How do they locomote?
                                                   -- Limb Morphology --
 
 
1. Varying tail lengths:
  • G. volans tail length-- 80-120mm. Tails are used to modify the position of the uropatagium flap by moving the tail up or down, therefore creating more or less lift when gliding.
  • S. carolinensis tail length-- 150-250mm.  Tails are used for balance when jumping between branches.
  • S. niger tail length--  200-330mm.  Tails are used for balance when jumping between branches.
2. Varying forelimb structures:

     Morphological differences between G. volans and both S. carolinensis and S. niger lend to differnent locomotive strategies.

 
 

Figure 1.  Bones of the left hand of the southern flying squirrel G. volans, showing tendons and ligaments invlolved in moving the styliform cartilage. (F =falciform bone; P =pisiform bone; S =scapholunate bone) 
 (adapted from: Thorington et.al. 1998)		 Figure 2.  Bones of the left hand of the eastern gray squirrel S. carolinensis.

 
Forelimb morphology of G. volans:
     --The aductor pollicis longus originates from the extensor surfaces of the radius and ulna. Its tendon bifurcates, part inserting into the metacarpal of the thumb, and the other inserting into the falciform bone. 
     --The falciform bone connects to the styliform cartilage by the styliform-falciform ligament. Directly underlying the styliform falciform is the transcarpal ligament (not shown) which extends between the scapholunate and pisiform bones.
     --The styliform cartilage itself is connected by ligaments both to the pisiform bone and the fifth metacarpal.(Thorington et. el. 1998)

Forelimb morphology of S. carolinensis:
     --There is no styliform cartilage in the gray squirrel.  A hypothenar pad is on the heel of the hand atached to the pisiform bone and the base of the fifth metacarpal, like the styliform cartilage of flying squirrels.
    -- The transcarpal ligament is attached to the falciform bone.(Thorington et. al. 1998)

More about FORELIMBS, next page....

Who are the squirrels? - Where do they live? - How do they live there?  - How do they locomote?(Limb function) - How do they "fly"?(Wing structure)  How do they eat? - How do they compare?(Other arboreal strategies) - How do you know so much? (Links and References)  - Tree Squirrel Home - Animal Phys. Home - Davidson Home

Sarah Muffelman, squirel chaser