I have volunteered for the Biodiversity Team at Oxfordshire County Council. They undertake numerous surveys and investigations on behalf of the County Council.  On this day I was to assist with the placement of a camera trap for detecting otters.

Oxfordshire County Council

Otter camera trap placement

08 May 2024

A drainage ditch is planned to be dredged and cleared of vegetation to allow it to carry run-off/overflow. Preliminary surveys have found no signs of bats or water voles. 2 ponds within a pre-defined distance have been e-dna tested for great crested newts, which has come back negative. At one of the previous surveys the presence of an otter holt was found: including footprints and spraint. The distance of this is sufficient that if it is a holt or a couch then development would not be hindered by it. However, investigation is required to determine if it is a natal den or not. If it is, then potentially the proposed development to the ditch could cause disruption – so other mitigation would have to be considered.

Background

Location of drainage ditch

Drainage ditch for dredging

To investigate the presence of otters a camera trap was to be deployed. Due to heavy rain it was not possible to set-up the camera trap the previous week so I was able to assist in its placement.

We had to wade through some fairly wet/waterlogged meadows, which caused us to have to double back to find a route. The otter holt was a hole in a large crack willow. There was otter spraint on the horizontal trunk, it was full of shells and we could see a crayfish claw.

Activity

The camera trap was a ‘no glow’ type to ensure minimal disruption to any otters. I helped attach it to a tree so that it could point at the entrance to the holt. It was interesting to see how it had a screen to aid positioning so that you could view what was going to be recorded. As well as being strapped to the tree, a bicycle lock was also used to ensure it was fixed in place. The battery (and SD card) are scheduled to be replaced on a weekly basis. At the time of visiting the entrance to the holt looked to be underwater.

Wet meadow

Otter holt location

Otter spraint

Images of camera trap set-up, and view to otter holt

Reflection

This was a very informative activity, giving me insight into some of the challenges ecologists face when surveying e.g. difficulties in getting to the site due to the waterlogged meadows and the fact that the camera wasn't able to be positioned the previous week. I also gained a better understanding of the rationale behind setting up the camera, along with practicalities e.g. changing of batteries/sd cards, attaching the camera and positioning it etc. 

I also saw first-hand indications of otter presence i.e. spraint, which will aid me in identification.

I was pleased that the trap subsequently captured an otter, with a short video shared, screenshot below:

Screenshot from camera trap video. Courtesy of Oxfordshire County Council.