One way that animals may adapt to urban environments is by expanding their diet to include anthropogenic food, as discussed in the earlier post “Is Anthropogenic Food Waste Driving the Evolution of Urban Animals?”. But how can we tell if urban animals are actually consuming enough anthropogenic food to change physiology and drive evolution?
We known that physiological responses occur in response to urban selection pressures–urban ants have a higher tolerance for increased temperatures often associated with urban cores and dark-eyed juncos in San Diego showed lower cortisol responses after handling compared to their more rural counterparts. Recently, urban raccoons were shown to be heavier and have higher levels of glycated serum protein (i.e. high blood glucose) than their rural counterparts. Studying physiological responses can help us better understand the selection pressures that urban organisms face and can clue us into the ways that organisms adapt to deal with urbanization.
Monitoring blood glucose is one way we can gain a better understanding of what urban animals are consuming. Unfortunately, there are several challenges to measuring blood glucose. Commercial glycated serum protein assays:
- are expensive (~$400 for 96 tests)
- are not quick for field sampling (~10 minutes per test)
- require a lot of blood per test (~20 ul per test)
The price point of these assays alone is enough to deter many researchers from this method. Add into that the long processing time and large amount of blood required — which, depending on the size of the animal, can be taxing to the animal — and it’s easy to see why these tests are not more widely employed. Other options for testing glucose require a full laboratory set up and are not practical for testing samples in the field.
In an effort to reduce costs and save time, I began looking into alternative methods for measuring blood glucose for my study system (pigeons) and reached out a friend that just finished vet school. He said, “Glucose levels do drop over time after sampled because it is still getting metabolized. That is where a hand held instantaneous tester might help.”
After a little more digging I came across a paper that compared a Biotecnica Targa 3000 biochemistry autoanalyzer (which uses enzymatic glucose oxidase activity and spectrophotometry to detect the results) and an Accu-Chek handheld glucometer (which is a photometric system that uses enzymatic glucose dehydrogenase activity). This study found that the handheld glucometer had high reliability for pigeon blood glucose concentrations — meaning that a commercially available meter is a great tool if you’re interested in assessing blood glucose levels!
I was able to find a glucometer on sale at CVS for $10 but the same one is available from Amazon at the time of writing this post. The test strips are also available from Amazon but I often end up purchasing them from my local pharmacy since I haven’t found a price difference. I’ve found the Accu-Chek meter super easy to use and it even records the reading along with the time the measurement was taken in case I forget to write it down.
Are you thinking about measuring blood glucose in urban animals? What method are you planning on using? Let us know in the comments below or on Twitter.
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