The mighty African lion is the undisputed king of beasts - though today, his title is more honorary than earned. Like his cousin the tiger, he has outgrown his ancestors, though his most dramatic attribute is his oversized mane - big, black, beautiful... and now so large and extensive that it covers most of his body, running down his belly to his hind legs and down his back almost to his tail, turning him into a veritable caricature of his own species. It impedes his vision and limits his time outdoors to brief excursions when the temperature is under eighty degrees, lest he fatally overheat. Centuries of prepared meals have shrunk his jaws and unintentional selection toward only the most docile, easygoing, easily bred lions have dulled his instincts, and he now does little more than lay around and show off his majestic form. Visitors awe at his regal pose and tremble when he roars - one of the few things he can still do, albeit for no practical purpose except to make himself feel important. He nor his ancestors have had to defend their territory for over five hundred years.
If he had to kill his own zebra on the sweltering savannah, he would starve in short order - if he didn't die of heatstroke far sooner. Not even a baby rabbit hopping through his enclosure catches his interests - it is a warm day, almost 80 degrees, and it takes all his effort just to lay motionless. Even the lionesses of his type are now almost as lethargic as himself.
He is perfectly, exquisitely adapted to life in the lion paddock at the Zoo, shaped by centuries of fine-tuned selection to produce a perfect specialist. There has never been a more perfectly evolved zoo lion. He does not balk at his confinement, he does not try to eat the staff, he is very docile with his mates and does not harm his offspring. He eagerly gobbles up his lion kibble, and is perfectly behaved for his check ups with the veterinarian. He is truly at the peak of fitness, flawlessly molded to thrive in this particular environment.
And nowhere else.