Environmentally, common animals still remain, alongside mutated, cross-bred (sometimes with humans) and extraterrestrial animals. Ironically, spotted owls are often shown to have replaced rats as common household pests. Although rats still exist, sometimes rats act like pigeons, though pigeons still exist, as well. Anchovies have been extinct for 800 years. Earth still suffers the effects of greenhouse gases, although in one episode Leela states that its effects have been counteracted by nuclear winter. In another episode, the effects of global warming have been somewhat mitigated by the dropping of a giant ice cube into the ocean, and later by pushing Earth farther away from the sun, which also extended the year by one week.