Same thing happens every year to me. I found the culprit last year and it is a squirrel. It snaps the head off just as it is beginning to open, takes a nibble and then rips it apart. At first I thought it was some strange insect. Then I blamed the resident chipmunk. I apologized to the chipmunk for cursing him after I saw the squirrel in action. That stinking squirrel won't let me have the pleasure of seeing even one gerbera daisy bloom left standing. I'm going to move them this year. I despise squirrels.

So it's the squirrels!! Never occured to me they'd be interested in them. Our yard backs into the woods so I've got a ton-o-squirrels visiting. Oh well...I do love thier antics so will just have to live with the flower loss. At least they let me enjoy the blooms for a few days before they rip them up!
And Sorry for the late reply...thank you opal52!

Planted gerbera daisies didnt make it 5 days and squirrel chewed off 6 flowers. I swear im getting a gun,its now legal in mi

I put peppermint plants and geraniums around the gerbera daisies that are planted in pots. A squirrel finished off the heads of the gebera daisies in one pot, so i added mulch on top of the pots yesterday. I’ll see if this works this week. (A last option would be to add grated Irish spring soap on top of the mulch).

I bought some motion sensors that emit lights and sound from Amazon. Just got today. I'm also going to try peppermint. We have some obnoxious mint I've been pulling from the garden for years, so I'm going to fight 🔥 with 🔥!