The intensity and fury of a hurricane is enough to drive many animals to avoid its path. Still, not everyone does so. A team of researchers has discovered that a rare species of bird characteristic of the Desert Islands, in the archipelago of Madeira, has a “unique” behavior in response to these phenomena: instead of avoiding hurricanes, it follows their wake, very close to the areas where the winds blow most strongly.

They are called howler monkeys and, so far, they are the only bird species in the world in which this behaviour has been observed, explains to the Observer Francesco Ventura, lead author of a study recently published in the scientific journal Current Biology and which involved tracking the movements of these birds. In some cases, they even followed the trail of hurricanes. for more than five days and over 2,400 kilometersA discovery that nearly made researchers “fall out of their seats,” says the biologist from the Woods Hole Oceanographic Institution (in the US state of Massachusetts).

The results show that not only are howler monkeys not bothered by these extreme events, but they also take advantage of them as an opportunity to feed. The closest one of the birds the researchers monitored came to a hurricane was about 50 miles away. “This is significant because is within the radius of maximum wind speedAnd we are talking about more than 80 km/h, on average, because we have no data. in the place“, adds the biologist.

A “Eureka” moment

Francesco Ventura was a simple PhD student at the Faculty of Sciences at the University of Lisbon when his fascination with howler monkeys began. It was thanks to a research project of the faculty, in collaboration with the Institute for the Conservation of Nature and Forests (ICNF), which he joined in 2018 to study these birds and the neighbouring howler monkeys of Madeira. At the time, little was known about these endemic species of Madeira and a GPS was placed on a small group to follow their movements, including 33 howler monkeys.

The research remained in Francesco Ventura’s mind even after his PhD until, late last year, the researcher, who now lives in the United States, dug up the data. He wanted to understand what led the two species to head for different destinations in the Madeira archipelago, but came up with much more “surprising” results. Almost by chance, in a sort of “Eureka” moment, he observed the interaction of the birds during the Atlantic hurricane season and realised that they were following in their wake.

Using data from the National Oceanic and Atmospheric Administration (NOAA), the biologist analysed six major storms that occurred in the North Atlantic between 2015 and 2019: Gaston, Ophelia, Lee, Gabrielle, Maria and Lorenzo. By comparing the location of the birds with the path of the hurricanes, he noticed that they were never far behind the path that the hurricanes followed across the Atlantic. “In our study we showed that these birds follow the path of hurricanes for days and thousands of kilometres. This is something quite new and exciting,” he highlights.

In most cases, birds were found between 160 and 400 kilometers from the center of the hurricane, Paulo Catry, a researcher at Ispa (University Institute), who also participated in the study, told Observador. This behavior is very different from what was previously known about bird species. When they sense the proximity of a storm, some, such as Chingolito, change their migratory patterns to escape its effects, but there are also records of others, such as albatrosses, that take refuge in the eye of storms (a calm zone) and fly there for 12 hours to avoid strong winds.

The “winged runners” in search of an easy meal

With a short beak, white chest and grey wings, howler monkeys spend most of their lives in the ocean, with visits to land being rare. It is on the cliffs of Bugio Island that the only known nesting colony of these seabirds in the world is found. It is estimated to be home to around 200 pairs, which is why they are classified as “vulnerable” by the International Union for Conservation of Nature.

“They are very adapted to being at sea and travelling surprising distances, always looking for favourable winds,” says Paulo Catry, from Ispa. According to the biologist, they fly quickly and with low energy costs, since thanks to the wind they do not need to flap their wings to move forward.

From the Pterodroma family, which means “fleeing wings” or “winged runner”, they inherit an appropriate name, since when they travel in search of food, a task they alternate with their companions while incubating the eggs. They can travel an average of 8,000 km and sometimes even reach 12,000 km in just two weeks.“It’s incredible that a nun bird that nests on the desert islands near Madeira can practically fly to Canada while shopping,” she explains.

During their journeys across the Atlantic, hurricane season provides them with easy meals. These birds feed on small fish, squid and crustaceans, which are usually found at depths of 18 to 900 metres. Since they cannot dive to these depths, they wait until nightfall for their prey to rise to places closer to the surface.

This effort is no longer necessary with the passage of hurricanes, as the winds cause the warm waters on the ocean surface to mix with colder waters in deeper areas. This causes the birds’ prey to rise to the surface, making them easier to catch.

More species are in the researchers’ sights

Asked about the origin of the behaviour of these birds, researchers admit that it is a “difficult” issue to study. They believe that it is partly innate, but also the result of a learning process. “In the juvenile stage, seabirds [grupo em que se inclui as freiras-do-bugio] have exploratory behaviour. We can deduce from the movements we follow that they are actually learning, but there is a part that we know is innate,” says Paulo Catry.

The team reports that, “impressively,” none of the birds they monitored were injured in the storms, despite having studied a small group, but they emphasize that there are risks. “If it really is an opportunity, it does not mean that it is free of danger. They seem to have learned to deal with this danger effectively and relatively safely,” says the same researcher. This was observed when, upon arriving near areas where the winds are stronger, the birds tended to land in the sea, waiting for the strongest area to pass by them and then continue following the hurricane.

The team also believes that there may be more birds following hurricanes. “It is possible that other predators are doing the same thing and nobody has noticed yet. And I am not just talking about seabirds,” says Francesco Ventura. He points out that it is possible that animals such as sharks, tuna and marine mammals also know how to take advantage of the effect of their passage. “It would be interesting to see if other species do the same,” he admits, adding that he already dreams of extending the research to more animals.