I don't think so... Intelligence isn't required for consent, it's informed willingness in the absence of coercion or manipulation. The other factor is the likelihood of harm - I think that covers the full ethics of what beings you can ethically fuck

There's a few ways to look at it

One of my parent's dogs once had sex with a handyman's foot to completion... By the time he realized what was happening it was over, and the dog wasn't very bothered. The guy was also very nice about it, but I bet he stopped wearing sandals to jobs

What if he was into it? It's not like the dog would care... He clearly knew what he was doing. If we're just horny dogs humping their feet, it's not like they're doing anything wrong by not kicking us off

It also reminds me of a YouTube skit where an 18 year old boy goes to an adoption agency to find a 16 year old girl to adopt, with clear implications. It's a dark joke, but I think it lines up with this nicely

Let's say there's an alien species far more advanced than us. We're too dumb to even understand the basics of their technology, so to them we're basically pets - they can keep us around, but we're at their mercy. Now, there's an issue - a human could believe, even falsely, that we have to have sex with them or there will be consequences. We could even believe it's expected of us - and that's not coercive

Now let's say that same species came to Earth, guaranteed the health and happiness if every human, and made tinder for humans who want to have sex with an alien. In that case, if you handle it correctly, you can minimize or eliminate coercion from the act

Maybe the aliens don't even have sex... Maybe they just think humans are cute, and they enjoy making us feel good the way we enjoy petting animals

I don't think intelligence plays into any of this - consent isn't about intelligence at all. It's about willingness in an uncorrupted state