To understand the Spiny-Tailed Iguana's personality, I'm testing them in the field. One such examination is called the Open Field Test (OFT). Its origins reside with the fear perceived by some rodents when they can no longer touch their world -- when they are in the open, likely at greater risk of predation.
Theory suggests that bolder animals will explore the open area more than will shy animals. This makes some sense if you prefer to hug the sides of your world, touching physical objects. In
Ctenosaura similis, an omnivore that often feeds in open areas, how useful is the OFT to measure fear -- and is there a statistical difference between bold and shy iguanas in their exploration of the OFT arena? Does Bold Pale Blue-Black-Red (PbKR) explore the arena more than shy Brown-Red-Green (BrRG)?
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| PbKR: Bold |
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| BrRG, on tree roots near the pergola. A very shy iguana. |
To begin to answer that question, I constructed a 10' x 10' testing arena, seen below, and rigged a digital video camera on the station ladder to record 10 minutes of exploration per animal. I use an imaging tool to superimpose a grid on the area and score how many times an animal crosses the grid as well as other behaviors (jumping up sides of the walls, attempting to climbing the ladder, sitting, etc.
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| Open Field Testing arena with tripod on ladder to digitally record test. |
It may be that bold and shy animals have similar levels of exploration because the OFT is not a good test of fear in this species. They may all be equally irritated from the loss of a visual field and spend energy searching for an escape route. While it would be fruitful to have personality tests that work for all taxa, this strikes me as unlikely -- especially in an animal that often feeds in an open field!
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| White-Orange-Green (WOG) grazing on the lab lawn (open field). |
