30 November 2014

Keeping Score

This post has been on my to-do list for a while but it was Codger's comment on my previous post that got me moving on it. I'll be using some of the new reports I've been working on for WildLog to share some of the my camera trapping data. The charts are still a work in progress so I hope everything goes well and that I haven't missed any glaring bugs... (Again the usual warning: this isn't "scientific" data, just some basic analysis of my own random data collection.)

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.

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.

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.


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.

Species accumulation curve for mammals captured using camera traps
The species accumulation chart for birds looks more or less the same as the one above. Proving again what a big influence a new location and habitat niches can have on discovering new species, be it mammal , or bird.

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.

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.

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.

The active time of all bird observations

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.

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.

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?".

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.

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.

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.

22 November 2014

The Elusive Fox

There is one species that has been on my camera trap wish list for years, the Cape Fox.

Wherever I went I'll heard stories about Cape Foxes being seen in the area "only a year or two ago". I would get my hopes up, but nothing ever showed up on the camera traps. The closest I ever got was this photograph from years back at Tygerberg.

Possible Cape Fox (Silwervos - Vulpes chama) at Tygerberg Nature Reserve

Unfortunately this was the only photograph I got and I'm not confident enough to be 100% sure whether it is a Cape Fox or not. Initially I leaned towards Bat-Eared Fox (which is in fact not a true fox). I did a blog post about it which can be seen over here. Since then I've changed my mind and am now leaning towards it being a Cape Fox, but I just can't be sure.

When I got to Koeberg the reserve manager mentioned that she saw a small fox-like animal recently. I've heard this sort of story before and didn't get my hopes up too much, but at least there was a chance.

Then, a few months later it happened!

Cape Fox at Koeberg Nature Reserve


It isn't the most awesome photo ever, but at least this time I can be sure it is a Cape Fox. I really wanted a better photograph. Over the next few months I kept an eye open for signs, and saw plenty of tracks, sometimes even fairly close to where I had a camera trap. However, after a year of camera trapping at Koeberg I only camera trapped the Cape Fox this one time.

The Bushnell Trophy Cam was set to take three photos per trigger. Below is a cropped version of the last photograph in the series.

Heading straight towards the camera trap

What makes the Cape Fox interesting is that it is the only true Fox (genus Vulpes) found in Southern Africa.

The Cape Fox is on the smallish side, measuring only 30cm at the shoulders and weighing about 3kg. Like most members of the dog family they tend to mate for life.

They will usually forage alone and both parents care for the young. The male will bring food to the female as well for the first few weeks after the pups are born.

Although the fox is still elusive, at least I now know it can be done :)