River Cam: When the Predators are Away the Mice Come Out to Play

With winter approaching I have put out the first of my trail cameras in anticipation to see what wildlife is occurring along the river, local to me, this year. Last years was a success with a whole host of wildlife including Kingfishers, Barn Owls, Tawny Owls, Otters, Badgers, Stoats and Mink. Hopefully this year the camera will not be stolen but lets just wait and see what we get. 

I put the camera trap out last week and have just looked at the footage, no Otters unfortunately this time but its early days and there's plenty of spraint around there. They are likely occupying another part of the territory at the moment and as we saw last year there were often large gaps between sightings of both the male and the female and cubs. Other than a little observation on feeding moorhens, the main highlights from this initial session were rodents. 

Brown rats are a common feature of riverine habitats and can be particularly abundant where arable land occurs like at the study site. This mixture of agriculture providing lots of grains for feeding on, along with a riverbank that supports rough grassland and scrub along with the watercourse itself provides excellent foraging habitat and breeding/nesting habitat. Rats provoke a lot of dislike owing perhaps to their appearance (spikey hair, arched back, long bald tail, long muzzle, bulgy eyes) and of course the disease risk associated with them. This one was initially taking an interesting in the camera trap but thankfully decided not to try eating it. 

This opening in a long swathe of riverside grassland is a hazardous area which needs to be crossed by small mammals. Straying away from the cover of the grassland puts them at increased predation risk, especially given what we have seen using the bridge previously. This Field Vole was unsurprisingly fleet footed as it passed through before changing its mind and coming back. This is actually a new species on the River Cam. Its small size, rounded head, small eyes, lack of obvious ears, short pale tail and pale overall colouration should be compare with the woodmouse below.  

From memory I don't think we've recorded Woodmouse on River Cam previously either. Along with Brown Rat, Woodmouse was regularly recorded over these first few nights. All rodent species are at their peak density at this time o year, following on from the summer breeding season and before cold winter weather, starvation and predation has started to whittle away the population, which reaches a low in the early spring prior to breeding. The lack of any predators around so far and the time of year is perhaps making them bold, additionally most young rodents disperse in autumn after the breeding season. Note the long dark tail, dark back, more jumpy kangaroo like movement, big ears, big eyes.