Approach to the anorectic reptile (Proceedings)
There is no question that the most common health problems associated with captive reptiles are diet related. These can be from nutritional deficiencies, such as is so commonly seen in the Green Iguana, excessive calorie consumption, as in overweight animals, or the most common problem, anorexia, or a lack of appetite.
The single most important factor to point out is that anorexia is a symptom, not a disease. There are numerous causes for a reptile to lose its appetite. These underlying causes must be identified and corrected before the problem will be resolved.
That is, when an animal is "off-food" there has to be a reason for it. It may be psychological, or it may be medical. Although this may seem elementary to most readers, it bears mentioning. It is essential that the veterinarian understands the natural history and biology of the particular type of reptile that they are treating. If they do not know, they must have a ready reference source. If one is not available, then, ethically, they should refer it to someone that has the proper training.There are very few animals whose dietary requirements are completely understood. This small group includes common domesticated animals such as the dog, the horse and the cat. However, research continues daily and scientists are still finding out new and critically important information. For instance, as recently as just a few years ago, the connection between cardiomyopathy and taurine was discovered
The further you get away from domestication (and reptiles and amphibians are probably just about as far away as you can get) the harder it is to match a captive animal's free-ranging diet.
Take the common fence lizard for an example. It is housed in an old aquarium. A 100 watt lamp is used for basking and heat. The owner throws in a few pieces of old wood (how natural), and then tosses in a handful of crickets that were purchased at the local pet store. Since the owner is a member of a herpetological society and is into state of the art husbandry/care, the crickets are dusted with a vitamin D3 supplement to be extra sure that the right nutrition is being provided. A little shaved cuttlebone is added to the vitamin dust to ensure that the calcium:phosphorus ratio is at least 2-2.5:1. How can this lizard not do well?
Well, hold on for a moment. Let's analyze what just happened. First of all, where does it say that crickets are the right food item for the lizard? This animal is an insectivore, and therefore, it must eat crickets (that is the common logic so prevalent in pet stores).
Think about it for a moment using this analogy: A person is driving along and suddenly finds themself feeling hungry? They might be craving a Big Mac, but they don't pass by any Golden Arches, so out of desperation they settle for a Whopper.
Think of the lizard and the crickets again. When a person is hungry, at least they get to have the Whopper their way. If they don't want mustard or tomatoes, they can leave them off. If they don't want more calcium on their burger, they can tell the kid behind the counter in the little crown to hold the cuttlebone.
The lizard in the cage doesn't have the option of choice; it's hungry, so it eats whatever it is fed.
Nobody knows exactly what a proper diet is for a reptile or an amphibian. All we can do is extrapolate from our knowledge based on the few well quantified species of mammals. For instance, we know that dogs and cats need vitamins and minerals, therefore we assume that reptiles and amphibians do as well. But, how much?
It is a known fact that over-feeding of the mineral calcium, and the vitamin D3, and exuberant use of UV lighting can cause soft-tissue mineralization in iguanas, turning the lizard into a rock. People always ask how much vitamin/mineral supplement to use. Nobody knows the correct answer. If anyone states exactly how much to use, don't believe them. Definitely don't buy any land from them.
Let's get back to our lizard friend. We feed crickets because everybody else feeds their lizards crickets. For the most part, they are inexpensive and convenient to obtain, and, they look sort of like grasshoppers (?).