CritterCam - the search for a water vole. Part 2

Following on from my previous post, this is the second report on my attempts to catch a water vole on a trail camera. The second camera was about 50m away from the first, the position of both cameras being determined by where I could get some field of view for them near water.  It was difficult because there was mostly just a trickle of water under the grass and rushes.  This was the position of the camera.

There were again plenty of views of voles but most were field voles. This time I used a 150mm cut section of reed as a calibration and unlike the piece of raspberry cane which was dragged off by the voles (I wonder what they did with it) the reed was ignored and stayed more or less in place.  Here are field voles near the reed.

Checking through the videos I did eventually see a larger vole.  Bank voles are 8-11cm long (head and body) with a tail 50% of body length, field voles are 9-11.5cm long with a tail <40% of the body length and water voles are 14-22cm with a tail 60% of the body length.  Obviously the young of each species are smaller.

Here is the calibration reed.

And here is the large vole with the same calibration line.  It measures about 14cm so it must be a water vole.

Unfortunately it doesn't show its tail on the video so we can't use that to check but it is too big even for a large field vole.  As you can see on the video it dragged the apple away and didn't show itself again.  At the start of the video a small vole dashes across, perhaps a bank vole or field vole.  The last clip is a very brief glimpse of a larger vole three days later.

So that is all I saw, not quite as exciting a video as I was hoping for.  There were lots of other brief views of small voles, which could have been bank voles or field voles or young of either species and more brief views of common shrews, wood mice and meadow pipits but once the apple had been dragged away there was nothing to tempt the voles out into view again.

I plan to have another attempt to get better water vole pictures next May when I am up there again.  I may try slightly lower down the stream in the hope of finding a bit more open water and a clearer view.  I think I'll also use larger pieces of apple so they don't disappear so quickly and perhaps fix them so they can't so easily be dragged into cover.  After the excitement of finding three shrew species on the other camera I may put down bait for shrews as well.

Water voles are widely but sparsely spread in this country and are rare in Northumberland.  The map shows sightings reported to iRecord in the last 20 years, indicated by small blue squares, mostly around the rivers South Tyne and Allen in the south west of the county.  This site (red arrow) is about 10km north of the South Tyne and 20km south-east of Kielder (green arrow).

The water vole is one of our most threatened mammals, having lost about 95% of its former sites and being classed as "endangered" on the Red List.  The population decline has mostly been caused by predation by American mink with loss and fragmentation of habitat as additional factors.  In an effort to reverse the decline the Northumberland Wildlife Trust has organised a water vole reintroduction programme - Restoring Ratty.  Since 2016 over 1600 water voles have been released around Kielder in the far west of the county.  Donor animals were collected from the North Pennines, Yorkshire and Scotland and taken to Devon for a captive breeding programme.  The offspring are brought back north for release around Kielder Water.

Kelly Hollings, Northumberland Wildlife Trust's Project Officer in the Restoring Ratty project, says that the released voles have migrated from their release sites to smaller streams and ditches so more recent releases have been in such places, perhaps similar to the one I have been investigating.

The site I have found is between the Kielder release site and established populations farther south.  With luck (and hard work by the Wildlife Trust) water voles will continue to spread and different populations will link up.  This experience also shows that in wilder parts of the country there may be a few more about than are known.

CritterCam - the search for a water vole. Part 1

This all began in May, when I was doing my bird count near the Wark Forest for the BTO Breeding Bird Survey.  At one point I glimpsed a small mammal running across the track out of the corner of my eye.  It was dark, vole-shaped and rat-sized so I wondered if it could be a water vole.  There is a very small stream running through a pipe under the track, no more than 300mm in diameter, and because of the dry spring weather there was almost no water flow.  The habitat is poor unimproved wet grassland with mostly rushes rather than grass at that point, not a habitat I associated with water voles.  (I used to see them 50 years ago in a slow-flowing lowland river.)

Although the BTO BBS records mammal sightings I wasn't confident enough to record a water vole.  I did, however, send a message to Kirsty Pollard, a water vole expert at Durham Wildlife Trust and she passed my email on to Kelly Hollings, Northumberland Wildlife Trust's Project Officer in the Restoring Ratty water vole re-introduction project in Kielder.  Kelly was very encouraging and said the habitat was good for water voles, similar to some of the release sites in Kielder, so I went back with three trail cameras in July.  The cameras were in for a week, one close to where I thought I might have seen a water vole and two on a slightly larger but still very small stream (<500mm across) a couple of hundred metres away.  They recorded hundreds of videos and on a first look through I couldn't see much very exciting.  There were lots of glimpses of small mammals and I could identify field voles and wood mice, as well as reed buntings, meadow pipits and a roe deer's ankles.

Before giving up I had another look through the videos and could pick out a few where the voles looked bigger.  They were all on the on the trickle of a stream where I had my first sighting and there was very little on the other cameras.  It is difficult to judge scale although there is a slice of apple visible in the first clip.  I sent a very brief extract to Kelly and she replied that she was 99% sure it was a water vole.

So I went back earlier this month with two cameras and put them both on the first stream.  In most places it is difficult to see any water at all as it runs underneath the vegetation.  I spent time clearing a view and making sure the apples were better positioned.  Between them the cameras recorded almost 700 video clips so it is taking a while to work through them.  The first camera was set up here.

There are plenty of images of voles but I think they are probably all field voles.  Bank voles are 8-11cm long (head and body) with a tail 50% of body length, field voles are 9-11.5cm long with a tail <40% of the body length and water voles are 14-22cm with a tail 60% of the body length.  On the video it wouldn't be easy to tell a field vole from a bank vole or a juvenile water vole without seeing the tail but in some images the tail is clearly visible and is short.  (The other name for a field vole is short-tailed vole.)  The first two voles in the video are small whereas the last one which appears briefly nearer the camera looks larger although it still clearly has a short tail.

I also put a piece of raspberry cane next to the apple, 150mm long to act as a scale but the voles didn't approve of my measuring stick and moved and then removed it.

One very interesting sighting was of three shrews - water shrew, pygmy shrew and common shrew.  You can see that shrews don't eat apple but they are very curious (and very fast).  To find all three species in the same place on the same night was a pleasant surprise.

There are another 390 videos from the second camera so I'll report back soon on those.

WatervoleCam

This was a chance observation on a camera set to look for otters.  I noticed a small animal scurry across the bottom of the picture for a brief moment.  It is obviously a vole but is a bit out of focus and the freeze frame is blurred.  It is too close to the camera so it is not easy to judge its size.  On the other hand it is in water, and from where it went it would have to be a confident swimmer as it is some distance before it could get out again.  The vole wasn't in view at the start so I am not sure what triggered the camera (there is the intriguing possibility that it was following another one which moved out of view in the time it took for the camera to start recording).

On this freeze frame we can see its tail but it is blurred and curving away from the camera so it is hard to judge the length.

I was hoping this was a water vole so I sent the video to the Natural History Society of Northumbria who sent it on to Kirsty Pollard of the NE Water Vole Project based at Durham Wildlife Trust.  And Kirsty has confirmed it is a water vole. This is only the second sighting of a water vole in Gosforth Nature Reserve in recent years.

Because the video is so short I have added two slow motion replays so it is easier to see the vole.

My friend and fellow naturalist and photographer Chris Castling took a photo of a swimming water vole in Gosforth Nature Reserve last year, the first observation in the reserve for many years. You can see his photo here.  After Chris saw his water vole I tried for nine days and nights to catch one on a trail camera without success, so this latest finding was a real bonus.

This map, from the National Water Vole Database and Mapping Project shows the distribution of signs of water vole presence in 2006 - 2015.  The location of Gosforth Nature Reserve is shown by the red arrow and, although water voles were very rare in Northumberland, signs (green dots) were detected nearby on The Ouseburn, so it isn't all that surprising that they should still be around, even if rarely seen.

The water vole is Arvicola amphibius, sometimes also Arvicola terrestris.  Water voles were common when I was young but the population crashed to only 5% of its former level, mainly because of habitat loss and predation by American mink (Neovison vison), a non-native invasive species.  There was a 30% loss in 2006-2015 so the problem is continuing.  Protecting water voles involves improving habitat, controlling mink and, occasionally, reintroduction.  There is a reintroduction programme, Restoring Ratty, in Kielder Water and Forest Park (blue arrow on the map above) which you can read about here.  It is a five year project with 1500 voles released so far.  The hope is that they will spread down the North Tyne and link up with a population in South Northumberland.