Getting along with the neighbors
Many animals live near or in cities, occupying parts of the environment where they regularly encounter humans. Because of this, tolerance to us may be important for our animal neighbors. A common way to measure tolerance to humans is to measure the distance at which animals flee from an approaching human, a measure known as “flight initiation distance”. When animals are fearful of humans they flee at greater distances. Being too fearful can be costly. Every time an animals flees it could be missing out on a meal, an opportunity to mate and also spending energy to run away. Animals can relax their fear responses if they learn that humans aren’t actually attempting to eat them. A recent study set out to test how skinks varied in their response to humans and how variable their responses were.
Skirting skinks
Williams and colleagues studied the azure tailed skink (Figure 1, left) in Mo’rea island in French Polynesia. They compared skink populations that varied in foot traffic. When an observer spotted a skink they would walk slowly towards the skink and measure the flight initiation distance. At this point they would drop a flag on the floor to mark the location. When the skink settled, they would approach the skink again, repeating the steps above. By testing consecutively they measured how variable an individual’s response was after each flush.
Skinks from high and low foot traffic had similar flight initiation distances (Figure 2, below). However, skinks tolerated closer human approaches at the low traffic site than at the medium one. Interestingly, they report that at low traffic sites skinks were more variables in their escape behavior. This could be an indication that response to humans is less variable at sites where humans are frequently encountered. One caveat is that because of a storm they only sampled 16 skinks in the more pristine site. Because they sampled 39 lizards in the human dominated site differences in sample size could also account for the degree of variability.
Good escape responses makes good neighbors
The topic of whether animals modulate their escape behavior in response to humans has recently received a lot of attention. Many studies draw the conclusion that because fear response are commonly lessened in areas with more humans that animals near humans are desensitized to them. However, few studies repeatedly test individuals to see if the response has been fixed. We cannot effectively draw conclusions about desensitization without re-testing individuals. This studied accomplished this is an elegant way by sampling the same skink continuously. Their findings that flight responses were less variable in areas of abundant human traffic could be due to desensitization to humans. However, I think a follow up with greater sample sizes and perhaps looking at other related behaviors are needed before we can say for sure.
Featured Photo (top) by Chris Brown USGS.
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