Paul Borokhov ES 100 : Paper critique
Introduction: provided a decent background on herbicide-prairie animal interactions and a motivation for performing the study. However, it would have been worthwhile to explain to uninitiated readers the relationship between gophers, prairie dogs, and voles so provide more context for the earlier studies.
Methods: it’s not entirely clear why the seventh pair was not introduced from the very beginning of the study. Overall, the methods seem sound, though it is unclear why just the active salt of the pesticide was used, instead of applying the pesticide itself. In addition, the application of 12-12-12 fertilizer was not explained, nor were its impacts on wildlife mentioned anywhere.
Results: the mention of Krebs et al. observing high numbers of voles in enclosures gives me some pause about the appropriateness of the grid sizes used in the study. There was no mention anywhere of typical “in-the-wild” vole population densities and whether the smaller size of the grids could have had any effect on the results.
Trapping efficiency, as a concept, was not really explained, nor why the differences in trapping efficiencies were different between the two plots in just two months. The line charts could have been clearer, as it's a bit hard to distinguish the difference between the style of the two lines (perhaps more spaces between the dashes?). I'd be curious to know the reasons for population declines in June, as well as November and December.
The difference between survivability of male vs. female voles in the treated vs. untreated grids makes the case for why the sex ratio was male-skewed in the treated grid; however, what is not explained is why the survival time was higher – and significantly so for the males – in the treated plot. It would have also been worthwhile to include survivorship data at 14 weeks for the untreated plot, rather than just the treated plot.
I wonder why the significant difference in the Margalef richness index *before* application was not investigated or further elaborated on at all, as well as the similarity of evenness values between grids.
Discussion: the authors mention a side experiment that was run, in which captive voles were fed giant foxtail. However, they simply present us with the results, which support their hypothesis, without telling us any further details about the experiment itself. In addition, they cite Dooley as discovering that protein content decreased in the treated grid; again, no mention is made of the untreated grid. Is it possible that foxtail protein content decreases in general due to seasonal changes?