If you have ever wanted to know what it’s like to live life as a dolphin, take a trip into the blue abyss through James Nestor’s Deep: Freediving, Renegade Science, and What the Ocean Tells Us About Ourselves.
The book is a first-hand introduction to freediving. The underwater diving technique, sans-SCUBA gear, was, until recently, remarkably widespread among fishing communities worldwide since time untold. Freediving is still used today by a handful of traditional fishing folk — and by some devoted researchers who want to come face-to-face with their cetacean subjects.
Nestor explains that humans share some of the physiological faculties that are used by modern marine mammals, but that few of us landlubbers have any idea what we’re capable of. He learns from the masters how to hold his breath, virtually to the point of blacking out, and explains in vivid detail the seemingly frightening techniques that he is taught.
Along the way, Nestor introduces us to a group of extreme athletes that compete to stay underwater for the longest and to dive to the deepest depths. These athletes certainly know what they’re capable of — but they often overestimate their abilities, in a mad rush for glory within their small community, with sometimes crippling or even deadly results.
To reach greater depths than can be reached with lungfuls of air alone, the book also describes humanity’s error-plagued history of building machines that help us plunge to seemingly fathomless depths. It explains the biology of much of what we have found once we got there.
Deep is a wonderful read that will entrance even the most knowledgable of ocean experts.
It’s inside an egg that genes combine to code for an individual, so we’re going to go with ‘the egg.’ Next question, please.
Which came first — the ostrich or the emu?
Looking at pictures of these flightless birds, you’d be forgiven for mistaking them for kissing cousins. They’re both swift-footed birds with buns of feathers hitched high — alluring outfits that show off their slender legs and necks.
But they’re not as closely related as they might at first seem.
Ostriches and emus are both ratites — members of a group of large flightless birds endemic to the Southern Hemisphere. Ratites were all thought to have descended from a common ancestor; examples of what scientists dub vicariance biogeography, or convergent evolution, in which members of once-conjoined populations become geographically separated, such as through the geological manifestation of a new river, gulf, or mountain, and then pursue their own evolutionary trajectories. In the case of ratites, they were thought to have gone their separate ways following the bust-up of Gondwana, from where their presumed ancestor was thought to have hailed.
Just a decade ago, in his book The Ancestor’s Tale: A Pilgrimage to the Dawn of Evolution, famed biologist and writer Richard Dawkins described ratites as a “truly natural” group. “Ostriches, emus, cassowaries, rheas, kiwis, moas and elephant birds really are more closely related to each other than they are to any other birds,” he wrote. “And their shared ancestor was flightless too.”
Dawkins’ statement reflected leading science from the time. But advances in molecular phylogenetics have since revealed the folly of longheld assumptions about ratite evolution. The apparent similarities between different species of ratites are now thought to have been the consequence of convergent evolution — the independent evolution of similar features by different species in far-flung places that inhabit similar ecological niches.
It seems that flightlessness just makes sense in the right environments. Research in recent years has revealed that selection pressures independently pushed the forebears of today’s ratites to shrink their wings, bloat their bodies, flatten their sternums, and evacuate the skies.
Several years ago, University of Florida researchers used BUCKy software to analyze the genomes of various birds, and found that the ratite family tree includes a surprising cousin — tinamous, an order of grouse-resembling birds from Central and South America. These birds spend much of their lives on the ground, but many of the species are perfectly capable of flying. The tanimous were found to be more closely related to emus then they were to ostriches, providing further evidence of the independent evolution of flightlessness in different ratites. The findings were published in the journal Systematic Biology:
“The independent evidence we obtained provided strong corroboration of the hypothesis that nonostrich paleognaths form a clade,” wrote the three scientists involved with the research in their paper. “This sharply alters our understanding of the evolutionary history of the flightless ratites by providing support for multiple losses of flight. It remains possible there was a single loss of flight early in paleognath history followed by a regain of flight in tinamous, but this is unlikely because the loss of flight appears to be a relatively easy transition for birds whereas the loss followed by the regain of flight has never been documented. The hypothesis that flight has been lost multiple times in the ratites suggests that some of the most distinctive morphological characters in ratites arose through convergent evolution.”
We asked one of the authors of the paper, Edward Braun, an associate professor in the university’s biology department, how this information and similar analyses could help answer our question. Which species is older — the emu or the ostrich?
Braun said that’s a tough question to answer; but he suggested a couple of alternatives, which he then answered.
“One valid question is, ‘When did ostriches start looking like ostriches, and when did emus start looking like emus?'” Braun said. “I suspect that, if the question is asked that way, the answer is, ‘About the same length of time.'”
“On the other hand, another way of asking the question is, ‘When did ostriches separate from other extant birds, relative to emus?’ The answer to that is clear. Ostriches have no close relatives. Ostriches separated from other birds a long time ago; probably in the Paleocene [66 to 56 million years ago], since there are middle Eocene fossils that are probably now extinct parts of the ostrich lineage. Emus are more closely related to rheas, kiwis, and quite close to cassowaries.”
Enjoy this fun video of emus and an ostrich playing with a motorized ball, which helps to reveal differences in the appearances of the species:
This new addition to the burgeoning bookshelf of global warming riffs provides a probing history of generations of climate inaction, both in the U.S. and internationally. Philosopher Dale Jamieson, currently a professor of environmental studies at New York University, offers this definitive account of failed climate negotiations as he meticulously explains the repercussions of ceaseless political dithering on greenhouse gas pollution.
What’s most extraordinary about this book is that it took Jamieson almost 25 years to write, beginning the manuscript he was 40 years old, and finally finished when he had nearly reached 60.
“I would like to say that it was a labor of love, but it was really an avocation that became an obsession,” Jamieson writes in the book’s preface. “When people asked me why my first attempts to write a book on this subject failed, I would say that it was impossible to write the book until I knew how the story ended.”
A major emphasis of the book is how America’s leaders, Democrats and Republicans alike, have so far prevented the U.N. Framework Convention on Climate Change from delivering any kind of international agreement that could actually make a difference for the world. And it was the ongoing failures of international climate talks that finally spurred him to finish his manuscript. “When Copenhagen went down the way it did, I knew that I had the story that I wanted to tell,” he told me.
The depth of knowledge of this climate-watching veteran shines through in the clarity of his oft-depressing, but always intriguing, assemblage of facts and illuminating observations.
This is not a book that dwells on the technicalities of the science of climate change. It focuses instead on ethics and politics. It’s not always an easy read. But, particularly for those who spend more time immersed in climate science than in the politics or philosophy of the warming crisis, it’s a read that’s well worth the time.
Some Australian kids don’t believe in the Easter Bunny.
The clutches of chocolate and colored eggs hidden in the yards and living rooms of environmentally-aware households Down Under are deposited, through orifice unknown, by the Easter Bilby.
Browse the easter sweets selection in just about any Australian store right now and you’ll find foil-wrapped chocolate icons of the adorable outback-dwelling marsupials.
Rabbits are ravenous, fast-breeding, and destructive pests in Australia, where they were introduced by hunters and graziers during the 19th Century. The bare rabbit-resembling bilby, on the other hand, is a native Australian species that’s vulnerable to extinction. Celebrating the Easter Bilby helps Australian kids learn about the ecological importance of native mammals — while avoiding the awkward passions for invasive counterparts that the Easter Bunny can imbue.
The beauty of the bilby lies in its relationship with Australia’s fragile, old, and nutrient-poor land. It digs through arid and semi-arid soils, bioturbing them, improving water drainage and reducing flooding and erosion. The digging helps spread seeds. It creates microhabitats for bugs and fungi. It turns over soils and helps with nutrient cycling.
The effect of native Australian diggers, such as bilbies, echidnas, and wombats, is “increased plant vigour and resilience, increased biodiversity and consequently improved ecosystem functioning,” scientists wrote in a Mammal Review paper published last year.
But Australian ecosystems have been ravaged during the past two centuries by introduced species, including rabbits, pigs, and camels, and by land clearing. The native diggers are hunted by introduced cats and foxes. Those pressures have helped push half of the nation’s digging mammals toward extinction, the researchers concluded following an exhaustive review of scientific literature. “[T]he loss of digging mammals has contributed to the deterioration of ecosystems,” they wrote.
Rabbits dig as well — but they apparently do not dig deep enough to produce the same benefits as bilbies. Previous research has shown that digging bilbies foster 80 percent more seedlings than do digging rabbits.
“When bilbies, bandicoots, and bettongs dig for food, their diggings are deep, roughly-conical pits which penetrate deep into the soil layers,” Murdoch University wildlife biologist Trish Fleming, one of the coauthors of the Mammal Review paper, told Wonk on the Wildlife.
“Rabbits dig shallower pits, which disturb a large area of the top soil layers. This would expose the soil to drying out, which means it’s less suitable for soil microorganisms or for new seeds.”
Then there’s the wee issue of rabbit plagues. Looking out across an affected Australian farm, the land can appear as if it is moving.
“Rabbits feed on soft shoots of plants, and then will dig up any vegetation within reach, including the roots and bark off trees. In plague numbers, they wipe out any living plant material. There are expanses of productive lands which have never recovered from plagues of rabbits,” Fleming said.
So go and get stuffed with caramel, Easter Rabbit. Aussies don’t need your type sniffing about in their gardens.
A cutie in decadent clothes — who can dance like no one is watching.
Sexual selection is a term coined by Charles Darwin to explain why some species have developed elaborately ornamental feathers and antlers — appendages that help woo mates. In humans, it has been argued that sexual selection pressures gave rise to facial hair and ample bosoms.
The elaborate trains of peacocks are among the most classical examples of sexual selection. During breeding time, peahens will visit areas where peacocks vie for their attention with spectacular dances. The peacocks raise their trains in a semicircle and whip them around, sometimes leaning them over the judging peahen. They shake their tail feathers and perform a jig with their feet.
A team of researchers set out to try to figure out just what actually interests the peahens during these spectacular courtship displays. They trained captive peahens to wear a patch over one eye and an infrared eye-tracker on the other. Then they watched while peacocks wooed their ridiculously-attired subjects inside black-plastic enclosures that minimized distractions.
After analyzing the footage and data, the scientists realized something surprising. The peahens weren’t looking at the tops of the brightly colored feathers. They were watching the peacocks’ lower regions.
“Based on the scanpath of where the females are looking, you can see that their gaze is focused on the lower train — that is, the lower feathers as well as the legs,” Jessica Yorzinski, an evolutionary biologist who studies animal communication, told Wonk on the Wildlife.
“The peahens may be assessing the width or symmetry of the peacock’s lower train and this could indirectly tell the peahens about the quality of that potential mate,” Yorzinski said. “For example, it’s possible that peacocks with more symmetrical trains produce peachicks that are healthier.”
So what’s the point of having such long and elaborate feathers if peahens are so interested in peacocks’ lower bodies? Yorzinski and fellow researchers explain their theory in a recent paper published in The Journal of Experimental Biology:
Even though we found that the peahens were primarily assessing the lower train, the upper train of the peacock may play an important role in courtship as a long-distance attraction signal in dense vegetation.
In The Descent of Man and Selection in Relation to Sex, published in 1871 (which the researchers awesomely cite in their paper), Darwin noted that peahens can appear coy and uninterested in males, despite the elaborate mating displays. Yorzinski and her colleagues helped explain this phenomenon by discovering that peahens spend more than two-thirds of their time scanning the environment for predators and the like, even as a beautiful peacock dances in front of them.
It’s nice to watch a beautiful dancer, but, from a peahen’s perspective, there’s not much point in finding an idyllically cute male if they’re going to be eaten before they get the chance to mate with them.
Trees don’t just provide habitat for arboreal and terrestrial creatures — dead trees that have toppled over in shallow waters are critical for aquatic wildlife. Woody habitat in lake littoral zones provides shelter for fish. It also supports the growth of algae and the like, which are eaten by herbivorous fish and other critters.
As the globe warms and as aquifers are sucked dry, lake levels in many parts of the world are falling. And as a lake’s water level drops, semi-submerged trees that ring the lake’s shallows can be left high-and-dry. That can decimate fish populations — harming birds and other species that feed on them.
“Reduced lake levels generally decrease littoral habitat, which is critical to aquatic food webs,” wrote University of Wisconsin researchers in a recent paper published by the Canadian Journal of Fisheries and Aquatic Sciences. “Fishes across all trophic levels are known to rely heavily on littoral food sources, with littoral zones supporting 65% of the consumption by lentic fish communities and 57% of their body carbon.”
The scientists sampled fish from 2000 until 2005 and again from 2007 to 2009 in Wisconsin’s Little Rock Lake, which is in the Great Lakes region. Declining water levels in the Great Lakes, which is Earth’s largest body of fresh surface water, are a major worry for scientists.
During the monitoring period, drought led to a decline in water levels of a little more than a meter. That left three quarters of the lake’s woody habitat stranded on land. The following graphs from the paper show the close relationship between water levels and woody habitat:
The sampling results painted a picture of an ecosystem in steep decline — a decline that the scientists linked to the loss of soggy wood.
Things got so bad during the drought that the scientists’ minnow traps started to come up empty.
“The rapid decline of the perch population was associated with the loss of available CWH [coarse woody habitat],” the paper states. “Perch first failed to appear in a trapping event in 2005, after only a 10% loss of CWH. No perch were detected in 2008 or 2009 after 58% and 72% of the available CWH had been stranded from the littoral zone.”
The loss of the perch was blamed on the declining water levels, with changed temperature and oxygen levels potentially contributing. A loss of food was also stated as a potential factor. As was the loss of spawning habitat and loss of shelter from predators due to the disappearance of woody habitat.
“Previous research has suggested the potential for predator–prey encounter rates to increase with reduced CWH, which would result in intense bass predation on perch. … [T]he severe depletion of the perch population might have been exacerbated by the relatively high densities of bass in Little Rock South, which initially increased with reduced lake level.”
Eventually, though, the largemouth bass were found to grow more slowly as the lake’s water level fell.
The study’s lead author, Jereme Gaeta, tells Wonk on the Wildlife that the findings have implications for a warming planet.
“Future climate projections are uncertain, but we generally expect evaporation to outpace precipitation in many regions such as northern Wisconsin,” Gaeta said. “Our research shows that loss of littoral habitat can change not only the way fishes interact but also change fish community and food web structure.”
To help protect aquatic communities from the loss of littoral woody habitat, the paper recommends manually placing dead trees in lakes — something scientists call tree drops.
“Potential preventative measures when lake levels drop are limited. Our best options are to protect and restore natural shorelines to ensure future inputs of woody structure are possible and, when water levels begin to drop, add trees to deeper waters or steeper shorelines,” Gaeta said.
As scientists have started to figure out what a mycorrhizal fungus really is, they’ve discovered that it might be a really fun guy.
I mean, ahem. They’ve discovered that it might really be fungi.
Genetic sequencing is revealing surprising secrets of arbuscular mycorrhizae. The discoveries are casting doubt on notions of fungal individuality and offering new ways of boosting the amount of food that’s grown the world over.
Mycorrhizal fungi, aka myco, are soil dwellers that forage for water and nutrients, which they exchange for sugars produced by photsynthesizing plants. As I explained recently in Grist, they cool the globe and boost crop yields.
Research during the past decade suggests that what many of us would assume was a single myco fungus might actually be lots of mini fungi bits — genetically diverse nuclei that live and work together inside what we would logically perceive to be a fungus. There, the nuclei collaborate to create long mycelia and hyphae that stretch from root to root, delivering water and nutrients up to the plants, and passing carbon from the plants down into the soil.
This proposed blend of different nuclei is called the heterokaryosis hypothesis (a heterokaryon is a cell containing genetically diverse nuclei) — and it’s highly controversial. A recently flurry of papers has concluded that it is flat-out wrong, but those findings have been criticized by scientists who subscribe to the hypothesis.
If correct, the hypothesis could help scientists solve a couple of longtime fungal mysteries.
For one thing, it could help explain how and why mycelia from seemingly different fungi fuse together as they snake through the soil.
It could also explain how these types of fungi reproduce. Molecular evidence tells us that the fungi exchange genes, which suggests that they are mating. But scientists have never been able to figure out quite how they’re doing it. The heterokaryosis hypothesis suggests it’s the nuclei within each fungus that are breeding. It appears that they are migrating through fusions between the hollow mycelia.
“Why this heterokaryosis thing is so important,” said Ian Sanders, a professor of evolutionary biology at the University of Lausanne, “is because — I believe — we can use these genetic differences among the nuclei to create fungi that make plants grow better.”
Sanders has been involved with research in Colombia, where fungi have been developed that boosted cassava yields by one fifth while requiring less fertilizer. The research program is being expanded to Africa, where cassava, a root vegetable similar to a potato, is a dietary staple.
The breakthroughs relied on breeding techniques that took advantage of fungal heterokaryosis. More such breakthroughs would mean bigger yields of crops, more food, and less world hunger.
(Speaking of food, it’s worth noting that the heterokaryosis theory has nothing to do with mushrooms. There are two main types of mycorrhizae. Endomycorrhizae, which are the subject of this article, are arbuscular. They pierce the roots of plants with tiny vesicles and arbuscules, which are microscopic organs that helped both kingdoms of life adapt to life on land some 460 million years ago. It is the other type of mycorrhizae, ectomycorrhizae, the less common and less ancient union that engulfs roots without penetrating them, that produces mushrooms.)
Endomycorrhizae fungi infuse the roots of nine out of ten crop varieties, yet we know precious little about them. That’s largely because of complications inherent in trying to study an organism that’s intricately woven into the body of another; the result of nearly a half billion years of interdependent evolution.
The heterokaryosis hypothesis has its detractors. They point to research, such as this paper published this month in PLOS Genetics, in which nuclei sampled from a single fungus were nearly genetically identical. Supporters of the hypothesis point to findings from other research where vast genetic diversity appears to have been discovered. Sample sizes in some of the experiments have been very low, and just a few strains have been analyzed, making all of the results highly contentious.
One believer in the hypothesis is Toby Kiers, a mycological researcher at Vrije Universiteit Amsterdam. “It’s a neat concept, because even within an individual you’ve got individuals,” she said.
[Kiers] has secured funding to watch mycelia squeeze through tiny mazes, peering at them through microscopes as they trade nutrients with plants for sugars under different conditions. The goal, she says, is to “study their decision-making skills.”
Kiers’s research will combine cutting-edge microscopy and mycology with old-fashioned breeding techniques in a bid to select the most useful fungal strains. “They’re quite easy to select on,” she said, “because there’s so much genetic variability — even within a single hyphae, within a single spore.”
Animals can evolve to survive global warming by changing their behavior and by changing their bodies. Butterflies are particularly sensitive to climate change, and changes in their behavior have been well documented — most notably in their migration patterns and ranges. North American Butterfly Association president Jeffrey Glassberg recently told the Maryland Independent that climate change is affecting Rhopalocera on a vast scale. “There’s a whole suite of butterflies whose ranges are retreating,” he said. (Such changes are the subject of Flight Behavior, a novel by Barbara Kingsolver dealing with climate change.)
And now comes the first evidence that butterfly larvae are changing the internal workings of their bodies to help them cope with warming temperatures.
University of North Carolina scientists studied the optimal feeding temperatures of Colias spp. caterpillars from California’s Sacramento Valley and Colorado’s Montrose Valley. The frequency of very hot days and nights at both sample sites have increased since the 1970s, when a similar study with the same caterpillar populations was conducted. Caterpillars feed best within specific temperature ranges, and the researchers discovered that the caterpillars have evolved to feed at higher temperatures. The results of the study were published in the journal Functional Ecology:
This study is among the ﬁrst to show population changes in physiological performance in response to recent climate change, although previous theoretical work has predicted such changes. While previous work has highlighted adaptation to seasonal timing, speciﬁcally photoperiodic cues, our work suggests that rapid adaptation to changing thermal regimes may also be an essential mechanism.
I asked lead researcher Jessica Higgins whether she thinks that butterflies are among the first organisms to adapt their physiologies to warming conditions — or whether she thinks this was just the first time that such changes have been detected by scientists.
“I do think that other organisms may be adapting, but we can’t detect it because of the lack of good historical data,” Higgins said. “What made my experiment so unique was that I had this snapshot of caterpillar physiology back in the 1970s. I was able to compare my results with what they previously found and then correlate it with temperature. I think my study highlights that there can be adaption to physiological traits — not just changes in seasonality, which has been the main focus of previous adaptation-to-climate studies. “
Great white sharks are among Earth’s most formidable predators. They are apex predators. They prey on fish, mammals and birds — but nothing preys on them.
And in Western Australia, the state government, tired of losing surfers and other beach-goers to the toothy jaws of these ferocious elasmobranchs, has become a predator.
“The preservation of human life is our number one priority,” said Troy Buswell, the state’s fisheries minister, in announcing new policies that will see white sharks killed if they venture within a kilometer of popular beaches. The state’s decision to cull sharks has sparked a global controversy, and polling suggests that even West Australians are overwhelmingly opposed.
“The decision by Western Australia officials to cull sharks off the coast is alarming,” said Ashley Blacow, a policy and communications official with nonprofit Oceana. “Sharks play a critical role in keeping ocean ecosystems healthy. The presence of sharks ultimately increases species stability and diversity of the overall ecosystem. White sharks in particular are a vulnerable species and they should be protected, not killed.”
One of Western Australia’s most controversial approaches to culling sharks will see floating drums placed around beaches, attached to baited hooks. The trapping equipment are known as “drum lines” — and conservationists regard them as appallingly cruel. Drum lines are illegal in many parts of the world, including in the U.S. One shark expert described the killing method as “archaic” in an interview with Nature.
“Drum lines are 55-gallon steel drums with heavy tackle-like chains or large lines connected to bait,” David McGuire, director of Shark Stewards, told us. “They’re usually anchored to the bottom or they can be linked in chains. I’ve seen them used illegally in Mexico to catch sharks. Essentially, the shark bites the bait, is hooked, and drowns.”
Perhaps most troublingly, there is a lack of scientific evidence that such culling actually protects humans from shark attacks. It might feel satisfying to kill a member of a species that has been killing humans, but that sense of satisfaction might be more of the revenge variety than anything else. Hawaii culled nearly 5,000 sharks between 1959 to 1976, yet there was no change in the rate at which sharks attacked humans in those same waters.
Unfortunately, it may take years of shark culling and shark attacks before the West Australian government can determine whether its new policies are having the effect that it desires.
“True effectiveness cannot be assessed by simply counting the number of sharks captured and killed,” writes University of Hawaii researcher Carl Mayer in an article published by The Conversation. “Demonstrable effectiveness means a measurable decrease in shark bite incidents in response to culling activities.”
Is it better to kill an orphaned fawn, or is it better to leave it alive, left to try to survive alone in a menacing world?
That unpalatable question is not a hypothetical one in Scotland, where some 60,000 red deer are culled every year — part of an effort to keep populations down to protect crops and woodlands from the hungry grazers.
“Shoot both female and juvenile where-ever possible,” the guidelines state. “Where possible target calves first and maintain vigilance for orphaned calves. ”
Josephine Pemberton, a professor at the Institute of Evolutionary Biology, University of Edinburgh, wanted to know whether that policy was scientifically wise. Using funding from the U.K. National Environmental Research Council, Pemberton and five other scientists analyzed data from censuses of a red deer population on Scotland’s Isle of Rum dating back to the 1970s.
What they found was that depriving a deer of its mother’s care and protection before its second birthday triggered resounding impacts. Orphaned males and females were more likely to grow haggard and die young. Males were hit particularly hard — and male orphans had trouble growing antlers as they matured, reducing their chances of winning mates and reproducing. As for female fecundity? “Although we failed to find evidence that female orphans paid a reproductive cost,” the scientists wrote in their paper, which was published in August in the journal Behavioral Ecology and Sociobiology, “we cannot discount an effect on female physical condition.”
Pemberton said the results show that young deer should be killed if they are orphaned by a hunter — even if they are old enough to not seem helpless.
“If anything, our results suggest that if a young animal is still going around with its mother in its second year — and they often do — you should try and shoot it then, too,” Pemberton said.
But that’s easier said than done. And not just because shooting a fawn must surely be a heartrending task for even a hardened stalker.
“Although culling calves with their mothers is in the best practice guidance, stalking is a tough job done largely alone,” Pemberton said. “Stalkers are often under pressure to shoot a lot of hinds. Shooting the pair takes time and effort and we know they don’t always manage to do it.”