Volcan de los Murcielagos

Every evening near Calakmul, the forest performs a geyser of wings. The Volcan de los Murcielagos - the bat volcano - is a collapsed sinkhole cave whose mouth opens in the jungle floor beside highway 186, home by day to a colony estimated in the millions: several species of insect-eating bats packed into one of the largest known roosts in Mexico. At dusk they leave for the night's hunt, and the exit is the spectacle - not a trickle but a sustained, rotating column, a tornado of bats spiraling counterclockwise out of the earth for half an hour and more, audible as dry wind, dense enough to bend like smoke when a hawk or falcon strikes the stream. Community guides walk visitors the short trail to the rim viewpoints, time the emergence - which shifts with season and weather - and keep the etiquette: quiet voices, no flash, no descent. The colony's insect consumption each night is measured in tons, a pest-control service the region's farms bank on. As a curtain-raiser or encore to Calakmul's ruins, nothing on the peninsula matches it.

The landscape

• The emergence - a spiraling column of millions at dusk.
• The predators - hawks and falcons working the stream at dusk.
• The sinkhole - the volcano-mouth cave in the forest floor.
• The sound - wingbeats massed into weather.

When to go

Arrive an hour before sunset any dry evening; the flight runs year-round but rain can mute or delay it. Pair with a Calakmul or Becan day ending eastbound.

Good to know

Timing shifts nightly - guides know, but patience is part of the ticket. Mosquitoes attend the same show; cover up. Flash photography is banned and pointless anyway - bring eyes, not lenses.

Nearby

Becan, Chicanna and Xpujil's ruins line the highway; Calakmul's gate and the biosphere's dawn wildlife lie just west.