JonathanRyan.org

A: He sits on an acorn and waits.

Or, for a quicker solution he can use this device patented by Hermann Reiche in 1891.

[The invention enables] heavy quadrupeds to walk up and mount the top of the platform, as shown by the elephant in the drawings, or, in other words, “to enable an elephant to climb up a tree.”

Via Dis and Pandemonium