"Kami ingin tahu populasi kucing di pulau ini."

Translation: We want to know the cat population on this island.

[Rick392366]

Kami ingin tahu populasi kucing di pulau ini.
Meaning: We want to know the cat population in this island.

I think it should be 'on this island' instead of 'in this island'.
(reported)

[Fosdick1]

Why can't I say "We want to know the population of cats in this island"?