Mulan Mimicry

While I waxed eloquently about mimicry in my 2023 book, The Liars of Nature and the Nature of Liars, I left several tricks up my sleeve for the sake of brevity. Thankfully, this blog gives me a chance to amend that, as I’ve already talked about small birds impersonating the big shots and lady mice playing ferret to keep the wrong suitors at bay.

In this essay, I’ve joined forces with Xitong Liang at Peking University to introduce a new type of mimicry: Mulan mimicry, where female animals imitate their male counterparts. We opted for the name “Mulan” because, according to the sixth-century Ballad of Mulan (or《木兰诗》in Chinese), she disguised herself as a male warrior to fight northern invaders—basically, an ancient superhero story that even got the Disney treatment, not once, but twice! So, we figured, why not name this kind of mimicry after this lively legend?

Now, about this Mulan mimicry, it made its grand debut in 2021. In a paper published in Current Biology, Jay Falk, Michael Webster, and Dustin Rubenstein revealed their escapades in Panama, where they embarked on a four-year quest of capturing and tagging 436 white-necked hummingbirds (Florisuga mellivora) before setting them free. But here’s the twist: some young females decided they wanted a taste of the male lifestyle. So, they got themselves a makeover, complete with snazzy blue head and neck plumage (please see the images). Males and these female impostors were a real puzzle to tell apart, leaving the researchers scratching their heads and resorting to genetic tests. The results were jaw-dropping: impostors accounted for a whopping 28.6% of all adult females (1). It’s almost like the birds decided to have a little fun and see if anyone would notice the switcheroo!

A male (or female imposing male) white-necked hummingbird

By Lip Kee / CC Lisence: BY-SA 2.0

A "normal" female white-necked hummingbird

By Alejandro Bayer / CC Lisence: BY-SA-2.0

Why on earth would hummingbirds engage in such cross-dressing antics, you ask? Well, it turns out they take their territory quite seriously, as if they’ve invested in prime real estate. So, the researchers decided to play matchmaker and orchestrated a little experiment. They introduced both regular female hummingbirds and their male-impersonating counterparts into the wild and watched the drama unfold. The verdict was clear: Wild males had a strong penchant for the “real deal” females, showing off their most charming moves, whether it was an aggressive territorial dance or a suitor’s serenade.

Now, when they placed male hummingbirds side by side with their impostor female companions, the wild males were in for a perplexing surprise. Not only did they fail to spot the difference, but they also toned down their aggression levels. Apparently, males, peevish and bellicose, have to play diplomacy, as they are tenacious in defending their territories (2). Female impostors, it seems, had a knack for avoiding the hummingbird equivalent of reality TV drama, and they even earned brownie points for their discretion, as other females and different hummingbird species were less inclined to stage an avian brawl around them.

But does this newfound peace translate into more dining opportunities for these Mulan females? To find out, the researchers turned to outfitting the birds with PIT tags, the equivalent of barcodes in our supermarket. After 278 days of fine dining surveillance of 28 such feeding stations equipped with tag readers, the statistics revealed that female impostors got to enjoy more uninterrupted feasts than their regular counterparts. It seems that humoring male pretenders is not only an art but also a strategy for the survival of female hummingbirds. So, donning the male disguise seems to have real benefit.

You might wonder, is this whole “Mulan mimicry” thing exclusive to the white-necked hummingbird, or do other species also have secret gender-bending societies? The researchers conducted a thorough investigation, scrutinizing over 16,000 specimens from 307 different hummingbird species. Their findings were nothing short of a birdwatcher’s bonanza— female impostors lurking in around a quarter of the hummingbird species! If you exclude species where males and females show no difference, then it’s safe to say that Mulan mimicry accounts for a whopping 40% of all hummingbirds.

Now, why don't all the females in the bird world opt for this dashing disguise? It appears that sporting a flashy male costume may have its downsides, like drawing the wrong crowd. You see, predators might develop a taste for hummingbird impostors, and these fancy females might inadvertently leave male suitors scratching their tiny bird heads. After all, it’s a tricky business to court someone who looks almost exactly like you. These are just theories, though, waiting for science to unravel the mysteries of the avian fashion scene. So, while the hummingbirds keep us guessing, they’re also teaching us a thing or two about the fine art of dressing for survival in the animal kingdom. Nature's masquerade ball, anyone?

But before we wrap up this avian adventure, here's a little teaser for you: Mulan mimicry isn’t just a hummingbird monopoly; it's also a style statement for butterflies and damselflies. Yes, you heard that right! It seems that the art of disguise knows no bounds in the animal kingdom, and we’ve got some delightful tales from the world of winged wonders waiting in the wings for a future blog post. So, stay tuned for the next chapter of our animal masquerade.