Bowels and Movements

BY: Alexandra McInturf and Lea Pollack

It’s a classic scene: a majestic humpback whale breaches, thrusting its mass into the air. Its pectoral fins wave as it turns to land with a splash. It disappears into the depths before resurfacing, exhaling a spout of steam from its blowhole. We watch in awe, but there’s something missing in this description that may detract from the animal’s elegance. bam1

The whale is probably pooping.

Unless you are a behavioral ecologist, it’s doubtful that you think much about this unsavory process, but it happens all the time. While some animals are more theatric, others exhibit more stealth. Regardless, no matter the animal, it poops.

First, let us examine this process from a different perspective. Could there actually be anything valuable within this waste? If we take a deeper look at the composition of poop, these little piles of droppings are actually bundles of energy potential. Plants, in particular, use the nutrients from waste, combined with sunshine and water, to photosynthesize and grow. Animals that feed on plants or plant-eating organisms then obtain those nutrients. Poop has the potential to support the entire food web in an ecosystem.

If we return to the breaching whale, this behavior has more than just an aesthetic purpose. When marine mammals return to the surface to breathe, they naturally excrete waste. In doing so, they supply nitrates to the upper reaches of the ocean. Tiny plant organisms known as phytoplankton wait for just this kind of nutrient influx. As they feast on the whale poop, they are feasted upon by other tiny marine animals known as zooplankton. As it happens, zooplankton is the favorite food of the mighty whale. The whale is a living, breathing nutrient-recycling bin.

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Importantly, as organisms move, their poop moves too. Therefore, understanding how and why animals move around their habitats is crucial for understanding how and where nutrients are transported. For example, an animal’s movement path can create hot spots, or patches of nutrients, as animals often revisit the same places. It might be a nest, a fruiting tree, or the best mating spot. Naturally, when animals continually congregate, they concentrate their poop in those locations. This excrement can supply important nutrients to the plants in the region. Counterintuitively, an organism’s poop can help improve the place where an organism revisits.

As much as we may ignore it, excretion is an essential bodily function that has an important role in ecological systems, fertilizing the landscape and cycling nutrients within food webs. We should take pride in the fact that humans are actually the best poop movers in the world. We have built vast infrastructure, incredibly moving waste across ecosystem boundaries from the terrestrial to the aquatic. We even concentrate it in certain places, creating sewage hot spots that other organisms may like to visit (even if we don’t). So the next time you enter the bathroom, remember: you are performing an ecological service.

Alexandra McInturf is a second year PhD student in the Animal Behavior Graduate Group, specializing in movement behavior and conservation in elasmobranchs. 

Lea Pollack is a 3rd year Ph.D. candidate in the UC Davis Graduate Group in Ecology.

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