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Ravens and wolves form social attachments with each other and take huge advantage of each other.
Both animals eat meat. When wolves killed a prey, ravens eat from the left over cadaver and scavenge it. Also, ravens lead wolves to preys or cadavers. The ravens fly and the wolves follow. Ravens also alert wolves to dangers.
They also play with each other. For example the ravens dive at the wolves and then speed away or peck their tails to try to get the wolves to chase them, or wolf cubs chasing after teasing ravens.

"It appears that the wolf and the raven have reached an adjustment in their relationships such that each creature is rewarded in some way by the presence of the other and that each is fully aware of the other’s capabilities."
Also very interesting: Bernd Heinrich wrote in ‘Mind of the Raven: Investigations and Adventures with Wolf-Birds’: "Ravens can be attracted to wolf howls. The wolves’ howls before they go on a hunt, and it is a signal that the birds learn to heed. Conversely, wolves may respond to certain raven vocalizations or behavior that indicate prey. The raven-wolf association may be close to a symbiosis that benefits the wolves and ravens alike. At a kill site, the birds are more suspicious and alert than wolves. The birds serve the wolves as extra eyes and ears."