Abstract
SynopsisAnimals live in heterogeneous environments must navigate in order to forage or capture food, defend territories, and locate mates. These heterogeneous environments have a variety of substrates that differ in their roughness, texture, and other properties, all of which may alter locomotor performance. Despite such natural variation in substrate, many studies on locomotion use noncompliant surfaces that either are unrepresentative of the range of substrates experienced by species or underestimate maximal locomotor capabilities. The goal of this study was to determine the role of forefeet and hindfeet on substrates with different properties during walking in a generalized sprawling tetrapod, the tiger salamander (Ambystoma tigrinum). Adult salamanders (n = 4, SVL = 11.2–14.6 cm) walked across level dry sand (DS), semi-soft plaster of Paris (PoP), wet sand (WS), and a hard, noncompliant surface (table)—substrates that vary in compliance. Trials were filmed in dorsal and anterior views. Videos were analyzed to determine the number of digits and surface area of each foot in contact with the substrate. The surface area of the forelimbs contacting the substrate was significantly greater on DS and PoP than on WS and the table. The surface area of the hindlimbs contacting the substrate was significantly greater on DS than on all other substrates. There were no significant differences in the time that the fore- or hindfeet were in contact with the substrate as determined by the number of digits. We conclude that salamanders modulate the use of their feet depending on the substrate, particularly on DS which is known to increase the mechanical work and energy expended during locomotion owing to the fluid nature of its loose particles. More studies are needed to test a wider range of substrates and to incorporate behavioral data from field studies to get a better understanding of how salamanders are affected by different substrates in their natural environment.
Highlights
Locomotion plays an important role in an animal’s ability to obtain food, avoid predation, defend territories, and locate mates
We predicted that salamanders would adjust the area and duration of the stride cycle that their feet were in contact with the substrate based on substrate type and properties
Salamander forelimbs had more surface area in contact with the substrate when walking on dry sand (DS) and plaster of Paris (PoP), whereas salamander hindlimbs had more surface area in contact with the substrate when walking on DS in comparison to locomotion on other substrates
Summary
Locomotion plays an important role in an animal’s ability to obtain food, avoid predation, defend territories, and locate mates. The impact of locomotor performance on fitness has motivated studies of many aspects of locomotion across diverse species. Many of these studies were performed under laboratory conditions on level, noncompliant surfaces that likely underestimate animal’s ability to make kinematic adjustments that could maximize locomotor performance in natural environments. Quantifying the kinematics of how animals move on noncompliant surfaces is an important first step to understanding animals’ locomotor capabilities, and provides a basis from which to build on the complex interactions between the locomotor strategies of animals and their environment. Collecting data on substrates that better match those encountered in nature can provide useful insight into the behavioral plasticity of animals
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