Grodd possesses Incredible Telepathy, and can read minds at a range of 250 miles.
Many more than a gorilla should be allowed to have; he can also mentally absorb a talent from anyone he encounters.
The Legion of Doom * The Secret Society of Super-Villains
Grodd was the greatest scientific genius among the highly evolved and extraordinarily intelligent gorillas living in Gorilla City, a hidden civilization in equatorial Africa. Grodd made repeated unsuccessful attempts to conquer Gorilla City and the world, most of which were thwarted by the second Flash. (An account alleging Grodd and the other gorillas of Gorilla City to be extraterrestrials is totally erroneous.)
Years ago, Grodd used his telepathic powers to read the mind of Solovar, Gorilla City's leader, and thus discovered how to control the minds of others through "force of mind." Grodd returned to Gorilla City, and psionically took control of its soldiers. Solovar enlisted the aid of the Flash, who defeated Grodd. Later, Grodd apparently lost his new power.
Still later, Grodd used an evolution accelerator to transform himself into a human being. Calling himself Drew Drowden, Grodd found a means to give himself tremendous mind-over-matter powers. Upon reverting to gorilla form, Grodd lost those powers and was again defeated by the Flash.
Unable to escape his Gorilla City cell physically, Grodd killed his own body and projected his mind into the body of a human named William Dawson. Dawson's released mental essence began wandering the cosmos. Eventually, Dawson's body turned into a duplicate of Grodd's original gorilla form. Sometime later, Grodd somehow regained his power to control the minds of others and his mind-over-matter powers, and could use all these powers in his gorilla form.
Dawson's mental essence returned to Earth and transformed an anonymous derelict into a highly evolved human form, into which Dawson's mind projected itself. Calling himself Psykon, Dawson used the great psionic powers he had acquired to battle Grodd. Grodd forced an exchange of minds with Psykon, but Grodd's own psionic powers were to weak to maintain Psykon's physical form. Psykon's body devolved back into the derelict's form, and Dawson, now in Grodd's body, used his fading mental powers to cloud Grodd's mind and to turn Grodd's body back into his own human form.
Grodd has since regained his full intelligence and mental powers and has psionically transformed back into his gorilla form. He is currently imprisoned in Gorilla City.