27 March 2014

Duiker Data

One of the most common species at Koeberg Nature Reserve is the aptly named Common Duiker.

Common Duiker (Gewone Duiker - Sylvicapra grimmia) giving the camera a smile

One might be expected to get "bored" of loads of common species on your camera traps, but not me. In fact, for me it is exactly the opposite. Each new Duiker photograph is exciting. Why? Because it increases my sample size. You see, the nice thing about common animals are that, well, they are common. As a result they give you lots of data and large sample sizes to play around with. This makes it much easier to see trends in their behaviour.

The most obvious way in which camera traps can shed light on animal behaviour is by recording the animal performing the action in front of the camera. In other words a direct observation.

Common Duiker using its preorbital gland to scent mark

One of the first photographs I got of Duiker at Koeberg was of this individual scent marking a twig using it's preorbital gland. The preorbital gland is a slit of smooth skin in front of the eyes that have glands inside that secrete a tarry substance. You can see the Duiker applying it to one of the twigs in the animated GIF above.

Another obvious way in which camera traps records behaviour is via evidence that some event took place in the past. In other words an indirect observation.

Slightly injured Duiker photographed at Koeberg Nature Reserve

This individual has a strange injury on it's hind leg. My guess would be that it was injured while fighting with another male.

Photographs of direct and indirect animal behaviour are great, but it only gets you so far. What really gets me excited is when I start putting all the "nothing-out-of-the-ordinary" observations together and new trends start to emerge!

I like the spiffy pair of ears on this young male

A few days ago I started capturing all my camera trap data from Koeberg. Some of you might know that I use WildLog to keep track of my camera trapping exploits. The reporting features in WildLog are in need of some love, but I'm still happy that there are at least some features already available. (I'm planning a big overhaul of the reporting features in the "near" future.)

I wrapped up the new version of WildLog (now v4.1) last week and it's now available over here. (Some of you might also have notice that I'm slowly but surely restructuring and improving this blog and the MyWild site. It's a work in progress, but I hope it will be better organised afterwards.)

After importing new data I like to poke around a bit in WildLog and look at some maps and reports. It was during one of these exploratory sessions that I noticed the time of day report of the Duiker.

The observations below are, more or less, ordered by date, with the oldest ones on the left and the newest ones on the right. I started camera trapping at Koeberg during the spring, and this data stretches towards the beginning of March which is heading towards the end of summer over here in the Southern hemisphere.

The current report from WildLog shows the time of day for each Duiker observation at Koeberg

OK, so by now some of you might be thinking: "What's this guy on about? Those are just some randomly coloured lines...".
To which I'll respond: "True, those lines are indeed coloured, but they don't appear to be random at all."

Now I'll be the first to admit that the way I captured and interpret this data is far from "scientific" and not fit for any peer review journal by a mile, but when I notice trends like this in "informal data" I just can't help but wonder whether there might be some reasonably solid biological mechanism behind it all.

Most field guides and books I checked indicate that Duiker are mostly active during dawn and dusk, preferring dusk over dawn. That's all good and well, and looking at my modest sample size I can see that there are indeed many purple (dusk) lines, in fact double the amount of dusk observations compared to dawn. However there are many more day and night observations, but that isn't what caught my eye.

They also say that Duiker will become more nocturnal in areas close to human danger and more active during the day when undisturbed. But, I think it is safe to assume that the Duiker at Koeberg haven't experienced any meaningful change in human activity in the past couple of years. With the majority of observations at the nature reserve during the day it would appear that these Duiker aren't troubled by humans.

What I find interesting is that there seems to be a gradual shift from being almost exclusively active during the day to being active mostly at night. I decided to export the data to CSV (to open it in a spread-sheet application) and try plotting the data using an area chart.

To be honest, I'm very pleased with the result. It really seems to confirm my hunch. The chart below shows the percentage of day vs. night visits over time. Notice how the percentage of dawn and dusk sightings stay more or less constant, but the day and night percentages gradually change over time.
Duiker observations by time of day over time, based on camera trap data

It would appear that the Duiker are more active during the day in the cooler months of spring when the Western Cape still gets lots of cold and wet days. They then gradually shift towards more nocturnal activity as the days warm up. By the end of the dataset the Western Cape is at its hottest and then we also notice the most nocturnal activity.

So from my small sample size I'd venture a guess that the Duiker at Koeberg are adjusting their activity pattern in accordance with the seasons. It will be very interesting to see whether this trend continues and then reverses as we get closer to winter.

Duiker in some typical vegetation for this area

The Duiker activity pattern might sound "obvious" but many species at Koeberg do not show any noticeable difference in behaviour. For example Porcupines are always very strict about being nocturnal, regardless of the season, and the Caracal and Steenbok both tend to lean towards diurnal activity throughout the entire period.

This is what I like about WildLog, it does not try to be a super scientific tool, but it does provide some fancy tools for amateur nature enthusiasts, to help them sink their teeth into animal behaviour and come up with some crazy theories of their own. This is exactly what I had in mind when I started developing WildLog.

I'm looking forward to improving the reports in WildLog. That area chart looks like a winner and I'll definitely add something similar in the next version of WildLog.

Only male Duiker have horns, this one has a broken horn, does it make him less manly?

Another interesting photos, although not really a "good" photo, was this one of a male Duiker with a broken horn. I guess it happened while settling a score with a rival male. Unlike deer, antelope don't grow new horns every year. This broken horn can help to identify this individual in the future, although it isn't 100% accurate because there is a chance that another individual might get a similar injury.

The flies on his back must be extremely annoying and probably a bit of a health hazard. I hope that most are of the normal "house fly" variety and not all related to this monster below.

A type of Horse Fly (maybe Philoliche zonata) commonly encountered at Koeberg

These flies are huge and very persistent. For some reason they feel very attracted to my trousers... I found them intriguing at first. They are large, about the size of the front segment of my little finger.

There are many pollinating flies in the Fynbos biome and initially I thought that this was one of them. I assumed that the straight "mouth" was only used for drinking nectar and pollinating flowers... Boy was I wrong! I found it out the hard way when one of these monsters drilled that needle into my arm! I think I was lucky at first because they had a hard time penetrating the fabric, but when they land on exposed skin they dig in!

These large flies are rather common at the reserve and must be a real pest for any poor animal that crosses it's path.

From what information I could gather both sexes feed on nectar, but the "females are also voracious blood-suckers, attacking a range of vertebrates from frogs to mammals". They can spread disease, so it's best to avoid the nasty bite as much as possible.

I'll wrap up with a much smaller fly that has a more vegetarian nature, ergm, make that the adult has a more vegetarian nature. The larva of these flies pray on the eggs and larva of other insects.

A type of Bee Fly (maybe some Systoechus sp.)

19 March 2014

Curing The Corporate Blues

I've been having an absolutely miserable time at work this last couple of days (much worse than the usual drag) and am in dire need of some serious cuteness to cheer me up!

Karoo Bush Rat (Boskaroorot - Otomys unisulcatus) hard at work cheering up someone's day

Being stuck behind a computer for 8 hours a day is hard enough, but when your a biologist at heart and you are stuck in the corporate web as well, then things can get very hard indeed.

But for me nature is never too far away. It is always there, waiting for you to discovered it's wonders. In fact I actively avoid places where nature isn't close at hand. It must be very hard living in a country or city without a healthy dose of nature close at hand to soothe those aches and pains from modern living.

Just what the doctor ordered

I get great joy from nature conservation because it allows little creatures like this to live out their lives to their fullest, the good times and the hard times, allowing them the space to be what they are.

Maybe one day somewhere somehow I'll find my own little place under the sun, deeply intertwined with nature's roots, where I can be free to live out my potential. But until then there are scary times and long struggles ahead.

I believe this fellow is practicing for the annual Koeberg Twig Fighting Championships (he looks like a contender)

I've been saving these photographs for the right time, and now seems to be just that time. These Karoo Bush Rats are such warm hearted little charmers.

Keeping company

One thing about camera trapping that I'm very grateful for is how it opened up the wonderful world of the small mammals to me. There are so many wonderful species that are so much more than just "rats" and "mice". So many species live out their amazing and mysterious little lives in a magical wilderness.

Every family has their problem children and these two might be them... From the way the one in front is holding that piece of grass I really hope he isn't smoking it...

Nature teaches us so much. One thing that struck me about these little fellows is that these rodents, somehow, manage to have a closer and more caring family than probably most humans ever will. I'm sure they have their fights and bad days too, but it really struck me how much they enjoyed each other's company in such a relaxed and natural way. It makes me think of why autistic people often respond better to animals than to humans.

If rodents can be sweet, and I'm sure they can, then this little family seems to be as sweet as they come

I don't have the energy to do a proper scientific post about these little charmers, so I'll save some of the footage for a later time when I can do them some more scientific justice.

09 March 2014

Golden Mole Goodness

Long time readers will know this area as the Woody Cape. In 2012, while helping with the construction I took the opportunity to do a lot of camera trapping in the area. During last year's December holiday I decided to take some camera traps with me again.

I noticed some small mole hills popping up on the new "lawn" and thought that this is the perfect time to try out some subterranean (aka underground) camera trapping.

Scout keeping me company while I clear a hole for the camera trap

I've been toying around with the idea of camera trapping moles for a while, but when I saw Codger's underground adventures I knew I had to give it a try myself.

It was December holiday and I had a camera trap, time and an eager mole at hand. What more can you ask for?

I identified a recently pushed up mole heap and then started to dig it open. I found using my hands worked best, since it was easier to follow the tunnel by touch. Once I reached the main horizontal tunnel I started to clear some space for the camera trap.

I placed the camera trap on the opposite end of the hole as the tunnel

From previous experience with camera trapping small mammals at close range I knew that the video mode works best. At this close range the focus will be slightly blurry, but the animal will be close enough to the camera to compensate somewhat for the blurry images.

I placed my trusty Bushnell Trophy Cam at the far end of the hole and used an old tile to cover the hole. I then covered everything with a layer of soil. And waited...

Video: First signs of life...

My first glimpse of the little fellow was of it kicking some dirt towards the camera. I was frilled! I decided to improve my setup a bit and cleared a larger section of the tunnel.

Over time I was rewarded with one amazing video clip of a Hottentot Golden Mole.

Most Golden Moles have a "metallic" shine to their fur, which you can see reflecting the flash from the camera trap. Golden Moles are eyeless and have no external ears, nor tail. The tips of their snouts are covered by hard skin which, combined with their powerful front claws and webbed hind feet, makes for impressive digging tools.

Video: Hottentot golden mole (Hottentot Gouemol - Amblysomus hottentotus) underground

Getting any footage of these little critters were trickier than one would expect. Firstly, and to my surprise, I got a lot of false triggers. (I'm pretty sure the false triggers weren't super fast moles zipping past.)

At first I had the camera's sensor turned to high sensitivity, but that just filled the SD card with continues false triggers. The camera worked best at the normal sensitivity setting, which resulted in a manageable amount of false triggers.

I think some of the false triggers might by caused by bugs crawling around in the tunnel and over the sensor. I also suspect that the tunnel has some sort of ventilation system which might cause hot air to move around in the hole. The sun baking on the top of the tile covering the hole also can't help the situation much.

Another thing that surprised me was how often the camera would not pick up the mole at all, or trigger very late.

Video: Investigating the camera trap

On numerous occasions I would lift the tile from the top of the hole to find the tunnel filled with loose soil. Expecting great results I would start working my way through the video clips, just to find absolutely no sign of any Golden Mole. Amongst the false triggers I would notice only a sudden appearance of a huge pile of loose soil. Somehow the mole managed to fill an entire tunnel in front of the camera without it triggering even once. My guess is that this is due to either the mole being hidden behind the dirt which it is shovelling, or since Golden Moles are known to enter torpor, maybe they can somehow regulate their body temperature to such an extent that the camera does not distinguish them reliably from the hot air and soil in the tunnel.

It is difficult to make out what is going on in the still photographs, video seems to work better

I felt bad tormenting the little critter by always clearing open the tunnel. Every time I clear it, the Golden Mole would faithfully fill it up with soil again. It clearly doesn't like people messing with it's tunnels. Once it has decided where a tunnel should or should not be it sticks to the decision.

Digging through and moving soil around must be very energy intensive for such a small creature. They are only about 12cm long, weighing about 60g. After a few days of torturing the tiny animal by undoing it's hard work, the little critter decided to send me a message. When I lifted the top of the hole I found the front half of the hole, not just the tunnel, filled with soil. (Again with absolutely no footage of the little fellow actually doing it...)

The camera's view before...

The camera's view after...

To my mind this is an incredible amount of soil to be moved to seal off a tunnel, but I guess if the tunnel won't stay sealed then this persistent little digger won't give up either. Adding this to the heaps of soil I've cleared away earlier I felt to guilty to continue with the camera trapping and removed the camera. I'm sure if Golden Moles can feel satisfied then this little fellow must have done so.

Now, according to the literature I have nothing to feel bad about. These Hottentot Golden Moles are said to by able to dig 4-12m of tunnels per day. This heap might just be the result of a morning's work.

Fast forward two and a half months later and I find myself with some of my camera traps at home for some TLC and a blog post about a Golden Mole in the pipeline.

Now, I already know I have some Cape Golden Moles living in my yard in Cape Town. So I thought I'd try the same trick here at home.

Camera trap setup in my front yard

One particular section of my front yard regularly shows signs of Golden Mole activity, but to be honest I've found their tunnels almost everywhere in my yard. The surface tunnels are less noticeable during the dry summer months, but I assumed they must still be active. I searched for an old surface tunnel and started to open it up, like I did with the Hottentot Golden Mole's tunnel. Sure enough, I soon found a more permanent tunnel deeper down. I used some old roof tiles to cover the hole and placed the camera trap inside.

At first I tried the high sensitivity option again, but again I got lots of false triggers. I selected the normal sensitivity option and tried again. This hole doesn't get as much direct sunlight as the previous one and it was covered by much more soil and old twigs, so I guess the false triggers must be from the mole's built in air-conditioning or bugs.

Video: Cape Golden Mole (Kaapse Gouemol - Chrysochloris asiatica) underground

I've encountered this little gem before. Have a look at my old post over here.

The white marks where the eyes should be easily distinguishes this Cape Golden Mole from the Hottentot Golden Mole found earlier, 750km away, in the Eastern Cape.

Unfortunately not much is known about Golden Moles in general. You'll only find these amazing little creatures in Africa (most of which only live in southern Africa), so don't confuse them with European or American Moles. They are also not even closely related to Mole Rats.

Golden Moles are great in gardens and don't disturb the plants too much, especially if you give them time to establish some permanent tunnels. They eat insects and similar small critters and are in fact a huge benefit to have in your garden. They will consume a vast amount of pesky insects, free of charge, year round. If I have one complaint then it is that my local Golden Moles don't seem to have developed a taste for snails, yet...

Above ground view of the Golden Mole's home in my front yard