Adaptation is defined as the structural and physiological adjustments in organisms to cope with fluctuations with its intermediate environment.Animals living at higher altitute exhibits a striking number of adaptations in terms of morphology,physiology and behaviour.
Adaptations are the main modification innduced both by environment and genetics evidenced by existence of animals pre-adapted to particular habitat eg;Yak adapted not only to high altitude arctic and desert conditions and tanned as one of the highest dwelling animals of the world.Those high altitude animals with can withstand the greater difference in altitude are termed as an Eurybarc. Eg Yak,Ibex,Tibetan Gazelle(species of antelope) of the Himalayas and Vicunas(Wild south Americian camelids),Illamas(domesticated southern Americian camelids)of Andes.Stenobarc includes the high altitude animals which have the ability to endure lesser differences in altitude eg;rabbbits,mountais goats ,sheeps and cats.
Body structure allows an animal to find,consume food,defend itself and reproduce its species.Structural adaptations include changes in the body parts like;
- Size:They are larger in size than their counterparts of lower altitudes.This means the larger the size,the less surface area in proportion to the mass and less dessipation of heat from the body(Bergman’s Law) .High himalayan birds such as Bearded vulture and Golden Eagle are larger than their counterparts in the same family.
- Shortening and contraction of body parts:In consonance with such a reduction in their body parts(necks,tail,ears and legs) have reduced surface area of their body to enjoy the previlage of less heat radiation in acute cold(Allen’s Law).eg pallas cat.The head is depressed and ears are remarkably short and erect making cat more efficient in its predatory operations at high altitudes.
- Dark coloration and pigmentation:Animals confirmed to coniferous forest exhibit darker coloration to cope with incresed humidity and frequent ultraviolent radiation eg;long eared bat,northern bat and brown fox.Animals living at and above the snow line have a lighter color of fur to match the surroundings for defensive camoflage and to absorb less heat in the cold climate(Blober’s Law).
- Hair Insulation:Yak(outer coat and inner coat),feet covered with hair,high altitude living animals have long fluffy and soft fur and much wool,at least in winter.This hairy coat not only retains body heat but also protects from deleterious effects cosmic radiation including uv rays at high altitude.
- Fur consistency:Chiru has finest underwool,pallas cat(fur of throat,chest belly and thigh)has long thick and coarse hair with loose underwool of closely matted hair.
- Long Furry Tail:Snow leopard serve as blanket and fat deposition
- Less number of sweat glands:To loose less water
- Large Nostrils:To loose less water while breathing
Special superior thermoregulatory mechanisms
Generation of body heat
- by the fast metabolic burning of food as fuel
- metabolism is high to generate more body heat
- affords an effective mechanism against cold
- Arctic mammals must generate ten times more heat than a tropical one
Adaptation towards low oxygen tension
- at high altitudes have resulted in fast circulation and pulse beat
- there is more heat weight in relation to body weight as in birds and mammals
- proliferation of RBC’S occur rapidly in high altitude animals to increase the oxygen carrying capacity of blood
- the domestic cats are unable to live at high altitude
- in dogs the high affinity for oxygen is very high
- the uptake of oxygen in lungs of high altitude animal is high
- to economize the water level required by the body the excreta becomes firmed with progression of altitude
- in high altitude sheep and goats and the yak,the urine elimination is less in quantity
- The ethological/behavioral adaptations of high altitude animals is remarkably modified
- large herbivores are adapted to keep reserve and stock of food material to meet the challenges of adverse high altitude condition
- the canids of uplands and himalaya always move in packs to kill the larger prey showing a social organization that rarely quarrel
- in contrast domestic animals often graze in herds,overgraze and damage grassland ecosystem of high altitude