Male Hormones Make Female Lemurs Queen

The traditional way of the animal kingdom is that males rule, and females reap the benefits of being pampered baby-makers. Of course, there are always exceptions, especially among birds, arachnids, and even humans. However, there is one exception that came as a bit of a surprise. Female lemurs, it seems, will often bully their mates, stealing food, marking territory, and even ruling over their neighbors. Now researchers think they have determined what makes these imposing lady lemurs so different.

"If a male lemur is enjoying a patch of sunlight, for example, a female is likely to push him aside and take his spot," Joseph Petty, who studies the animals and their social patterns with the Duke University Lemur Center, explained in a recent statement.

Traditionally, when this kind of dominant or 'bullying' behavior occurs, the largest and strongest of a group are the instigators. This usually characterizes alpha males, but not all the time. Among spotted hyenas, for instance, females can steal prizes and even expect the privilege of eating first because they are heavier than males.

However, that's exactly why female dominance among lemurs is puzzling. They are not larger, stronger, or more deadly than their male counterparts, so what could it be that gives them a knack for dominance?

Hormones, Petty and his colleagues argue, is probably the root of this unusual behavior. Like most mammals, female lemurs have significantly less testosterone than males regardless of their location or species. However, when the researchers compared six lemur species, they found that the females of some have higher testosterone levels than others.

Petty and evolutionary anthropologist Christine Drea then tested 30 lemurs from six closely-related lemur species in all. In four of the species, females are at the top of the pecking order, and in the other two species the sexes have equal status.

Predictably, they found that the dominant females from the lady-run species had significantly higher male hormone levels than the females from the two remaining groups.

"It's strong evidence that hormones are playing a role," Petty said, adding that evolution likely had a hand in making this common among some whole species.

In other creatures, like birds, elevated testosterone often means the young need to be aggressive to survive. A similar pattern may have occurred with some lemurs, with it eventually leading to an intriguing change in who dominates who.

Results and methods of the study were published in the journal Scientific Reports.

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