Working with Camera Trap Pictures

Hi, my name is Richard. I am a volunteer on the same Earthwatch team as Michelle. For the first few days I was doing much the same things as she did, but since then I have been spending more time back at the centre working on the pictures taken from the camera traps.

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Katy (at the back in the picture above), our Field Team Leader, loads the pictures from each station onto one of the laptops which we work on. To give you an idea of the scale of the task, our team has picked up more than 30,000 pictures.

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The cameras take colour pictures during the day (including ones of us switching off the other camera in the pair when we arrive at the station!), and black and white infra-red pictures at night. Some animals, like the leopard above, can just see the infra-red flash, and seem to find it very interesting. But most of what we get are things like the baboons and bushbuck below.

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The first job then is to delete all of the pictures with nothing of interest. There are two main reasons why we have pictures like that. One is that the cameras work by detecting movement, and when they see something move, they take three pictures at intervals of one second, so that fast moving animals are often out of shot by the second or third picture. The other is that the cameras are often triggered by things like grass waving in the wind.

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The pictures are tagged with information like time, date, phase of the moon and camera location, so that nothing gets lost, as you can see at the top of the aardvark picture above.

Once we have deleted the pictures with nothing on, we sort them into different folders. There are three broad categories: predators, such as leopards and the serval and civet below; prey, such as the baboons, bushbuck, aardvark and warthogs above; and “others”, covering people, vehicles and domestic animals (mainly cows). Within the predator and prey categories, we sort the pictures by species and camera station, so that all the pictures of a particular species at a particular station are in one folder on the laptop. They can then be used by a computer program which does things like matching up the pictures of an animal taken at the same time from opposite sides.

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There are two cameras on each station, usually placed facing one another either side of a track or trail, so that we get pictures of both sides of the passing animals, like the leopard below. This is important for identifying the leopards from their spot patterns, which is what Howard and Arleda are doing in the picture at the top.

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The researchers can then use the information about which leopard was where and when to work out the area over which each leopard ranges, and the way in which this changes over time.

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