You should be able to use
https://appid.appspot.com/_ah/api/apiname/version/saveAnimalData
As your final destination url when calling. blobstoreService.createUrl(destination)
.
Just bear in mind that the request here is not your original submission. GAE will first call an internal URL (the one created by the blobstoreservice), store the blob and then call your destination URL so whatever info you send will be lost before reaching your endpoint (eg AnimalData will be null)