New research from Lucy Bates and colleagues examined elephant data spanning 28 years and found that, when females fake it, they were usually in the company of a younger female. Because the younger female was coming into heat for the first time, the researchers hypothesize that older female relatives might be trying to teach the youngsters how to get the right guy. The research was published online at PLoS One (full article here).
Females display sexual willingness for about week while they are ovulating (for more detail about the elephant oestrus cycle, check out this site). Their display includes, ”holding their heads and tails high, walking with an exaggerated gait, and displaying increased tactile behaviour towards males.”
The males they are trying to entice are the sexually mature (ie: 25-years or older) “musth” males. Elephant males enter a “musth” period about once a year. During this time, they are sexually active, have high levels of testosterone and are dominant to non-musth males. They are preferred by mature females in-the-know because they will protect a female they have mated with from unwanted advances by other males.
But musth males can be scary to a young female (they are much bigger), which is thought to be why these females run away from them. Instead, they mate willy-nilly with immature males, not knowing any better. Older, wiser females won’t mate with young, non-musth males. But how did they learn which males to go after?
The researchers used the extensive dataset from the Amboseli Elephant Research Project in Kenya to compare three hypotheses about why female elephants fake oestrus.
1. Just because. Faking oestrus has no purpose.
2. By faking it, females will somehow increase the reproductive fitness (or number of babies) of the faking female.
3. Faking oestrus increases the faking female’s fitness indirectly, by increasing the fitness of her relatives. In this case, that would be her young female relatives.
While the data they looked at didn’t completely support any of these three hypotheses, they were able to rule out #1 and 2 and found good evidence for #3.
They found 19 instances of false oestrus (about 2% of all recorded oestrus events). While only 9% of real oestrus events occurred between two females in the same family at the same time, 58% of false oestrus events occurred at the same time as a younger female relative was going into oestrus for the first time (except in one case, where the female relative–a daughter–had already given birth at least once).
While the data are enticing, they are far from conclusive. First, the numbers are small. Only 19 instances of false oestrus were identified, and only 11 of those occurred in the presence of a young female relative in real oestrus. The fact that the other 42% of false oestrus events were not in the presence of these younger females argues that there may be another purpose to faking it besides teaching.
The researchers also didn’t find any evidence that the older females were having a direct effect on teaching the younger females which males to mate with. Those young females still went around mating with non-musth males.
But let’s go back to the original hypotheses for a second.
Is false oestrus just random, a byproduct of pregnancy hormones or something? While many of the females in false oestrus were pregnant, not all of them were. A couple were actually too old or oestrus or pregnancy; they were past elephant menopause. And the fact that faking it happened disproportionally in the presence of young females that were in oestrus for the first time argues against randomness.
Does faking it increase the female’s own chances of reproducing? Unlikely. Like I said, many of those females were already pregnant. The others were lactating (not able to get pregnant) or too old for making babies.
So maybe it’s something long-term, a way of pointing out to these young females that musth males aren’t scary. That they’re actually the ones you want to be mating with. And pointing this out when the younger female is first experiencing all those sexy hormones seems like good timing. Maybe she doesn’t get it right away, but after a getting harassed by younger, less sexy males often enough, she will get the point.
I wonder how this idea could even be properly tested? Try raising a female without any guidance or examples of proper oestrus behavior and see if she ever “gets it”? It’s pretty much an impossible experiment.