How do male dog know when a female is pregnant?

Male dogs don't actually know a female is pregnant in the way that humans understand. They don't have the cognitive ability to process the concept of pregnancy.

However, there are some things that might change in the female dog's behavior or appearance that could signal to the male dog that something is different:

* Hormonal changes: A pregnant female's body releases different hormones, which can subtly affect her scent. This might be noticeable to the male dog, though he wouldn't necessarily understand the reason.

* Physical changes: As the pregnancy progresses, the female will get larger and more round. This could be noticeable to the male dog, although he might not connect it to pregnancy.

* Behavioral changes: Some pregnant females become more affectionate, while others become more protective or irritable. These changes could be perceived by the male dog, though he wouldn't understand the reason.

It's important to note that male dogs don't exhibit any special behaviors towards pregnant females. They may continue to interact with her in the same way as before. There's no evidence to suggest that they understand the significance of pregnancy.