The trouble with shade

Who knew that shade could be so problematic? A couple of weeks ago, I wrote about how shade seems to be my biggest obstacle in reconciling how the cameras see the world vs. what is actually going on. My job is to figure out how to make things right.

To start with, the camera traps are up on trees.  Mostly. As you know, the cameras are on a rough grid layout – 225 grid cells, each 5km2 (2.236km on each side)  — covering a total of 1,125 km2 of Serengeti’s center. This kind of design makes sure that we are covering enough of the landscape to capture the bigger picture of animal distributions and movements. Each camera is roughly at the center of each grid cell – on the closes suitable tree to that center point. Some trees are big and shady; some are small and spindly. In the woodlands, there are trees everywhere; on the plains, the camera-trap tree can be the only tree for miles.  And sometimes there are no trees at all, and here the cameras get put up on metal poles.

IMG_8301 SitePhotoPoles

These different habitats are important to capture. I think that animals might behave very differently in areas with lots of trees than they do in areas with very few trees. When it comes to the aggressive interactions between carnivores, for example, trees, shrubs, and tall grass provide great hiding places for the smaller species. It’s like trying to hide from someone you don’t like in an empty room vs. in a really huge, crowded shopping mall.

OpenArea

It’s a lot harder to hide from lions here

...than here

…than here

The problem is that camera traps work better in some habitats than others – at least for certain species. Say you are a huge, muscle-bound lion. Even standing is tiring in the Serengeti heat, and you spend your days breathing heavily even at rest. You like shade. A lot. If you are out in the open plains, a single shade tree will stick out for miles, and you’ll probably work your way to it. Chances are, that tree has a camera. In the woodlands, though, there are lots of trees. And the camera trap could be on any one of them. So even if you’re searching for shade, the chances of you walking past the camera trap in the woodland are far smaller – just because there are so many trees to choose from.

Here’s a map of the study area – green shows more densely wooded areas, whereas yellow marks the plains. Camera traps that have captured lions are shown with circles; the bigger the circle, the more lions were seen at that trap. I know for a fact that there are more lions in the northern half of that map than in the southern half, but the lions out on the plains seem to really like getting their picture taken!

NightVDaylabeled

The pattern looks a little better at night than in the day, but it’s not perfect. So perhaps shade isn’t the only thing affecting how these cameras “see” lions in different habitats.

As depressing as this problem seems at first glance, I’m optimistic that we can solve it (enter Kibumbu’s new GPS collar!), but those methods are material for another day. In the meanwhile, what else do you think might be going on that attracts lions, or other animals to trees, besides shade?

Advertisements

Tags: , ,

About ali swanson

I'm an ecologist studying how large carnivores coexist. I spend way too much of my time trying to stop hyenas and elephants from munching my camera traps!

7 responses to “The trouble with shade”

  1. Aradia Farmer says :

    Trees are good for climbing in too, either to hunt, hide, or rest.

  2. Lee Angeline Kuck says :

    If there is shade, and the species seeks it and is a social species, might the potential of social interaction be an attractant?

  3. Anne Whitaker says :

    Food – leaves, bugs, little critters, etc…

  4. Tor Bertin says :

    It’s interesting that you seem to have fewer stations capturing images during the night than during the day. Are the number of captures roughly equal, being offset by greater numbers of captures at certain stations (e.g. BO7 / KO4)? Why would you have a comparatively larger number of stations being triggered, albeit with fairly few captures, during the daytime?

    Excited to see the lion movement data you’ve collected.

    • ali swanson says :

      Tor, that’s a *great* question. My best guess at this point would be the attraction of shade during the day means that lions might go out of their way to visit a tree in daylight, but might walk on past it at night.

  5. ali swanson says :

    There do seem to be a lot of reasons why the animals use trees besides shade – certainly for climbing (for leopards and sometimes lions). One thing I didn’t realize until pouring through the photos is that carnivores are using trees not so much for social interactions but for *communication* — specifically, scent marking, as you can see here: http://talk.snapshotserengeti.org/#/subjects/ASG000700t

    Cheetahs in particular seem to be really scent-oriented, hence the many close-ups of both ends!

Trackbacks / Pingbacks

  1. Things are looking up! | Snapshot Serengeti - December 16, 2013

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: