This is literally what I get when I Google “non-conservative force”.
From the very first link (to Wikipedia), here’s a more detailed explanation:
A conservative force is a force with the property that the work done
in moving a particle between two points is independent of the taken
path. Equivalently, if a particle travels in a closed loop, the net
work done (the sum of the force acting along the path multiplied by
the distance travelled) by a conservative force is zero.
Which would imply that the work done against a non-conservative force on a closed path is not zero.
By conservation of energy, the amount of energy (potential + kinetic) lost by your otter should be equal to the work done against any non-conservative forces.
