Howler monkeys are falling dead from trees amid scorching heatwave

MEXICO CITY: The heat in Mexico is so extreme that howler monkeys are falling dead from trees.

Since May 16, at least 138 of these midsize primates, known for their roaring vocal calls, have been found dead in the Gulf Coast state of Tabasco, according to the Biodiversity Conservation of The Usumacinta group.

Some were rescued by residents, including five who were taken to a local veterinarian who fought to save them.

“They arrived in critical condition, with dehydration and fever,” said Dr. Sergio Valenzuela. “They were as limp as rags. It was heatstroke.”

While Mexico’s brutal heat wave has been linked to at least 26 human deaths since March, veterinarians and rescuers say it has killed dozens, possibly hundreds, of howler monkeys. On Tuesday, about a third of the country saw temperatures reach 45 degrees Celsius (113 degrees Fahrenheit).

In Tecolutilla, Tabasco, dead monkeys started appearing on Friday. A local volunteer fire-and-rescue squad brought five of the creatures in the bed of a truck.

Usually intimidating, howler monkeys are muscular and can grow as tall as 90 centimeters (3 feet), with equally long tails. Some males weigh over 13.5 kilograms (30 pounds) and can live up to 20 years. They have large jaws and a fearsome set of teeth and fangs, but are best known for their lion-like roars, which belie their size.

“The volunteers asked for help, asking if I could examine some of the animals they had in their truck,” Valenzuela said on Monday. “They said they didn’t have any money and asked if I could do it for free.”

Valenzuela placed ice on their limp hands and feet and hooked them up to IV drips with electrolytes.

So far, the monkeys appear to be recovering. Once listless and easily handled, they are now in cages at Valenzuela’s office. “They’re recovering. They’re aggressive … they’re biting again,” he said, noting that’s a healthy sign for these usually furtive creatures.

‘Babies are very delicate’

Most aren’t so lucky.

Wildlife biologist Gilberto Pozo counted about 138 monkeys dead or dying on the ground beneath trees. The die-off started around May 5 and peaked over the weekend.

“They were falling out of the trees like apples,” Pozo said. “They were in a state of severe dehydration, and they died within minutes.” Already weakened, the falls from dozens of yards up often finished the monkeys off.

Pozo attributes the deaths to a “synergy” of factors, including high heat, drought, forest fires, and logging that deprives the monkeys of water, shade, and the fruit they eat. However, he notes that a pathogen, disease, or other factor can’t be ruled out.

For people in the steamy, swampy, jungle-covered state of Tabasco, the howler monkey is a cherished, emblematic species. Local people say the monkeys tell them the time of day by howling at dawn and dusk.

Pozo said local people—whom he knows through his work with the Biodiversity Conservation of The Usumacinta group—have tried to help the monkeys they see around their farms. But he notes this could be a double-edged sword.