Collisions between whales and ships are often fatal for many marine mammals, including whales, but researchers say expanding mitigation measures to less than 3% of oceanic surface would reduce the chance of fatal strikes.

Every year thousands of whales are injured or killed after being struck by ships, particularly the large container vessels that ferry 80% of the world’s traded goods across the oceans.

Collisions are the leading cause of death worldwide for large whales, but global data on vessel-whale collisions are hard to come by, impeding efforts to protect vulnerable species. A recently published study in the journal Science has quantified the risk of such collisions worldwide for four geographically widespread ocean giants that are threatened by shipping: blue, fin, humpback, and sperm whales.

In the paper, “Ship collision risk threatens whales across the world’s oceans,” researchers report that global shipping traffic overlaps with about 92% of these whale species’ ranges.

“Whale-ship collisions have typically only been studied at a local or regional level — like off the East and West coasts of the continental U.S., and patterns of risk remain unknown for large areas,” said lead author Anna Nisi, a University of Washington postdoctoral researcher in the Center for Ecosystem Sentinels. “Our study is an attempt to fill those knowledge gaps and understand the risk of ship strikes on a global level. It’s important to understand where these collisions are likely to occur because there are some really simple interventions that can substantially reduce collision risk.”

The research team found that only about 7% of areas at highest risk for whale-ship collisions have any measures in place to protect whales from this threat. These measures include, first and foremost, speed reductions, both mandatory and voluntary, for ships crossing waters that overlap with whale migration or feeding areas.

“Lowering vessel speed in hot spots also carries additional benefits, such as reducing underwater noise pollution, reducing greenhouse gas emissions, and cutting air pollution, which helps people living in coastal areas,” Nisi said.

Other options include changing vessel routings away from where whales are located, or creating alert systems to notify authorities and mariners when whales are nearby.

Briana Abrahms, a University of Washington assistant professor of biology and researcher with the Center for Ecosystem Sentinels, noted that implementing management measures across only an additional 2.6% of the oceans’ surface would protect all of the highest-risk collision hot spots that have been identified.

Co-author Bob Kenney, an emeritus marine research scientist at the University of Rhode Island’s Graduate School of Oceanography, contributed some 41,000 whale sightings from the extensive database he has curated since 1986.

“The most pressing problem with ship collisions in the North Atlantic is the critically endangered North Atlantic right whale, with four known to be killed by ships in 2024 out of a population of around 370,” he said. “One of those was a nursing mother, so its dependent calf could not have survived. While the species was not included in the new global study because of its limited distribution, it’s another example of the threat posed by ship collisions with whales.”

The highest-risk areas for the four whale species included in the study lie largely along coastal areas in the Mediterranean, portions of the Americas, southern Africa, and parts of Asia.

The international team behind the study, which includes researchers across five continents, looked at the waters where these four whale species live, feed, and migrate by pooling data from disparate sources, including government surveys, sightings by members of the public, tagging studies, and whaling records. The team collected some 435,000 unique whale sightings.

They then combined this novel database with information on the courses of 176,000 cargo vessels from 2017 to 2022 — tracked by each ship’s automatic identification system and processed using an algorithm from Global Fishing Watch — to identify where whales and ships are most likely to meet.

The team found that mandatory measures to reduce whale-ship collisions were rare, overlapping just 0.54% of blue whale hot spots and 0.27% of humpback hot spots, and not overlapping any fin or sperm whale areas. Though many collision hot spots fell within marine protected areas, these preserves often lack speed limits for vessels, as they were largely established to curb fishing and industrial pollution.

For all four species the vast majority of hot pots for whale-ship strikes — more than 95% — hugged coastlines, falling within a nation’s exclusive economic zone. That means that each country could implement its own protection measures in coordination with the U.N.’s International Maritime Organization.

The authors hope the study spurs local or regional research to map out the hot spot zones in finer detail, inform advocacy efforts, and consider the impact of climate change, which will change both whale and ship distributions as sea ice melts and ecosystems shift.

Note: Here’s a video that shows the collision hot spots.