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An In-depth Comparison of Cold-blooded and Warm-blooded Animals

An In-depth Comparison of Cold-blooded and Warm-blooded Animals
On the basis of regulation of body temperature, all animals are categorized into two groups. Mammals and birds are generally warm-blooded animals, whereas fish and reptiles are cold-blooded animals. This post provides you with a detailed comparison of these two categories of animals.
Komal B. Patil
Last Updated: Jun 2, 2018
Evolutionary Adaptation
Scientists believe that animals acquired the quality of warm-bloodedness, in order to defend themselves against fungal infections which are abundantly prevalent among cold-blooded animals.
Thermoregulation is the property by which an organism regulates its body temperature in accordance with that of the surrounding environment. Animals are grouped into two categories depending on the type of thermoregulation exhibited by them. The animals who possess the ability to maintain their internal body temperature irrespective of the temperature of the surroundings are called warm-blooded animals or endotherms, whereas the animals whose body temperature fluctuates along with the changes in the environmental temperature are known as cold-blooded animals or ectotherms.

Variations in the type of thermoregulation may be caused due to a change in the circadian rhythm or depending upon the developmental stages of an animal. They may also be caused as a result of stress. The core concept will be clear after reading the differences between these two types with examples.
Cold blooded animals
Warm blooded animals
Cold-blooded Animals Vs. Warm-blooded Animals
  • Ectothermy: Regulation of body temperature by external processes like basking in the sunlight.
  • Poikilothermy: Functioning of the animal's body processes across a wide range of temperatures.
  • Bradymetabolism: Capacity to alter the rate of metabolism according to the environment, e.g. hibernating animals.
  • Endothermy: Regulation of body temperature by internal processes like muscle shivering.
  • Homeothermy: Maintenance of a constant body temperature for the proper functioning of the body's processes.
  • Tachymetabolism: The rate of metabolism remains almost constant all the time.
Body Temperature
  • Varies with the changing environmental temperature.
  • Remains constant irrespective of the surroundings.
  • Rate of metabolism increases in warm surroundings, and decreases in cooler surroundings.
  • Rate of metabolism remains more or less constant.
Cooling mechanisms
  • Evaporation of bodily fluids.
  • Increased blood flow to body parts that will help in heat loss.
  • Loss of body heat by coming into contact with a colder object.
  • Getting wet in a lake, or any other such water body.
  • Adaptations including burrowing habits and being nocturnal in nature.
  • Evaporation of body fluids in the form of perspiration or panting.
  • Flattened and heavily vascularized extremities that aid in heat loss, such as the ears of an elephant.
Heating mechanisms
  • Residing near a warm current of air or water.
  • Residing in an insulated nest/burrow.
  • Basking in the sunlight.
  • Alter/inflate body shape and size.
  • Storing energy in the form of fat.
  • Counter-current blood flow.
  • Moving feather or hair shafts on the skin to slow down movement of air across the skin.
  • Presence of shortened extremities.
Food requirement
  • Minimal amount that is enough to sustain it.
  • Constant and large amount of food to provide enough energy for all of its body processes.
Level of activity
  • It increases with higher temperatures and decreases in cold conditions.
  • It is constant irrespective of the temperature.
  • They can survive on minimal amount of food and energy, and can alter its metabolism as and when required.
  • They have greater stamina and can survive in almost any type of environment, and exhibit a stronger immune system.
  • They are easy prey to fungal and bacterial infections, and cannot reproduce in cold conditions.
  • They require a constant and large food supply.
  • Reptiles and amphibians such as snakes, lizards, fish, crocodiles, alligators, frogs, etc.
  • Mammals and birds such as, whales, dogs, cats, elephants, humans, eagles, etc.
This categorization helps in gaining an understanding of the physical adaptations and behavioral traits of most animals. But as with any rule, there are exceptions to this classification as well. Bats, for example, can alter their metabolic rates. They exhibit the ability to switch between cold-bloodedness and warm-bloodedness in response to their level of activity. Despite being cold-blooded, honey bees can increase the temperature of the hive by flapping their wings to keep the hive warmer in winters.