Why does a sloth hardly move, and when it does, why does it move so slowly? How come a sea otter needs to eat 20% to 30% of its body weight every day? The sloth and the sea otter are on completely opposite sides of the spectrum in regards to metabolism, activity levels, and caloric intake, yet both have survived and flourished through hundreds of thousands of years of Earth's history. How is this possible and why have they each been successful? The reasons, and answers to these questions, provide great examples of adaptations that helped ensure the survivability of different species - at least until humans entered the picture.
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First, let's look at the habitat where our two extreme animals live. Sloths inhabit the tropical rainforests of Central and South America, where the temperature is always warm - without much variation. They live in trees, which provides them plenty of food and shelter. The sloth can use its more constant (in terms of temperature and food resources) environment to provide the conditions its body needs to function - for example, sloths have one of the slowest mammalian metabolisms and virtually lack the ability to regulate their body temperature. Since sloths live in the constantly warm rainforest, they do not need this capability to survive. |
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Sea otters on the other hand, live in the ocean environment of the northern hemisphere, ranging from Alaska down into California. This habitat is often a place with cold temperatures, combined with harsh and unpredictable conditions. Temperatures can reach near freezing, thus requiring that sea otters have the means to maintain their relatively warm internal body temperature. Adaptations for conserving heat (like thick fur) and high food intake to maintain a high metabolic rate, lead to greater survivability. |
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While the sea otters' adaptations make a lot of sense, let's not discount the sloths as they have some really unique adaptations as well. Believe it or not, slow movements and long periods of inactivity are a wonderful adaptation for avoiding predators! Sloths have a stomach that covers about two thirds of their body - a great way to store up nutrients and then "deposit them" only once or twice a week! Their hair is even specially modified to encourage algal growth. In turn, the sloth's fur takes on a brownish-green hue, thus providing them with another great natural predator defense - camouflage! |
Adaptations to environmental conditions continue to evolve over time, given the change(s) is slow enough so the species' population can survive and adjust to the new conditions. Throughout history, there have been a few catastrophic events that have changed the face of the Earth and the life upon it. And now, because humans have the ability to create environmental change so rapidly, we are in the midst of another major Earth altering event. If the Earth becomes uninhabitable for sloths and rainforests, sea otters and oceans, and countless other ecosystems, it will also be uninhabitable for humans. In order to survive, we all need to adapt to a more species balanced Earth.