Certain types of feline leukemia can cause rapid and substantial weight loss in large cats  The lion in City Zoo has clearly lost a tremendous amount of weight in recent weeks
Ttherefore, the lion in City Zoo definitely has feline leukemia
Animals in the wild tend to choose mates based on external visual signals of health, such as plumage and fur. If an animal in the wild lacks the requisite signals, potential mates are reluctant to approach. Ttherefore, any animal that does successfully mate is more likely to display the expected signals to potential mates.