a common inhabitant of bee hives. Waxworms should be kept refrigerated, but always allowed to reach room temperature prior to feeding. They are fairly high in fat (24%) and contain 15% protein. As such a fatty food, they make excellent treats, and are ideal for putting weight on ill animals.

Reptiles (lizards especially) really enjoy waxworms, but care must be taken to avoid overfeeding, as obesity and related health issues may occur.

GIANT HISSING COCKROACHES - Gromphadorhina portentosa You have probably seen these massive roaches on television and in the movies many times (Fear Factor comes to mind). They grow to impressive sizes of up to 4 inches, but despite their intimidating appearance, are completely harmless. They are an ideal food for large monitors and other insectivores that would otherwise require tremendous numbers of smaller insects to feel satiated.

They can be offered as food at any size, although are most often fed off as adults for reasons previously discussed. Aside from monitors and tegus, large lizards and chameleons absolutely love these roaches, and they are highly recommended as a means for offering dietary variety.

FRUIT FLIES - Drosophila sp. Many species of frogs and chameleons are so tiny when they are born that even pinhead crickets pose a challenge. For these animals, and for dart frogs of all sizes, fruit flies make an ideal food. Often sold in cultures, fruit flies will continue to reproduce and provide many generations of flies as long as a few mature flies are always left in the culture.

SILKWORMS and GOLIATH WORMS Silkworms (Bombyx more) and Goliath worms (Manduca quinquemaculata) are the new kids on the block in the world of reptile feeders. Silkworms are medium sized, soft bodied worms that are naturally high in calcium as a result of their dietary preference for mulberry leaves.

Goliath worms are also sold under the names Horned worms and Green Giants. These worms reach impressive sizes (up to 4 inches) and grow incredibly fast. They are actually the larvae of the hummingbird moth, but make excellent feeders even in their larval stage.

Both of these worms are highly nutritious, and widely used by chameleon keepers. However, any appropriately sized reptile will appreciate a treat of one or two of these worms from time to time.

CONCLUSION Variety is the spice of life, and the same holds true for reptile foods. Feeding your pets the same food every day for its entire life would not only be terribly boring for the animal, but as discussed earlier, can not possibly provide an adequate array of vitamins and minerals. In the wild, reptiles have access to a huge selection of different prey items, each having grazed on different foods themselves, providing a varied and stimulating diet for the reptile.

As reptile keepers we can do our best to help our pets stay healthy and live long lives by offering a variety of different sizes and species of feeder insects. Also, by gutloading and supplementing these prey items we can insure that our reptiles are receiving the very best nutrition possible, with only minimal work on our part, and maximum benefits for the animals.