All posts by John Upton

Racing pigeons juice city populations

Stray homing pigeons appear to be boosting feral populations / Flickr: mugley

By John Upton

Visit any of the world’s cites and you will almost certainly encounter hordes of the world’s most ubiquitous and well-adapted avian urban dwellers.

The humble rock dove, or pigeon, is derided as a flying rat, spreader of disease and graceless depositor of mounds of guano. But it is also a prized domestic species that has been bred for nearly 5,000 years as a food source, message deliverer, racer, and show bird boasting a startling array of plumages and physiques.

It is this very popularity that has seen the species transported around the world, where captive and racing birds have escaped into the wild to establish vast feral populations amid the same irritated humans who were responsible for its spread.

Cities suit rock doves superbly. Before they were domesticated, the birds nested along cliffs in Europe, North Africa and parts of Asia. Today, buildings in cities provide plentiful cliff-like environments for their nests; humanity’s wont to waste grants them plenty of grain and other food; and the hostile nature of cities for most large animals protects them from predation, although raptors are increasingly moving into cities to feast on their meat.

Feral rock dove populations are virtually immune to human-led efforts to snuff them out. And new research suggests that pigeon racers could be constantly fueling the wild populations with physical prowess-imbuing genes, helping to spawn today’s urban super-pigeons.

University of Utah researchers studied the genes of hundreds of domestic and free-living pigeons in the United States in an effort to map their family tree. What they discovered, and reported in February in the journal Current Biology, was a free flow of genes from specially bred racing pigeons into the wild.

Anywhere from five to 20 percent of racing pigeons fail to complete any given race. Some fall prey to predators. But others may simply get lost, or choose to not return home, and then blend into wild populations, where they coo and carry on and breed with feral lovers.

“[Racing homers] are bred for speed, endurance and navigation ability,” researcher Mike Shapiro told me. “They’re great flyers, unlike many of the ornamented or other exhibition breeds, so it’s not too surprising that they do well in the wild.”

All free-living rock pigeons in North America are feral, having first arrived some 400 years ago, with modern racing pigeons appearing a couple of centuries ago, Shapiro said, meaning that all of the continent’s populations must have been established by domestic breeds at some point.

“We hypothesized that they probably had major genetic contributions from racing homers because the breed is so popular and they, perhaps more than any other breed, have ample opportunities to fly free and escape,” Shapiro said. “This hypothesis is supported by our genetic data.”

Next time you see a broken-legged pigeon plunging its filthy face into trash strewn by the side of a busy street, spare a moment to give thanks to pigeon racers for potentially growing the species’ vigor. After all, these dumpster divers help push our wasted French fries and other food scraps up a nascent food chain and into the stomachs of the awe-inspiring hawks and Peregrine falcons that also inhabit our cities. That seems better than leaving the food to rot – and belch out its hydrocarbons as climate-changing methane.

Some of the pigeon breed studied by University of Utah researchers / Courtesy: Current Biology

[This pigeon story was requested by reader John Fleck. Request your own here or on my Facebook page!]

Your favorite wildlife goes here

By John Upton

What’s your favorite plant, animal, pathogen or natural phenomenon? Let me know in the comments section or on my Facebook page. I’ll pick at least one suggestion, dig up the latest scientific research about it and write a blog that’s guaranteed to fascinate. If I don’t get any ideas I swear I’ll just write about my favorite kingdom of life, fungus, from now on!

My brother with a finger’s worth of swarming bees.

Climate change — megadroughts may fuel American monsoons

By John Upton

Vast regions of the Northern Hemisphere are currently being saturated by monsoons. In many warm climates, including parts of India, Australia and Africa, intense summertime storms satisfy much of nature’s and farmers’ yearly thirsts for water in weeks- to months-long blitzes.

A monsoon in Arizona / Flickr: Arizona Parrot

For most of the year, winds blow dry air from North American deserts over Arizona, New Mexico and Texas. But as these southwestern states heat up in July and August, the winds shift and begin flushing vast volumes of water into the region from the gulfs of California and Mexico, fostering the North American Monsoon.

These winds carry moisture overland, but they can’t make it fall from the sky. Clouds must be seeded with tiny particles before they will dissolve into falling rain, and a major seeder of clouds worldwide is dust. Dust can also induce rainfall by altering atmospheric temperatures.

Researchers at the Pacific Northwest National Laboratory in Washington recently used computer models to determine that heating effects of desert dust boost North American Monsoon rainfall by 40 percent. The dust’s seeding properties likely have further impact.

“Our next plan is to include this seeding effect in the model,” lead researcher Chun Zhao told me.

The discovery, published earlier this year in the journal Atmospheric Chemistry and Physics, suggests that monsoons could counterintuitively grow more intense if climate change produces a terrifying phenomenon that’s forecast to afflict the region: Megadrought.

“The deserts during the megadrought will expand outwards, which means creating more desert surface area,” Zhao said. “Our simulations imply that megadrought may emit more dust and increase the precipitation over the Texas and Arizona regions.”

Tortoises, toads and other creatures native to the southwest are well adapted to the wild weather extremes wrought by the region’s seasons. This new research suggests that these extremes are set to exacerbate as the climate changes. There’s a good chance that the rugged creatures of the desert will adapt better to these extremes than we do.

New Mexico during monsoon season / Flickr: Rohit Chhiber

 

Copper — invisibility cloak for salmon eaters

Coho salmon lose their trouble-is-a-brewin’ nose when swimming in copper-polluted waters / Flickr: USFWS Pacific

By John Upton

Salmon face a litany of badass predators during their short but meandering lives. After hatching, baby salmon must dodge hungry fish as they swim downstream and into the open ocean. Once in the ocean, they are preyed upon not only by fish and fishermen, but also by sea lions and other marine mammals. After they’ve grown for two to three years, the fish must make the perilous stream run one more time, this time against the current and often into the mouths of waiting bears, in a desperate bid to reach their spawning grounds.

The salmon can’t fight back or use poisons or barbs to defend themselves. Instead, when a predator is near, they lock down, freezing their movements in hopes that they will become invisible to the marauder.

But what happens when the marauder becomes invisible to the salmon? New research suggests that humanity’s wont to pollute has handed such an invisibility cloak to creatures that feast on salmon.

Salmon rely on their keen sense of smell to detect predators. They don’t so much smell the predators, instead they smell a chemical alarm dubbed Schreckstoff that’s released from the shredded bodies of their attacked and battered brethren. But the sense of smell is compromised when the fish swim in water polluted by copper, a common pollutant that flows into streams from mines, farms, buildings and roads.

Washington State University researcher Jen McIntyre set up an experiment to determine whether copper pollution leaves salmon more vulnerable to predators. Into tanks she deposited juvenile coho salmon and a predator species named cutthroat trout, along with Schreckstoff and small amounts of copper.

Salmon that swam in clean water froze in the tanks and managed to escape initial strikes by the trout nine times out of ten. But salmon that were swimming in copper kept blithely on swimming, and they were captured on the first strike 30 percent of the time, often within five seconds.

“They’re not in lockdown mode,” McIntyre said in a statement that coincided with publication of her results in the journal Ecological Applications. “Predators can see them more easily.”

That’s nifty for hungry fish, but not so promising for the populations of salmon that are clinging to survival in polluted waterways around the world.

French fry to falcon — a modern food chain

By John Upton

A hunk of potato planted in a field sprouts into a leafy plant. A potato swells in the soil beneath the low canopy, fostered by water, fertilizer and pesticide, before it is torn out by a tractor and scrubbed and sliced by machine. A sliver of it tumbles into a plastic bag that is filled, sealed, frozen and trucked to a downtown fast food store.

When I was reporting for the Bay Citizen last year, editor Jonathan Weber snapped this falcon feasting on a pigeon outside our newsroom windows

The French fry is boiled in oil and lands in the bottom of a cardboard holster. The customer’s gluttony is satiated before his super value meal is done and the chip lands near a trash can, spinning in a waterfall of leftovers and packaging. It is grabbed by a rock pigeon which, hours later, is snatched up by a Peregrine falcon and fed to fledglings in a nest on an office building’s roof.

Peregrine falcons were nearly wiped out in the United States by the 1970s, their shells made fatally fragile by DDT sprayed to keep mosquitoes at bay. The poison bioaccumulated in the food chain and became concentrated in the falcons. The remarkably large raptors recovered spectacularly after the chemical was banned and American Peregrine falcons were removed from lists of endangered species in the 1990s.

As the populations recover, they have mastered the city environment, nesting on buildings and bridges. By preying heavily on the ubiquitous pigeons that eat our voluminous waste, they have established a food chain that runs from farm to trash to scavenger to urban predator.

But new and old threats nag at these birds all around the world.
Old: Falconers steal chicks from nests to be reared as hunters (and, increasingly, for lucrative commercial purposes – landfills hire falconers to scare away seagulls).
New: Toxic flame retardants used in furniture seep as dust into the environment and have been discovered bioaccumulating at high levels in Peregrine eggs.

The flame retardant threat is pronounced in California, where a strict law based on outdated science mandates the use of such chemicals at certain levels. Last week, Gov. Jerry Brown ordered a review of the 37-year old law in a bid to protect human health and wildlife. The review, by the California Bureau of Electronic and Appliance Repair, Home Furnishings and Thermal Insulation, is expected to establish a new industry standard that will be adopted as law by other governments.

The threat of poaching, meanwhile, is as established as the milleniums-old sport of falconry. To help curb that threat, scientists often try to keep vulnerable locations of nesting falcons a secret.

Here is a video from YouTube of commercial falconer Steve Vasconcellos keeping gulls away from a dump at Half Moon Bay, California. Vasconcellos was in talks with the San Francisco Giants to scare seagulls away from the waterfront ballpark, but the franchise’s operations manager recently told me the team had balked at the price tag, which I understand would have been well over $100,000 a year.

Male fireflies — vigor of youth an aphrodisiac

Flickr user James Jordan used a flash and a slow shutter speed to capture a firefly’s glow

By John Upton

Evenings are sparkling across great stretches of the northern hemisphere, where pulses of nitric oxide are being produced in fireflies’ abdominal cells to trigger harmonies of alluring green-yellow flashes. The nitric oxide briefly prevents parts of the cell that turn sugar into useful energy from consuming oxygen, allowing that oxygen to penetrate deeper into the cell, where it fuels a light-producing reaction involving a compound devilishly dubbed luciferin.

The constellations are cacophonies of courtships – the beetles have emerged from years of larval life spent underground, where they munched on worms and similar prey – and now they have mere weeks to procreate. Every night of their short adult lives is dedicated to procreation: Males fly and flash their wares, while females prop themselves on grass blades and invisibly judge their suitors. When a female likes what she sees, she flashes a response that draws him near.

While these unheard mating calls bring males and females together, new research published in Proceedings of the Royal Society – Biological Sciences reveals that something far more substantive determines the male’s success as a breeder.

The male wraps his sperm in a sustenance-rich package called a spermatophore, which is offered to the female. Adult fireflies do not eat, and spermatophores help provide females with energy needed to produce, bury and lay their eggs.

Fireflies emerge in warm months to breed / Flickr: davedehetre

Tuft University researchers Sara Lewis and Adam South discovered that the size of the spermatophore offered by a common North American firefly is more influential than the flashiness of his bioluminescence in determining whether he will sire young. The larger a firefly’s spermatophore, the more likely it is that a female will invite him to mount her — and, once they have copulated, the more likely it is that she will lay eggs bearing his young.

That means the virility of youth is crucial in helping a male firefly pass on his genes to the next generation.

“Our previous work has shown that making those spermatophore gifts is costly to males,” Lewis told me. “The gifts get smaller across sequential matings, and males’ mating rates slow down.”

The researchers also discovered hitherto unknown steps in the hours-long copulation of Photinus greeni, the species of firefly studied, which they explain in this video:

What’s that bumblebee buzz?

Flickr: bagsgroove

By John Upton

The seemingly menacing deep buzzing noise produced by a bumblebee rings out only when the insect reaches a flower. It’s not a warning or a threat, nor is it a noise produced by flight. It’s called sonication — rapid movements of a bee’s muscles that create vibrations to shake pollen loose from a flower’s anther.

This feeding strategy is also known as buzz pollination, and it’s a faculty lacked by the smaller European honeybees. But the sound is disappearing from landscapes everywhere along with the bumblebees that produce it. In a story that coincided with national pollinator week, I reported yesterday for Grist on the decline of native American bumblebees, a terrifying phenomenon that has long been overshadowed by the plague of colony collapse disorder.

Bumblebees need flower-rich habitats and they need to be able to feed without sucking up insecticides. Every flowering plant relies on pollination, and bumblebees do much of that work.

Here’s a video from YouTube showing a sonicating bumblebee. Perhaps you remember a time when this sound was more common.

Frog-attacking fungus flourished before mass extinctions

Mountain yellow legged frogs of the Sierra Nevada might join the list of species that have disappeared due to the fungal pathogen B.d. / Flickr: USFWS Pacific Southwest Region

By John Upton

Scientists had never encountered anything like it.

Discovered in the late 1990s by researchers trying to figure out why frog populations were disappearing around the world, Batrachochytrium dendrobatidis, or B.d., has already wiped out perhaps 200 to 300 amphibian species. It has shaken ecosystems, starving birds and other frog eaters and allowing insects to run rampant.

“We have something the world has never seen before,” Vance Vredenburg, a biology professor at San Francisco State University who specializes in amphibians, told me earlier this year. “It’s jumping from species to species to species.”

The recent discovery that chytrid was present in New England in the 1960s, three decades before the disease’s effects were noticed, points to the alarming possibility that the die-offs are the result of worldwide environmental degradation.

B.d. is a type of chytrid — a member of the most primitive division of fungus: Chytridiomycota. Toadstools, molds and all of the other forms of fungus evolved from chytridiomycotes. Chytridiomycotes today are the smallest and simplest type of fungus, but these wily grandfathers still pack one helluva punch.

Before a frog is infected, it is hunted down by swarms of tiny chytrid zoopores that propel themselves through the water by flapping their tail-like flagella. The pathogen changes shape and burrows into the frog’s skin, which it consumes while it creates more zoospores, causing the frog to grow more layers. Many species can tolerate the parasites at low doses, but once a frog’s skin is infected with enough of the fungus it will go into cardiac arrest, its electrolyte levels thrown out of balance and its tiny heart stopped. (Weirdly, some species, including the American bullfrog, appear completely immune.)

“We find literally hundreds, and tens of thousands — I’ve seen it myself — dead animals on the shorelines of lakes,” Vredenburg said.

Research led by University of California, Berkeley ecologist Jamie Voyles helped explain how the fungus kills. What’s less clear is why it apparently started to cull amphibians all around the world at about the same time.

B.d. under a microscope / Flickr: AJC1

Kathryn Richards-Hrdlicka, a doctoral candidate at the Yale School of Forestry and Environmental Studies, took samples from 10 species of amphibians preserved in formalin at the Peabody Museum of Natural History. She reported Tuesday in the journal Methods in Ecology and Evolution that the fungus was infecting frogs in New England as long ago as 1968, the year in which one of the oldest of the studied specimens was collected.

“It’s possible dieoffs did happen back then and no one noticed, although die-hard herpetologists around here tell me someone would have noticed,” Richards-Hrdlicka told me. “I think it’s possible that when B.d. came to New England, it may have wiped out the more susceptible lineages or gene pools and what we’re left with today are those gene-pool winners.  That may explain why I can pick up 10 frogs here and three to four of them will be infected, with light zoospore loads, and show no signs of infection.”

Alternatively, rampant world trade could have brought two chytrid strains into contact that merged to spawn a super pathogen, as other B.d. researchers have hypothesized.

But Richards-Hrdlicka also said that the changing environmental conditions facing all species around the world right now might simply make frogs more vulnerable to the chytrid than they were in the past.

And there’s the rub. When frogs were disappearing without explanation in the 1990s, many speculated that the chordata class amphibia was acting like a canary in a coal mine, dying off before other types of animals because they are so sensitive to their environment.

The discovery of B.d. muted that suspicion, but now we know that B.d. was present long before these prominent collapses. Previous studies showed it was lurking in Africa in the 1930s.

Fungus is the great decomposer. When animals and plants are stressed, their defenses weaken and they can be eaten alive by fungus, which treats its prey as though it is dead flesh awaiting decomposition. So perhaps the mystery of the disappearing frogs really can be traced back to just about everything that is out of whack with our environment: Climate change, pesticides, habitat loss, water diversions, water degradation, air pollution, you name it.

Scientists had never encountered anything like B.d.

Until 2006.

That’s when bats in a cave in New York started dropping dead from white nose syndrome. Since then, the disease, which is caused by a type of soil fungus that chews through the mammals’ wings, has spread rapidly west, killing an estimated 7 million hibernating bats in just six years.

“That’s really similar,” Vredenburg said.

Arctic trees could heat the planet

By John Upton

Trees and shrubs suck water up from the earth and into their leaves through super-thin straws in their trunks called xylem. When sunlight hits a leaf, it causes some of that water to evaporate, which in turn draws more water up from the roots through the xylem. This solar powered plumbing system keeps plants hydrated, allowing them to combine carbon dioxide from the atmosphere with water from the soil to create sugars essential for their growth. This process of photosynthesis also releases waste oxygen, which is breathed by animals and fungi.

Tundra swans migrate north to breed in Arctic tundras / Flickr: chiptape

But the system starts to fall apart when temperatures drop below freezing and the water turns to ice. Some plants produce antifreeze, and some have evolved to seize on short growing seasons when melted water is briefly available, but most simply cannot survive in the Arctic or Antarctic. Either the frozen water is too rigid to move through the xylem, or water freezes and thaws inside the plant, creating deadly bubbles that wreck its insides.

That’s the main reason that tundras are so barren — water in the soil is often locked up as ice that is useless to most plants, especially to tall trees.

As tundras heat up and ice wanes, forests are blooming in new places. Logically, one would expect these new and expanded forests to slow climate change by sucking up the atmosphere’s burgeoning carbon dioxide supplies and turning them back into oxygen.

But a new study published in the journal Climate Nature Change suggests that such logic might not prevail. That’s because the soils of tundras are home to vast reservoirs of carbon that could be stirred up and spewed back into the atmosphere by the return of the forests.

The researchers compared carbon levels in the heathlands of tundras in northern Sweden with those in nearby birch forests, which are replacing the heath as Earth heats up. They discovered that the amount of carbon stored in the low-lying heath vegetation and in the soil beneath it exceeded the amount stored in the forests’ plants and soil.

“Counterintuitively,” the researchers wrote in the paper, “increased plant growth in the European Arctic could result in C (carbon) being released to the atmosphere, accelerating climate change.”

To explain this counterintuitive result, the researchers found that frenetic plant activity in birch forests during the summer growing season triggered the decomposition of old organic matter in the soil, causing the ecosystem to leak more carbon than it captured.

Lead researcher Iain Hartley, a geography lecturer at the University of Exeter, warned that more studies are needed in a wide range of Arctic environments to determine whether expanding forests will indeed exacerbate global warming. (Unlike many other arctic tundra environments, those studied by the researchers lacked a permafrost.) But the findings point to that as a major risk.

“At the moment, the results are relevant to a particular change in vegetation,” Hartley told me in an email. “There is a lot of further study required to try and work out how carbon storage will change as forest colonises tundra in different areas of the Arctic.”

Our ape brethren — some kill, some love

By John Upton

Five to seven million years ago, as the climate cooled around them, our ancestors began to shy away from some of their hitherto ilk. The forefathers of ourselves and of the neanderthals stopped sleeping with the foremothers of the bonobos and the chimpanzees, and vice versa. We went our separate evolutionary ways.

A female bonobo. All she needs is love. / Flickr: Princess Stand in the Rain

While wanderlust scattered our predecessors around the world, the other apes remained exclusively in Africa. Some 2 million years ago, the African landscape was cleaved by a new cascade — the Congo River. Unable to cross this vast waterway, the other apes split into two species. The bonobos lived on the river’s south; the chimpanzees to its north.

With the extinction of the neanderthals 30,000 years ago, these two species of apes became our closest relatives. We share 98.7 percent of our genes with each of these species. Bonobos and chimps, meanwhile, share 99.6 percent of their genome with each other.

But those tiny genetic divergences belie dramatic differences in behavior that developed as the bonobos and chimps evolved into independent species.

A male chimpanzee. Natural born killer. / Flickr: Rickydavid

The chimpanzees developed and refined the darkest sides of the human character. They rape, they murder, they form gangs and posses that fight deadly battles.

The bonobos, meanwhile, came to adopt our make-love-not-war traits. They frolic and revel in merrymaking from the time they are babies until they die. They live in peaceful matriarchal societies. And they freely sleep with multiple partners to bond and have fun — including with same-sex partners.

The genetic differences and similarities between the three ape species were announced this week in the journal Nature by an international team of scientists after they sequenced a bonobo’s genome for the first time. Human and chimpanzee genomes were sequenced previously.

But the new genetic data doesn’t reveal why the two sides of the human character are divided so dramatically between our two closest relatives. The researchers speculate that our shared ancestor may have exhibited the entire spectrum of behaviors, just like us.

“Chimpanzees and bonobos each possess certain characteristics that are more similar to human traits than they are to one another’s,” the researchers wrote in the paper. “No parsimonious reconstruction of the social structure and behavioural patterns of the common ancestor of humans, chimpanzees and bonobos is therefore possible. That ancestor may in fact have possessed a mosaic of features, including those now seen in bonobo, chimpanzee and human.”

The Congo River is the world’s deepest river. Flickr / United Nations Photo