The Red Kangaroo: Macropus Rufus

The Kangaroo is an endotherm. Endotherms generate heat from their body’s metabolism. So their internal body temperature is independent of the external temperature. Endotherms eat more food than ectotherms. This higher food intake results in an increased level of metabolism, which is required to produce heat.

The Red Kangaroo inhabits inland plains throughout Australia. They prefer open plains where trees and bushes are scarce.

The fur on Kangaroos maintains an insulating layer of trapped air that slows down heat exchange with the environment. The thickness of the air layer can be increased in cold conditions by contracting muscles that lift the fur away from the skin.

Adaptations to the cold include increased metabolic processes, shivering and sun basking. Metabolic processes generate heat and keep the body warm. Shivering increases muscle activity and produces heat and basking in the sun also keeps the body warm.

In hot conditions Red kangaroos seek shelter from the sun to escape high temperatures. Kangaroos also lick their forelimbs where the blood vessels run close to the surface of the skin and heat is lost from the body. The evaporation of the saliva is thought to have a cooling effect. The light colour of the fur reflects heat, panting and sweating also help to keep the kangaroo cool. However, since their body is covered by fur kangaroos have a limited ability to sweat, and rely heavily on panting to increase evaporation of water across the moist surface of the tongue. The posture of the red kangaroo with the tail pulled into the shade of the body minimises the surface area exposed to the sun this minimises the amount of moisture lost.

Since enzymes have strong temperature preferences, usually around 37&ºC, their efficiency is reduced outside their preferred ranges. Kangaroos have a fairly constant body temperature so that they can use enzymes which are efficient at those certain temperatures. The ability to maintain a constant body temperature also allows for a broader geographical and ecological distribution.

King Brown Snake: Pseudechis australis

The King Brown Snake is an ectotherm. Ectotherms cannot maintain constant body temperatures and their temperatures fluctuate with changes in ambient temperature. The activity of ectotherms is greatly affected by these changes in temperatures. The body’s temperature is regulated by heat gained from the environment.

The King Brown Snake is found in every state of Australia except for Victoria and Tasmania. King Brown Snakes inhabit woodlands, hummock grassland, chenopod scrubland and almost bare gibber or sandy deserts sheltering under timber, rubbish piles, burrows and deep soil cracks. They are not found in rainforests

In cold conditions King Brown Snakes absorb heat by exposing as much as possible of its body surface to the warmth of the sun. They do this by changing the shape of their body; a flattened body exposes a greater surface area to the sun. Snakes increase the blood flow in vessels close to the skin as they bask in the sun so more heat is absorbed and transported to inner body tissues and organs. Snakes are usually active during the day however if temperatures are too high they become nocturnal and their active period is at night. They also seek shade to prevent overheating.

Snakes tend to be sluggish because their hearts are unable to pump sufficient blood to supply the oxygen needed for vigorous activity. Therefore snakes use anaerobic respiration during muscular activity.

Snakes lose and gain heat in four ways:

Evaporation – Wind increases heat loss

Convection

Radiation – Heat gain by solar radiation, reflected solar radiation and Infa-red radiation

Conduction – Laying on warm ground

These adaptations assist the King Brown Snake in temperature regulation.