Melissa Kaplan's
Herp Care Collection
Last updated January 1, 2014

Basal Metabolic Requirements for Reptiles

©2000 Melissa Kaplan


Every healthy body at rest expends a certain amount of energy just keeping the organs functioning and blood circulating. The amount of energy this requires is called the basal metabolic requirement (BMR). A young animal who is growing, and sick animals, require more energy (measured in kilocalories, or kcals), than a health body at rest, as does a normally active adult.

Reptiles who, due to illness, rapidly lose more than 10% of their body weight, or more slowly over time lose more than 20% of body weight, or who are unable to self-feed enough to ingest at least 85% of their BMR need to be supported nutritionally, either by hand-feeding, force-feeding prey, or re-feeding enterally (special food prepared to be administered by mouth) or parenterally (products developed to be administered by injection/IV).

As a general rule of thumb, the slurries described in my Emaciation (Starvation) Protocol article should be fed at the rate of 2% of body weight every 24-48 hours to a hydrated reptile, in divided doses if necessary. Herbivores who typically feed daily should be fed daily; carnivores may be fed every 48 hours, but dividing and administering the slurry daily provides a steadier stream of energy and less spiking of the blood sugar. If the individual is one who is highly stressed by handling, the less frequent feedings may be the better way to go.

For those of you who like to do things the hard way, you can calculate the metabolic requirements yourself. It's simple when you have a calculator with a square root key:

Weight.75 x 10 = kcals per 24 hours

In other words:

(((weight x weight x weight) square root) square root) x 10 = kcals per 24 hours

Please weigh your iguana - don't guess at the weight. I find that many people over- or under-guesstimate weights. Small reptiles can be bagged (in a pillowcase, for example) and placed on food or baby scales; weigh the bag separately and deduct its weight from the weight you got measuring the bagged reptile. If you have a good scale used for humans, weigh yourself holding the reptile and deduct from that weight your own weight (don't guesstimate that, either!).

You will need to weigh your reptile daily to see if he is losing or gaining weight, and adjust the kcals you feed accordingly as he gains or loses. If a sick reptile keeps losing weight, or weight loss is rapid, get it to a reptile vet.

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