I have a 9-month old female and a 7-month old male Basset. Maggie has just had her first heat, lasting nearly three weeks. We have been VERY diligent to prevent breeding at this young age, and have every reason to believe we have been successful. Brutus has not been interested in Maggie for about three days, she had not had any discharge for about 10 days or so. Yesterday--after the three-day lull in mating attempts--her kennel linens were definitely blood-stained, and now she is aggressively and relentlessly attempting to mount Brutus (head or rear end, she really doesn't care). He is definitely NOT INTERESTED, and gets very frustrated with this behavior, resulting in two nipping, snarling dogs. What is this?? Is this something to be expected, or do we need to consult our vet at this point??