The hikes require what level of fitness. I am 71 and of average ability.
The treks aren't terribly difficult, but you can ask for the short trail to be sure you're not walking for hours. You should be prepared for insects, wear long sleeves and long pants and a hat. Be sure to get up early for the birdwatching boat ride and bring binoculars if you can. The guides are excellent, so take advantage of that.
We did two hikes: one short nighttime hike (1 hour), and one longer morning hike (about 2,5/3 hours). The hikes are quite short and not strenuous. It's just the humidity and heat that can make it a little bit more challenging. Also very muddy, but you'll get rubber boots to march through the mud. There is one part on the longer hike where we had to go through a mud swamp, which was a bit challenging but also very entertaining. The guide will help you if you need assistance.
I'm sure you will be just fine! The guide is very helpful and will do anything to get you to the good places. He told us a story that they even hosted someone in a wheelchair once!
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