The tracks are the size of my hand; four-toed, no claw marks, unmistakably those of a tiger. Fourteen of them are dented into the reddish earth at the edge of a clear felled area. The prints lead downhill between some straggly bushes and peter out, or are smothered by the tread marks of large tractor tyres.
At one point, you can see where the tiger has skidded on the slope; four gouges in the mud ending in deep, round holes where its toes sunk in. The ground is hard now and bears the marks of a spattering of raindrops.
The hunter-fisherman who shows us the footprints reckons the tiger was here several days ago. "It's a large male, maybe two-and-a-half metres long, who is here in the summer, but travels to the coast every winter," he says. No, he hasn't seen it himself.
With the threat of an encounter with a tiger (or, more likely, a bear), you would think we would be taking no chances. But we are armed with two axes between four of us (used for cutting firewood), and as I write, Dave is stretched out sunbathing on the riverside shingle.
We have reached the confluence of the Ubilaya and Armu rivers, and it's breezy next to the rapids, so there are no midges for a change. Even Sergei, our guide, seems far more relaxed with my daily wanderings into the forest, on the grounds that, with one tiger covering a territory of 160 square kilometres, there is little likelihood of us actually meeting one (unfortunately, but we will keep on trying).
So here we are: a rest day; a good day for the sun to shine at last.
Tonight we set up the satellite phone and laptop, and once again video-conference with children on summer school in Knowsley. While I look at them on the screen and answer their questions about the expedition, there really could be a tiger - or two - right there in the bushes behind me.
Simon Chapman is head of physics at Morecambe high school, Lancashire, and author of The Monster of the Madidi (Aurum Press) and the Explorers Wanted! series for children (Egmont). Throughout his expedition he will be video-conferencing with summer schools in Knowsley (www.kirkbyclc.org.ukexplorers) via satellite phone. You can follow him every week in The TES