North Atlantic right whales rise toward the surface to feed after dark, a behavior that had not been reported for the species before, according to a study published Sept. 16 in PLOS One. The tagged whales also spent roughly a quarter of their time outside a zone that bars motorized boats, leaving them without its protection for a meaningful share of their summer feeding.

The finding matters because most protections against ship strikes depend on people seeing whales. Aerial and vessel spotters trigger slowdowns, and bridge crews watch for blows and backs at the surface. At night, that system largely goes blind, and the new data show that night is when these whales are most likely to be feeding near the surface.

With about 380 right whales alive at the start of 2024, according to NOAA, every avoidable death affects the species' odds of recovery. The whales migrate along the U.S. East Coast and calve off the Southeast, so gaps in protection anywhere in their range matter to American waters.

Suction-Cup Cameras and a Machine-Learning Model

A team led by Jay Kirkham of Dalhousie University in Halifax attached suction-cup tags to 23 right whales in the Shediac Valley, part of Canada's southern Gulf of St. Lawrence, during July 2023 and July 2024. Each tag carried a video camera plus sensors that recorded depth, movement, sound, and light, and tags stayed on for nearly 11 hours on average. Co-authors included researchers from the University of New Brunswick and NOAA Fisheries.

Four tags kept a clear view of the whale's mouth, allowing the researchers to mark exactly when a whale was feeding. Right whales feed by swimming with their mouths open to strain tiny copepods, which slows them and forces harder tail strokes. The team used those confirmed feeding moments to train machine-learning models to recognize the same movement pattern in the rest of the data.

The best model agreed with the researchers' manual classifications 95% of the time, according to the PLOS news release on EurekAlert. Applied to all recordings, it estimated the whales spent 11% to 76% of their time feeding, an average of 11.4 hours a day.

Shallow Feeding After Dark Changes the Risk

The depth pattern followed the clock. By day, tagged whales fed deep, averaging about 156 feet (47.7 meters), often along the seafloor, and the study includes the first video of the species feeding close to the bottom. At night, average feeding depth rose to about 47 feet (14.2 meters), with surface feeding most common in the first hours after 9 p.m., according to Earth.com, which interviewed Kirkham.

The whales are likely following their prey. Copepods gather in dense layers at depth during the day and migrate upward after dark. "Avoidance of right whales relies on visual observation," Kirkham told Earth.com, adding that this becomes very difficult at night.

The zone finding adds a second layer. Transport Canada enforces a vessel exclusion zone over the Shediac Valley from June through September, with motorized boats prohibited inside. The tagged whales spent 74.6% of their time inside it, more at night than by day, which left them outside its protection about a quarter of the time.

Older methods also missed much of the night feeding. Researchers have often inferred feeding from dive shape, assuming a whale that dove and held a steady depth was eating. Compared with the video, that approach worked well by day but identified less than half of actual feeding time at night.

What the Tags Can and Cannot Show

This is a peer-reviewed observational study with clear limits. It covers one feeding ground in one month across two summers, so it does not show whether nighttime surface feeding happens all season or in U.S. waters such as Cape Cod Bay. An open mouth does not prove swallowing, since the behavior could serve other purposes such as rinsing the baleen, and some feeding likely went uncounted when the camera lost sight of the mouth.

Most importantly, the study does not measure collisions. It cannot say whether ship strikes are more common at night, only that the whales spend more nighttime hours near the surface, where vessels travel. The research was funded by Fisheries and Oceans Canada through the Canada Nature Fund for Aquatic Species at Risk.

A Policy Debate Over Speed Limits and Detection Technology

The findings arrive during an active U.S. policy debate. Under current rules, most vessels 65 feet or longer must travel at 10 knots or less in Seasonal Management Areas along the East Coast at certain times of year. In March, NOAA Fisheries published an advance notice of proposed rulemaking on vessel speeds seeking input on replacing seasonal speed restrictions with alternative management areas and technology-based strike-avoidance measures. The comment period closed June 2.

NOAA has said it wants measures that maintain or enhance conservation while reducing burdens on industry. The Kirkham study does not evaluate any specific technology, but it underscores a practical requirement: any detection system meant to replace or supplement speed limits would need to work in darkness, when visual spotting fails. Kirkham said what is still needed are tools that can find right whales at night, along with vessel operators and a public aware of the risk.

The species remains listed as endangered under the Endangered Species Act, and entanglement in fishing gear and vessel strikes are its main threats, according to NOAA Fisheries' right whale species page. NOAA has also had an Unusual Mortality Event in place for the species since 2017.

For boaters, anglers and whale watchers, the practical steps are clear. Follow posted speed zones and voluntary Slow Zones, keep the legally required 500-yard distance from right whales in U.S. waters, and report sightings, injured whales, or entanglements to NOAA or the U.S. Coast Guard. Operators traveling at night along the East Coast should slow down in known whale habitat, since visual detection is limited after dark.

Kirkham's team has continued tagging through the early summer of 2026, and future seasons should show whether the nighttime pattern holds beyond July. NOAA has not announced when it will publish a proposed rule following the advance notice. The central question is whether protections designed around daylight can adapt to a whale that does much of its feeding in the dark.

What Readers Want to Know

What did the right whale study find?

Tagged whales fed near the seafloor by day and much closer to the surface at night, a behavior not previously reported for the species. They also spent about a quarter of their time outside a Canadian vessel exclusion zone.

Why does nighttime surface feeding matter?

Ship strike avoidance relies heavily on spotting whales, which is very difficult at night. Whales feeding near the surface after dark are closer to vessel traffic when crews are least able to see them.

Where was the study done?

In the Shediac Valley in Canada's southern Gulf of St. Lawrence, during July 2023 and July 2024. The species also migrates along the U.S. East Coast.

How did artificial intelligence help?

Researchers trained machine-learning models on camera-confirmed feeding events. The best model matched human classifications 95% of the time.

Does this prove more whales are hit at night?

No. The study did not measure collisions. It shows the whales spend more nighttime hours near the surface.

How many North Atlantic right whales are left?

NOAA estimated about 380 individuals at the start of 2024.

What should boaters do?

Obey speed zones, stay at least 500 yards from right whales in U.S. waters, slow down in whale habitat at night, and report sightings or injured whales to NOAA or the Coast Guard.