Sure, it’d probably never occur in the wild. What, with girzzly bears living primarily in great wooded expanses of Northern America, and the Silver back living in the mountainous jungles of the African jungle. Granted the grizzly bear is an exceedingly incredible swimmer. They have to be. Catching salmon as they leap up raging waterfalls is a perilous task at the best of times. The rocks are slippery, the salmon are horny and the water; unforgiving. One slip and, with out a reasonable amount of swimming nous, it’s curtains for everyones favourite 500kg, furry, killing machine. However, it is ridiculous to imagine a grizzly swimming the immense spans of the pacific oceans, then trundling the African plains, in order to square off against the great silver back gorilla.
Having said this, let’s imagine that by some fluke of nature, a male silver back gorilla happened upon a grizzly bear in an environment that was that was both agreeable and comfortable for both animals. They stare at each other for what seems like a life time, but is in fact only a second or two at most. Something passes between them, almost like an understanding but filled with hate, for each beast considers this imagined wooded glen to be with in the realm of his territory. Suddenly, and with out warning, they simultaneously issues forth a blood curdling war cry.
And it. Is. On.

First let’s look at the stats:

The Silver Back Gorilla

The Silver Back is 1.8 metres (5 ft 11 in) and weighs in at 230 kg (510 lb). This is one hefty primate. It has large, sharp canine teeth that could easily pierce the flesh of a human. Couple this with arms strong enough to rip the arms off of Hulk Hogan and you’ve got your self one serious biped. This bad boy will punch, bite, roundhouse kick and rape anything that pisses him off.

And guess what?

This Grizzly bear has just pissed him right off.

So how does the bear measure up?

Kodiak Grizzly Bear

An adult male Kodiak Grizzly Bear stands up to 1.5 m (5 ft) tall at the shoulder when it is standing on all four legs. When standing fully upright on its hind legs, a large male could reach a height of 3 m (10 ft)… Holy fuck! Ten feet tall! A monolith when compared to the silver back. They weigh around 680 kg (1500 lbs), which is nearly three time more than our african primate friend.
When you consider that the Grizzly has big fuck off claws, big old chompin’ teeth and a skull that can withstand a shotgun blast, you have to say that the Silver back is some what out classed.

My prediction

The grizzly will straight up slaughter the Silver back (unless the silver back retreats to the jungle and recruits more silver backs. Somewhere in the region of 10. OR he learns to use human weapons, such as a .50 Cal machine gun).