2018-2019 Grant in Aid of Research
Seasonal Diet Variation in Thirteen-Lined Ground Squirrels (Ictidomys Tridecemlineatus) in Southwest Michigan
Austin J. Menzmer
Thirteen-lined ground squirrel diet has been studied previously in Colorado, Iowa, and Indiana. However, all of these studies used stomach contents analysis to determine diet. No such studies to my knowledge have been conducted with methods designed to save the squirrels’ lives.
I plan to study the diet of thirteen-lined ground squirrels in Michigan using microhistological and isotopic analysis of fecal samples, two easy methods of gaining diet information without sacrificing the life of the animal. In microhistological analysis, a reference collection of plant and insect matter will be collected to compare against collected fecal samples. Both the reference and fecal samples will be sent to Micro Composition Laboratory (Ft. Collins, CO) for professional analysis. Isotopic analysis will document ∆13C (a measure of 13C/12C) and ∆15N (a measure of 15N/14N) in both potential food items (plants and arthropods) as well as in fecal samples; these ratios will be used to infer the proportion of diet allocated to C4 versus C3 plants (higher values of ∆13C indicating more C4), and to infer proportion of animal matter in diet (∆15N is enriched up the food chain).
My aims are to identify and estimate relative abundance of different food types of thirteen-lined ground squirrels through the active season while preserving the life of the squirrel. Based on the Indiana study results and that state’s geographical proximity to Michigan, I hypothesize that mouse-ear chickweed (or similar plants) and butterfly larvae will be important diet items in the spring, clover (or similar plants) to rule diet in the summer, and crabgrasses (or similar plants) being preferred in the fall. From the same study, I hypothesize that butterfly larvae will also be consumed in noticeable amounts in the summer, but the preference shift to grasshoppers in the fall.