An intensive survey of historically important blue whale habitat in the Galápagos Islands ended without researchers finding a single blue whale. The absence was unusual in an area that provides the endangered animals with places to forage and rest during their long migrations.

From October 2025 through January 2026, the team searched around San Cristóbal, Isabela, Fernandina, and Santiago islands. It also surveyed the Bolívar Channel, an area known for high marine biodiversity and whale sightings.

The original goal was to attach a satellite transmitter to a blue whale so researchers could learn more about the animals’ migration routes. Without any whales to tag, the expedition could not complete that part of its work.

The scientists still collected information that could help illuminate the mystery. They measured temperatures and gathered plankton samples at multiple locations and depths throughout the water column.

At the surface, water temperatures ranged from 25.52 to 27.56°C, or 77.9 to 81.6°F. At a depth of 100 meters, or 328 feet, temperatures ranged from 19.11 to 19.67°C, equivalent to 66.4 to 67.4°F.

Those readings were higher than normal for that time of year, creating a possible explanation for why the blue whales stayed away. The unusual distribution of temperatures was also visible deeper beneath the surface.

Water at 20°C, or 68°F, is usually found at depths between 20 and 45 meters, or 66 to 148 feet. During the expedition, however, the researchers found that temperature between 78 and 96 meters, or 256 to 315 feet, deep.

The plankton samples revealed another potential obstacle for the whales. Their food was concentrated at one depth, while water matching the whales’ ideal temperature was found at a completely different depth.

One possible but unconfirmed reason for the altered ocean conditions is El Niño. The climate pattern is characterized by higher temperatures, more floods and droughts, and shifting rainfall patterns across the Pacific.

“Currently temperatures in the eastern Pacific are on course to be 4°C [7.2°F] above the average, which is far beyond anything seen before. If that trend continues, we could see an incredible El Niño event,” climate scientist Professor Mat Collins told the Guardian.

Ecuador declared a nationwide Red Alert in August because of El Niño’s effects. Still, the failure to locate whales during the survey does not establish that they have abandoned the Galápagos.

Daniela Alarcón, scientific lead of the expedition, is a professor and researcher at Universidad San Francisco de Quito and the Galápagos Science Center. She said the findings could help researchers ask more precise questions about the whales’ presence.

“Not finding whales during an intensive search effort does not mean they have stopped coming to the Galápagos. By combining these records with oceanographic data, we can begin asking better questions about the conditions that determine their presence and how much their movements may vary,” Alarcón said in a statement.

Other sightings show that blue whales were present before and after the expedition. In August 2025, before the study began, 45 blue whales were recorded through the monthly monitoring protocol.

After the study ended, a blue whale and calf were seen at Punta Pitt, San Cristóbal, in September 2026. That sighting was reported through a citizen science network.

Yacqueline Montecinos, leader of WWF’s Eastern Pacific Blue Corridor initiative, said conservation efforts must account for the full scale of whale movements. “To conserve the largest animal on the planet, protecting only the places where we are able to see it is not enough. We need to understand and protect the entire route that makes these encounters possible. That is the scale at which whales move, and it is also the scale at which we must approach their conservation,” Montecinos said.