Are sloths really so slow that algae grows on them?

While we may unfairly think of the sloth as a lazy animal and buy onesies design to look like them as a way of expressing our own laziness, they are a valuable part of the ecosystem and, in many ways, an eco-system themselves! The coarse hair of a sloth is more than just a nice coat. It actually is a complex ecosystem that plays host to algae and… moths. The sloth moth is a species whose entire existence revolves around the sloth. And in return for hosting these little insects in its coat, the sloth has what is essentially a little edible garden of algae that the moths help fertilize. It’s about as homemade of a meal as you can imagine.

Monga Bay explains, “The fur of a sloth doubles as a personal, edible garden ecosystem that house a collection of diverse microorganisms, many of which are found nowhere else. A prominent member of this mobile ecosystem is the pyralid moth (Cryptoses species) whose entire life-cycle is dependent on the sloth. When a sloth descends to the forest floor to defecate, a pregnant female moth will leave her host and lay her eggs directly in the sloth’s dung. The larvae develop entirely within the dung, and when they emerge as adults they fly into the canopy to search for mating grounds in sloth fur, thus continuing the moth life-cycle.”

Meanwhile, those moths living in the sloth’s fur provide a benefit for the sloth. The New York Times puts it like this, “Burrowing into its fur, they mostly shed their wings and live there happily for the rest of their days, mating and dying in a safe, protected environment. After they die, their bodies are decomposed by the host of fungi and bacteria in the sloth’s fur. The metabolic products of this decay, especially nitrogen, are the feedstock for the specialist algae that grow in the sloth’s hair shafts. The researchers guessed that the sloths might be eating the algae from their own fur, and that this could be the purpose of the whole system.”

Though it appears that the sloth does benefit from having a digestible food source that it carries around with it, it isn’t clear quite yet just how much energy it gets from the algae and how much of a supplement to the sloth’s usual diet it provides. But the fact that researchers have found out that the growth of algae is much more complex than slow movement and slovenly grooming habits is alone something that changes the way we think about these animals and their role in an ecosystem (or their role as an ecosystem!).


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