system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does an animal's body know when to drop it's winter coat?
gpt
In true ELI5 fashion;


Changing of coats can be to a variety of things such as the lengnth of time the sun is out, temperature and diet. It varies species to species but it's usually down to hormonal changes caused by day length and temperature.