SNAP-NC: Spay Neuter Assistance Program of North Carolina

Are mammary tumors are common in unsterilized female dogs?

Yes, Mammary tumors are a problem for one in four unsterilized female dogs. Dogs spayed before their first heat are protected from mammary tumors, but once they've gone through two or more heat cycles, they have a 1 in 4 chance of developing them. Half of mammary tumors are cancerous, so it's important to have them removed and submitted for testing. A recent study showed that dogs spayed during mammary tumor removal were less likely to develop additional tumors than dogs that were not spayed. Mammary tumors most often affect middle-aged and older unspayed female dogs. Small-breed dogs are at greatest risk. The mammary glands closest to the hind legs are most commonly affected.

We adopted a abandoned female (looks about 6 - 8 mths old) about 2 weeks ago. She has evidently gone in heat in the last few days and is humping our male dog ...who is humping her back. We have her covered until her surgery...and keep them apart as much as possible. Why does she hump him also?

This is likely just "confusion" on the part of an adolescent dog's part. She does not know any better and this is likely the first time her hormones have been active if she is as young as you think. Her mounting behavior will likely give way to standing-to-be-mounted in the next few days. Be sure to keep both dogs apart from one another. The female's heat cycle will last about 3 weeks long.

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