Water voles and willow trees

The water vole conservation handbook [1998, Strachan) mentions that 227 different species of plants have been recorded as being eaten by water voles.  The ones that live live along the Ock usually prefer sedge in spring and water crowfoot & arrowhead in summer.
However, a colony found whilst undertaking a BBOWT water vole survey seem to have a predilection for eating willow leaves.
.

.

.
Maybe it's because there is a lack of sedge in this part of the river due to over the overhanging willow trees, but they certainly have the dexterity for it, as none of fallen off yet.
.

.
If they don't fancy willow, then at least one enterprising water vole has found a way to use a willow branch to get at those hard to reach nettle heads:
.