Whales transport nutrients across entire ocean basins in their urine

Whales are not just big – they’re important contributors to healthy oceans. When they poop, they move nutrients from deep water to the surface, benefiting organisms in the marine food web. 

Now, new research has shown that whales also ferry substantial quantities of nutrients for thousands of miles in their urine and other bodily outputs.

Delivering nutrients across the ocean

In 2010, experts revealed that whales, feeding at depth and pooping at the surface, offer a critical resource for plankton growth and ocean productivity. 

The latest study, led by the University of Vermont, has found that whales transport abundant nutrients horizontally across entire ocean basins. 

These nutrients typically travel from rich, cold waters where whales feed to warm equatorial regions where they mate and give birth, delivered in large part by their urine – though sloughed skin, calf feces, carcasses, and placentas also play a part.

“These coastal areas often have clear waters, a sign of low nitrogen, and many have coral reef ecosystems,” said Joe Roman, a biologist at the University of Vermont, who co-led the research. 

“The movement of nitrogen and other nutrients can be important to the growth of phytoplankton, or microscopic algae, and provide food for sharks and other fish and many invertebrates.”

A long-distance nutrient pipeline

The researchers found that in oceans worldwide, great whales – including right whales, gray whales, and humpbacks – carry around 4,000 tons of nitrogen each year into coastal zones in the tropics and subtropics. 

They also deliver more than 45,000 tons of biomass. Before commercial whaling decimated whale populations, this offshore-to-inshore “nutrient pipeline” could have been three or more times larger.

For instance, scientists estimate that thousands of humpback whales migrate annually from a vast foraging region in the Gulf of Alaska to a smaller breeding area in Hawaii. 

The team shows that the nutrient inputs – tons of excretions, skin, and carcasses – provided by whales in the Hawaiian Islands Humpback Whale National Marine Sanctuary are about double the amount brought in by local oceanic processes.

The whale conveyer belt

“We call it the ‘great whale conveyor belt,’ or it can also be thought of as a funnel because whales feed over large areas, but they need to be in a relatively confined space to find a mate, breed, and give birth. At first, the calves don’t have the energy to travel long distances like the moms can,” Roman explained. 

Another factor is that the whales likely remain in shallow, sandy waters to muffle their calls. “Moms and newborns are calling all the time, staying in communication,” he added. “And they don’t want predators, like killer whales, or breeding humpback males, to pick up on that.”

Therefore, nutrients that are widely dispersed over feeding zones become concentrated in limited tropical and subtropical habitats, “like collecting leaves to make compost for your garden,” as Roman put it.

Large animals, massive migrations

During summer, fully grown whales gorge on krill, herring, and other prey in high-latitude waters near Alaska, Iceland, and Antarctica. Recent studies indicate that North Pacific humpback whales can gain about 30 pounds daily in spring, summer, and fall. 

This substantial fat build-up supports an incredible migration: baleen whales routinely travel thousands of miles to tropical breeding grounds without eating. Gray whales, for example, make a nearly 7,000-mile journey between feeding grounds off Russia and calving sites along Baja California. 

Meanwhile, some humpback whales in the Southern Hemisphere migrate over 5,000 miles from waters near Antarctica to areas off Costa Rica.

During these treks, they burn off hundreds of pounds a day and excrete substantial amounts of nitrogen-rich urea. One Icelandic study found that feeding fin whales can release more than 250 gallons of urine daily, while humans typically excrete less than half a gallon.

Living life on a different scale 

Whales have the longest migrations of any mammal and are outsized creatures in every sense. 

“Because of their size, whales are able to do things that no other animal does. They’re living life on a different scale,” said co-author Andrew Pershing, an oceanographer at the nonprofit organization Climate Central. 

“Nutrients are coming in from outside – and not from a river, but by these migrating animals. It’s super-cool, and changes how we think about ecosystems in the ocean. We don’t think of animals other than humans having an impact on a planetary scale, but the whales really do.”

Circulatory system of the planet 

Prior to commercial whaling that started in the 1800s, nutrient transfers would likely have been much larger, Pershing argued. He noted that researchers do not yet fully understand inputs from blue whales – the largest animals on Earth – which were heavily hunted in the twentieth century. 

“There’s basic things that we don’t know about them, like where their breeding areas are,” said Pershing, noting that humpback populations are recovering in some places, but blue whale numbers remain severely diminished.

“Lots of people think of plants as the lungs of the planet, taking in carbon dioxide and expelling oxygen. For their part, animals play an important role in moving nutrients,” said Roman. 

“Seabirds transport nitrogen and phosphorus from the ocean to the land in their poop, increasing the density of plants on islands. Animals form the circulatory system of the planet – and whales are the extreme example.”

The study is published in the journal Nature Communications.

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