Humpback whale mother and calf. (Credit: Martin van Aswegen, NOAA permit 21476)
In a nutshell
Migrating baleen whales transport thousands of tons of nutrients from cold, nutrient-rich feeding grounds to warm, nutrient-poor breeding areas through their urine, placentas, skin, and carcasses, boosting marine productivity.
This “great whale conveyor belt” concentrates nutrients in small breeding areas, fueling phytoplankton growth, which supports entire food chains, including fish and sharks.
Before industrial whaling, this nutrient transport was three times greater. While conservation efforts are helping some whale populations recover, threats like climate change, ship strikes, and entanglement could limit their ability to restore these lost ocean connections.
BURLINGTON, Vt. — Baleen whales are quietly performing an ecological service of global importance. These massive marine mammals don’t just wow us with their size and songs; they’re also running what scientists have dubbed “the great whale conveyor belt,” a nutrient transport system that moves essential elements from cold, productive waters near the poles to warmer, nutrient-poor tropical breeding grounds.
A new study published in Nature Communications shows that gray, humpback, and right whales transport about 3,784 tons of nitrogen yearly to their winter breeding grounds, potentially fueling the production of more than 18,000 tons of carbon. This represents one of the largest long-distance nutrient movements documented in nature.
The research team from the University of Vermont’s Gund Institute for Environment and other American universities has measured for the first time just how massive this nutrient movement really is. Their work reveals that before commercial whaling decimated whale populations, this nutrient transport was likely three times greater, showing yet another ecological impact of historical whaling that we’re only now beginning to grasp.
The Power of Whale Pee
“These coastal areas often have clear waters, a sign of low nitrogen, and many have coral reef ecosystems,” says co-lead study author Joe Roman, a biologist at the University of Vermont, in a statement. “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.”
In the ocean, nutrients often determine how productive an ecosystem can be and, therefore, how much life it can support. Many tropical and subtropical areas where whales give birth lack essential nutrients. When whales arrive from their feeding grounds, loaded with stored energy and nutrients, they give these ecosystems a vital boost.
Whales move nutrients across huge distances. After feeding heavily in cold waters during summer, many species travel thousands of miles. Southern Hemisphere humpback whales swim up to 8,300 kilometers (5,160 miles) from Antarctic waters to tropical breeding areas. Gray whales journey more than 11,000 kilometers (6,800 miles) between Russian feeding grounds and breeding spots along Baja California.
During these migrations, whales transport nutrients mainly through their urine, which contains nitrogen-rich urea. They also release placentas during birth, and when whales occasionally die in breeding areas, their carcasses deliver huge amounts of nutrients to these ecosystems. Sloughed skin and calf feces add to this nutrient flow.
Nature’s Nutrient Funnel
“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,” says Roman.
Many whales travel thousands of miles from their summer foraging areas to winter grounds for breeding and calving. Nitrogen and other elements can be released in the form of urine, carcasses, placentas, sloughing skin, and feces (primarily from nursing calves). Humpback whales of the Central North Pacific, shown here, primarily feed off the coast of Alaska and spend winters in the shallow waters of the Hawaiian archipelago. Click to expand. (Illustration by A. Boersma; text adapted from original study in Nature Communications)
For most species studied, the feeding grounds are much larger than the breeding areas. North Pacific gray whales, for example, have summer feeding grounds up to 46 times larger than their concentrated breeding areas. This means that nutrients gathered across vast ocean regions become concentrated in small breeding grounds, amplifying their impact. Roman compares this to being “like collecting leaves to make compost for your garden.”
The whales likely stay in shallow, sandy waters because it muffles their sounds. Roman explains that mothers and newborns communicate constantly, and they need protection from predators like killer whales and from breeding male humpbacks that might disrupt the vulnerable calves.
In Hawaii, researchers found that humpback whales release about 3,142 kilograms of nitrogen daily through urea, about 125-175% of the nitrogen that enters from ocean mixing during the breeding season. This means migrating whales deliver more nitrogen to Hawaiian coastal waters than the ocean’s physical processes during whale season.
“Because of their size, whales are able to do things that no other animal does. They’re living life on a different scale,” says co-author Andrew Pershing, an oceanographer at 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.”
This nutrient transport doesn’t just help tiny organisms. When whale calves or adults die in breeding areas, they feed scavengers like sharks. Tiger sharks and other large shark species have been spotted feeding on whale carcasses in breeding grounds. In places like Australia and Brazil, sharks breed nearshore during the whale season, suggesting that migrating whales might be an important food source for these top predators.
While seabirds also transport nutrients between ecosystems, whales move them across entire ocean basins, spanning thousands of kilometers. Seabirds typically transport nutrients across much shorter distances, and many of their contributions end up on land rather than in marine ecosystems.
“Lots of people think of plants as the lungs of the planet, taking in carbon dioxide, and expelling oxygen,” says Roman. “For their part, animals play an important role in moving nutrients. 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 Future of Ocean Nutrients
Conservation efforts that help whale populations recover could restore this important nutrient transport service. However, recovery faces many challenges beyond direct hunting. Ship strikes, fishing gear entanglement, ocean noise pollution, and climate change all threaten whale populations.
The research team’s findings suggest that populations of humpback and right whales in the Southern Hemisphere will likely peak around 2050 before declining due to climate-driven changes in ocean temperature, sea ice, and primary productivity.
These ocean giants are running nature’s most impressive fertilization system, delivering hundreds of gallons of “liquid gold” daily to marine ecosystems that desperately need it. Who knew whale pee could be such a big deal for healthy oceans?
Paper Summary
Methodology
Researchers compiled data from whale tracking databases and supplemented this with aerial and ship-based surveys. They focused on four coastal species with clear migration patterns: gray whales, humpback whales, and North Atlantic and southern right whales. By mapping summer feeding grounds and winter breeding areas, they calculated the “funneling effect.” They estimated nitrogen transport through urea excretion, placenta release, and whale carcasses, using data from fasting elephant seals to estimate excretion rates.
Results
These whale species move approximately 46,512 tons of biomass, 4,874 tons of carbon, and 3,784 tons of nitrogen to their winter breeding grounds annually. Before commercial whaling, this nutrient transport would have been almost three times higher. In Hawaii, whale-transported nitrogen exceeds the vertical nitrogen flux from ocean mixing by 125-175% during breeding season.
Limitations
The study has limited data on migration patterns for blue, fin, and minke whales. It couldn’t precisely quantify nutrient transport through whale feces or skin sloughing. Uncertainty exists in some biological parameters, though sensitivity analysis helped address these gaps. Improved whale population monitoring would help refine future estimates.
Discussion and Takeaways
Whales operate the largest known long-distance nutrient transport system on Earth. The concentration of nutrients in small breeding areas magnifies their ecological impact. Historical whaling disrupted these nutrient networks, and ongoing conservation efforts could help restore them. Climate change threatens this recovery, with Southern Hemisphere whale populations likely peaking around 2050 before declining due to changing ocean conditions.
Funding and Disclosures
This research was supported by a Fulbright-National Science Foundation Arctic Research Grant, NASA Biodiversity Grant, Horizon Europe Marie Skłodowska-Curie Actions Grant, and Whale and Dolphin Conservation. The Projeto Baleia Jubarte, which contributed Brazilian humpback whale data, is sponsored by Petroleo Brasileiro S.A. The researchers declared no competing interests.
Publication Information
The journal paper, “Migrating baleen whales transport high-latitude nutrients to tropical and subtropical ecosystems” was published in Nature Communications on March 10, 2025. The team included scientists from the University of Vermont, Aarhus University, Florida International University, University of California Santa Cruz, and Climate Central Inc.