Leeches are back, and that is good news

A wet-season survey of our oldest plots in the Western Ghats found leeches at densities no one has recorded since planting began. The team was there to count other things and ended up counting leeches instead, because there were too many to ignore.

Leeches need two conditions, and a degraded slope offers neither. They need damp shade, which means a canopy closed enough to hold moisture through the day. And they need a steady supply of warm-blooded animals to feed on, which means mammals and birds passing through in numbers.

Five years ago this ground was coffee monoculture, open to the sun and largely empty of the larger animals. A leech would have starved there. Their return is a backhanded measure of two things going right at once, a canopy that has closed and a food supply that has come back.

The same plots are where camera traps have picked up a tiger and a survey found the shrub frog last seen in 2009. The leeches fit the same story from the bottom up. The whole forest floor is wetter and more alive than it was.

The survey team did not enjoy collecting the data. Anyone who has spent a wet day in the Ghats prising leeches off their ankles knows the feeling, and there was a fair amount of swearing logged alongside the counts.

They counted anyway, because the count is the point. Restoration does not always announce itself with charismatic animals. Sometimes the clearest sign that your forest is recovering is the small unpleasant thing crawling up your boot.