Researchers have discovered that humpback whales across the globe are saving animals from killer whales. The whales can be seen confronting killer whales and chasing after them on more than one occasion, an unusual behavior that has baffled world experts.

In 2009, marine ecologist Robert Pitman, a researcher with the Southwest Fisheries Science Center in the NOAA, spotted a pod of killer whales hunting a Weddell seal. The orcas were able to remove the seal off the ice but as they were about to kill it, a humpback whale came out of the water to save the seal.

The whale placed the seal on its belly to keep it out of the water where the orcas could snatch it again. When the orcas finally left, the seal swam off to another more stable ice.

It turns out that this is not a rare occurrence. In a study published in the journal Marine Mammal Science, an investigation led by Pitman found that whales saving other smaller animals from orcas have become increasingly common over the years.

The international team of researchers looked into 115 recorded encounters between humpback whales and orcas that happened between 1951 and 2012. The team noticed that the whales usually worked in pairs.

It turns out that in 89 percent of the encounters, the humpback tried to intervene when the killer whales were trying to kill their prey, which include gray whales, ocean sunfish, sea lions and seals. However, the whales’ effort only worked in 18 percent of the cases.

This behavior remains a mystery to researchers. Some believe that this is a warning sign to keep the orcas from hunting the whale’s calves. Others claim that this is simply a demonstration of altruism in animals. Hence, researchers assert that further studies are needed to determine the reason behind this behavior.