Other otter traces (feeding grounds, caves, entry points, swimming tracks)

Do not count as concrete evidence since they are not clearly assignable!

There are many reasons for a collection of fish scales on the ground: anglers, raptors, minks or even muskrats, might have eaten fish there. Fully skeletonized fish is usually a sign for of rats. Fish that has been caught by otters is only seldom left with a full skeleton. It is typical for otters to leave big fish with a deep bite mark on their throat.

Even with dead frogs it is difficult to assess,  if an otter, a polecat, a mink or another animal was the culprit. Otters often flay their captured toads and leave the skin as an empty shell. 

It`s difficult to tell which animal created and used a cave in the embankment or close to the water. Only  clear tracks (or feces)  found nearby allow a relible determination.

Which animal used these entry points is only possible to distinguish with animal tracks- if there are any to be found.

Swimming tracks –like these— or traces of bubbles underneath the ice may have multiple causes and do not have to be necessarily created by an animal.