Hypothermia with Iguanas, as with other reptiles, can cause two kinds of serious problems.
First of all, reptiles aren’t capable of producing their own body heat and are hence dependant on their surroundings. Large animals take longer to heat up but also loose the heat a lot slower than small animals.
Secondly reptiles normally live in tropical environments and therefore require a higher temperature than animals who originate from more moderate climates. Iguanas are not adapted to the lower temperatures we have here and can not cope with them. Iguanas that escape from their heated environment or end up in cold water could easily get hypothermia.

What is hypothermia?

With birds and rodents, the body will try to generate heat by shivering; the created heat will support the internal organs by withdrawing blood from hands and feet. Reptiles loose heat when the outside temperature is below their minimal temperature. They are not able to generate heat or to maintain their body temperature.
Sand and water absorb heat and retain it. Reptiles that live in holes in the ground have fewer problems to keep their temperature up.

Species that go into hibernation tend to retreat to a hole or the bottom of a lake or a river. These hide-outs make sure their body temperature does not drop below freezing. When spring returns and the earth is slowly heated up by the sun, the reptiles also warm up and return from their state of hibernation. This is normal for regional species.
Neo-tropical and tropical animals are not able to go into hibernation and will die when exposed these temperatures.
Hypothermia happens when the body temperature is so low the tissue will degenerate because of the low blood circulation. All bodily functions will come to a halt.

Hypothermic reptiles

Reptiles that suffer from hypothermia tend to have a darker color. This will ensure a maximum absorption of heat during the warming up. When the reptile is hypothermic and has been lying in a dark environment, the color will brighten as the animal gets colder. This indicates that the change of color is not sufficient to determine whether the animal is suffering from hypothermia or not. A hypothermic reptile will feel cold and will barely move. The body will be rigid and there will be little to no pain reactions.

The treatment of hypothermia

The heating of the reptiles should happen very slowly and gently. When the reptile’s body temperature is raised to fast tissue damaging can occur.

  • Prepare a tepid bath with a water temperature of about 21 degrees Celsius and place the reptile gently into the bath. Make sure the reptile is not able to move around too much. Make sure the head and nostrils of the reptile are elevated and can not submerge.
  • After the reptile has been in the bath for about 20-30 minutes, remove it from the water and dry it gently with a bath towel. When the animal is left damp or wet, the water will evaporate and the body temperature of the reptile will drop again causing the cooling down blood to cool down the animal’s internal organs.
  • After the reptile has been dried off, put it in a warm towel and place it in the terrarium on top off a warm-water bottle or beneath a heating source. Slowly build up the temperature to the recommended height over the course of an hour. As soon as the reptile has heated up, maintain this temperature for a while. Then slowly increase the temperature to the temperature of the hottest place in the terrarium.
  • As soon as the reptile has acquired the right temperature give it some water to drink. When you have to force the reptile to drink, try and use a pipette. Do this very slowly and a small amount at a time. This will give the reptile the opportunity to close off its vocal track so the water will not flow into the lungs.
  • When treated in time and when the reptile is not exposed to temperatures below freezing, the reptile should fully recover from the hypothermia. Within the day the reptile will eat again and will commence its usual day rhythm. Some animals can appear a bit quieter, this will pass.

Why Hypothermia is not a good option for euthanasia

When reptiles are exposed to temperatures below freezing, the fluids surrounding its cells will start to form ice crystals. This happens long before the reptile looses consciousness and is very painful.
Euthanasia through hypothermia is hence only applicable when the animal is under anesthesia.

Author: Evert Henningheim

Bibliography: Melissa Kaplan’s, Herpcare collection, 2007, Stephen L. Barten DVM, Euthanasia of reptiles, News from the North Bay, Feb 1994

Source: Dr. Marja Kik, veterinarian for reptiles