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| For those not statistically inclined I've mixed in some bugs like this Corn Cricket (Koringkriek - Hetrodus pupus) for your viewing pleasure |
I've been camera trapping, off and on, for the past 6 years (since 2 March 2008). In this time I've recorded about 4430 camera trap observations using mostly Bushnell and Cuddeback cameras.
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| If the charts are hard to read, try clicking on the images to view the full size image |
The first comparison I wanted to make was to see just how many of the camera trap observations are from mammals and how many from birds.
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My primary focus is on mammals and I'm happy to see that the largest piece of the pie is for mammal observations. Camera traps really are great tools for monitoring animals, especially mammals. It would be virtually impossible to get a dataset like this without the help of camera traps.
Next I wanted to see how many species I've camera trapped in each creature category.
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In total I have been able to camera trapped about 135 species. I say "about" because there are some species I'm not completely sure about. Some of the tiny mammals can by especially tricky to tell apart in photographs.
I've been fortunate enough to have a steady stream of new species through the 6 years of camera trapping. The chart below shows the rate of new mammal species captured over the years.
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| Species accumulation curve for mammals captured using camera traps |
Below is a breakdown of the number of camera trap observations for each mammal species.
There are 3 species that are very frequently camera trapped, but I'm pleased to see 10+ species that have a good number of observations and isn't really overshadowed by the dominant 3.
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| I guessing those red beads on this caterpillar are some form of parasite... |
Because my camera traps are usually active for the entire day/night cycle the data can give a good idea of what animals are active at what times.
The chart bellows takes the 3 most frequently photographed mammals and compares the time at which the animal visited the camera trap.
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It is quite interesting to see the distinctly different activity patterns. The Porcupine is clearly nocturnal, the Four-Striped Grass Mouse clearly diurnal and the Bushbuck likes to be active during early mornings and late afternoons.
There is also the obvious difference in activity patterns between mammals and birds, but it is nice to see it reflected in the data. The first chart is for the birds only, and the second chart for mammals only.
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| The active time of all bird observations |
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| The active time of all mammal observations |
The problem with comparing the times directly is that sunrise, sunset, etc. can differ remarkably between two sites that are far apart, or even at the same site during different seasons. With WildLog I try to auto-magically assign a "time of day category" to each time based on the estimated sunrise and sunset times at that location. Below is a chart using this time of day category for all bird observations.
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| Time of day categories for bird observations using camera traps |
From the chart it can be seen that birds are much more frequently camera trapped during the middle of the day (mid morning to mid afternoon), with over 50% of captures being during this period. There is also a higher activity pattern in the mornings, compared to the afternoon. Again, no new news, but still good to see represented in the data. (This dataset is dominated by Francolin and Guineafowl records.)
As can be seen from the chart below the mammals have a much more even spread of activity, with an almost even split between diurnal and nocturnal activity.
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| Time of day categories for mammal observations using camera traps |
The mammals, similar to the birds, also have a slight decrease in activity in the afternoon, before the night shift swings into action. (In this dataset the diurnal Four-Striped Filed Mouse and nocturnal Porcupine nicely balance each other out.)
Seeing these differences between mammals as a group and birds, bring the question to mind: "Why are they different?".
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| A species of Handmaiden next to a small body of water |
On average I have camera trapped 4.09 species per camera trap set, with the lowest number being 1 and the highest 24. (Well, actually I sometimes don't get any species as a set, for various reasons, but I don't record those.)
Lastly, I've also tried to get some idea of how long the average camera trap visit lasts using the time between subsequent photographs. (By default when importing the photographs into WildLog the application will group all photographs together into one observation until there is 2 minute, or greater, period without any activity.)
As can be seen from the chart below by far the most of the visits to the camera traps are less than 10 seconds, in other words the animal is simply walking past the camera trap. The vast majority of my camera trap sets don't use any scents or baits.
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| Duration of a mammal's visit to a camera trap |
At the 1 minute mark there is a peculiar "bump". My theory is that it is, at least partially, the result of the slow response time of the Cuddeback camera traps. The Cuddebacks take 30+ seconds to re-arm before the next photo can be taken. The Bushnells can take 3 photographs and re-arm in under 10 seconds, making them much more accurate at estimating the duration of a visit.
The couple of visits with a duration of 7+ minutes are mostly when an animal decides to rest or eat in front of the camera trap, for example it often happens on hot days if the camera is placed next to a good source of shade, etc.
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| This Monkey Beetle on a flower seems fitting to wrap up this monkey business :) |
I hope that most of the charts made sense. I enjoy playing with these charts and "interpreting" the data. I'm sure I'm making a lot of mistakes. But I'm also sure there is a lot more to that can be learnt from charts like these.
Interesting charts. You ask the question why are birds more diurnal in general than mammals? My guess has to do with the nose verses the eyes. Birds have a poor sense of smell. They rely upon their eyesight. Mammals have a keen sense of smell. They are less dependent on their eyesight to get around. What are your thoughts on the subject?
ReplyDeleteThanks John.
DeleteMy thoughts are much in line with yours. During my pondering I tried to think back further to the origins of birds and mammals. Recent talk about dinosaurs being fairly colourful, and how feathers and flight might have first emerged as sexual selection traits also makes me think that birds were in a way "doomed/destined" to be diurnal. Flying must surely be easier during the day or without a heavy nose. Birds dominate the niche of diurnal flight, but isn't it mammals that have mastered flight during the night? Maybe the birds have gone so far down the "day/eyes/flight path" that the night was/is open for competition.
I can spend a lot of time pondering these "what ifs" and "whys" :)
Impressive undertaking and results. This kind of exercise can inform the camera trapper, and I'll be you felt good when you summed it all up. Good on you.
ReplyDeleteThanks Codger. It has been very informative indeed.
DeleteThe new charts and reports looks excellent. I can wait to put them to use myself and see how my results correlate with yours. When will your new release be available?
ReplyDeleteIs it possible to also create a report that shows the number of captures per day over the period that the camera was set up, with a split between daytime and night ?
Thanks Roelof :)
DeleteI really want to try and get a stable release out early next year, ideally before end of Feb. I'm currently trying to wrap the initial implementation up. There is still lots of room for improvement, but I want to get it in a usable / functional state first. Then I can improve on it in future releases.
Yes, there is a report like that in the pipeline. Your idea of splitting on day/night sounds interesting, I'll see what I can do.
Henry, don't know if Cuddeback still do upgrades for your versions, but the last update for the newer Attack has added a Fast as Possible setting, and the camera now re-arms within seconds.
ReplyDelete