Enjoy a closer look at the Water Shrew in a new blog by local naturalist and volunteer, Christopher Wren.
One of the main advantages of trail cameras is that they offer insights into animal behaviour that otherwise we would never see. One of my cameras is set up in a box to record Weasels that visit nearly every day. The camera sometimes also records Wood Mice, Bank Voles, Common and Pygmy Shrews and even Rabbits and Grey Squirrels that visit the box looking for food. Every now and then I put in a dead Wood Mouse from a trap in my attic – under a slate to give the camera time to react before the Weasel takes it. Recently there was a big surprise when a Water Shrew turned up and took the mouse – the mouse is as big as the shrew and the slate is much heavier. The camera box is in the wildlife corridor not far from Gosforth Nature Reserve but is about 300m from the nearest watercourse.
A Water Shrew’s normal diet is Freshwater Shrimps, Caddis Fly larvae, that sort of thing, and on land it will take beetles, worms, millipedes, etc, but taking a dead mouse was very unexpected. I did find a 2002 report of Water Shrews assumed to be taking carrion but I don’t think it has ever been filmed before.
Water Shrews are active around the clock, especially at night. They find their food by scent and touch, with a sensitive nose and whiskers. This shrew is an adult female, seen here searching for food in the dark.
As I had no more mice I have been leaving casters (fishermen’s casters, blowfly pupae). And as fast as I put them out the shrew takes them away. She comes back twice a minute (I edited out the gaps in the video) so her nest or food cache can’t be more than 12s travel time away, so only a few metres. Water Shrews give birth to several litters up until August so I suspect this one may have young somewhere close by.
Occasionally the shrew will eat the casters in the camera box instead of carrying them away. On one night she ate two dozen or so within a few minutes, each time carrying the food to one entrance to eat it and squeaking excitedly all the time. She certainly looks well fed.
One interesting thing is that there have many fewer Weasel visits to the camera box since the shrew first appeared, about two a week compared with previously about two a day on average. I don’t know if that is just coincidence or if the weasels might be put off by the shrew. That seems unlikely – I would have thought a weasel would be a threat to the shrew – although shrews are said to be distasteful to predators and the Weasels may know about the shrew’s venomous bite.
A Water Shrew uses its venom to paralyse its prey so it can eat it later if there is a surplus. The next trail camera video, recorded in Gosforth Nature Reserve a couple of years ago, shows a Water Shrew caching food, something that was known about but I think had never been observed before. The shrew was hiding its prey just above the waterline and later when it felt a bit peckish it came down from its nest for a quick bite to eat. Another fascinating insight into the life of this rarely seen small mammal.