I'm guessing that cats tend to sleep a lot . . . .
Predators generally spend a large portion of their time sleeping. There's no point in hunting when you're not hungry, because then you'd have to expend extra energy defending your catch against scavengers and hungrier, more motivated predators. Domestic cats,
Felis silvestris libica, sleep an average of sixteen hours a day.
. . . . so yet again, this can only be done in warmer climates.
Well... in colder climates they aggregate it into one long hibernation. This retards the metabolization of stored fat to make the nap even longer, and aggregates the waking hours into the warmer seasons when food is most abundant.
Fourth, there's the herbivores (hippos, rhinos, buffaloes, elephants, etc). Out of pure speculation, I'm guessing that they're more aggressive because everything else around them is.
They are generally only truly
aggressive in their courtship rituals. Or in the case of pack-social (vs. herd-social) species, the alpha male defending his leadership position. (Herd-social herbivores typically have a female leader and her only job is to guide them to the next rich grazing area; as long as she does a good job nobody objects, and if they do they're welcome to go find their own dadgum food.) Otherwise their violence is strictly reserved for
defensive action.
gorillas, tigers, elephant and the rest, they are all going extinct some time soon. I don't see much effort to save these creatures when you compare it to the amount of money we waste on crap we don't need. This year is the year Chinese year of the Tiger next time round there wont be any tigers left to celebrate, shameful us.
There are actually very well-funded conservation efforts on behalf of most endangered species. The problem is that in poverty-struck regions most people will poach an animal or guide an illegal hunting party to bring in money, before they will allow their family to starve. It's difficult for even the "greenest" well-fed Westerner to get very angry at them for that.
Eco-tourism has become a hopeful business for many remote regions. Tourists with cameras will pay as much as a hunting party to be guided through a jungle full of exotic beasts. This has the wonderful advantage that the beasts are still alive when they go home, so you can get another batch of tourists to pay for the same privilege.
Many animals are killed in defense, and there are clever ways to solve this problem. Lions take a huge toll on livestock in Africa, and the farmers have the usual choice between killing them and letting their village suffer from malnutrition. Now there is a third choice: American breeders of Anatolians, a huge ancient livestock guard dog from Turkey with the head of a mastiff and the body of a greyhound on steroids, are shipping free dogs to Africa. Two of them can run off a whole pride of lions who, despite the legendary stereotype, are not really very brave.
Zoos and academic research centers do a fine job of maintaining bloodlines of endangered species. Each one has only a small population, but they swap breeders, and being scattered all over the world there's little chance of an entire species being wiped out by a plague.
Not all humans who share their habitat with endangered species are indifferent to their plight. The people who live in the region of India that is the last refuge of the Asian Lion are adamant about protecting their cats, to the point that they demand more safeguards than the government recommends.
Finally, the pet trade is unfairly criticized. The days of people capturing animals in the jungle and shipping them to Europe and America to be "tamed" are on the wane. Parrots, in particular, are widely bred domestically, both in large commercial operations and by hobbyists with one or two pair in their den. This has the advantage that a chick can be "imprinted" on humans as soon as its eyes open, thereby being automatically domesticated, the key to a healthier, stress-free life. The huge, purple Hyacinthine Macaw is the poster child for the endangered species awareness movement, yet as a former aviculturist I would wager that there are more breeding pairs of that species safely coddled in the United States than there are dodging bulldozers in the Brazilian jungle. The black Palm Cockatoo very nearly became extinct in its native New Guinea due to a virus, but a breeder in Minnesota kept a secret, protected population disease-free, and the species is once again viable, and even so prolific that you can buy a pair for about $50,000.
Don't give up on the endangered species, because you don't need to give up on
Homo sapiens. 
