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Monday, 21 January 2013

"U" is for Unknown

CCF has carried out a number of camera trapping surveys, and also maintains a network of cameras positioned for ongoing monitoring of the wildlife on our land.  While we are mainly focused on cheetahs, there are many other species out there, and the cameras will trigger no matter what passes them by.  In this series of weekly blog entries, I will use these pictures to illustrate some of the wealth of animal life in Namibia - one species per week.  I hope you will enjoy seeing a little more of our world here in the bush.

U is for… Unknown!

With every camera trap survey, there are always some pictures that we just cannot identify.  In some cases it is because the animal is too far away, especially at night.  In others, it is too close, so much so that we get an extreme (and unfocused) close-up of the hide.  In still more cases the animal is moving too fast, or just catches the edge of the frame and all we see is a tiny part of a leg or tip of a tail.

Different camera traps react in different ways, and have radical differences in performance.  Some have a very narrow field of view, others are very wide.  Some react slowly, the more expensive ones react faster.  A few see colour at night, while most use infra-red LEDs to illuminate the scene and therefore produce purely black and white images.

The basic theory however is simple.  The vast majority of camera traps work in the same way as motion sensors in many burglar alarm systems, by tracking a warm body moving against a colder background.  They are generally ineffective in the desert because the ambient temperature is often similar to body temperature, and also cannot detect reptiles such as crocodiles while in water. 

To avoid running through batteries at a fast rate, cameras generally wait in standby mode with just the motion detector active.  When that is triggered, the camera powers up and take a photo.  In some cameras it can mean a delay of several seconds during which time a fast moving animal may have exited the frame.  There is also a further delay while the first image is processed by the camera before it can take a second image.  This can be more than 15 seconds, which means that if there is a coalition walking past, you'll only get the lead animal.

As I mentioned above, night time images are generally illuminated using IR LEDs, thus avoiding animals being spooked by the bright glare of a regular flash.  LED flashes also recharge faster than conventional flashes, so multiple pictures can be taken as rapidly as the camera can process images.  The downside, however, is a reduced distance over which animals can be illuminated.  Many cameras can only light up an animal up to 10m (33 ft) away, with the best reaching out to double that. 

Our initial deployment of cameras used the Bushnell Trophy Cam which is a good middle-of-the-range camera trap, and probably the best you can buy for $200USD each.  Over time, however, we've seen quite a high failure rate of these cameras in the harsh conditions of the Namibian bush.  All of our cameras are deployed continually for years at a time in bright sunlight, torrential rain, and temperatures ranging from a few degrees below 0C (32F) up to 40+C (104+F).  Some are knocked by passing antelope, played with by tenacious baboons, chewed on by hyena, or infested by ant colonies.  Protective metal security boxes help extend their lives, but even with those they are far from invulnerable since the most delicate parts, the lens, sensor, etc, have to remain exposed.

Taking the lead from the Smithsonian Institute, and several other large research bodies, we have been slowly switching over to cameras manufactured by Reconyx.  They are built to much more exacting standards, and have proven much more reliable.  In addition, they are significantly higher performance cameras with lightening fast trigger speeds, and almost as rapid processing and recovery times.  In every performance category they outperform the competition. However, this comes at a price.  The basic model is $450USD, with others in the range costing up to $650USD. 

Far fewer unknown images are recorded by our small group of Reconyx cameras, and most of those occur at ranges where cheaper cameras would have picked up nothing at all.  Ideally we'd like to switch over entirely, especially as the older cameras die, but I suspect the cost will force a compromise.  Hopefully over time however we will slowly reap the rewards that faster, more reliable, and longer ranged cameras will bring.

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