High altitude zones constitute a...
- Size: They are larger in size than their counter parts of lower altitudes (Bergman’s Law). This means that larger the size, less surface area in proportion to the mass and less dissipation of heart from the body. This adaptation is seen in the Himalayas Langur (Presbytis entellus ajax), Common Palm Civet (Paradoxurus hermiphroditus velloroxus) and Woody Wolf (Canis lupus). High himalyan birds such as Bearded Vulture and Golden Eagle are larger than their counterparts in the same family.
- Shortening and Protrusion of Body Parts: In consonance with such a reduction in their body parts (neck, tail, ears and legs) have reduced the surface of their body to enjoy the privilege of less heat radiation in acute cold (Allen’s Law). In Himalayan Palla’s Cat, the head is depressed and ears are remarkably short and erect making cat more efficient in its predatory operations at high altitudes without being exposed to the risk of predators.
- Dark Coloration: Animals confirmed to coniferous forest exhibit darker coloration to cope with increased humidity and frequent ultraviolet radiation e.g. long eared bat, northern bat and brown fox. Presence of heavy pigmentation in nival insects is admittedly correlated with high intensity of light especially UV against which pigmentation serves as a protective mechanism (Mani, 1962). Animals living at and above the snow line have a lighter color of fur to match the surroundings for defensive camouflage and to absorb less heat in the cold climate (Glober’s law). The change in absorption (metachronosis) in snow bound area dwellers is highly interesting in Lynx, Foxes and other mammals. The color becomes faint or absent in winter coats. The arctic bear, snow hare, snow cock are forms with coloration. This not only enables them to match their surroundings, but also to absorb less heat. It is, however, essential to remember that the bases of the hairs in all such light colored fur animals are darker, which provide protection for them against frequent UV radiation at high altitudes e.g. Pika, Snow Leopard, Snow Bear, Palla;s Cat and Leopard Cat. This explanation further supports the fact that in small mammals especially burrowing and small cave sheltering forms the surface fur is always soft and light in coloration or even without pigmentation as it needed not directly protect the animals against UV radiation.
- Hair Insulation: High altitude living animals have long, fluffy and soft fur and much wool, at least in winter. This hairy coat not only retains the body heat by providing insulation against cold climatic condition, but also against deleterious effects cosmic radiation including UV rays at high altitudes. In Wild Yak (Bos grunniens), shaggy fringes of coarse hair hangs from its flanks and cover the chest, shoulders, thighs and lower half of the tails. The hair forms bushy tufts between its horns and a great mane of its neck. The undercoat of small hair provides additional warmth in rigorous winter conditions. In Himalayan Tahr, Markhor and Yak, the neck, breast and even the sides are covered with very long and thick hair to form a scarf or apron protection against the blow of cold winds. In some cases even the sole of feet have become covered with hairs (Himalayan Weasel, Hill Fox, Pikas). The hairs on sole of feet in all in habitats of rocky areas of high mountain elevation provide suitable traction for running on rocks. In Himalayan Lynx Long tufts of hair on ear which frame face as specialized adaptation for coldest biotopes.
- Fur Consistency: With the progression of altitudinal zonation, the distribution of rough and hard hairs on mountain mammals becomes less and sparser compared to thickly distributed soft and woolly fur and under fur of high altitude mammals. The Himalayan Chiru (Pantholops hodgsoni) has the finest under wool to withstand cold. In Palla’s Cat the fur of throat, chest, belly and thigh is considerably longer than on the flanks which help cat to protect against severe cold while lying or sleeping on snow covered or frozen ground. A unique exception seen in Yak in Ladakh and Tibet is its long, thick and coarse hair and loose under wool of closely matted hair.
- Long Furry Tail: Thick legs and disproportionately long tail of Snow Leopard are most suitable adaptation for coping with the extreme cold of high altitude environment in the glacier of permanent snow inhabited by this fascinating cat. The long tail rolls around the body like a blanket and keeps the animal warm and insulated. This tail also functions to store fat from which it draws subsistence where food needed.
- Large Nostrils: Large nostrils of Chiru are furnished inside with extensive air sacs quite obviously suitable adaptations to low atmospheric pressure as they enhance breathing in rarefied air. Snow Leopard has large nasal cavities to utilize more oxygen from the rarefied air. This factor explains why bats are absent above snowline (nocturnal habit and membranous wings that is sparsely haired). A base wax like patch (cere) at the base of the upper part of beak is prominent in high altitude predaceous birds such as Lammergeir and golden eagle.
- Limb Modification: Animals like Snow Leopard have broader paws on their short legs suitable for adaptations as it presents animals from sinking in snow. The paddled feet of Tibetan Wolf is highly advantageous over hoofed animals for running swiftly on the snow. The forked and pointed hooves of musk deer are efficient tools for running rapidly in snow. In Himalayan Tahr, hooves are well designed for gripping high altitude rocks. The hoof pads are very soft, slightly convex posterior and surrounded by a hard horny rim which serves as a purpose similar to that of nails on the outside edge of a mountaineer’s boot. Large predatory birds of high Himalaya (Golden Eagle and Lamergeier) have strong and highly prehensile claws for gripping large preys. The legs are covered with thick feathery insulation adapted against rigorous winter of the Himalayas.
- Thin Skin: Skin is comparatively thinner in high altitude animals than in their counterparts in lower altitudes.
- Open Root of Incisor: Most high altitude animals such as some Himalayan Rhodents and South American Vacunas have open roots on their incisors.
- Moderator Band in the Heart: A special structural modification in the heart is an oblique and well developed band of muscles called “Moderator band” in ungulates (including domestic and wild sheep). The function of this muscular structure is to prevent over distension of the heart to pump large amount of blood in high altitudes.
- Variation in Species and Number: They show a wide variation in number and species compared to their counterparts in the lowlands.
- Less Number of Sweat Glands: They have fewer sweat glands and exhibit minimum respirations and evaporation. They conserve water in dry air of tropic highlands and high altitudes and also adjust against high water loss from lungs.
- Number of Glomeruli: It is less in all high altitude animals compared to species living in plains and thus forms less urine and excreta.
- Shape and Size of Erythrocytes: Each RBC layer large oval or elongated in shape to afford more surface for oxygen in some form such as fishes and birds. In Vacunnas, RBCs acre numerous but small in size to afford expeditions transfusion of oxygen.
- Cellular Water: The skin tissues are adapted to hold lesser amount of unbounded or cellular water (free water).
- Subcutaneous Fats: Hibernating high altitude animals such as Snow Bear contain numerous fat deposits which serve as food stores against inclement climatic conditions. These deposits also provide solar insulation especially against ultraviolet radiation. In Snow Leopard the tail functions for food storage from which it draws sustenance when food is scarce.
- Myoglobin: Amount of myoglobin in the tissues of the diaphragm and animal population living at high altitude.
- Hooves: High altitude Artiodactyls (even-toed hoofed animals) have splayed and pointed hooves (Himalayan Chiru) that enables them to survive efficiently. This enables them to surpass their enemies in speed on steep and rocky mountain. The Himalayan Musk Deer has mobile feet with long pointed central hooves that enables animal to have confident foothold on slippery rocks and snowy slopes at high altitudes.
- Position of Eyes and Ears: Small ears and eyes are placed high on head of Snow Leopard enabling animal to reconnoiter for prey location with least exposure of its head. In Pallas’ cat, short wide set of ears drops down on sides of head so that inner side and upper margin hardly rise above the highly featured forehead. This enables to follow prey without being exposed to its prey.
- Small Pupil in Eyes: Pupils in eyes of Snow Leopard and other high altitude cats are small and round for successful predatory life in high altitude environment.
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