TUCKER, S.C.*; BUTLER, M.A.; Univ. of Tennessee, Knoxville; Univ. of Tennessee, Knoxville: The Effect of Load on Burst Speed on the Lizard Iguana iguana

The effect of load has a potentially important impact on animals� locomotion. Heavy loads may reduce initial velocity or acceleration to the point that an animal can no longer escape predators or capture prey. Loads can be a common occurrence as animals experience load naturally through obesity and pregnancy. Yet few studies have examined the effect of load quantitatively using locomotion kinematic techniques. An external load was applied to individual lizards of the species Iguana iguana to see how it affects their ability to run. We used loads which were proportional to the body weights of each individual lizard. The treatments were 0%, 10% and 20% of body weight, applied in random order. Dorsal and lateral camera views recorded the lizards� runs at a high speed of 250 frames per second. The two camera views were used to reconstruct motion in 3-D. A marker placed on the lizard�s back (mid-shoulder) was digitized to study the instantaneous velocity and acceleration. Gait parameters such as stride length, stride duration, step length, step duration, and duty factor were also measured. These measurements were taken to try to understand the expected reduced speed that occurs with an application of external weight. However, preliminary results show that external weight does not affect the instantaneous velocity and accelerations as it does the gait parameters.