They progressed slowly, with Du You not being particularly impatient. Since they hadn't caused much commotion, the elves up ahead were unlikely to have discerned their presence. On the way, they certainly ran into a seemingly endless crowd of Tree People.
Perhaps because some people had just passed through, the elves had increased the number of Tree People stationed in these parts. The sheer number of these hard-to-damage Tree People was daunting. Ordinary people, even with a Colonist in their group, would probably fail to escape if they were not careful and ended up surrounded.
Further, getting through without stirring up some noise was practically impossible.
Perhaps this was why the elves felt safe enough not to station men here. If they knew what was going on here, they'd be furious. Thankfully, on the human side, elves tend not to launch large-scale attacks.
As evening approached, the group finally reached the end of Gloomy Canyon.