Christine Drea: You’re actually mucking about with very important social signals. All of a sudden, Betty doesn’t smell like Betty anymore. We don’t even know who she smells like. This is weird!
Dr. Christine Drea is an animal behaviorist at Duke University. She’s talking about her study – the first of its kind – that analyzed the impact of a form of birth control on the chemicals that make up an animal’s unique scent. In this case, the animals were lemurs – a type of primate related to monkeys and apes. Drea’s study showed that birth control dramatically altered the way the lemurs smell.
Christine Drea: It’s exactly like a fingerprint. It’s called a scent signature. We have these in the pattern of our skin. We have it in our voice. We have it in our scent.
Female lemurs in Drea’s study were given the contraceptive DepoProvera.
Christine Drea: It not only affected the chemical signals of fertility but it also obliterated the signals of an animals individual identity, your scent signature that says “you are uniquely you.” It’s their kinship. It’s their genetic quality. All of that gets either completely lost, or scrambled or subdued in some way.
Drea suggested that when an animal’s scent is “off”, confusion in mate selection can result. Changing an animal’s scent might even prevent members of a group from getting along, she said. She added that scent-based research is so new, it’s impossible to generalize about how birth control – or any other drug – might be affecting humans or another animal species.
In this particular experiment, Dr. Drea worked with Depo Provera (medroxyprogesterone acetate), a drug very similar to progesterone, a hormone normally produced by the ovaries every month as part of the menstrual cycle. Drea explained that her team measured the change in chemicals in lemurs given the drug via fluids obtained from them. (All the samples were non-obtrusively obtained, she noted.)
Christine Drea: If you take a sample from a normal female, she will show something around the vicinity of 300 different chemicals in her secretions. Contracepted females lost some of the normal complexity of the scent signal. There were some chemicals they lost completely. They also started expressing compounds before that we had never seen expressed in an intact female. They were somehow manufacturing odors that were different from what they normally manufacture
In other words, female lemurs given contraceptives didn’t smell as they normally do. What’s more, Drea said, the new scent profile of the female lemurs on contraceptives tended to be similar. That is, these various lemurs smelled (too much) like each other. She said that the males noticed this change in scent, and appeared not to like it very much.
Christine Drea: Males definitely spend much more time investigating, sniffing, licking the odors of females when they’re intact than when they’re contracepted. In other words, they prefer the odor of (non-contracepted) females.
Beth Lebwohl researches, writes and helps produce science content in audio and video formats for EarthSky. She is one of the authors on EarthSky.org, a script-writer for our podcasts, and helps host our English science podcasts in 90-second, 8-minute and 22-minute formats. Beth came to EarthSky in 2006 from the American Museum of Natural History's Department of Astrophysics, where she was surrounded by some of the greatest telescope-building, equation-wielding, code-writing physicists of our time. And they made her think . . . this science thing . . . it's pretty cool.