At least 234 threatened howler monkeys have died in tropical forests in the south-eastern Mexican state of Tabasco, wildlife non-profit Cobius said on Monday, a figure nearly triple that of a month ago which it attributed to a nationwide heatwave.
The over 200 death toll represents only the areas that the Mexican wildlife conservation group was able to study, and the group said the actual figure must be higher.
Local media had in May reported at least 85 howler monkey deaths, as temperatures surpassed 45°C amid an extended drought that has drained the country's reservoirs, only now beginning to be replenished by the start of the rainy season.
Though rains have now started across the country, Cobius said in a statement published on social media this "will not solve the emergency, but only provide some time to undertake real conservation action."
While Tabasco state has faced consistent high temperatures, Cobius said howler monkey populations were also suffering from hunting, excessive logging, habitat degradation, competition for space and new diseases passed on 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.
It said some monkeys it studied suffered from pulmonary edema, or wet lung, after breathing in smoke from forest fires.
The mantled howler monkey, living in Mexico, Central America, Colombia and Ecuador, is classified as vulnerable on the International Union for Conservation of Nature (IUCN) Red List, which last carried out a global assessment in 2015.
