Iguanas: The Vegan Lizard
Why are members of the iguanidae family herbivores?
Many of us know that iguanas feed solely on plant matter, but the reason why goes much deeper than vegetation just being the most readily available food stuffs. Members of the Iguanidae family are described as being true herbivores, the reason for this is to do with their specially adapted digestive system.
Most reptiles and amphibians have something called a monogastric digestive system, the same as you and me. There’s no need to lecture you on how it works, you’ve (hopefully!) learned the basic ins and outs of it in your school biology lessons. But in case you haven’t (or you’ve forgotten), there’s a handy picture at the bottom…
However, iguanas don’t have quite the same set up. Plant matter contains cellulose (used to make plant cell walls) which is very difficult to break down. Monogastirics can’t do it, so how do iguanas? Iguanas are part of a group of animals known as hind gut fermenters. Other animals in this group include tortoises, rabbits, guinea pigs, horses, rhinos and elephants.
They all have something called a caecum which sits after the stomach and small intestine. The caecum contains microflora (bacteria) which ferments the food which has yet to be digested. The fermentation process then produces something called volatile fatty acids which are then used by the iguana as energy which is why we all eat in the first place right? That’s what I tell myself anyway…
Another clever adaptation of the iguana’s digestive system is the length of the tract. Plant matter contains an awful lot of fibre which takes a long time and is difficult to digest. The iguana’s digestive tract as a result, is much longer proportionately than a monogastric digestive system.
The combination of these two adaptations ensure that iguanas extract the most out of their plant based diet. They are specially designed to digest the indigestible and cannot make the most out of any other kind of diet. In fact, insects and small mammals cannot be properly digested by them and can cause impaction which has been known to kill. Iguanas are incredible lizards with a fascinating digestive system, if you have had an iguana encounter, send in your photos and I may feature it in the gallery!
To find out more about the different digestive systems, visit the vet science website here.