FH, have you ever heard of high humidity as another cause for cattle bunching up?
That seems so counter-intuitive as to be not true, but it sure appears to be so.
Yesterday, when gathering some hiefers for A-I work, from a pasture that runs maybe 100-150 or more elevation variation from lowest to highest points, they found them in a washout in the nw corner of pasture all clustered together, panting from the heat. Got them to the corral, SLOWLY, and sprayed them down a bit before doing whatever the day called for, preparing to inseminate Tuesday.
I think the flies were not much in evidence, at least I heard no comment on that score.
mrj