By Steve Westerman

SOME weeks ago (before the latest Covid lockdown), I had the opportunity to watch two juvenile otters as they explored a section of the river Wharfe (see Denis’ Nature Notes, December 2, 2020). Initially there was also an adult in the area - their mother, I think. The youngsters seemed relatively independent, but stayed ‘glued’ to each other.

Otters are territorial. Adults often have long ranges in river environments. There is a good deal of variability, but for males this can be as much as 25 miles.

This provides some ‘insurance’ against local problems, such as lack of prey, flooding, drought, human disturbance, etc. However, it does mean they are frequently on the move, often travelling substantial distances each night/day, and periodically relocating when environmental factors make it advantageous or necessary.

This is consistent with my experience of seeing otters in the Wharfe. For a given location, otters tend to be around for a short period of time, perhaps a few days, but then can be absent for months.

The continuing recovery of the UK otter population from near extinction in the 20th century has been helped by the fact they are somewhat adaptable in the types of riparian environment they will use. For example, there are many reports of otters in urban rivers: youtube.com/watch?v=9Ipyqb67i94.

However, they do need sheltered places, where they can get out of the water, feed, and rest. Some of these will be below ground (holts) and some above ground (couches, hovers).

There are somewhat conflicting views as to the number of resting places that are needed and the spacing between them. A distinction can be made between ideal habitat and what is required.

Based on radio-tracking data of otter behaviour, one Swiss study suggested that ideal otter habitat would have undisturbed resting places with vegetative cover every 140 metres. Other sources conclude that intervals could be much greater, pointing to the fact that otters sometimes feed in quite exposed places and then travel some distance to reach cover.

In my view, for the sake of otters and other wildlife, the issue of habitat loss should be given urgent consideration with regard to the river Wharfe near Ilkley. In many places, vegetation is being cut back, and free-running dogs are making more and more paths along the banks and down to the water. It’s nice that large numbers of people are enjoying the river. It’s just a pity that we don’t seem to have a coordinated plan that encourages co-existence with wildlife. Without this, how long will it be before we are saying, “I remember when we used to have otters, and kingfishers, and dippers, along this stretch of river”?