At least 234 threatened howler monkeys died in tropical forests in the south-eastern Mexican state of Tabasco this month, according to wildlife non-profit Cobius on June 24. This figure marks a nearly threefold increase from the previous month, attributed to a nationwide heat wave.

The 200-plus death toll represents only the areas that the wildlife conservation group could survey, and they believe the actual figure must be higher.

The mantled howler monkey, which lives in Mexico, Central America, Colombia and Ecuador, is classified as vulnerable on the International Union for Conservation of Nature (IUCN) Red List.

In May, local media reported up to 85 howler monkeys had died as temperatures soared above 45 degrees Celsius during a nationwide drought and heat wave in Tabasco. The severe conditions have depleted the country's reservoirs, which are now slowly refilling with the onset of the rainy season.

Despite the nationwide rainfall, a statement from the group on social media emphasized that this "will not solve the emergency, but only provide some time to undertake real conservation action."

Tabasco state has consistently endured high temperatures, exacerbating challenges for howler monkey populations already threatened by hunting, extensive logging, habitat degradation, space competition, and new diseases transmitted by humans and domestic animals.

"These factors, in synergy with the higher temperatures, cause heat stress which causes acute inflammation and above all contributes to a totally inefficient immune system response," Cobius added.

(With input from Reuters)