Iwahig Firefly Watching

The Iwahig River runs through mangrove a little south of Puerto Princesa, and after dark a community-run association paddles visitors upstream in small boats to see the fireflies. The insects congregate in particular mangrove species along the banks in numbers dense enough that a whole tree pulses, and the guides - former fishermen and farmers from the barangay, trained for the work - point out the difference between males signalling from the branches and females answering from lower down. Paddles disturb bioluminescent plankton in the water at the same time, so the blade leaves a blue trail. Motors are not used on the firefly stretch and torches are kept off, which is the point: the whole experience depends on darkness, and phone screens ruin it for everyone in the boat. Trips run nightly and are best around the new moon, when there is least light. The same association runs a daytime mangrove paddle.

What's there

• The lit mangroves - trees pulsing with congregated fireflies.
• The paddle trails - bioluminescent plankton in the water.
• The guided commentary - the community guides' account of the insects.
• The dark river - no motors, no torches on the firefly stretch.

When to go

Year-round, after dark. Around the new moon for the darkest sky and the best display; heavy rain cancels trips.

Before you go

Darkness is the whole experience - no flash, no torches, no phone screens, and photographs essentially do not work. Numbers vary night to night. The boats are small and the trip involves getting in and out on a muddy bank.

Nearby

Puerto Princesa is forty minutes north; Honda Bay and the underground river are the city's other trips.