- Tree living animals which lead an arboreal mode of life.
- They are classified into three types based on the adaptation to the arboreal or scansorial mode of life.
1.Wall and rock climbers
- Provided with claws and adhesive discs in their limbs.
- They can easily move on the plain surfaces of the walls.
- Kangaroos use their tail as a balancing pole to leap from rock to rock.
- Gecko-Lizard is a typical example of wall climber.
- Usually nest on the trees.
- Periodically makes visit to the ground for gathering foods.
- e.g, sloth bear, rodents, African flying squirrel.
- Usually tree dwellers.
- Further divided as:
b)Forms suspended beneath branches and
c) Forms swinging by the forelimbs.
- They possess following adaptations:
i)Strong chest and ribs
- They have strong chest, ribs and limb girdles.
- Thorax is sub-circular in shape and the ribs have greater curvature.
ii)Strong girdle bones
- Pelvic and pectoral girdles are strong to support the body weight during climbing and hanging.
- Ilium of pelvic girdle is very broad and it serves to support the viscera.
iii)Grasping type of feet
- Feet are prehensile or non-prehensile type.
- Adhesive pads are present in many forms on the tips of the digits or underneath the sole of feet.
- Lamellae might be present in some cases on the ventral side of the digits.
- It helps to create vacuum to stick to the surface.
- Stout and laterally compressed body is present.
- Such body offers the least resistance while running.
- It is one of the common features among the arboreal forms.
- It is very long and used to balance the body during locomotion.
- e.g., primates, opposums, pit vipers, etc.
- Branch runners- squirrel, marsupials, lemurs, etc.
- Forms suspended beneath the branches- sloths, bats, etc.
- Forms swinging by the forelimbs- primates (gibbons and apes).
- Long protrusible tongue makes them easy to catch the prey.
vii)Presence of neck
- Neck helps to locate preys and enemies as it provides mobility to the head which enhances the efficiency of eyes.
- Digits are with sharp and well developed claws.
- Help the animal in walking and climbing on branches of tree and other vertical surfaces.
ix)Changeable body colour
- Can change their body colour.
- Protect the animals to hide from the enemies.
- Phenomenon is called mimicry.