Counting cats

Wildlife Research in Belize

Conservation research on Belizean mammals

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Estimating abundance of elusive low density forest species

Because each jaguar has a unique spot pattern, individuals can be identified and counted. Cameras are placed in pairs at each station, so that both flanks of the jaguar are photographed as it walks between the pair of cameras. These flank shots function as a ‘finger print’ to identify the same individual in subsequent photographs.

Jaguars are famous for their forest habitats, wide ranges and elusive nature. How, then, does one assess how many there are?

We use camera traps as a non-invasive method of counting jaguars.

The cameras are placed strategically throughout the study area. When an animal passes the sensor, the camera is triggered to take a photograph and record the time and date.

Ideally a station should act as a funnel, channelling the jaguar between the two cameras. In forest habitats, natural funnels include game trails and streams; however established hunting trails and logging roads are frequently used by jaguars.

In primary forests, where the understorey is open, there may be multiple alternative travel routes for jaguars, and so is little opportunity for funnelling animals between cameras. A higher density of cameras may be necessary to cover all possible routes and increase capture probability.

In secondary forests with very thick undergrowth there may be no obvious place to put a camera. A simple rule of thumb ... if you can’t walk there a jaguar is unlikely to want to walk there either! One option is to open up a new trail; if there are cats in the area they should start using it eventually, as long as it leads somewhere they want to go, such as a creek or game trail.

In this way we can study a large number of jaguars via a non-invasive method which would be logistically impossible with live-trapping.

Camera trap

Within a study area this method can tell us the minimum number of jaguars alive. If capture rates (number of jaguar photographs within the survey period) are high enough, capture histories of the sampled individuals can be used to estimate abundance using capture-recapture population models. The models assume geographic and demographic closure, therefore the survey area needs to be as large as possible, and the survey period limited to approximately two months. The models also assume that all individuals in the survey area have a chance of being photographed; therefore neighbouring camera stations need to be close enough together so that every jaguar’s territory overlaps with at least one station.

The use of capture-recapture models for estimating abundance from camera trap records of low density species still needs validation. For more information please see our Publications (in particular Harmsen 2006 and Foster 2008).

Cameras are located to maximise capture rates based on animal spoor and local knowledge.

Spot the difference! … here are right flanks from several female jaguars. How many different individuals are there?

Big cat tracks, scrape mark with scat, and scratches on a tree trunk help to identify suitable areas to locate camera stations

Local knowledge can be invaluable when exploring new study areas for suitable camera locations

A creek bed running through otherwise impermeable undergrowth may function as a natural funnel for large mammals

Finally, camera traps in tropical locations have to be able to withstand high humidity, heat, and heavy rainfall. Here we present a novel design by Mr Arthuro Ramos to reduce camera exposure to sun and rain, made only from a garbage bag, some tying wire and a little bit of genius. No double-sided sticky tape required ...

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