Major revelation: If you're flying in the swamp, wear a ghillie suit to not get you and your flier immediately get spotted and targeted. (only works when the wild rhynio is currently attacking something, don't randomly go up to a stationary rhynio and not expect to get chased)

This is similar to bug repellant but it also benefits your flier too.

The ghillie suit makes you not have to worry about 2 major dangers of the rhynio:

Its massive aggro range

&

Prioritization of you over other creatures (similar to a Rex but way worse)

Obviously, if you and another creature are in its aggro range and you are closer to it, there's a chance it might attack you first, but overall if you're wearing a ghillie suit, you don't have to worry about flying high above the swamps anymore to evade the rhynios.