Anatomical Adaptions

Trees serve as shelter to many diverse living organisms. Adaptations of arboreal animals present a perfect example of the core hypothesis used in biology – ‘Form Fits Function.’ The specialized anatomical adaptations of tree-dwellers are perfectly engineered for the function it executes. Arboreal animals form an interesting group from different taxa, including mammals, birds, reptiles, insects, and arachnids. All these organisms are very different from each other. Yet, they are represented in a category of arboreal animals since they perform common tasks, present similar behavioral patterns, and show evolutionary anatomical adaptations to survive in a tree or forest. It is observed that arboreal animals are mostly concentrated geographically in tropical forests but are also found throughout the world in all forest ecosystems. Surviving in the trees poses fascinating challenges for arboreal animals, like raising offspring, locomotion through the trees, opting for shelter in extreme weather, and food gathering and storage. All these challenges are conquered by anatomical adaptations.

Prehensile Tail

• Arboreal limbed animals such as spider monkeys, opossums, tree pangolins, anteaters, etc., have a prehensile tail. 
• They are primarily used as an anchor to balance the animal’s body while climbing, hanging, or swinging from the trees.
•  These especially adapted tails serve a variety of additional tasks such as food gathering, manipulating, and holding an object.

Gliding Membranes

Several arboreal animals have developed a unique anatomical adaptation to descend from the trees. 

• This adaptation of flexible membranes between the forelimb and hindlimb helps increase the surface area of an animal without adding weight, allowing them to glide from trees. 
• The gliding and parachuting actions also bridge the gap between the trees. 
• Examples of animals that use gliding as a locomotory descendent movement include flying squirrels, geckos, flying frogs, and more.

Limb Length and Strong Grip

This specialized anatomical feature is exclusively observed in primates. 

• This feature includes long, strong arms for gripping branches, crossing gaps between trees, and other resources such as fruits. 
• Scientists refer to this special ability of primates to swing with long arms from one branch to another as ‘Brachiation’. 
• Besides long arms in brachiating primates, they also possess some other beneficial features like shorter spines, flexible wrists allowing free movement, small fingernails instead of long claws, smaller thumbs, and long curved fingers for better gripping of branches. 

Center of Gravity

Arboreal animals have a characteristically lower center of gravity to maintain balance and minimize the chances of falling from the tree while climbing and swinging. Other ways to maintain the center of gravity are accomplished by changes in posture, altered body positions, diagonal sequence gait, and smaller body size.

Adhesion and Gripping Feet

Adhesion is an anatomical adaptation alternative to claws. Wet adhesion via suction or capillary action can be commonly observed in arboreal salamanders and tree frogs. Dry adhesion that functions via van der waal forces to adhere to substrates is seen in geckos.

Animals dwelling in trees must have a strong grip to hold on tightly to the branches. Arboreal primates and limbed animals possess hairless fingertips allowing the animal to squeeze the branch between the fingertips to generate friction. Other useful adaptations opted for by these animals include adhesive pads, claws, and flexible ankle joints that can turn forwards and backward to stay in one place.