The brutal heat in Mexico is causing howler monkeys to drop dead from trees

In southern Mexico, the deep and raspy roars of howler monkeys reverberate through the lush jungles enveloping the city of Comalcalco. The sound — akin to the rumble of distant thunder or the grumble of a large engine — usually crescendos around dawn and dusk, signaling to residents the beginning and end of each day.