Could this be an Otter feeding site?

[Otter Spotter]

Hi,

I have recently been doing lots of research into the recovery of the Otter population in my area and I had a tip off from a local wildlife enthusiast of lots of Swan Mussells being found at the side of a huge lake near where I live.

They are generally situated on the bank and the majority of them tend to have a very small hole in the shell, simular to a drill hole and I am of the very strong opinion that these have been produced by Otters? and I was really looking for backup on this theory.

There are a number of water birds around but I cannot think of one that would have the strengh to open the shells in this way.

Also a number of the shells still have small stones attached to them so they must have been dived for and brought to the bank.

Look forward to hearing your theories.
Thanks
Take care
Andy

[stigofthedump]

Hi Otter Spotter. I've not welcomed you to WAB yet, so welcome. I really don't know if it could be otters, have you Oyster catchers on the lake? They sometimes hammer holes in shells to gain access to the contents.
Sure a mammal person will be along shortly to help out.



Vince

[The Woodman]

Andy, you describe an interesting observation.

Does each half shell have a single hole and what size are the holes?

Any chance of uploading a picture?

I've done a bit of a trawl through my Otter books and found not a lot on Swan Mussel in Otters diet!

It could be that the following comment re spraint content makes knowledge of Swan Mussel predation difficult.

In Marie Stephens "The Natural History of the Otter" Anodonta cygnea is mentioned thus:
These (very large specimens, weighing about 6 oz. each) were not tackled until already opened. They could not be identified in the spraint, as none of the shell was eaten".

Another reference re captive Otter says that when offered the mussels were pushed around as if with amusement but not opened.

Remains of native and Signal Crayfish I've found in spraints and charnel piles have inconsistent holes in carapaces.

Swan mussels are not easy to open with bare hands, almost impossible. However, the shells are thin in comparison to other freshwater mussel species and easily broken.

[Otter Spotter]

Hi ,

thank you for taking so much trouble to answer my question.

I will get a sample and post a picture as soon as possible.

As far as I know ther are know Oyster Catchers and this location is a perfect spot for Otters with easy access to a fantastic waterway system which would have a great appeal.

there tends to be on most shells I have found two holes one in each side about the same thickness of a drinking straw.

there are lots of them around the lake in patches, generally either on the bank or on landing platform used by fishermen.

There have been no sightings of Otters in this area and this is why I am so keen to confirm there may be a chance it is Otters and I will then do regular observations to see if we can spot them.

Thanks again for your help I will post the pictures as soon as i can.
Take care
andy

[Dogghound]

It doesnt quite sound rite for a mammal in my eyes, There would really be 4 puncture marks two on each side. A mammal is less likely to puncture like this but to chew into the shell. It sounds like fishermen have dragged them up/or floods etc and crows (or other birds) have been at them.

[shirl]

I found alot of similarly opened swan mussel shells during a water vole survey at a series of ponds. We guessed it might be the fishermen who were using the mussels as bait for carp etc not that I know anything about fishing so could of course be wrong.

Shirl

[nightshade]

I was reading my Jack Hargreaves "The Old Country" when I came across a couple of paragraphs about otters.
"At night they gather them up on the bank, always at particular feeding stations ....."

[ChrisJB]

Originally Posted by shirl

I found alot of similarly opened swan mussel shells during a water vole survey at a series of ponds. We guessed it might be the fishermen who were using the mussels as bait for carp etc not that I know anything about fishing so could of course be wrong.

Shirl

Fishermen will use freshwater mussels for carp, and occasionally tench I think.

Chris