They’re not kitten around. A respected Polish scientific institute has classified domestic cats as an “invasive alien species.” Research done by the Polish Academy of Sciences (PASIFIC) determined that the damage cats cause in terms of hunting and killing birds and other wildlife was enough justification to consider the animals invasive. Scientists argued that the ‘Felis cactus,’ more commonly known as the house cat, “100% met” all criteria to land itself on the list of invasive species due to t