Is this a mating call on OtterCam?

Here is a sound I haven't heard before.  The dog otter usually scent marks at the top of the bank as he goes down but this time he let out a shriek or yelp halfway down and again after entering the water.  (Make sure the sound is on).

The next night he ran up the bank so quickly that the first two cameras missed him completely and the last two only got a very brief glimpse of his tail.

Fortunately they all switched on and recorded sound.  Here are cameras 2, 3 and 4 listening as he went off into the reedbeds.

All the otter sounds I have recorded before were from the females or the pups but none of them sounded anything like this.  Paul Chanin, in his book Otters, says "the lonely Eurasian otter is not a particularly vocal animal".  He quotes Philip Wayre as describing three main types of otter call, although I think these were mainly from hand-reared or captive bred animals.  The sounds were: a contact whistle (which I have heard mainly from pups); a "hah" from the mother to warn of danger (there was a similar snort from the dog on the trail cameras recently); and more complex sounds described as chittering, chuckling, snickering and twittering.  Searching on line I couldn't find a description of a sound or call like the one in the videos above but I did find a commercially available video where a similar sound is described as "calling for a mate".

The dog otter has been showing up on the cameras most nights recently and the mother and pup nearly as often.  I think the pup will leave its mother in the next few weeks so she will soon be ready to mate.  I expect the dog otter realises this and is advertising his availability.