In terms of zoology, why are there big cats and not big dogs?

The reason is their hunting strategy. Wolves and dogs are persistence hunters, which means they try to track and run their prey over long distances so their prey build up body heat and lactic acid to the point of exhaustion. When the prey can no longer run and basically fall to the ground due to overheating and/or exhaustion, the dogs or wolves will then move in for the kill. African wild dogs and grey wolves both hunt the same way. The San Bushmen of Southern Africa, who are the closest relatives of all non-Africans, also hunt the same way. To use this strategy, wolves and wild dogs cannot be very large because if they are large, then they, not just their prey, will also overheat, since large animals have proportionally smaller body surfaces and cannot get rid of excess body heat quickly. The San Bushmen can also avoid overheating because humans have lost our body hair and can sweat efficiently to cool off. During the last ice age, wolves (such as the dire wolf) were a little bigger because there was less danger of overheating, and because prey was also larger, since prey animals can benefit from being larger during a cool climate, allowing them to conserve heat. When the ice age ended the dire wolf and other large ice age mammals became extinct. Applying the same principle, the Mexican subspecies of the grey wolf, which currently lives near southern Arizona and New Mexico, are smaller because they live in warmer areas. The Canadian population of the grey wolf, OTOH, are much larger because of the cooler climate.

Cats, on the other hand, use a different hunting strategy. They stalk prey to try to move as close as possible before making a short final sprint. Their retractable claws allow them to walk silently. They are also very well camouflaged so that prey cannot easily see them. Cats build up a lot of body heat and lactic acid during the sprint, so they cannot pursue prey over long distances. Since their prey has not been exhausted by being pursued over long distances, cats need to be big to have the strength to bring down their prey.

i agree with you that big cats are distributed more (cougars, lynx, lions, tigers, cheetahs, leoprads and many others). it is possible to call wolves and foxes as big dogs, s they belong to canine species. However, there wer big dogs that gone extinct millions years ago, like Epicyon haydeni - the biggest representative of Canidae family ever/ The height at the shoulders of this North American predator of Miocene epoch was about 90 cm. Some dog breeds can be of the same height at the withers. Record in this regard is now owned by a German mastiff and the Irish wolfhound - about 110-cm

in case you get the dogs as a puppy, it relatively is going for use to it via the time it relatively is grown and in a position to do any injury. it is extra of a character trait and how the dogs is raised instead of a brilliant dogs, small dogs subject, or possibly a breed subject. some breeds would not be perfect, something with a severe preycontinual, like a pitt bull won't be the final selection, whether it additionally would not propose that it relatively is impossible. it relatively is the style you develop the dogs. My mother and father have Rat terriers (severe preycontinual) and my mother and father canines could in all possibility kill a cat in the event that they have been given ahold of it, My mom in regulation on the different hand has rat terriers besides and so as that they've approximately 10 cats working around, the canines don't fret them in any respect. So the two way, as long simply by fact the dogs is socialized with the cat, it is going to no longer be a issue.

it appears that there were dog like animals as large as lions or tigers. but apparently none that large survived to modern times

"... estimated the largest known specimen (AM 68108) to weigh 600 kg."

http://en.wikipedia.org/wiki/Amphicyon

"... it had a length ... of about 11 feet (3.4 m) and a height from the ground to the shoulder or middle of the back of about 6 feet (1.8 m). ... is estimated to have weighed up to 1,700 kg (3,700 lb). ..."

http://en.wikipedia.org/wiki/Andrewsarchus

"... the largest Hyaenodon species was much larger, being 500 kilograms (1,100 lb) and around 10 feet. ..."

http://en.wikipedia.org/wiki/Hyaenodon

the only big dogs left are wolves. most foxes are smaller than dogs. dire wolves were quite large- a stout pony sized creature.

I think it has something to do with their genes...