Why It's Nearly Impossible to Castrate a Hippo

Chances are you've never wondered how difficult it is to remove the testes of a hippopotamus. Other people have been thinking hard about it, though, because in fact it's almost impossible.

Before sitting down to emasculate a common hippopotamus, Hippopotamus amphibius, it would be reasonable to ask why. They're a threatened species, so usually conservationists try to make more baby hippos—not fewer. But in zoos, hippos turn out to be prolific baby-makers. Females can live for 40 years and may birth 25 calves in that time. This would be great news in the wild, but zookeepers don't always have someplace to store a new two-ton animal.

Male hippos can also be aggressive toward each other, at least while they have all their man parts. For both of these reasons, zoos may want to have their male hippos fixed. But there are a few factors working against them, explains a new paper in the journal Theriogenology (that's reproductive science for vets) by an international group of authors.

The first challenge is that hippopotamuses hide their genitals. The testes are inside the body, instead of outside in a scrotum. (Other mammals in the internal-testes club, since you asked, include the armadillo, sloth, whale, and platypus.) This makes the hippo's testes totally invisible from the outside. Combined with a penis that the paper's authors describe as "discreet," it means it's hard to tell males from females at a distance.

Another problem is that testes aren't in the same place from one hippo to the next, and they may "retract" even farther during surgery. Hippopotamuses are also difficult to safely put to sleep. "In the past, hippopotamus anesthesia has been fraught with serious complications," the authors explain.

After moving past the anesthesia problem (they used an apparently safer blend of drugs, delivered via a dart to the hippo's ear), the researchers turned to the anatomical problems. Their answer was ultrasound. Once they had positioned the animal, they used ultrasound imaging to find the testes—then used it again after cutting into the hippo, if the testis they were looking for had scooted farther away from them.

Even after finding the sneaky organs, the procedure wasn't simple. The depth of the testes' hiding places varied by as much as 16 inches from one hippo to the next. Everything had to be done deep inside the animal's body, making it hard to see what was going on. "Grasping the testicle with forceps proved laborious" in most of the animals, the authors write. They also mention using a "two-handed technique" and "moderate traction." The whole hour-and-a-half procedure, based on a method for castrating horses, is described in detail for anyone who wants to try it themselves.

All ten hippos in the study were successfully castrated, though one died shortly afterward, following a complication from a unknown pre-existing condition. Over the next six months, the authors checked in with the zoos housing the hippos to see whether their behavior or interaction with other animals had changed. There were four cases where zoos wanted their hippos fixed to ease aggression between males; in all four, the problem seemed better. (One zoo, though, reported that castrated males were harassed more by females.) Overall, the authors think their technique will help zoos take better care of their hippos.

The final challenge to hippopotamus surgery—what should be a challenge, anyway—is that the animals spend most of their time in a pool of water packed with feces. The animals in the study lowered their stitched-up bellies into this infectious slurry as soon as they had a chance. Yet all of them healed from surgery without trouble. Hippos in general seem to be especially good healers, the authors write.

A possible explanation for the animals' healing superpower is the "red sweat" or "blood sweat" that oozes from their skin. It's not really sweat and it doesn't contain blood, though it is red. The pigments in this skin secretion have been found to absorb UV light, making the "sweat" a potential sunscreen. The pigments can also keep bacteria from growing. So a built-in antibiotic may be what keeps hippos from getting infections after they tussle and bite each other (or after meddling vets come and cut out their manhood). However the red sweat works, it shows that a hippo's secrets don't end with the location of his testicles.


Images: Charlesjsharp (via Wikimedia Commons); drawings by Eva Polsterer (from Walzer et al.).

Walzer C, Petit T, Stalder GL, Horowitz I, Saragusty J, & Hermes R (2013). Surgical castration of the male common hippopotamus (Hippopotamus amphibius). Theriogenology PMID: 24246424

Newly Discovered Flower Makes Fake Pollen to Fool Bees

"I was certain it was something new when I saw it," says Chris Martine of the bush tomato species he discovered in the Australian outback. It's a scrappy, spiny shrub with crinkly purple flowers that thrives on fire. It also uses treachery to survive, disguising its female flowers with fake male parts and even fake pollen.

A botanist and biodiversity scientist at Bucknell University, Martine explains that the new plant "was on the radar of a few local botanists as being an oddball." Martine had been studying related species for a decade, so when his lab analyzed this plant's DNA, he recognized that it was something different. He went to Australia to document the species in person and dubbed it Solanum cowiei after botanist Ian Cowie at the Northern Territory Herbarium, who first introduced him to the plant.

The diverse Solanum genus includes plants ranging from potatoes and tomatoes to eggplant and nightshade. The Australian bush tomatoes that Martine studies grow little fruits that can be edible or quite poisonous, depending on the species.

Martine discovered that compared to its relatives, S. cowiei is especially well adapted to the fires that sometimes sweep through its habitat. The plants live in large groups of clones tied together by underground root systems. In an area that had recently been burned clear, Martine found S. cowiei plants springing up and blooming while other species lagged behind. This means that after a fire, these plants have a competitive edge over all their neighbors in getting to pollinators.

The new species's method of reaching those pollinators is a weird one. S. cowiei grows separate male and female flowers, and like about a dozen of its close relatives, it disguises the female flowers with fake male parts and pollen. Under an electron microscope, the false pollen grains look like brand-new tennis balls. Real pollen grains are closer to old ping-pong balls, with large dents or grooves on their surface—these are the weak spots where a narrow tube may later burst out of the wall of the pollen grain, carrying the plant's sperm to an egg.

Why bother with the ruse? Solanum flowers don't have any attractive fragrance to lure their pollinators, or nectar for insects or birds to drink while they're dusted with pollen. Instead, these plants rely on pollinators that want to eat the pollen itself. Certain foraging bees use pollen to feed their young, Martine says. "So if you want one of these bees to visit your flowers, you have to have to have the visual cue of the anthers," a flower's male parts. "And if you want them to come back to flowers like yours again, you have to give them some reward to take away."

Martine and his collaborators are now studying whether this fake pollen is any better or worse for young bees to eat than the real stuff. "Is there a difference in what they are getting?" he says. "Can they tell?"

The "oddball" bush tomato isn't the only plant Martine finds intriguing. He produces an online video series called "Plants Are Cool, Too!" ("Can an animal make its own food? No! Can an animal feed the whole world? No!" the theme song declares.) Martine started this series after working with kids who were interested in science and realizing that they knew a lot about animals, but not so much about plants. People browsing online are more likely to encounter a cute cat video, after all, than one about cattails. So he started putting together episodes that highlight some of the "coolest" plants, along with the botanists who study them.

The next full episode should be out in January, he says, and it includes an especially cool moment: a new species of mustard plant being discovered. "Our guest expert looked down during shooting and said, 'Hey, wait a minute,'" he says. "I don't know how often new species are discovered while a camera is running, but it can't be very common."

Photo by Kym Brennan.

Christopher T. Martine, David E. Symon, & Elizabeth C. Evans (2013). A new cryptically dioecious species of bush tomato (Solanum) from the Northern Territory, Australia. PhytoKeys DOI: 10.3897/phytokeys.30.6003

Turtle Moms Choose Their Babies' Genders by Where They Build Their Nests

If turtles had realtors, their motto would also be "Location, location, location!"—but not because they care about a scenic vista. The spot a mother turtle chooses to dig her nest determines whether her young will be males or females. This might even be the most important factor in her decision.

A female painted turtle (Chrysemys picta) is not an over-involved parent. She digs a hole in the dirt, lays a batch of eggs there, and buries them. Then she returns to her freshwater life without giving the nest another thought. The eggs incubate and develop under the soil while the summer wears on. Hatchlings finally chip their way free in the late summer or early fall, but in cooler parts of North America they don't leave the nest right away; they stay hunkered down with their siblings to hibernate until the following spring.

Sometime in the middle of the summer, a significant event happens inside each buried egg: the developing turtle becomes male or female. Its sex hasn't been determined by its genes like ours is. Instead, as with many other reptiles, the temperature in the nest tilts the egg toward one sex or the other. Cooler nests produce males and warmer ones make females. If the nest stays within a narrow temperature range, hatchlings of both sexes will crawl out at the end of the season.

Timothy Mitchell, a Ph.D. student in ecology at Iowa State University, studies a population of painted turtles living in northwestern Illinois. These particular turtles have been under close watch by scientists for more than two decades, but it hasn't become clear whether turtle moms are active in determining their hatchlings' sex—do they choose nest sites that will best balance the sex ratio of their eggs? To find out, Mitchell set up a kind of nest-building competition between himself and the mother reptiles.

Mitchell scoped out 20 nests in his study site, a forested area near the Mississippi River. Right after the mothers left their nests behind, he went in and dug the eggs up. Then he tucked the eggs into artificial, Styrofoam-box nests. Half the eggs from each batch went into a box right next to where their mother had left them, buried at the same depth to create a controlled replica of the original nest. The other half went into a box at a site Mitchell selected at random.

(How do you randomly place a turtle nest? Mitchell used a random number generator to choose a distance away from the original nest, up to 30 meters. Then he flung a pencil in the air and walked in whatever direction in was pointing when it fell. If the resulting location was, say, in the Mississippi, he tried again.)

Just before they were due to hatch, the eggs were dug up and brought to a lab. Mitchell monitored their hatching and then returned the tiny turtles to their artificial nests for hibernation (along with a sprinkling of eggshells, as if the turtles had been there the whole time). He checked on the baby turtles once more in the spring.

Temperature sensors hidden in the nests revealed that sites chosen by turtle moms were a little warmer than Mitchell's randomly selected ones. This meant they were more open to the sun; nests that were shaded by vegetation were cooler.

Between the original nest sites and the random ones, there was no difference in the number of eggs that survived all the way through hatching and hibernation. But there was a major difference in sex ratio: while the turtle moms' nest sites produced roughly equal numbers of boy and girl turtles, the hatchlings from Mitchell's randomly placed nests were about 80 percent male.

"This strongly suggests this process of sex ratio selection is influencing where Mom chooses to nest," Mitchell says, "as opposed to selection to have eggs survive."

Wherever she builds her nest within this forest, a painted turtle mother can be assured that her young will survive equally well. But it's in her best interest to keep the sex ratio balanced. In the long term, turtles that tend to build male-heavy or female-heavy nests will lose out when the population swings in that direction, because young turtles of the opposite sex will then have better mating prospects.

A warming climate is a threat to any species whose sex ratios depend on the temperature. But if female turtles are savvy enough to leave their eggs in exactly the right sex-balancing spot, should we stop worrying about them? "That is still the big question in the field!" Mitchell says. He thinks moms' choice of nest sites will be a crucial part of how this species responds to climate change. But many other factors will matter too, like the fragmentation of the turtles' habitat and how the climate affects their predators. Turtle moms today know how to build a perfect nest for their offspring , but that balance may be as fragile as eggshells.


Image: Timothy Mitchell.

Timothy S. Mitchell, Jessica A. Maciel, & Fredric J. Janzen (2013). Does sex-ratio selection influence nest-site choice in a reptile with temperature-dependent sex determination? Proceedings of the Royal Society B DOI: 10.1098/rspb.2013.2460

Cooler Than Your Environmental Club: An Interview with My Little Sister about the Adirondack Youth Climate Summit

Teenagers who want to cause a disruption don't have to ride a skateboard anymore; these days they can do it on a bike generator. Earlier this November a crowd of students came together in Upstate New York to share ideas about greening their schools and addressing climate change on a small and large scale.  My youngest sister, Leigh, is a senior in high school and was at the conference for her second year. I asked her what they did there, and she told me about energy efficiency, celeriac soup, and how her generation is going to do things differently. (I never did get a straight answer about some Facebook photos, though.)

*****************

Hi Leigh! So who attends the Adirondack Youth Climate Summit?

There were about 150 students representing 27 colleges and high schools around New York, mostly from the Adirondack region. Each school could send 5 to 6 students along with a teacher chaperone. Students at my school had to write an essay explaining why they wanted to go to the summit and what interest they had in climate change. (Most students I talked to were shocked that my school had been so selective because their schools just brought their entire environmental club.)

By the way, I hope email is OK. Would I have more generational cred with you right now if I were conducting this interview via SnapChat or something?

I have to say, I much prefer the transfer of information through text bubbles containing less than 140 characters attached to a picture I can only view for 10 seconds on a 4-inch screen...but I guess this will do.

What kinds of workshops did you go to?

I got to attend three different workshops of my choice on the first day, splitting up with my school group so that we could cover more ground. I attended the three that were geared towards successfully sustaining a school garden and implementing younger students into climate action, because that's what I've been focused on at school the past couple years. The rest of my team attended workshops about composting, green teams, energy efficiency, biofuels, and recycling.

I hear the food was a highlight.

The food was absolutely delicious! All the meals and snacks were provided by local farms and vendors. They had vegetarian, vegan and gluten-free options, and Ben & Jerry's (a major sponsor of the summit) provided ice cream the second day. I caught myself enjoying kale chips and even tried parsnip and celeriac for the first time in a delicious soup that a Culinary Arts professor from Paul Smith's College made. (See recipe below.)

As weird as it sounds, I think the presence of wholesome, fresh, unprocessed food really boosted everyone's brain power for a few days.

And there were speakers too?

Brian Stillwell of Alliance for Climate Education kicked off the summit with a catchy, motivating presentation about climate change and the science behind it, followed by Brother Yusef Burgess of Youth Ed-Venture and the Children & Nature Network, who spoke about using the power of nature to transform and educate youth. Later in the afternoon Dr. Susan Powers, the Associate Director for Sustainability at Clarkson University, presented to us the outcomes of climate change in both our best and worst case scenarios.

Mark and Kristin Kimball, who own Essex Farm in the Adirondacks, hosted the dance party, fed us freshly harvested carrots, and encouraged our generation to be the driving force of the climate movement—and, more importantly, to have fun doing it. They made the point that these days, things like smoking cigarettes or dumping gasoline into a lake are considered "socially unacceptable," but that took time. Now, it is our time to make not caring about the environment be socially unacceptable.

Was it valuable just interacting with the other kids there, from different kinds of schools? Were you learning and getting ideas from each other?

YES. The second day, there was a 2-hour poster session where all the schools displayed posters of their current "green" efforts and plans for the future. I had a chance to talk to so many different schools and share ideas about outdoors clubs, gardening problems, recycling efforts and cafeteria food. I had conversations with a high school that was having trouble even starting an environmental club due to the lack of support from administration, and on the other end of the spectrum, I talked to a school that had livestock and taught all their science classes on a farm.

We also had the amazing opportunity to Skype with Finland, where they were holding a similar youth climate summit modeled after ours in the Adirondacks. Despite the sound lag and language barrier, it was still inspiring to see that kids our age halfway around the globe are facing the same problems we are.

It looks like you guys had a lot of fun at this dance party. In your Facebook photos I observed electric guitar, someone crowdsurfing, a guy in a sailor hat juggling fire, and what appeared to be people using ropes to move a large rock. Are these the elements of a good party for the young environmentalist crowd?

I think these are the elements of any good party, actually. Moving the rock could have been a metaphor for how teamwork can move the world or something, but it was really just for the fun of moving a rock. We were told that our generation will make it through this difficult time in climate change only if we have fun in the process.

What sorts of ideas or projects did you bring back from the summit to use at school?

The second day of the summit, all the teams were given 2 hours to create their school's "Climate Action Plan" and a detailed timeline to present to the rest of the schools at the end of the day. Our team decided to focus on 4 major projects in the coming year: improving the school garden, building a bike generator for the lobby, holding a bi-annual school-wide locker clean-out to donate gently used school supplies and teach proper recycling, and finding places to cut the school's phantom energy usage (a.k.a. the wattage used by electronics when they're turned off but still plugged in).

You may not know this, but back when I was at your school I belonged to an "environmental club" too. This meant that a couple of us would go to all the classrooms after school and pull trash out of the blue bins, because otherwise the maintenance guys refused to recycle. Is it fair to say things have come a long way?

Simply put, yes. We have a recycling bin in every classroom, our cafeteria serves vegetables from a number of local farms, quarterly grades and comments are now only available online, our drinking fountains are now water-bottle filling stations, and we have a garden that brings vegetables to the salad bar. We have solar panels on one building and another LEED-qualified building, with another one in the construction phase.

I think we're also a little cooler than your environmental club, because now we are the "Green Avengers," equipped with a logo and a Facebook page.

Are you optimistic about climate change? Do you come back from an event like this feeling like you're part of a group of people who will actually make a difference, whether it's through school-level projects now, or after college as policy makers? Or are we pretty much screwed?

Both times going to the summit I came back incredibly high in motivation, but I knew if I didn't write down all my ideas and get acting quickly, I would lose my energy. Spending time around so many like-minded people definitely makes me excited to get out there and make change.

It also reminds me we have to be able to work on our own and not rely on the work of others because that's part of the attitude that brought us to this predicament in the first place. As Dr. Powers told us, even in the earth's "best-case scenario," we'll still experience rising global temperatures. It's just up to my generation to slow the acceleration of carbon dioxide emissions and provide the optimistic attitude.

Celeriac and Parsnip Soup
Yields 18-24 servings (reduce if you're not feeding a youth summit)

Ingredients:
5 pounds cubed celeriac root
5 pounds chopped parsnip
6 tablespoons olive oil
15 cups vegetable stock
1 bundle thyme
1/2 teaspoon salt
1/2 teaspoon ground black pepper

Preparation:
Preheat the over to 400°F. Toss the celeriac and parsnip with the olive oil. Arrange the vegetables in a single layer on a foil-covered baking sheet. Roast them 35-45 minutes, flipping once, until they are tender and golden brown. Combine the caramelized vegetables with the stock and other ingredients in a pot over medium-high heat. After bringing to a boil, let the soup simmer for 15 minutes. Put all the food through a blender or food processor until smooth and serve hot.

Images: The Wild Center (top); Leigh Preston (bottom).

Bees Can Smell How Much Sex Their Queen Has Had

Just because girl talk between bees is wordless doesn't mean it lacks for intimate details. When sister honey bees gather around their queen, they can tell from her pheromones whether she's mated—and how much. What they learn may determine whether they let her live.

The queen honey bee doesn't do much day-to-day ruling, but she does lay nearly every egg in the hive. Her daughters become worker bees, who keep the colony running. Pheromones that the queen and the workers emit—then spread through the hive as they touch antennae and clamber over each other's bodies—carry the signals that maintain order. Among other laws, the queen's pheromones tell workers not to lay eggs of their own.

When the queen's egg-laying prowess starts to fade, though, her workers will replace her without sentimentality. They prepare special queen egg chambers and feed royal jelly to the chosen larvae (who will battle once they emerge, leaving only one queen standing). Then the workers sting the old queen to death. "It can take up to 6 weeks for the new queen to produce a new cohort of workers," says Elina Niño, an entomologist at Pennsylvania State University. So the process harms the hive's productivity, in addition to the dispatched queen herself.

Along with colleagues at North Carolina State University (where she worked at the time) and Tel Aviv University, Niño investigated whether the queen honey bee is honest when she sends pheromone messages to her workers. If the queen could fake the pheromones that say she's in great shape, it would keep her colony loyal for longer. To find the answer, the researchers set about artificially inseminating some bees.

New queens mate just once in their lives, in a sex spree that involves lots of males (called drones). They store all that sperm and use it, a little bit at a time, to fertilize the eggs they lay for their remaining years. The scientists gathered groups of queen bees who had not yet mated with any drones. Then they simulated sex in several ways: Some queens had a needle inserted into them to mimic the physical aspect of mating. Some received actual semen (mixed from the contributions of multiple bachelor bees), in either a large or small volume. Others were pumped with a large or small volume of salt water.

Several days later, the unfortunate queens were offed. The researchers extracted the contents of two pheromone glands, one at a queen bee's mouth and the other near her stinger. Chemical analysis showed that in the pheromones from the bees' back ends, there was a difference between queens who'd been inseminated (or faux-inseminated) and those whose insides were still empty. The pheromones from the jaw gland seemed to carry even more specific information: each group of queens (inseminated for real or with salt water, holding a large or a small volume of whatever it was) had a distinct chemical signature.

But how would worker bees respond to these signals? The scientists put their pheromone extracts onto glass plates and set them down by groups of worker bees. They hoped to take advantage of a bee behavior called the "retinue," in which workers cluster around a queen while licking her and touching her with their antennae.

The worker bees treated the pheromone puddles like real queens. But not all queens were equal. The researchers saw that workers were most attracted to pheromones from queens who were full of semen, rather than salt water. They also preferred pheromones from queens with a larger volume of semen stuffed inside of them.

"Colonies headed by multiply mated queens are more productive, more resistant to diseases and more likely to overwinter successfully," Niño says. In other words, queens that have mated with lots of drones produce hives that are healthier, because they're more genetically diverse. So it would benefit worker bees to be able to sniff out their queen's sexual history and "act accordingly," Niño says. This might mean ousting a queen who hasn't gotten around much, and gambling on a new queen instead.

For beekeepers, the results add new importance to having a healthy queen. Just because a queen is laying eggs, Niño points out, doesn't mean she can keep her subjects loyal. Workers that don't like the smell of their queen's pheromones, perhaps because she hasn't mated with an adequate number of drones, may execute her. Beekeepers who want to avoid that drama should make sure their queen has plenty of partners—because when she talks to her workers about her sexual past, she won't be able to lie.


Image: by Dude-K (via Flickr)

Niño EL, Malka O, Hefetz A, Tarpy DR, & Grozinger CM (2013). Chemical Profiles of Two Pheromone Glands Are Differentially Regulated by Distinct Mating Factors in Honey Bee Queens (Apis mellifera L.). PloS one, 8 (11) PMID: 24236028

Beetles Show There Is Such Thing as a Free Lunch, and It's a Weapon Attached to Your Face

If the rhinoceros beetle were the size of an actual rhinoceros, its horn could be 16 feet long. Male beetles grow this gargantuan face-fork so they can win mates (why else?). And even though evolutionary science would predict that the beetle pays a price for this appendage, it seems to come absolutely free.

Males of many animal species wear showy accessories: antlers on deer, long tails on birds. Growing one of these accessories often comes at a cost. For example, energy spent growing one large body part may leave another body part smaller, as seems to be the case with the dung beetle's horns. Or the showy feature may make the animal more vulnerable, as in the Bahamas mosquitofish, which grows a large sperm-delivery organ to impress females but then can't swim away as quickly when chased by predators. Females benefit from being choosy, because males that can afford to spend resources on a fancy headpiece or tail demonstrate that they're hardy or have good genes.

Erin McCullough, a PhD student at the University of Montana, Missoula, and her advisor, Douglas Emlen, have been putting rhinoceros beetles through the wringer to try and find the cost they pay for their giant horns. Individual males grow horns of widely varying sizes. In the Japanese rhinoceros beetle, Trypoxylus dichotomus, horns range from a stubby 7 millimeters to a towering 32. In other species, the largest horns are 10 times the length of the smallest ones.

In a previous paper, the researchers showed that larger horns—somehow—don't hurt the rhinoceros beetle's ability to fly. Now, they measured the horns of T. dichotomus beetles and compared their size to the insects' legs, wings, eyes, and genitalia. They also tested the strength of the beetles' immune systems. And by marking beetles with paint, releasing them outdoors, and recapturing them later from the same area, the researchers assessed whether larger horns make a beetle more likely to die.

The result was a big goose egg. Nothing. If you're a rhinoceros beetle, there is apparently no trade-off to growing the biggest horn you can.

So why aren't all horns huge? Males with larger bodies are able to grow disproportionately longer horns than smaller beetles; Emlen found in an earlier study that this is tied to the beetles' insulin levels. "Males that have poor nutrition and therefore have low levels of circulating insulin simply can’t produce big horns," McCullough explains.

Still, if big horns are so great, evolution might favor males who can use their good nutrition to grow ever-larger appendages. Why is there any limit on the size of the horn? "I think the primary reason...is because they are weapons that are continuously tested in combat," McCullough says. Male rhinoceros beetles use their horns to fight each other for the best territory on tree trunks and branches. Grappling over sap-rich sites, they wield their horns like pitchforks to pry rivals loose. "So it doesn’t benefit a male at all to have a horn that’s so large that he can’t use it properly," she says.

McCullough is currently testing that idea by measuring the force needed to pry a male beetle from a tree and comparing it to the force needed to snap the beetle's horn. She thinks longer horns are at more risk of breaking, and that this may be what limits their size.

The reason rhinoceros beetles escape paying for their horns might be that they're functional, and not merely a decoration. When birds pay a price for a showy tail, it ensures that only the genetically strongest birds can give the best display to females. If unhealthy birds could cheat and grow fancy tails at no cost, females would no longer benefit from favoring good tails—so they'd stop paying attention at all, and males would stop bothering. But because there's a cost, the system works. In the case of the rhinoceros beetle, McCullough and Emlen believe cheaters are weeded out because they can't fight with their oversize horns. This means the flashy gear comes for free—as long as the beetle knows how to use it.


Erin L. McCullough, & Douglas J. Emlen (2013). Evaluating the costs of a sexually selected weapon: big horns at a small price. Animal Behaviour DOI: 10.1016/j.anbehav.2013.08.017

Image: McCullough & Emlen.

World's Ugliest Fish Jam Each Other's Mating Calls

Perhaps understandably, the male toadfish doesn't rely on his looks to attract females. He uses a bellowing, foghorn-like call to lure the ladies instead. But he'd better beware of his neighbors—nearby toadfish, a scientist has discovered, use short grunts to stealthily jam each other's signals.

In the spring, at the start of breeding season, male oyster toadfish nestle into rocks and debris on shallow seafloors in the western Atlantic. From his hidden nest, the male sends out his tuba blasts. A female who hears something she likes comes to the nest and glues down her eggs. Then she leaves the homely male to fertilize the eggs and guard the young till they're grown.

The breeding season stretches to the beginning of fall, and during this time male oyster toadfish have been observed grunting as often as 200 times an hour. When sending out their signature mating calls, neighboring males alternate with each other so as to be heard more clearly. But more often, they make quick little grunts that do overlap with others' calls.

To find out why toadfish interrupt each other like this, biologist Allen Mensinger of the University of Minnesota, Duluth, gathered a small group of male toadfish in an artificial pond. The pond was lined with underwater microphones to capture the fishes' calls. Bricks and concrete slabs were stacked into simple shelters on the bottom of the pond. After a couple days in their new home, the oysterfish agreeably moved into their "nests" and started calling out for females. (Those, however, were lacking.)

Each toadfish that Mensigner recorded had a distinct "fundamental frequency" (the lowest note it produced) to its mating call. In other words, each fish called with its own voice. But out of the thousands of recorded toadfish sounds that Mensigner analyzed, the majority were short grunts that interrupted other fishes' calls. And when a grunt overlapped with another toadfish's mating call, that call's fundamental frequency—its voice—was altered.

Mensinger thinks the grunts essentially jam the signals from the bellowing toadfish. In this way, interrupting toadfish might make their neighbors' carefully tuned calls less attractive to listening females.

The interrupting fish time their quick grunts to end before their neighbors' mating calls do. Mensinger thinks this protects the interrupters from being detected. Don't worry too much for the toadfish, though—despite their apparent gamesmanship, a few males managed to breed successfully when Mensinger threw some female fish into the artificial pond later in the season.

To hear the oyster toadfish in all his uninterrupted beauty, click here.


Image: by EricksonSmith (via Flickr)

Allen Mensinger (2013). Disruptive communication: Stealth signaling in the toadfish. Journal of Experimental Biology DOI: 10.1242/jeb.090316

Fish Evolve Stabbier Genitals When Predators Are Near

Like sock garters and homburg hats, the equipment used by our great-grandparents doesn't always cut it for later generations. Certain male fish have evolved differently shaped genitals depending on what other fish share their caves. Attracting females, though, doesn't seem to be as important as not getting eaten.

Most fish reproduce simply by scattering a lot of of eggs and sperm around their environment. But a few types of fish are "livebearers": their eggs are fertilized and hatched inside the female's body, then come swimming out as fully formed miniature fish. Many sharks bear live young. So does Gambusia hubbsi, the Bahamas mosquitofish.

The main difficulty of reproducing this way—at least, the main difficulty from a male perspective—is getting the sperm inside the female's body. You can't just leave it around the ocean and hope for the best. Males in the mosquitofish's family solve this problem with an organ called a gonopodium. The body part's overall size is subject to a couple of different evolutionary pressures: Females of some species prefer a larger gonopodium. But carrying around the bigger organ slows males down when they're trying to escape predators.

Justa Heinen-Kay and R. Brian Langerhans at North Carolina State University were curious about just one part of the gonopodium. The tip is tiny but weapon-like: about one millimeter long, it carries bony hooks, spines, and teeth. It's not big enough slow males down while swimming, or visible enough for females to judge it. Yet the authors wondered whether other evolutionary pressures might be acting on this spiky little body part.

The researchers collected mosquitofish from water-filled, vertical caves in the Bahamas called blue holes. Certain populations of mosquitofish live in caves that also contain their predator Gobiomorus dormitor, the bigmouth sleeper. Other populations live with few predators, and can swim and mate—a process that may or may not involve female cooperation—without the threat of being eaten.

Comparing mosquitofish from 10 caves with predatory bigmouth sleepers and 12 caves without them, Heinen-Kay and Langerhans saw that the fish had evolved different genital shapes. Male mosquitofish that lived with a lot of predators had longer tips on their gonopodia, and those tips were more densely covered in bony bits.

This sturdier, stabbier tip may help a male to work more quickly and efficiently, whether or not the female wants him to. The authors speculate that when predators are nearby and time is short, this genital shape is an advantage. Bony hooks "may serve as holdfast devices," and a longer shape might get sperm farther inside the female while pushing out anything competitors have left behind. But in caves without predators, they add delicately, "males may rely more on cooperation and less on genital shape."

However it helps, modifying the shape of their genitals must be a powerful tool for mosquitofish. Over and over again, fish populations living with predators have evolved in the same way. It's a trend that's here to stay—despite what their ancestors might think.


J. L. HEINEN-KAY, & R. B. LANGERHANS (2013). Predation-associated divergence of male genital morphology in a livebearing fish. Journal of Evolutionary Biology DOI: 10.1111/jeb.12229

Image: Heinen-Kay and Langerhans.

Coloring In Birds' Bellies with Magic Marker Makes Them Healthier

Remember when you were a kid and the magic marker boxes always had some sort of really elaborate drawing on the back? As if to say, "Buy these eight wide-tip Mr. Sketches and you, too, will be able to create a photorealistic portrait of a scarlet macaw"? But when you bought the markers and tried to copy the picture, it always came out as a stupid magic marker bird? You might have gotten more realistic results by coloring directly on a real animal. Some scientists tried this, and changed the birds' entire quality of life.

In North American barn swallows (Hirundo rustica erythrogaster), males and females with darker-tinted bellies are able to have more young. But they don't get their tan tummies by lying in a UV bed. The birds develop their color months before the breeding season starts, and it depends on both genetics and their health at the time.

Biologists call dark bellies on barn swallows an "ornament," like long tails or showy sets of antlers in other species. These traits may not serve a practical purpose, but they can advertise to potential mates how healthy or hardy the animal lugging that long tail around is.

Ecologist Maren Vitousek at the University of Colorado, Boulder, and her colleagues wanted to know whether barn swallows' ornamental belly feathers could also work in the other direction. A bird's health or fitness affects the color of the feathers—but can the color of the feathers also affect the bird's health?

The researchers captured 60 female barn swallows in Colorado, shortly before the time of year when the birds would be pairing off with mates. Using marker, they colored in the entire belly area of half the birds. The shade—PrismaColor light walnut no. 3507—was within the natural range of hues for barn swallows. Then the scientists sent the newly made-over birds back out into the world.

About a week later, the scientists began to recapture the birds. (They found 36 out of the original 60.) Ordinary, uncolored birds had higher levels of oxidative damage in their blood than when they were first captured. Their bodies had been under stress. But birds with darkened feathers actually had less oxidative damage than before.

Vitousek, who's now at Cornell University, thinks coloring in female birds' belly feathers made their lives easier. "Darker plumage may signal social status in barn swallows," as it does in some similar birds, she says. If so, other birds may have judged their tanned peers to be of higher status, and possibly more likely to win a fight. "As a result, they may be challenged less," she says.

Even though birds or other animals sometimes develop their showy traits well before the mating season, this kind of feedback loop would let these traits remain honest signals of how healthy an animal is. Fitter birds make darker feathers, and darker feathers seem to keep birds healthier by sparing them harassment. "What we are finding is that the appearance of an individual alone can also influence physiological state—and probably fitness—by changing social interactions," Vitousek says.

And all it takes to change a bird's social status is a quick pass with magic marker. Maybe it can be a post-retirement hobby for that Mr. Sketch package artist.


Maren N. Vitousek, Rosemary A. Stewart, & Rebecca J. Safran (2013). Female plumage colour influences seasonal oxidative damage and testosterone profiles in a songbird. Biology Letters DOI: 10.1098/rsbl.2013.0539

Image: by Walter Siegmund (via Wikimedia Commons)

This post has been submitted to the 2013 blog contest held by the National Evolutionary Synthesis Center (NESCent).

For Diguise, Female Squid Turn On Fake Testes

The best way to stay out of trouble, if you're a shimmery, color-changing little squid, might be to paint on some pretend testes. Scientists have found that certain female squid can switch on and off a body pattern that makes them look male. They use a never-before-seen cell type to do it, and it may be all for the sake of keeping the actual testes owners far away.

The opalescent inshore squid, Doryteuthis opalescens, lives in the Eastern Pacific and is one of the main species caught for food in the United States. So you'd think someone would have noticed its trick before. But the animals shift their colors all the time, and no one seems to have paid much attention to a certain bright stripe particular to females.

Daniel DeMartini, a graduate student at the University of California, Santa Barbara, "observed the female squid rapidly switching the stripe on and off," says his advisor, Daniel Morse. He decided to gather a few hundred D. opalescens squid in laboratory tanks and watch them work.

DeMartini found that females can opt to turn on a bright white stripe on their mantles, highlighted by a line of iridescence on both sides. This happens to look pretty similar to a male squid's testis, which—in his less colorful moments—is visible as a long white shape inside his transparent body.

The authors speculate that female squid might use this stripe as a disguise when they want to avoid harassment by males. "In this species of squid, mating occurs in dense assemblages of animals, with the females subject to repeated bouts of mating by multiple males," Morse says. By switching on her white stripe and mimicking a male, a lady squid might be able to fend off some of these mating attempts, protecting both herself and any fertilized eggs she's carrying.

Morse is less excited about this act of deception, though, than he is about the cells that squid use to pull it off. Within the white stripe region, specialized cells hold proteins called reflectins inside many spherical packages. These proteins start out colorless. Upon receiving a signal from the brain, the packages shrink into dense blobs. The varying sizes of the blobs make them reflect all different wavelengths of light, so that the cells as a whole appear bright white. It's the same way we humans make white paint, Morse says: small, dense particles of titanium dioxide are suspended in the liquid, and the combination of different-sized particles ensures all light waves are reflected at once.

Earlier, the authors found reflectins in the same squid's color-changing cells. Instead of turning from transparent to white, these cells can move between many different colors. In this case, "the reflectins are packed in accordion-like folds or pleats in the cell membrane," Morse says. When the brain tells the proteins to clump together, the accordion folds close up—and depending how far they close, the cells will reflect different wavelengths of light, from red all the way to blue.

It's fitting that squid have ten arms, because this one seems to have a surprise up every sleeve. As to whether it's still hiding anything more surprising than fake testes, we'll have to wait and see.


Daniel G. DeMartini, Amitabh Ghoshal, Erica Pandolfi, Aaron T. Weaver, Mary Baum, & Daniel E. Morse (2013). Dynamic biophotonics: female squid exhibit sexually dimorphic tunable leucophores and iridocytes. Journal of Experimental Biology : 10.1242/​jeb.090415

Images: DeMartini et al. (Top: a close-up view of an iridescent stripe in a female.)

Male Frogs Grip Mates with Pheromone-Injecting Thumb Spikes

There's nothing subtle about the wooing of European common frogs. Males grow spiny pads on their thumbs during the breeding season, the better to grip their mates. As if that weren't enough, the pads also seem to channel pheromones out of a frog's hands and straight into his female partner's body.

Frogs fertilize their eggs out in the open, so you might think there'd be no need for all this effort. Yet males of most frog species can be seen during the mating season "taking a piggyback ride" on their mates, as a group of scientists in Belgium euphemistically puts it. Technically called amplexus, the male-on-top position allows him to fertilize the eggs just as the female sends them out of her body.

In some frog and salamander species, males further ensure their success by temporarily growing tough, often spiky pads on their forearms or thumbs. Earlier research discovered glands of some sort sitting beneath these pads, but it wasn't clear what the glands did. So the scientists in Belgium decided to take a closer look at the hands of one such animal: Rana temporaria, the European common frog.

The scientists used micro-CT scanning to build a 3D image of a male frog's thumb pad. They saw that glands underneath the pad led to ducts, which traveled up through the pad to pores on its surface. It appeared that the grippy gloves donned by males for the mating season were also some sort of delivery system.

But what were they delivering? An analysis of proteins in the glands turned up a group of molecules the authors dubbed "amplexins." They're in the same family as certain proteins found in male mammals' reproductive organs, as well as a courtship pheromone in salamanders. In humans, proteins from this family help regulate how eggs and sperm interact.

Comparing thumb pads in the breeding season to shrunken-back thumb pads during the rest of the year, the scientists saw that amplexin production suddenly dropped off near the end of the breeding season. During the rest of the year, the frogs didn't make amplexins at all.

A male who's already got his hooks—literally—into his partner probably doesn't need to worry about courtship. But the authors speculate that amplexins in these frogs might be pheromones that speed up the mating process. Female frogs' chests are often scraped and scratched by their mates' spiny thumb pads, and this may be how a male delivers the pheromones to his partner: straight into her circulatory system.

Hey, it works for Cupid and his arrows. Female frogs, though, would probably give this system two thumbs down.


Image: by Erik Paterson (via Flickr)

Bert Willaert, Franky Bossuyt, Sunita Janssenswillen, Dominique Adriaens, Geert Baggerman, Severine Matthijs, Elin Pauwels, Paul Proost, Arent Raepsaet, Liliane Schoofs, Gwij Stegen, Dag Treer, Luc Van Hoorebeke, Wim Vandebergh, & Ines Van Bocxlaer (2013). Frog nuptial pads secrete mating season-specific proteins related to salamander pheromones Journal of Experimental Biology DOI: 10.1242/jeb.086363

Multitaskers Make the Best Lovers, Say Tree Frogs

It's not an impossible demand. It's just that a male tree frog can choose to spend his energy doing one thing or another thing, and females prefer that he does more of both. The best multitasker might be allowed to fertilize her eggs.

"The males gather in ponds in the evening and begin to call," says University of Minnesota ecologist Jessica Ward, setting the scene. The species in question is called Cope's gray tree frog. Next, she says, females come to the pond and spend a few minutes listening to nearby males. Then they choose for mates the ones whose calls they find most attractive.

What's attractive? There are a couple of ways a Cope's gray tree frog can make his song stand out from others in a chorus. The frogs can increase the speed of their calls, making more trills per minute. Or they might make each one of those trills last longer.

Ward and her colleagues set out to test whether male frogs can only devote energy to one of these factors at a time. And, they asked, are females more attracted to "multitaskers" who can manage both at once?

By haunting parks in the middle of the night with recording equipment, the researchers captured a thousand total calls from 50 different frogs. They found that males who called more often made shorter calls, and those who called less often made longer calls. In other words, there's a trade-off: when a frog puts more energy into one aspect of his song, he has to skimp elsewhere.

Next, the researchers interrupted male and female frogs that were already clasped together to do the deed and carried them back to the lab. The females were put into sound chambers, where they heard two different male frog songs at a time and could choose one to approach. The artificially generated songs had varying call lengths and speeds. Female frogs, it turned out, preferred the songs that had the best combination of long and frequent calls: the more male effort a song would have required, the more a female liked it.

Male frogs, meanwhile, were put into a kind of competition. They sat in a sound chamber and trilled away first on their own, then while hearing the sound of other frogs singing. Males adjusted their own songs when their neighbors were singing at the same time, making each call longer. But they also called less frequently, so the total amount of effort they put into each call stayed the same.

Males may already be expending almost all the effort they can to sing, Wade says. She thinks males who can make their calls faster and longer at the same time are somehow more fit than others. A study in a related species showed that frogs who put more effort into their calls were better swimmers, for example. So females may be onto something when they choose the male with the most difficult song to father their eggs.

This type of multitasking, where a tradeoff exists between different aspects of an animal's performance, has also been studied in birds. Wade says this is the first multitasking study in frogs. Though it's tempting to imagine humans caught in our own version of this trap—asked to attend to an impossible number of factors at once to be maximally attractive—Wade thinks of a different species next. "The multitasking hypothesis may also apply to some spiders," she says.


Image: Cope's gray treefrog by Geoff Gallice (via Flickr)

Jessica L. Ward, Elliot K. Love, Alejandro Vélez, Nathan P. Buerkle, Lisa R. O'Bryan, & Mark A. Bee (2013). Multitasking males and multiplicative females: dynamic signalling and receiver preferences in Cope's grey treefrog Animal Behaviour, 86 (2), 231-243 DOI: 10.1016/j.anbehav.2013.05.016

Gibbon Moms Help Daughters Practice Their Singing for Future Mates

Before their daughters grow up and leave home, mothers may impart some lessons in the womanly arts—for example, the proper way to whoop and hoot with your mate while sitting in a tree branch. As an adult, a female gibbon sings elaborate duets with her male partner. But before she leaves the family, her mother seems to take responsibility for the daughter's vocal lessons.

Young gibbons spend many years learning to vocalize like adults. By age six or so, "sub-adult" apes can match the vocal prowess of a grownup. Mothers and daughters often sing at the same time, though it's not clear why. Researchers traveled into the rainforests of Sumatra to make audio recordings of gibbon families and try to figure out whether these sing-alongs are significant.

Lead author Hiroki Koda of Kyoto University and his colleagues studied six families of agile gibbons (that's a species name, not just a descriptor). Koda explains that gibbons are monogamous, and male and female young grow up with their parents before departing the group to find their own partners. Each family in the study included a nearly adult daughter, and the researchers captured recordings of these daughters and their mothers singing together.

They found that some daughter gibbons were better than others at singing in sync with their mothers. They were also better at matching their mothers' tunes. But these talented daughters actually duetted with their mothers less often. Koda thinks that's because the ones who "showed more skillful songs" are the most mature, and are nearly ready to leave home. Daughters who still need the practice sing with their mothers more often.

Here, a mother and daughter gibbon match each other's calls as they sing together:

The researchers also found that mothers who sing more often with their daughters—the ones who are still giving lessons—modify their own songs more when they do so. Koda says this may be similar to the "motherese" that humans speak to their babies. Like human moms talking slowly and at a high pitch, gibbon moms alter their vocalizations when duetting with their daughters.

Koda says that in the past, primate calls have been seen as "completely different from human language development." Rather than learning from their parents, young monkeys and apes seem to figure out their calls on their own. But this is the first evidence of mothers helping offspring learn to vocalize in gibbons—or any other nonhuman primate.

By paying more attention to vocal interactions between parents and offspring, Koda thinks scientists might discover other examples of primate parents getting involved in their children's learning. (After that, maybe they'll discover primate parents getting too involved. "Don't you take that tone with me, young lady! I heard what you just hooted!")

Images: Top, singing gibbon by patries71, via Flickr (not, as far as I know, the study species). Bottom, a mother gibbon from the study by Hiroki Koda.

Hiroki Koda, Alban Lemasson, Chisako Oyakawa, Rizaldi, Joko Pamungkas, & Nobuo Masataka (2013). Possible Role of Mother-Daughter Vocal Interactions on the Development of Species-Specific Song in Gibbons PLOS ONE DOI: 10.1371/journal.pone.0071432

Tone-Deaf Birds Disrupt Society, Are Easier to Get into Bed

While male birds are singing elaborate arias and flashing their feathers, it's easy to imagine their female counterparts are unimportant actors. Duller and quieter, all a lady bird has to do is hold still and let one of these frantic performers mate with her. Yet in brown-headed cowbirds, at least, the quiet female keeps the whole society in order. Scientists discovered this by targeting a tiny portion of the female brain and frying it.

Males of the species Molothrus ater use their songs to compete with each other and to woo females. Once a a mating pair forms, they stay faithful to each other for the whole mating season, the male guarding his partner from rivals.

Near the top of the bird brain, a region called nucleus HVC controls females' choosiness toward their potential mates. Scientists at the University of Pennsylvania and Wilfrid Laurier University performed brain surgery on female cowbirds, carefully destroying only this region. Then they put their lobotomized females back into the dating arena to see what would happen.

First, the ladies listened to recordings of male songs. The researchers played tunes sung by a variety of males and observed the females' responses. (When they like what they hear, female cowbirds show it by crouching down in a copulation-ready pose.)

Normal females were choosy, only responding to the highest-quality male songs. Females who'd had brain surgery, though, responded positively to every song.

The researchers wanted to see what effect the females' new, lax attitude would have in cowbird society. So they put post-surgery females, normal females, and males in one big group together. Then they watched.

At first, it looked like nothing was different. Females missing their HVC seemed to act the same as females with intact brains; once they were all together in the aviary, there was no clear difference in how often females approached male birds or in how they "chattered" back at males to encourage their singing.

Nevertheless, something had changed. The other birds in the aviary treated post-surgery females differently. For one thing, females missing their HVC were serenaded by a greater variety of males, even once they'd chosen a mate. Normally, a female who's bonded with a male hears his song almost exclusively. This is a measure of how strong the bond between partners is, says study author David White. Now, with more males bending a female's ear, her pair bond was weaker.

There were other changes too. With the altered females introduced into the group, female birds competed more for mates. And the whole hierarchy of male birds, which is established before the breeding season starts, was disrupted. Male cowbirds sing at each other to show who's dominant. After the HVC-less females came to live with them, the rules about which males were dominant singers shifted significantly.

"The result in this paper turned everything around for us," White says.

Previously, it had seemed to be the male cowbird's responsibility to create a strong bond with his partner. Females appeared to be passive agents in the group. "They don't sing, they don't fight," White says. "They don't, to our eye, do much of anything." Yet when the choosiness was erased from females' brains, the whole group dynamic changed. "Now we could see that it was the female that was playing a much more active role in pair-bonding, and in all sorts of other roles within the social network," White says. Everything depended on her song preferences.

Incidentally, it's not clear why female cowbirds bond with males at all.

Females have likely evolved to pick mates whose songs demonstrate—somehow—that they have the best genes. Then the males keep singing to the females throughout the breeding season, strengthening the bond between them.

Usually, White says, bird couples only form strong bonds when both parents will need to care for the young. But cowbirds "are very bad parents overall" who abandon their eggs in the nests of other birds. The powerful bond between cowbird partners "really makes no sense," White says.

Yet once they're bonded, males direct almost all their singing to their partner and never try to mate with other birds. "They follow each other around, they eat together, he comes when she calls him," White says. If a female dies or disappears, he adds, "her pairmate just becomes a wreck. We call it the widowed male phenomenon."

After the loss of his mate, the male gives up for the season. "He flies around looking for her," White says. To him, at least, the quiet female never seemed unimportant.


Maguire, S., Schmidt, M., & White, D. (2013). Social Brains in Context: Lesions Targeted to the Song Control System in Female Cowbirds Affect Their Social Network PLoS ONE, 8 (5) DOI: 10.1371/journal.pone.0063239

Image: female brown-headed cowbird by JanetandPhil (via Flickr)

Scientists Unsure Why Female Flies Expel Sperm and Eat It

She's apparently a picky mater but not a picky eater. The female of a certain fly species, after mating with a male, dumps his ejaculate back out of her body and onto the ground. Then she gobbles it up. Despite new hints that this behavior may help the female choose which partner fertilizes her eggs, or keep her healthy in times of famine, scientists are still a little perplexed by it.

Various female insects, spiders, and birds are known to expel the male ejaculate from their bodies after the deed is done. In some cases, it seems to let them decide which male's sperm reaches their eggs. Females don't always choose who mates with them, but that doesn't mean they have no choice in their progeny's fatherhood. (This kind of female choosiness about sperm can lead to evolutionary arms races between males and females. The "copulatory plug" is a popular tool among male insects, spiders, reptiles, and even some mammals.)

Eating the ejaculate, as Euxesta bilimeki does, is less popular. This fly lives on agave plants and mates pretty much all the time. "Females can be observed escaping male advances in chases that can last more than an hour," write Christian Luis Rodriguez-Enriquez and his coauthors from the Instituto de Ecología in Veracruz, Mexico. Using videocameras and careful meal planning, they tried to divine a reason for the female flies' behavior.

Out of 74 females that the researchers recorded mating, every one expelled and ate the ejaculate afterward. The researchers then killed the females and pulled them apart with tweezers to look for sperm inside their various storage locations. They found that three-quarters of the females had kept some sperm from their male partner, while one-quarter had expelled it all.

There was no obvious rule to which sperm the females kept. There were some patterns, though. For example, females that mated with larger males, then waited longer before expelling the sperm, were more likely to keep some. Since the female's behavior doesn't seem random—and since it's possible for her to keep no sperm at all—the authors think she may be choosing between mates after the fact.

This could explain why the female expels the sperm, but not why she eats it. In another experiment, researchers fed female flies various diets and measured whether supplementing those diets with ejaculate made them healthier. When female flies were starved entirely, the extra snack did help them live longer—but under normal circumstances there was no difference. The authors report their results in Behavioral Ecology and Sociobiology.

"Our study appears to have raised more questions than provided answers," the authors admit. They expected there would be some clear nutritional benefit to justify the females' tastes.

Rodriguez-Enriquez and his coauthors speculate that the ejaculate-as-meal habit may have evolved as a "nuptial gift." This is an edible present that male insects sometimes give to females as part of their courtship. Usually it's nutritious—a nicely wrapped dead bug, say—but in some cases it's just an empty sac. The ejaculate may be, like these gifts, just an edible empty gesture.

(The above is a video of Euxesta bilimeki flies mating. It doesn't look any different from what you're imagining, but the soundtrack is a nice twist.)

Rodriguez-Enriquez, C., Tadeo, E., & Rull, J. (2013). Elucidating the function of ejaculate expulsion and consumption after copulation by female Euxesta bilimeki Behavioral Ecology and Sociobiology DOI: 10.1007/s00265-013-1518-5

Image and video: Rodriguez-Enriquez et al.

Need the Time? Ask a Rooster

"The connection with the sun coming up is a misconception," asserts an article in the rural lifestyle magazine Grit. "Roosters crow all the time." Some roosters in Japan would like to loudly disagree. They've shown scientists that their crowing has everything to do with what time of day it is—something they don't even need the sun to know.

Tsuyoshi Shimmura and Takashi Yoshimura, both of Nagoya University in Japan, investigated whether a rooster's crowing is tied to its circadian clock. That is, does the bird's internal sense of night and day determine when it's noisiest? Or do roosters crow at random hours—"morning, noon and night, not to mention afternoon, evening and the parts of the day that don’t have names," according to a disgruntled neighbor-to-roosters quoted in the Grit story?

Like any scientists studying how animals follow the sun's rhythms, the researchers began by shutting their subjects indoors. In a controlled environment, they kept the roosters on a strict schedule of 12 hours in the light and 12 hours in the dark.

Recordings showed that the roosters did not crow at random. A sudden burst of crowing came two hours before the artificial dawn, and the birds gave another "cock-a-doodle-doo" immediately after the lights came on. (Though in their country, the authors point out, it's "ko-ke-kok-koh.")

Then the scientists turned the lights out entirely, keeping the birds in a permanent night. The roosters at first continued to follow crowing cycles of roughly 24 hours, with only their internal clocks keeping them on schedule. Over the course of two lightless weeks, this rhythm gradually wound down.

In the barnyard, though roosters need their circadian alarm clocks for any pre-dawn crows, they can rely on other cues to trigger their crowing at sunrise—say, the sun. So Shimmura and Yoshimura next checked whether light itself causes crowing.

Starting with roosters that were living in permanent night, they tried exposing the birds to a little bit of light at the dawn hour. A few of the roosters crowed. When the researchers used brighter and brighter light, more and more of the birds crowed in response, as if recognizing the sun. A sound recording of other roosters crowing also worked to set their birds off.

Yet just flipping on the lights wasn't enough to make a benighted bird start crowing. When the light and sound signals came at "dawn," the roosters readily responded. When researchers used the same signals later in the "day," their birds didn't respond as strongly. And when they tried the signals at "night," the roosters didn't crow at all.

Even though they were living in permanent dark, roosters weren't fooled by seeing a fake sun at any old time. To get them crowing in earnest, the signals of sunrise had to come at the same time that the birds' bodily alarm clocks rang.

Roosters seem to be expert timekeepers. This knowledge, though, may not make come as much consolation to their neighbors.


Shimmura, T., & Yoshimura, T. (2013). Circadian clock determines the timing of rooster crowing Current Biology, 23 (6) DOI: 10.1016/j.cub.2013.02.015

Image: by -JvL- (Flickr)