THE EVOLUTION OF A PROJECT

... and the beauty of some non-natives  

Yesterday, I mentioned differential digestion rate and hinted that it is important. Now it is time to find out how considering it and other pieces of information shaped my methods.

Specifically, when I was first developing a proposal about doing a diet study I read a number of papers and many weighed and measured the volume of the items in the animal’s stomach. Also using these values, they made comparisons using age, size, and gender. It was easy to embrace the idea of doing this because allows me to report on my research results using quantitative methods. 

In addition to reading papers on turtle diets, I read ones done by ichthyologists (fish biologists) and ornithologists (bird biologists). Both groups have a long history of doing diet studies. One point they both discuss is that it is impractical to attempt to determine what percentage of the diet is a particular food resource or kind of food resources. This is because each food item has a different rate of digestion (differential digestion rate). In addition, turtles eat whenever food is available rather than on a schedule. Further, preserving the contents of the stomach in any preservative alters the weight and mass of some items but not others. For example, ethanol alcohol (a common preservative) dissolves fats, thereby reducing the mass of fats.

The only way I can reasonably discuss what foods make up their diet on a percentage basis is to lock them in cage (i.e., a zoo) and present them with a wide variety of food choices and measure what they eat each day. Of course, the minute you put an animal in an artificial setting its exercise and diet change.

Therefore, all I can do is portray what they were eating before capturing them. The next time I will tell will begin to explain what I am doing to add robustness to the research.

"Many weeds and ornamental plants have been here so long that the soil and the organisms in it are an ideal habitat for them. Because of this, many native plants cannot successfully live in these soils. In fact, many of the remaining native animals rely on these non-native plants. This is sometimes vexing for urban ecologists."