Camera Trap Overview, Types & Features - University of Oxford · Camera Trap Overview, Types & Features Specific Learning Objectives To introduce camera trap technology including
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• Optimum detection is where the temperaturedifference between target and background > 2.7degrees C. and can be unreliable when theambient temp falls within the temp range of mostmammals (31.5-36.5 C)
• Detector can be triggered by the movement ofpockets of hot air or by vegetation moving in thedetection zone
– Problem can be limited by avoiding camerapointing to area under sun incidence
Detection zone
Detection zone
• Area in which sensor is able todetect the target
• Important feature and notnecessarily = camera FOV
• Detection zone varies betweencamera models (15.8 – 324,1 m2)
• Camera with narrow detectionzone usually have fast triggerspeeds
• Can be increased to some extentby moving the camera furtheraway from the target which cancompensate for slow triggerspeed.
Trigger speed
Trigger speed (or “trigger delay”)• Rapidity with which the camera captures an
image relative to when the sensor detects thepassing target
• Critical feature
– A “fast” trigger speed (< 1 s) increasesrecording of targets; slow trigger speed mayresult in missing targets
– A slow trigger speed can be compensated forby a wide detection zone
– A fast trigger speed may be less necessary iftarget is attracted to a bait / feeding station
• Adjust the heat sensitivity threshold to adapt thesensor’s responsiveness to the target
• Generally high sensitivity is better to detectsmall-sized animals also in high temperatureenvironments where temperature gradients usedto trigger the camera are lower
• However, high sensitivity will increase chance ofmisfiring particularly by moving vegetation andwhen sunrays hit the target site
Infra-red vs white flash
Infra-red flash• Majority of cameras with IR flash
• Monochrome pictures at night
– Usually lower quality and resolution than day-time (species identification sometimesdifficult)
• Use less energy -> longer battery life
• Faster trigger speed and multiple pictures pertrigger
– No need to recharge as in the case of whiteflash
• Minimise spooking of animals and limit risk oftheft (covert)
White flash• Full colour at night
– Fundamental when shard and colourpictures are needed at night
• Can disturb the animals
• Xenon gas flashes not capable oftaking photo bursts due to rechargetime of flash
• Xenon gas flashes outperform whiteLED flashes with clear and sharpimages
• Consumes more battery power thaninfrared flash
Infra-red vs white flash Number of photos/videos
• Most infrared flash cameras are capable oftaking bursts of images in rapid sequence orvideo useful for
– animal identification
– behavioural studies and specific researchneeds
• However for video, data handling is more timeconsuming, memory cards are filled up fasterand power consumption is greater
Image resolution & clarity
• Majority of cameras take medium to highresolution images
• But sharpness and clarity of colour images ismore important for individual ID and species forsome especially sympatric species with similarmorphological features
• No of pixels is often larger than real due to pixelinterpolation.
• Increase in pixel no is often accompanied byincrease in digital noise and chromaticaberrations
• Plus the higher the image true resolution theslower the shutter speed
Batteries
Alkaline• Cheaper
• Non-rechargeable
• Start at 1.6V and discharge quicker thanLithium and NiMH batteries
– Flash strength (and thus detection range)decreases over time
• Usually a combination of weather, user experience and skill(position and programming), damage by animals, theft,poor equipment
• Trigger mechanism malfunctioning
• Pictures don’t contain any animals ->False triggers
Environmental factors
• Rain and humidity can affect functioning ofcameras and restrict deployment and servicing ofcameras in certain seasons
• Cameras are at risk from animal damage. Insectintrusion can be a problem. Elephants canfrequently damage cameras
Social factors
• Human vandalism and theft can be an issue.
• Cameras need to be robust and camera protective cases,use of dessicant sacs, security locking devices, crypticpositioning and camouflaging of cameras are possiblecountermeasures against these problems
• Agreement and support from local communities is oftenrequired to conduct surveys
• Photographic sampling is often required over difficultterrain and large areas. Deploying cameras can demandtravel to remote locations and often involving setting up,servicing and retrieving cameras on foot in difficultconditions. Appropriately trained local staff are thereforeessential
Choosing a camera
• Huge difference in performance betweenenvironmental conditions, so be careful
• Difficult to choose, but many reviews available
• Ask people with experience
– But not many have experience using manymodels!
• www.trailcampro.com A website devoted to evaluatingperformance of camera traps