Fan question: "Why do my two small dogs, who are brother and sister, mount each other during playtime?"
In Cesar Millan's response, he states that there can be two answers to this question based on the following factors:
Dogs that are not spayed or neutered
If you are witnessing your pups mounting each other during play, Cesar states that their actions could be a result of primal behavior. As mentioned by the ASPCA, when dogs are not spayed or neutered they have a strong urge to howl, mar, and roam in search of a mate. Sometimes this urge can even lead to fighting. And while it sounds like the fan's two pups are not fighting, they're certainly taking advantage of having the opposite sex available to them (if they're not spayed or neutered). Being wired to mate and reproduce and being isolated from other animals, the pair will most likely continue their mounting until they're both spayed and neutered.
A concern that Cesar Millan has if the two dogs are not fixed is that their mating could cause "neurological problems." As with any inbreeding case, the act of two siblings reproducing could result in mental and physical abnormalities and possible death. In addition, Millan mentions that owners should be more aware of spaying and neutering their animals as dogs are extremely overpopulated and there are unfortunately not enough good homes for them.
Dogs that are spayed and neutered
In the case that the fan's brother and sister pups are spayed and neutered, the pair is simply playing. Not directly thinking about mating, Millan believes that they're merely practicing dog behaviors as most do when engaging in play. Most pet owners with multiple dogs will notice a pair or group doing multiple activities together: digging, running, resting and yes, even mounting. It's a way to show affection and have fun with one another as friends and housemates.
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Photo credit: Cesar's Way