A Seal’s Spray adds a chapter to the science of spitting

On January 3, 2022, Clare Jacobs, a birdwatcher, was delighted to spot a rare white-tailed eagle, or Haliaeetus albicilla, in a nature reserve on the Isle of Wight in southern England. These birds, also called sea eagles or ernes, disappeared from the region about 250 years ago, but since 2019 more than twenty birds have been released on the island.

Ms. Jacobs pointed her camera at the eagle when she saw something moving in the water below: a gray seal. The large mammal jumped out of the waves and opened its mouth. “It scared me,” Ms. Jacobs said.

Then the seal spat a stream of water at the bird of prey. Although Mrs. Jacobs did not immediately realize it, this was highly unusual. Seals have never been seen spitting before, and virtually no reports of interactions between these two apex predators exist.

Ms Jacobs’s photos ended up with her daughter Megan Jacobs, who is a PhD student at the University of Portsmouth studying fossils, and David Martill, a lecturer at the school. Together, they published the observation last month in the journal of the Isle of Wight Natural History and Archaeological Society.

Both animals feed on fish, although eagles also target waterfowl and carrion, and the study authors reason that the seal most likely spat at the eagle to deter a potential competitor. It appears the seal told him to “go away,” Megan Jacobs said.

Sean Twiss, a professor at the University of Durham who has studied gray seals for 30 years, has never seen one spit. He thinks it’s possible the seal was meant to scare the eagle, or it was just playful. Seals often forage at depth and don’t usually forage in such shallow waters as this harbor, he said, so he couldn’t be sure what the motivation for the water spout was.

The find makes gray seals one of the few species known to spit. Among the most famous members of this coterie are cobras, which can shoot venom from their teeth into the eyes of potential predators with impressive accuracy. The ability has evolved three different times are among the cobra lineages, says Maarten Jalink, a researcher at the University Medical Center in Utrecht, Netherlands, who has researched the phenomenon.

Perhaps the most impressive spitters are archerfish, he said Stefan Schuster, who studies the fish at the University of Bayreuth in Germany. These tiny creatures, native to mangrove swamps in Asia and the western Pacific, knock insects and arthropods off leaves using jets of water, which they produce by pressing their tongues against the top of their mouths and squeezing quickly. They then quickly eat the fallen prey. This spitting ability requires exquisite body stabilization achieved by activating the fins, said Dr. Schuster.

It also requires incredible vision. The upper halves of archerfish eyes are sensitive to above-water colors and the lower halves to undersea hues, explained Cait Nieuwpoort, a researcher at the University of Oxford. “Their brains are able to take into account the refraction caused by having their eyes underwater but spitting at objects above water,” she added. Other fish, such as the Picasso triggerfish, have spit at her in aquariums and also use this behavior to find food under sediments and move things underwater.

Some spiders also spitthrowing around blobs of gluey webs to subdue prey from a distance.

Many mammals are known to cough, such as camels, alpacas and their relatives. Such emissions, including saliva and often stomach contents, are produced as a defense mechanism against perceived threats. But spitting can also be a more reasoned way to transfer water from one place to another. In a study published in 2020For example, Bornean orangutans extracted food from a hollow tube by spitting water into it. Some monkeys are also known to do so dissipate seeds over considerable distances from their mouths while eating, probably to feed more efficiently.

Dr. Twiss says that these kinds of special observations are often not published – which was almost the case in this case. And that’s a shame, he said, because rare observations can teach us a lot about the natural world and alert others to new behaviors we need to study.

The sighting is also the indirect result of the expansion of the gray seal’s range following a curtailment of hunting and the reintroduction of white-tailed eagles after centuries of absence. More discoveries await as populations of these and other species grow and reclaim old territory.