Schrödinger's Turtle: How Observing Ocean Animals Can Harm Them

We rely on roving ocean creatures to fetch us all kinds of data we couldn't get otherwise. Carrying cameras or GPS units or sensors glued to their bodies, marine animals collect data for human scientists about the health of ocean ecosystems or how their own species migrate. Yet lugging our equipment through the sea may be harder for these creatures than we realize. By tagging them, we might be slowing down or even harming the same species we're trying to preserve.

When scientists tag birds, the authors of a new paper in the journal Methods in Ecology and Evolution explain, they follow the "five percent rule": any transmitters they attach to a bird must be less than five percent of its body mass. This ensures the animal can still take off and fly without trouble. But underwater, heaviness doesn't matter as much. Everything gets a boost from buoyancy. What matters more, the authors say, is drag.

To study how drag from tags affects marine animals, NOAA scientist T. Todd Jones and his coauthors put turtles into a wind tunnel. They chose turtles because they're popular—more than 50 published studies per year involve sticking some kind of device to a turtle. Some sea turtle species migrate across entire oceans, so they may carry these devices for hundreds or thousands of miles. And most are endangered.

Instead of propping up live endangered animals inside their wind tunnel, the researchers built fiberglass models. These were casts of 11 types of turtle bodies, minus the front flippers, made from frozen or stuffed carcasses. (The carcasses themselves were too heavy to mount in the wind tunnel.) The researchers also compared a fiberglass cast to a real turtle carcass in water, to make sure the shell materials themselves didn't cause different amounts of drag.

Turtles, of course, don't fly. "Air and water are both fluids," Jones explains; by matching the Reynolds number—a measurement representing turbulence—of the wind to that of water, the scientists could simulate a swimming turtle. Wind speeds of 8 to 20 meters per second corresponded to turtle swimming speeds of 0.5 to 1.3 meters per second.

Attaching seven different kinds of tags to their fake turtles, the researchers saw that most devices increased drag on adult turtles by 5% or less. With a young turtle and a bulky tag, though, it's possible to double the normal drag on the animal. The authors provide charts that other scientists can use to estimate how much drag they're adding to a turtle, based on the animal's size and species as well as the size and shape of their equipment.

It's nearly impossible to tell how tagging equipment affects animals in real life, thanks to a Schrödinger's-turtle paradox: we can't follow the long-term activities of ocean animals that aren't tagged in some way, so we can only compare tagged animals to other tagged animals. However, Jones worries that putting a lot of extra drag—or even a little extra drag—on an animal like a sea turtle could be harmful. These species may burn through every last bit of their energy as they make long-distance migrations, so any extra burden could hurt their odds of surviving and reproducing. (The added brake on their swimming speed might also make them more vulnerable to predators.)

"By following our guidelines, researchers can minimize the drag effects to their study organism," Jones says. This should help keep animals as safe as possible, and keep scientists' results in line with natural conditions for the animals. "However," Jones adds, "sometimes the guidelines will suggest that a certain tag simply should not be used on a particular animal."

Since sea turtles sometimes carry barnacles on their shells, which also add drag, Jones recommends that researchers take the time to pry off a few barnacles while they're gluing on equipment. That way they can make up for some of the extra burden on the turtle, and perhaps alleviate their own guilt about replacing one pest with another.


T. Todd Jones, Kyle S. Van Houtan, Brian L. Bostrom, Peter Ostafichuk, JonMikkelsen, EmreTezcan, Michael Carey, Brittany Imlach, & Jeffrey A. Seminoff (2013). Calculating the ecological impacts of animal-borne instruments on aquatic organisms. Methods in Ecology and Evolution DOI: 10.1111/2041-210X.12109

Images: top, USGS/photo by Kristen Hart; middle, T. Todd Jones.

What Left-Handed Ultimate Fighters Tell Us (or Not) About Evolution

Don't despair, left-handers who have just smeared the ink across your paper yet again. You have a true purpose in life, some scientists say—and it's walloping other people in the head. A flying elbow drop would work too. Researchers recently pored over video of hundreds of UFC fights to test the idea that lefties evolved with an edge in hand-to-hand combat.

Various other animals show a preference for one paw, or one swimming direction, over the other. But humans are notable for almost always preferring the right side. Only about 10 or 12 percent of us are lefties. Is this because there's a cost to being a left-handed human (aside from the ink thing)? Lefties are smaller in stature, and there's some evidence that they don't live as long. If these effects really add up to a raw evolutionary deal, perhaps the reason there are any lefties is that there's some advantage too.

Enter the so-called fighting hypothesis, which says that lefties have persisted at low numbers because they have the element of surprise in a fight.

In order for this theory to make sense, you have to imagine that sometime after our ancestors came down from the trees but before they built weapons, punching each other became very important to their survival. And that despite our squishy outer coverings, valuable dextrous hands, and vulnerable heads, we are a species built for combat. It's a speculative theory. A recent review paper about the fighting hypothesis—which shared an author with the current paper—called evidence for the idea "not particularly strong."

Nevertheless, a group of researchers in the Netherlands chose to explore the theory using mixed martial arts fighters. The UFC "seemed like a very interesting arena to test this hypothesis," says lead author Thomas Pollet, "pun intended." Pollet is a psychologist at VU University Amsterdam. Since the UFC is "a fierce fighting sport hardly constrained by rules," the authors write, it might be a good representation of humans scrapping in an ancestral state.

Pollet studies handedness but didn't have a particular interest in the Ultimate Fighting Championship when he began the study. To get perspective from a fan, I wrote to my friend Ryan, who happens to love watching MMA fighting. He's also a lefty. "A left-handed fighter will lead with their right foot, jab with their right, and cross with their left," Ryan explained. This is all unexpected to an opponent who mainly fights righties. "The speedy jab will come from the opposite side, and the lefty fighter will naturally circle the ring in the opposite direction as well."

Studying recordings of 210 UFC fights, Pollet found that lefties were significantly more common than in the general population. More than 20 percent of the 246 fighters were left-handed. (You can tell by checking their feet; the back leg corresponds to the dominant hand. "UFC fighters only rarely switch between stances within or between fights unless their lead leg is...severely injured," the authors write.)

To look for a left-handed advantage, Pollet analyzed all the fights between a lefty and a righty. The results were an exact tie. A computer simulation in which the fighters' handedness was randomized led to the same conclusion: left-handers had no advantage over righties.

This alone might not disprove the fighting hypothesis. That's because the UFC represents the cream of the lawless-brawling crop. "A fighter must go through a minor league promotion in their home town before making it to the big stage," Ryan told me. On their way to the professional level, left-handed fighters might have an advantage, which would explain why there are so many of them in the UFC. But once they become more common—and face more opponents who are experienced at fighting lefties—their edge might disappear.

"I think it is a very attractive hypothesis," Pollet says. The advantage of being left-handed in a fight may depend on how many other lefties are around, but "testing frequency dependence can be hard," he says. He's hoping to compare results in the UFC to other competitions that include more amateurs.

Currently, Pollet and his colleagues are working on a meta-analysis of lefties in different sports. In tennis, for example, being left-handed can give players a boost. (My friend Ryan, who just happens to also play tennis, said that being a lefty gave him "a great advantage growing up." A lefty cross-court forehand shot, he explained, forces your right-handed opponent to return the ball with a weaker backhand.)

In addition to the UFC, left-handedness is especially common among badminton players, cricketers, and recent U.S. presidents. Maybe lefties can look to those areas to find their evolutionary reason for being. If they still feel existential angst, they can always go out and punch someone.


Image: by Krajten (via Wikimedia Commons)

Thomas V. Pollet, Gert Stulp, & Ton G.G. Groothuis (2013). Born to win? Testing the fighting hypothesis in realistic fights: left-handedness in the Ultimate Fighting Championship. Animal Behaviour DOI: 10.1016/j.anbehav.2013.07.026

Thanks to Ryan Sponseller for his thoughtful comments on handedness and punching dudes.

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.

Snoozing on the Weekend Won't Undo Workweek Sleep Loss

Does your workweek schedule dig you into an ever-deepening hole of sleep deprivation? Do you sleep in on the weekends to try to boost yourself back out? You're in good company. But even if you feel recovered by the following week, your brainpower might be suffering.

In a survey by the National Sleep Foundation, 40 percent of respondents said they try to "catch up" on sleep during the weekend. Pennsylvania State University professor and physician Alexandros Vgontzas, along with a group of colleagues, recruited 30 subjects to study how well this catching up really works. The subjects were healthy men and women between 18 and 34 (who didn't mind the prospect of sleeping with a catheter in their arm).

For two weeks before the study, researchers made sure subjects got 7.5 to 8 hours of sleep every night. Then the subjects came into the sleep lab. The experiment began with three "baseline" nights of 8 hours' sleep. For the next five nights, their sleep was restricted to just 6 hours, mimicking a full workweek of uncomfortably early rising. Then subjects had two "recovery" nights where they were left sleeping for 10 hours.

During most days of the experiment, subjects were allowed to go home and follow their normal routine—though monitors on their wrists made sure they followed strict no-napping instructions. At night, they returned to the lab. And after each phase of the experiment, subjects spent a full 24 hours undergoing tests: researchers tracked the levels of hormones circulating in their blood and gave them cognitive tests. They also asked subjects to rate how sleepy they felt. To measure their actual sleepiness, researchers had subjects lie down to nap, recorded how long it took them to conk out, and woke them up again—six times a day.

Predictably, subjects were sleepier during their week of sleep deprivation. It took them less time to fall asleep during the day, and the easiest time for them to nap was 9:00 in the morning (as opposed to 3:00 in the afternoon during the baseline period). After their two recovery days, subjects' sleepiness returned to normal.

One hormone the scientists monitored was IL-6, a marker of inflammation in the body. They found that IL-6 increased when subjects lost sleep. This fits with what earlier studies have found, and suggests one way sleep deprivation is bad for your health. IL-6 levels dropped back to normal after the two nights of recovery sleep.

The only measurement that didn't go back to normal was performance on a test called the psychomotor vigilance task (PVT). Subjects did this test every two hours during their lab days. In it, they watched a screen for ten minutes and pressed a button every time a certain number appeared. It's a test that measures a person's ability to sustain attention; astronauts on the International Space Station do a similar test on themselves to check for fatigue.

Subjects in the sleep study did worse on the PVT after their sleep-deprived week, and continued to do poorly even after two nights of catch-up sleep. Vgontzas says he doesn't know why this is. But apparently some function in people's brains hadn't recovered fully by the end of the experiment, even though they felt well rested.

It's worth noting that because there was a 24-hour testing period after each stage of the experiment, subjects actually had a sixth night of poor sleep before their "weekend." And some champion snooze-button users can sleep well past 10 hours on their real makeup days. Still, Vgontzas's findings suggest our brains are slow to catch up after losing sleep—specifically, our ability to pay attention suffers—and we might not know when we're mentally fatigued.

Vgontzas also doesn't know what the cumulative effect might be of living this way every week. On average, he writes, we need seven hours of sleep a night. (Though if you really can't sleep any later, a nap during the day will also help you recover.)


Image: by Phae (via Flickr)

Pejovic S, Basta M, Vgontzas AN, Kritikou I, Shaffer ML, Tsaoussoglou M, Stiffler D, Stefanakis Z, Bixler EO, & Chrousos GP (2013). Effects of recovery sleep after one work week of mild sleep restriction on interleukin-6 and cortisol secretion and daytime sleepiness and performance. American journal of physiology. Endocrinology and metabolism, 305 (7) PMID: 23941878

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

To Crash Others' Nests, Cuckoos Impersonate Birds of Prey

In the avian world, cuckoos are the villains you root for. These diabolical birds can trick others into raising the cuckoos' young instead of their own. From a thick playbook of deceptions, one trick cuckoos use is to impersonate local bullies. This apparently convinces their victims to let cuckoos walk right into their nests.

Cuckoos live all over the world, and most species are model citizens, building their own nests and raising their own offspring. But many species are so-called brood parasites, which sneak their eggs into other birds' nests. Some species match the egg's color to their host's eggs to disguise it, while others don't bother, depending how clever their preferred targets are. In certain species, male cuckoos goad the host parents into chasing them off while females creep into the nest and lay their eggs.

The parasitic cuckoo hatches earlier than the other eggs in its nest and gets a head start in begging the host parent for food. It may mimic the appearance of its nestmates. Often, it kicks them out of the nest altogether. The clueless host parent feeds and raises the young cuckoo until it can fly off on its own.

Obviously, it's in the best interest of host birds to keep cuckoos out of their nests in the first place. Parasitic cuckoos and their host species engage in a constant evolutionary arms race, with the parasite's tricks and the host's defenses always improving. Thanh-Lan Gluckman, a Ph.D. student at the University of Cambridge, and her advisor, Nicholas Mundy, studied one of these tricks: plumage that disguises cuckoos as birds of prey.

It's no secret that certain cuckoos resemble certain raptors, and vice versa. The hawk in the photo above (left) is named the African cuckoo-hawk because of the likeness. Gluckman and Mundy wanted to measure that likeness: How similar is the plumage of raptors and cuckoos? And is that similarity stronger in species that live in the same area, suggesting the cuckoos have evolved to mimic specific birds?

The researchers focused on the chest feathers, where many cuckoo species have a "barred" pattern that's similar to many raptors'. It makes sense that the cuckoo's front side would be disguised, rather than its back, because that's what a host bird sees as a cuckoo swoops toward its nest. (And the last thing it sees before its young are replaced with aliens.)

Using museum samples, the authors photographed the plumage of representative birds. Then they transformed the images digitally to represent how they'd look through a bird's eyes. Characteristics of the barred pattern—how big the markings are, how consistent or variable the pattern is, and so on—were compared between five Old World cuckoo species (each representing a different genus) and raptors that share their territory.

All five cuckoos had patterns that matched a local raptor, such as a hawk or buzzard that overlapped with their territory. But when the scientists compared pairs that didn't live in the same area, there was no match. This suggests that cuckoos don't just imitate raptors in general; instead, they've evolved to match specific birds that live around them.

If the raptor it's imitating is local, that means the cuckoo's intended victim—the bird whose nest it's about to invade—will recognize it too. Gluckman says the purpose might be frightening host birds so they don't attack, "or making them misjudge what the cuckoo is for long enough to access the nests." A cuckoo can toss its host's eggs from the nest and lay its own in just ten seconds, she says. Alternately, males that are imitating a dangerous raptor might convince host birds to chase after them, also buying the female time to sneak into the nest.

It will take more research to show exactly how host birds react to an approaching cuckoo disguised as a bird of prey. Probably how they should react is to just move underground, because nothing else seems to be working.


Images: Left, African cuckoo-hawk by Ken Clifton; right, Oriental cuckoo by Tom Tarrant (both via Flickr).

Thanh-Lan Gluckman, & Nicholas I. Mundy (2013). Cuckoos in raptors' clothing: barred plumage illuminates a fundamental principle of Batesian mimicry. Animal Behaviour DOI: 10.1016/j.anbehav.2013.09.020

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.