system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Do male animals like dogs or cats that have fathered children know that they are their children? If so, do would they treat them any better if they are put together?

This question always plagued me.
gpt
I know you asked about dogs and cats, but primates have an interesting spectrum of techniques. 

On one end, there are gorillas, who simply keep harems and thus know that all the kids that the females produce must be theirs, and thus care for them. 

On the other end are ~~baboons~~ bonobos which just have orgies all the time and care for the kids in the tribe because "heck, at least some must be mine" but don't otherwise know. 

For the latter strategy, competition for spreading genes works at the level of sperm: they literally rely on better sperm cells getting to the eggs faster than those of all the other males who mated with her.

The closer the species is to the second strategy, the higher the males' testicle-to-body ratio. 

In case you're wondering, humans fall about in the middle of that spectrum, with average testicle ratios and reliance on both "keep other men away from her" and "crowd out the other guys' sperm".