Looking for otters on the River Mease: November 2016
by Mat Bingham
My next project is to capture images of the otters on my local river, the River Mease. As I see it, there are two challenges with this; to start with I have to find the otters and then I have to convert a camera and lighting system to infra-red (otters cannot see infra-red). The camera will be remotely triggered by an infra-red sensor taking high quality photographs without disturbing them. More on the technical bits in later posts.
Firstly, a bit about the river. The River Mease is a lowland river carving a natural course through farmland sown mainly with barley, wheat and oilseed rape. Supplied by drainage ditches and runoff from the surrounding fields, it is a flashy river which has a tendency to burst its banks. The soil structure is fairly stable, supporting vertical banks that are good nesting habitat for kingfishers. There are stretches where trees of mixed species overhang the river, providing cover for wildlife. The riverbed is approximately one meter below field level where the soil abruptly encounters underlying bedrock. Hollows and bowls in the riverbed vary the flow and depth, supporting good numbers of bullheads and sticklebacks. Historical surveys suggest there are water voles on the river, although I have not seen any to date.
The idea of photographing the otters came to me when I was out for a walk along the river earlier this year and found some otter tracks at the confluence between a drainage ditch and the main river. There is a shallow sloping bank at this junction between water courses, and an otter had left the water leaving a set of really good, easily identifiable prints.
Where I had spotted the paw prints looked to be a good location to set up a trail camera. I returned the following week and set up a camera – which, for convenience, I shall call Camera 1. I also set up another camera upstream of this location – Camera 2 – to record movement along the river. I fixed Camera 2 to a tree with cable ties looking across the river. Camera 1 is located on the river bank, fixed to a bank stick looking at the area where I found the paw prints. I have been returning to the cameras every two weeks to swap over the memory cards and change the batteries.
It took about four weeks before I had any success. Camera 1 was triggered by a female otter with at least two cubs in tow. There are some old twisted trees with root systems extending into the river at this location, which makes me think there might be an otter holt located there.
Camera 2 didn’t record the family swimming upstream of this location. This probably means that the otter family headed off either along the drainage ditch or downstream of Camera 1.
Since the encounter with the female and her cubs I have not seen them again on the river. A few days after the encounter, Camera 1 recorded three beagles entering the river. Their owner didn’t walk in front of the camera, but I assume this was a dog walker and his three pets out for an early morning stroll. It’s possible that the female otter has not returned with her cubs because she picked up the scent of the dogs at the location of Camera 1. If this theory is correct we should see them again once we have had a good period of rain to wash away the dogs’ scent.
Camera 1 has also filmed a fox and a muntjac deer coming to the river to drink.
Since that first encounter, Camera 2 has repeatedly recorded a dog otter swimming upstream and downstream at different times and dates which suggests this stretch of river is in the heart of his territory.
I plan to set up a third camera, Camera 3, downstream of Camera 1, to better understand the otters’ movements.
So what do I know so far?
Well, there appears to be a family of otters on the river and also a male dog otter whose territory extends past camera 2.
It looks like I have found the otters but more fieldwork is required, and I need to set up a camera downstream of Camera 1 to gain a better understanding of their comings and goings before I set up the high definition camera next year. More to follow in future posts!