Hormones are major mood-regulators, as anyone who has been cranky before a period or had their reproductive organs removed for medical reasons can tell you. In fact, depression is a common side effect of such surgeries in humans. But does that extend to some of the most regularly de-hormoned animals out there---our pets? That's the thought-provoking thesis of a recent Slate piece
, and while there's been no systematic research on how such surgeries affect cats and dogs, a smattering of research has suggested that having your supply of hormones eliminated does affect the mood of mice and primates, free of the confounding influences one finds in humans. Madeleine Johnson of Slate describes one set of experiments:
[Researchers in Japan] reasoned these snow monkeys could model mood changes due to ovariectomy without confounding variables like the social stigma of barrenness that might affect women. The center picked 10 females of equivalent rank in the dominance hierarchies and removed the ovaries and uterus from five of them. The other five had their “tubes tied,” so were sterile but still had intact ovaries. Since the monkeys wouldn’t understand the biological ramifications of surgery, and would have similar social lives, any difference between the two groups could be attributed to ovarian hormones.
During an annual corralling of the monkeys three years after surgery, the authors noted that spayed monkeys ate and drank more, and groomed and had sex less—suggesting social impairment and stress. When researchers confronted the monkeys with a black rubber snake, four out of five ovariectomized monkeys backed away and closed their eyes. (The others touched the snake and played with it.) The scientists deemed this odd behavior a “non-adaptive” response to threat and novelty, and concluded that the presence of ovarian hormones keeps female macaques calm and socially engaged. Other research on the same Oregon snow monkey troop suggests spaying impacts serotonin levels.
The benefits of spaying and neutering---peaceful behavior, no marking of furniture, no endless litters of unwanted young---are so great, though, that it's hard to see how a dip in your dog's mood could outweigh them in the minds of most pet owners. If research eventually shows that pets are adversely affected---and we're a long way from that point---maybe getting pets' tubes tied or snipped be a better option than wholesale gonad removal.
Image courtesy of Teeejayy / flickr