OtterCam in the culvert

After a couple of weeks of dry weather the water level has fallen sufficiently for me to put a camera in the culvert again. This is good news because since the mother and cub split up there has been noticeably less otter activity in my recent site on the bank - the camera there is now mostly recording rat videos.  The camera in the culvert, on the other hand, is picking up an otter once or twice a night - 12 traverses in the first 5 days in fact.  The challenge is to decide whether it is all the same animal or whether there is more than one.

All solo otters look pretty much alike on slightly blurry freeze-frame stills from videos so I tried to standardise the pictures with the animal the same distance from the camera on the clearest few videos and it looks like this in date order (no 4 was already a bit closer at the start of the clip).

My impression is than nos 1, 3 and perhaps 5 are a bit bigger than nos 2 and 4.  It isn't easy because 1, 3 and 5 trot confidently past the camera whereas 2 and 4 seem to be trying to slink past without being seen.  But that in itself might be a significant difference.

It is more difficult when they are going the other way.  They are more inclined to run or bound through, perhaps because going against the water flow in a slippery pipe is more difficult, and the camera is sometimes a bit slow to pick them up.

Here is a video composite.  Of the retreating animals, the last one does look bigger.

In the second week the water level had dropped further so I was able to clamp the camera a bit lower down as well. Otters continued to use the pipe twice each night on average.  One intriguing finding was two recordings 10 minutes apart, both heading south.  The first animal is bigger and confident and the second is lower and again slinks past the camera so I am fairly convinced these are two different otters.  I don't know if the first is a dog and the second a female or the first an adult and the second last year's cub.  Either way I expect the first is male and the second female.

As long as it is safe I'll keep the camera in the culvert for the time being, although I think it will be a few months yet before we see more cubs.