That's true, but what I was alluding to is the fact that there aren't hordes of coyotes running around any major city. Artificially shifting the balance will surely have unintended consequences.
Reminds me of introducing mongoose to the Hawaiian islands to eat the rats - now there are two invader species there. Coyotes may not be as much of an invader species in Chicago as mongoose are in Hawaii, but we as a species have a pretty poor track record of attempted ecological control.
I believe the seasonal variation in measured decay rates is likely to be a mundane explanation, but I also believe that the evidence from RTG power output in the article you linked is too indirect to prove or disprove the hypothesis. The author goes into a lot of detail to model the RTG thermal efficiency but the variations in decay rates in the attached figure were on the same order as his estimated error in the RTG model. Conceptually, it seems like this is an experiment that can be repeated with a good Geiger counter on a cheap satellite without relying on indirect measurements.