An adult elephant must find up to 200 kilos of food each and every day if it's not to starve.

What does "if it's not to starve" mean in the sentence, in my opinion, it means if they do not want to starve. Is it such a fixed form?

Question

An adult elephant must find up to 200 kilos of food each and every day if it's not to starve.

What does "if it's not to starve" mean in the sentence, in my opinion, it means if they do not want to starve. Is it such a fixed form?

Answer

Infinitives are commonly used as adjectives or nouns. In your example, “to starve” is an adjective that modifies “elephant”. Grammatically, “the elephant is not to starve” is similar to “the elephant is not happy”. It is the same as if you created a sign saying “NOT TO STARVE” and attached it to the elephant. That would please the elephant who would be happy.