Captive insect-eating reptiles and amphibians (and perhaps invertebrates) are often plagued by nutritional deficiencies. A highly-varied diet is a great way to ensure adequate nutrition, but most keepers have access to only a few feeder-insect species; gut-loading (providing nutritious diets to feeders) is helpful, but detailed studies are lacking. While touring several Japanese zoos a few years ago, I was intrigued by the number of cricket species being bred as herp food, and resolved to investigate the species and diets I saw in greater detail. A recent article in Zoo Biology (2011, V. 30), which provides insights into carotenoid supplementation in three different cricket species, has re-sparked my interest. I’ll summarize below.
Carotenoids are pigments that occur in plants. Animals, as far as is known, cannot manufacture carotenoids but rather must obtain them through their diet.
Carotenoids benefit the immune system by acting as antioxidants, function in the reproductive and other systems, and are believed partially responsible for the health benefits enjoyed by people who regularly consume fruits and vegetables. We know little of their role in reptile and amphibian health, but many zoo nutritionists believe them to be important.
Three cricket diets were examined in the Zoo Biology study: wheat/wheat germ, fish food flakes and fresh fruits/vegetables.
As might be expected, crickets that were fed fruits and vegetables proved to have the highest carotenoid levels.
The fish flake diet resulted in intermediate carotenoid levels, with the lowest levels being seen in crickets feeding upon wheat germ.
These results held true for all 3 cricket species tested.
Three species of crickets were used in the study.
The Domestic, Brown or House Cricket, Acheta domesticus, the species most commonly used for pet food in the USA, is native to southwestern Asia but is now established nearly worldwide.
The Tropical or Decorated House Cricket, Gryllodes sigillatus, is not commonly seen in the trade, but is worth more attention. Hailing from Southern Europe, Africa and Asia, it is now established in Florida (surprise, surprise!), southeastern Texas, Louisiana and several nearby states. The Tropical House Cricket bears tiny wings and therefore contains less indigestible matter than other species. Like the other popular crickets, it breeds year-round when kept warm.
The Two-Spotted or Mediterranean Field Cricket, Gryllus bimaculatus, resembles G. veletis and some other American Field Crickets, but is larger and “meatier” (please see photo). However, it is equipped with powerful mandibles, so caution is warranted. Commonly used by European and Asian keepers, it is not often seen in the US. Japanese keepers informed me that the males fight savagely, but a single male can accommodate many females. It has also been reported as feral in Florida and Texas.
In the Zoo Biology study, Mediterranean Field Crickets achieved higher carotenoid concentrations (on all diets) than did Domestic or House Crickets. No species retained carotenoids for very long, so the timing of feeding is important, and bears further study.
Other Crickets and Grasshoppers
The world’s 20,000+ species of crickets, katydids, grasshoppers, locusts and their relatives (order Orthoptera) provide exciting opportunities for those interested in herp nutrition. Many of the 1,000+ species native to the USA are easy to collect and rear. Breeding is not as simple, especially for temperate species that need a period of dormancy, but well-worth investigating. Please see this article for further information on collecting and rearing native species, and write me with your ideas and experiences.
Some Orthopterans, such as the various wetas (please see photo), are among the world’s heaviest insects, and seem capable of being more herp predator than herp food!
In response to a virus that threatened House Cricket supplies, commercial breeders have begun working with the Jamaican House Cricket, Gryllus assimilis. Adults are equipped with formidable mandibles capable of breaking human skin and injuring various pets. Their use requires careful consideration…please see the article below and write in for further information.
African Field Cricket image referenced from wikipedia and originally posted by Danny Steaven
veggies image referenced from wikipedia and originally posted by mhaller1979