Paul Cool – 1999
Squirrels
order: Rodentia
family: Sciuridae
50 genera
260 species
flying squirrels
all except gliders: diurnal
Red Squirrel(Sciurus vulgaris) Woodland Trust
Squirrels and other animals with claws can run up trees.
Most animals, like cats and bears, can only come down a tree bottom first.
Squirrels however, can walk down a tree head first. As can be seen in these images, squirrels can twist their feet and hang from their hind feet.
Why is this? Anatomical information available on the internet provides little explanation. Do squirrels have a ball and socket ankle joint? Or is there another explanation? To investigate a road kill found on the road was examined.
No animals were harmed
Normal
Dorsiflexion
Plantarflexion
Supination
3D reconstruction CT scans show a stable ankle joint, but significant motion in the subtalar joint.
Thanks to Dr Victor Cassar-Pullicino and the imaging department at the RJAH orthopaedic hospital.
Dissection shows a stable ankle joint with a groove; not a ball and socket joint.
Bone dissection
Talus (left) and Calcaneus (right). The needle shows the orientation of the talar facet, allowing excessive subtalar motion.
Subtalar motion; left neutral position, right inverted.
Thanks to Andrew Biggs; RJAH photography, for taking the photographs
Practice
Final