It’s February 29 as I write this, also known as Leap Day! It’s a day that only comes around every four years, so some people have come up with traditions to celebrate this unique day.
One of those “traditions”? Leap Day used to be a day when women proposed marriage to men.
Now, of course, in 2024, this “tradition” is a bit ridiculous. Women can propose to men and vice versa any day of the year. But for the rest of the animal kingdom, males are typically the ones vying for the attention of the females. For some species, though, the situation is reversed.
Take, for example, jacanas, a family of wading water birds. There are eight species of jacanas found in tropical regions throughout the world. Also known as Jesus birds or lily trotters, jacanas have long toes and toenails that distribute their weight over a large surface area, letting them walk on floating vegetation. When their toes are fully spread out, a jacana’s foot can cover an area of 5 by 8 inches (12 by 20 centimeters).
And unlike many other animal species, most jacana females have a harem of males at their disposal.
Females are in charge
In all jacana species, the female is larger than the male, sometimes almost twice as large. This increased size helps the females collect as many male mates as they can defend from other females (the exception is the monogamous lesser jacana). In some species, a jacana female will create a harem of up to five males! She will then mate with her partners multiple times before laying four eggs in each nest.
During egg incubation, females will search for more males or defend their current mates from other females. A female jacana can have a territory as large as two football fields, which is impressive for a bird only around a foot long. If one of her clutches is lost, the female will lay a new clutch for that male.
Why males accept cuckolding
Female jacanas are typically quite blatant in their promiscuous ways and will mate in front of other males. Species like the wattled jacana also mate as many as 65 times for just one clutch of eggs.
The cuckolding bit of this story isn’t that uncommon in the animal world. In many “monogamous” species, females will sneak out to mate with other males. But what is uncommon is how open female jacanas are with their mating. The males know that there’s a good chance the eggs he’s incubating aren’t his. He’s seen his partner mate with his neighbor! In fact, for wattled jacanas, there’s as high as a 75% chance that the eggs he’s raising aren’t related to him.
So why does the male put up with this? Males in many other animal species will refuse to raise any offspring that might be someone else’s. After all, caring for kids is hard, and animals want to spend their energy raising offspring who are a part of their genetic line. But jacana males seem to be stuck with the short end of the stick. It would take too much time to find a less promiscuous female, so they stick with the one they have. Plus, there’s a good chance that some of his eggs are also being raised by one of his harem pals. The good news is that there’s almost always at least one egg biologically related to the father in his nest.
Dad of the year
But even if some (or most) of the chicks in the nest aren’t actually theirs, male jacanas make great fathers. They do most of the nest building, creating a floating nest from nearby leaves and stems. After the eggs are laid, the male keeps them warm and dry under his wings. He’ll even move the eggs to a new location if the original nest starts to sink or predators threaten the nest.
This stellar paternal care continues after the eggs hatch. Jacana chicks are precocial, which means they can walk and swim just hours after hatching. The male quickly starts teaching them how to forage for food and dive underwater when there’s danger. When the chicks are tired, they rest under the male’s wings. He’ll even carry them away from danger when necessary, resulting in a cute/creepy image of a many-legged bird.
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