As far as I'm aware you're right about the geolocation devices. This is a great podcast about a guy working on Project ICARUS, where they're working on tracking

As far as I'm aware you're right about the geolocation devices. This is a great podcast about a guy working on Project ICARUS, where they're working on tracking thousands and thousands of animals with small geolocation devices so we have much better data to work from - https://www.bigbiology.org/season-2#episode43 https://www.bigbiology.org/season-2#episode43. From what I recall the idea of tracking butterflies was something they were working on but hadn't cracked yet. I think it was towards the end of the podcast, but I'd recommend the whole thing.