Nature’s call, also known as the call of nature, refers to the need to use the toilet.

For example:

Jim is off answering nature’s call—he should be back any minute.

Is anyone else feeling nature’s call before we get back in the car?

I’m sorry, I need to answer nature’s call. I’ll be right back. 

He excused himself from the meeting to answer the call of nature.

Nature’s calling, so I’ll step outside for a moment.

She had to answer nature’s call after a long car ride. 

The marathon runners often have to answer the call of nature during the race.

Tradução:

A expressão idiomática “nature’s call ” ou “the call of nature” significa “o chamado da natureza”, “a necessidade fisiológica” ou “a chamada da natureza”. Ou seja, a necessidade de usar o banheiro.