Koalas are canopy-dwelling specialists that have several key adaptations suggested to increase stability in arboreal environments. The study of locomotor performance gives an understanding of both the challenges a tree-hugger may face, and the morphology that aids their resilience. Their arboreal habitats may represent one of the more challenging environments to all animals, as they are typically characterised by discontinuous substrates, often at significant heights from the ground. 

 

The specialized eucalypt diet is low in energy thus pushing them to sleep ~22 hours per day. They remain in trees unless searching for a mate, foraging for water or moving to new eucalypt patches. It remains unclear how habitat loss and increasing distance between food sources reduces their inclusive fitness given their low-energy diet. Habitat clearance means koalas must travel longer distances, which is not only energetically costly given their diet, but also increases the probability of vehicle collisions and dog attacks.

 

Koalas must climb vertical substrates with varying inclination and diameter, often with diverging branches or inconsistent surface texture. These creatures have developed effective ways to maximize their stability and cross the gaps between branches or trees.

 

Primates are thought to be some of the most optimized mammals to inhabit arboreal environments; their morphology and performance convey the stability demand tree-living requires. Long before primates were present on earth, the placental mammal and marsupial lineage diverged. The similarities between Koala and primate morphology are exemplary of convergent evolution. 

 

Koalas possess relatively long limbs relative to their body mass. They have powerful grasping hands and feet, they have an opposable hallux on their feet which other marsupials and primates possess. Koalas are zygodactyly, meaning they have two opposable digits on the hands, which allows them to create a strong grip. 

 

During locomotion, koalas’ initial contact with a given substrate is commonly the midfoot, heel or palm first; their toes are typically the last point of contact at the end of their stance phase. The stance phase was much longer than the swing phase, and the longer stance phase gives koalas adequate time to apply corrective torques using their grasping appendages. Koala’s typically have higher stride frequencies when on the ground, which may reflect a relaxation of substrate fear, as there is a reduced importance of foot placement on solid substrates. 

 

Koalas take longer strides but slower steps on narrow supports, resembling other arboreal specialists. The need for meticulous foot placement on narrow surfaces is evident by the placement of footfalls within a stride. The priority of koalas locomoting on narrow supports to extend feet contact time with the substrate. The hypothesized reasoning for this is to reduce peak forces on narrow substrates, which can lead to destabilizing or toppling moments. 

 

Gallops in many primates are used at top speeds, increasing their stride length as they move faster; however, in koalas, like other marsupials, it appears to be a transitional gaits between walks and bounds. When moving in terrestrial environments, bounding gaits are used for quick retreats to safety, but their relatively slow ground speeds may still leave them vulnerable. A koalas overground locomotion may also aid their overall fitness in a given environment.