Biological Strategy
Feet Maintain Traction
Mountain goat
AskNature Team
Image: Adam Zolyak / Flickr / CC BY - Creative Commons Attribution alone
Move in/on Solids
To obtain needed resources or escape predators, some living systems must move on solid substances, some must move within them, and others must do both. Solids vary in their form; they can be soft or porous like leaves, sand, skin, and snow, or hard like rock, ice, or tree bark. Movement can involve a whole living system, such as an ostrich running across the ground or an earthworm burrowing through the soil. It can also involve just part of a living system, such as a mosquito poking its mouthparts into skin. Solids vary in smoothness, stickiness, moisture content, density, etc, each of which presents different challenges. As a result, living systems have adaptations to meet one, and sometimes multiple, challenges. For example, some insects must be able to hold onto both rough and slippery leaf surfaces due to the diversity in their environment.
Attach Temporarily
Living systems must sometimes, temporarily, stay in one place, climb or otherwise move around, or hold things together. This entails attaching temporarily with the ability to release, which minimizes energy and material use. Some living systems repeatedly attach, detach, and reattach for an extended time, such as over their lifetimes. Despite being temporary, these attachments must withstand physical and other forces until they have achieved their purpose. Therefore, living systems have adapted attachment mechanisms optimized for the amount of time or number of times they must be used. An example is the gecko, which climbs walls by attaching its toes for less than a second. Other examples include insects that attach their eggs to a leaf until they hatch, and insects whose wings temporarily attach during flight but separate afterlanding.
- Animals
- Vertebrates
- Mammals
- Mountain goat
Mammals
Class Mammalia (“breast”): Bats, cats, whales, horses, humans
Mammals make up less than 1% of all animals on earth, but they include some of the most well-known species. We know first-hand some of the characteristics that make mammals unique, like having hair, being able to sweat, and producing milk through mammary glands. Another critical shared feature is a set of highly-specialized teeth. Unlike sharks or alligators, for example, whose teeth are generally all the same size and shape, mammals have differently shaped teeth in different areas of the jaws to target specific foods or foraging strategies.
The feet of mountain goats maintain traction when climbing using cloven hooves with a hard outer shell and soft, flexible inner pads, as well as slip-stopping dewclaws.
“The sides of a mountain goat’s toes consist of the same hard keratin found on the hoof of a horse or deer. Each of the two wrap around toenails can be used to catch and hold to a crack or tiny knob of rock…The mountain goat is shod with a special traction pad which protrudes slightly past the nail. This pad has a rough textured surface that provides a considerable amount of extra friction on smooth rock and ice. Yet it is pliant enough for any irregularities in a stone substrate to become impressed in it and thereby add to the skidproofing effect.” (Chadwick 1983: 50)
“Make a wide V with your index and middle fingers and try pressing down against something with their tips. Since walking on an artiodactyl hoof is anatomically similar to walking on the tips of two fingers, the mountain goat feels the muscles and tendons working against each other somewhat the way you do. It adjusts the tensions accordingly in order to fine-tune its grip on uneven surfaces…Now you will find that the more weight you put on your fingertips, the more they want to diverge sideways. In like fashion the mountain goat’s toes divide the downward force of the weight on a hoof. When your fingers, or the toes of the hoof, are placed on an incline surface, part of the weight continues to be directed sideways—a horizontal vector of force as distinct from the vertical vector. There is thus less net force being exerted in a singe downward line; hence there is less likelihood of overcoming the force of friction along that line and beginning to slide…What is going on here is a fanning out of forces. If all the downward force could be converted into sideways forces, it would in effect be canceled out…The third and final dimension is simpler to explain. Solid rock, talus, dirt or snow can become wedged in the crotch of the V and act as an additional brake.” (Chadwick 1983: 51)
Last Updated September 18, 2016
References
“The sides of a mountain goat’s toes consist of the same hard keratin found on the hoof of a horse or deer. Each of the two wrap around toenails can be used to catch and hold to a crack or tiny knob of rock…The mountain goat is shod with a special traction pad which protrudes slightly past the nail. This pad has a rough textured surface that provides a considerable amount of extra friction on smooth rock and ice. Yet it is pliant enough for any irregularities in a stone substrate to become impressed in it and thereby add to the skidproofing effect.” (Chadwick 1983: 50)
“Make a wide V with your index and middle fingers and try pressing down against something with their tips. Since walking on an artiodactyl hoof is anatomically similar to walking on the tips of two fingers, the mountain goat feels the muscles and tendons working against each other somewhat the way you do. It adjusts the tensions accordingly in order to fine-tune its grip on uneven surfaces…Now you will find that the more weight you put on your fingertips, the more they want to diverge sideways. In like fashion the mountain goat’s toes divide the downward force of the weight on a hoof. When your fingers, or the toes of the hoof, are placed on an incline surface, part of the weight continues to be directed sideways—a horizontal vector of force as distinct from the vertical vector. There is thus less net force being exerted in a singe downward line; hence there is less likelihood of overcoming the force of friction along that line and beginning to slide…What is going on here is a fanning out of forces. If all the downward force could be converted into sideways forces, it would in effect be canceled out…The third and final dimension is simpler to explain. Solid rock, talus, dirt or snow can become wedged in the crotch of the V and act as an additional brake.” (Chadwick 1983: 51)