Kagemaru Himeno illustration for one of the 4  “Pokémon Columns”  (ポケモン コラム)  published in May 1997 in the Pokémon Fanbook ( ポケットモンスター公式ファンブック) accompanied by this caption.

- Capture is permitted only when the number of individuals is excessive.

Pokémon Column 2 - The Safari zone, a rare Pokémon treasure

A large number of Pokémon inhabits the Safari Zone and it’s a literal paradise for them.  However, Pokémon that live here need to be protected, it’s actually a space where Pokémon can be observed without disturbing their ecosystem.