The positivity rate among chemicals tested in rats and mice is ~50%. This occurs in species such as California mice, oldfield mice, Malagasy giant rats and beavers. Introduced species include reindeer, hares, rabbits, Patagonian foxes, brown rats and cats. LC50 is 12.5-11.5 vol% for inhalation by rats and mice. Peter seemed to fear white rats and rabbits. All the pigs and most of the rats died. He has two dogs and two pet rats. Early attempts along these lines focus on the behavior of rats and pigeons. Evidence indicates taurine may be beneficial for blood pressure in male rats. There is evidence that the parasite concentrates itself in the amygdala of infected rats. Domesticated rats have a longer lifespan than that of wild rats. Exposure to PCBs causes hearing loss and symptoms similar to hypothyroidism in rats. Deficiencies in vanadium result in reduced growth in rats. Wistar rats are more active than others like Sprague Dawley rats. There are concerns as to whether breeding hairless and tailless rats is ethical.