Hunting for frogs on OtterCam

The otter caught and ate another frog in the pipe but this time it was so close that the camera could only see the top of its head.  For reasons I don't understand the second camera on the bank didn't record it, which was frustrating as the otter should have been in full view.  I moved the second camera closer and twice the next night an otter came through the pipe and spent a few moments hunting, presumably for frogs, but this time it didn't catch one.  The two episodes were about four hours apart and I can't tell if they were both the same animal.  It is pretty neat to get a glimpse of the otter's eyes and paws underwater so I have added a short slow motion replay at the end.  You can see how quickly it takes a breath as well.  The original video is very clear so I hope it comes through OK via YouTube.

Developing SmallMammalCam

I have been experimenting.  The aim is to adapt the trail cameras so they can record small mammals and still produce a pleasing video in a natural-looking setting.  I started off setting the camera to look through a hollow log.  The bank vole was happy to oblige but because it is quite an open and exposed situation it grabbed a seed each time and dashed into cover to eat it

The next step was to build a wooden tunnel to house the camera and to provide the animals with a bit of cover.  It had a perspex roof to let in light and a tube of bark as a lining to be more photogenic.  I was using a Wingscapes BirdCam Pro which has adjustable focus and records in colour at night using white LEDs.  Lots of trial and error with the focus, the strength of the lights, the angle of the camera, etc.  To start with the camera wasn't a tight fit so the animals came in beside it and were often facing the wrong way or sitting right up against the lens.  I made lots of design modifications but a limiting factor is the very shallow depth of field with this camera.  I did, however, get some promising pictures of bank voles, common shrews and wood mice.  Although wood mice are mainly nocturnal they don't mind the bright lights.  The camera proved difficult to aim down the bark tube and the narrow depth of field is a problem but you can at least see the potential here.  The sound isn't very good on this camera either and it has a colour cast which is difficult to correct with iMovie.

The highlight was the one animal I really wanted, a weasel.  Unfortunately a bank vole had pulled a bit of ivy into the field of view and the weasel was mostly too close to the camera but nevertheless it was quite exciting.  You can hear a wren's alarm calls in the background.

After this I decided to try the Browning cameras.  They have better colour in daytime but only infrared (black and white) at night, don't have adjustable focus and are only sharp beyond about 2-3m.  I have regularly been using +0.5 dioptre lenses from reading glasses to get better pictures of the otters at about 1-6m so I decided to experiment with stronger lenses using what you might call the Goldilocks Principle.    First I tried +4 dioptres but that was too close.  And +2 dioptres was too far away.  And +3 dioptres turned out to be just right, with a depth of field from 30-40cm.  I first tried it out with an open-ended and unlined box.  The disadvantage is that the animals feel rather agoraphobic and grab some food and dash for cover.  Occasionally the bank vole will sit for a while.

The shrew won't.  It moves so fast that often the camera can't cope and it either misses it altogether or just gets a view of its disappearing tail.  Sometimes the shrew returns while the camera is still recording so then we can see it.  I put a few very brief clips together.  This is in real time, not speeded up!

It is almost impossible to see what is going on so I slowed it down by ten times.  The super slow motion video shows that the shrew is choosing a sunflower seed every time, which surprised me because I had offered dried mealworms as well and it is an insectivore.  Notice that it runs so fast that often all four feet are off the ground.  And its brakes don't work very well.  It looks a bit like a cartoon character.

The Browning camera with a +3dioptre lens really is a step up in image quality so I am going to stick with that.  The next stage will be to make a more natural setting while still allowing in plenty of light in the hope that the animals won't dash off immediately.  So I plan to line the box with bark and close in most of the open end.  I'll post any interesting footage here and hope the weasel returns.

Frogs on the menu

It was in March last year that the camera in the culvert first recorded an otter eating frogs.  And in March this year it has done the same.   The otter took only nine seconds to go out and come back with a frog (I have shortened the start of the video slightly) and only 43 seconds to eat it, before going back to look for another one.

The second time it came back with a frog it sat much too close to the camera.  Fortunately it is a bit out of focus, otherwise it would be gruesome.  This time it took the otter only 33 seconds to eat the frog

The otter must be catching the frogs just outside the pipe which is a bit odd, partly because I have never seen a frog there and partly because it is all running water with no shallow edges, so not a place for spawning frogs.  I wanted to see what was happening so I set up a second camera but unfortunately the otter didn't catch or eat any more frogs there.  Perhaps it had eaten them all!

However, on the first night with two cameras an otter travelled through the culvert nine times, and the next night six times, far more activity than I have seen before.  At one point in the sequence there was an otter going south four times in a row, although never closer than 30 minutes.  As before, I can't reliably identify individuals but it strongly suggests there are at least two about.  The second camera didn't detect otters approaching from the water but could sometimes see them coming out of the culvert.  The next video shows two examples.

And this is how it looks in daytime, almost welly-deep even at the edges so not really froggish at all.

RoeDeerCam in the garden

It is three years since the roe deer were in the garden.  In the severe weather of February/March 2018 there was almost nothing left for them to eat and they were in the garden night after night eating the ivy.  The two winters since have been mild and the ivy outside wasn't eaten so I didn't open the gate.  Recently I saw the ivy on the other side of the fence was being eaten so I thought I'd try again.  I set up two cameras on the gate and the first night the deer came in.  First was a doe who very cautiously came just inside the gate but then retreated.  Moments later a first winter buck came in.  He was also very wary, listening and scenting the air but he did come just inside to eat.  Both deer were aware of the cameras but seemed unworried by them.

The mother preferred to eat outside and the young buck didn't come in far.  They stayed for about 40 minutes and then disappeared.  This is the view from the second camera.  The post is 1.27m high so you can see how small he is, only about 50cm at the shoulder

After that I left the gate open for another four nights but the deer didn't return, which was a pity as  the cameras were a bit better aimed.  The weather has been mild and there is probably enough to eat elsewhere.  At least the foxes were pleased that the gate was open as it saved them the effort of jumping over the fence.

OtterCam - The first two years

It is now two years since I started following the local otters with my trail cameras.  It has been a fascinating experience - I have learnt a lot about otters and I have had a lot of opportunity to adapt and develop the recording techniques and improve my video editing.  The otters have been pretty co-operative as well.  When I first started they were occasionally spooked when the infrared light came on but they very soon got used to it.  They usually sniff the cameras as they pass, perhaps to check it was just me, and, on one memorable occasion, the cub knocked the camera into the stream and chased it under water.

After centuries of persecution, inland otters are mainly nocturnal in the UK.  Daytime sightings on the cameras have been infrequent but there have been more recently, perhaps because I have put the cameras in better positions.  When they have appeared in the day the video quality has been very good.  The videos have improved over the two years as my technique has evolved.

The culvert has been the most profitable monitoring place because it is pinch point for the otters as they travel from one part to another of their territories.  There are technical challenges as I have to climb down into the stream as well as keeping a close eye on the water level and the weather forecast.  The culvert camera was the first to find new cubs in 2019 and 2020.

Recent recordings on the bank have been fascinating.  It is much better seeing the otters out of the water because we get a better look at them and can see more of their behaviour.  The route up the bank connects the water to the reed beds but is also a favourite sprainting site where they can leave a smelly message and see who has been there before.

The cameras have identified unusual or even unique behaviour.  Examples that come to mind are the mother trying to pick up the (large) cub by its nose, an otter breaking through the ice, and an otter eating frogs in the culvert.

The cameras have also recorded a variety of calls, showing otters can be vocal even though they are mainly solitary. The very first video recorded a cub chatting to its mum.  Since then I have picked up a snort (alarm), mother and cub calling for each other when separated, a cub piping for its mother, a dog's mating call, and probably several others.

Here is a video I didn't get round to posting before of an otter attacking a heron (out of shot) in pitch dark at 3 o'clock in the morning.  You can see it was trotting down the bank and suddenly accelerated, presumably because it saw the heron was there.  I am not sure whether the heron was fishing in the dark or roosting but it certainly got a nasty surprise, even though it sounds as if it got away.

My trail camera monitoring started in February 2019 and immediately found a mother and two almost full-grown cubs. By March 2019 the cubs had gone and I saw only solo otters until two cubs appeared on 11 September 2019.  They stayed around with the mother until January 2020.  Then single otters until a new cub on 28 June 2020.  This one stayed until mid January 2021 and now there are single otters again.

Otters are said to be non-seasonal breeders and to breed on average once every 18 months.  The pregnancy lasts about nine weeks.  The cubs emerge from the natal holt at about 12 weeks of age and start to follow their mother around from about five or six months.  They stay with her until about a year of age but this varies with the local habitat and the food supply (they probably mature faster if there is plenty of food to catch).

My local otters seem to be producing new cubs every year.  Of course, I can't tell if it the same mother or whether a new, already pregnant, female has moved into the territory but it does suggest there is plenty of food around.

When I started two years ago I was setting the cameras every now and then, for a few days a month, but now there are at least two in place all the time.  I have also gradually learnt where are the best places to find them.  It will be interesting to see what happens this year.

My 2020 Yearbook

At first I thought I might not have had enough photos for a yearbook last year, what with the lockdowns and all, but the foxes, sparrowhawks and bees in the garden, dragonflies and butterflies in nearby nature reserves, and badgers and otters on trail cameras were enough to fill the pages.  The print run was only two copies but you can have a look for free here.

Stocktaking

Wow.  This was exciting.  I heard a crash on the roof and when I looked out of the study window I saw a cloud of feathers and a fight going on.  A female sparrowhawk had taken a stock dove off the roof.  I ran for a camera and these were the first images, taken from about 1.5m.

The dove was still very much alive at this stage and I thought it might get away (it is heavier than the sparrowhawk - 300g v 250g) but the sparrowhawk had a firm grip.  I could hear a lot of commotion from jackdaws and crows who were presumably unimpressed by having a serious killer in the garden and the sparrowhawk was mantling (shielding her prey from other birds).  I think she couldn't see me because of the reflection of the sky in the window.

Eventually the dove succumbed (I have spared you the gruesome photos) and she dragged it off into a corner where I couldn't see it.  I managed to ease open the bathroom window slightly and changed to the Panasonic TZ90 which has a small lens and a silent shutter - the sparrowhawk was again about 1.5m away and this time I think she knew I was there.

Eventually she moved a bit and I moved a bit and I could get some better pictures.

Then she dragged the dove under the front of the car and out of my view.  I waited until nearly dark before going out and this was all that was left.

According to Ian Newton's book The Sparrowhawk (1986), a female sparrowhawk can eat up to 55g of meat in one sitting (20% of her body weight), so with a kill such as this it is not surprising that she concentrates on the breast meat, the flight muscles.  A female will eat about 22kg of meat in a year, and so needs a feed such as this on average once a day.  A pair of sparrowhawks will consume the equivalent of 2,200 sparrows or 600 blackbirds or 110 wood pigeons in a year - sounds a bit like a Henry VIII banquet.

It is tough on the stock dove but that's what sparrowhawks do.  And this is what a stock dove looks like when it is not being eaten.  Ironically, this photo was taken earlier in the same day on the (male) sparrowhawk's perch.  It may even have been the same bird.