Would this be considered primary literature? Also, is it observational or experimental?

Yes, the Journal of Thermal Biology is a legitimate peer-reviewed scientific journal (not one of the major ones, but it is published by a reputable group, Elsevier). Because it actually appeared in the January issue, it is a 2009 paper. The study is experimental (the variable is the breed of dog), because the scientists set it up in a way that was controlled and repeatable, and had just one variable - they didn't just observe what happened in nature (in which case there would probably have been differences depending on the dog and the situation).