Fig 1.
A) Images of one front foot of each species used in this study, displayed in proportion to one another, with species ordered by increasing body size. B) Experimental method used to record maximum adhesive force (Fc) and system compliance (C), showing G. vittatus with front feet placed flat on glass plate, just before plate extends upward (denoted by the arrow) away from gecko, and C) sample recordings from each species showing Fc and gecko stiffness (1/C).
Table 1.
Body size and toepad area of both front feet of the species used in this study.
Traits are shown as mean ± 1 s.e.m., with the range in parentheses.
Fig 2.
Relationship between gecko size (mass), maximum adhesive force, and adhesive area (toepad size).
A) As expected, a gecko’s maximum adhesive force significantly increases with increasing animal size. B) This increase in maximum adhesive force with animal size is partly due to the significant positive relationship between toepad size and body size in geckos.
Fig 3.
Relationship between animal size and maximum adhesive force.
A) Although toepad area significantly increases with animal size (as seen in Fig 2), this relationship only weakly explains the increase in maximum adhesive force associated with increases in animal size. B) Toepad size-adjusted maximum adhesive force (stress) for each species tested. Species are ordered by increasing body size. Boxes show minimum, maximum and median values for each species. Letters above boxes denote significant differences between species (P ≤ 0.01).
Fig 4.
Relationship between system (animal) compliance, animal size, and maximum adhesive force.
A) Gecko compliance significantly decreases as animal size increases. B) Maximum adhesive force significantly decreases with increasing gecko compliance (as animals get smaller).
Fig 5.
Relationship between maximum adhesive force and the area to compliance ratio.
There is a significant relationship between maximum adhesive force and the area to compliance ratio, with little unexplained variability (~ 8%), which shows that it is the combination of the gecko’s compliance and adhesive toepad area that best explains variation in maximum adhesive force. Note: Dotted line shows slope of 0.5, for reference.
Fig 6.
Results from tests of system compliance using a range of spring compliance.
A) Experimental set up of “model gecko”. A gecko-like adhesive created in the same manner described in prior publications [25], namely stiff fabric with a coating of a soft elastomer (see materials and methods for details), is attached to a glass plate fixed in the Instron in the same manner as in geckos, springs of variable compliance mimic whole body compliance found in natural gecko species. B) Force-extension output of four springs, with the adhesive pad area (A = 300 mm2) remaining constant for all experiments. Increasing slope with increased spring stiffness mimics results found in geckos. C) Scaling relationship of maximum adhesive force versus area to compliance ratio. Note, that .