Why Pumpkin Toadlets are So Bad at Jumping

     This research article explains the effect of evolutionary miniaturization on the vestibular system of pumpkin toadlets, a clade of tiny frogs found in Brazil. The semicircular canals of these mini frogs are the smallest ever recorded in adult vertebrates, and as such the frogs have no postural control while jumping and are unable to tell which way is up during a jump. Because of the frogs' small size, endolymph is unable to move effectively through their semicircular canals, and thus they exhibit the lowest sensitivities to angular acceleration of any adult vertebrate. Three alternative hypotheses for the uncontrolled jumping behavior were hindlimb morphology, behavioral compensation, and defensive behavior. While there are some possible explanations for potential evolutionary benefits to an uncontrolled jump and landing, such as playing dead to deter predators, it seems most likely that the uncontrolled landings are in fact an after-effect of vestibular dysfunction. The vestibular dysfunction in these frogs causes other problems as well, including feeding and rapid movement. This causes the primary form of locomotion for these frogs to be a slow walk or crawl, with jumping used less and only when rapid motion is needed, such as for an escape. These frogs demonstrate the current understanding of the lower limits of vertebrate body size.

PLEASE watch the attached video and see how terrible these frogs are at jumping. This video and others are available to be downloaded in the additional resources section of the linked article.