Posts Tagged ‘Nature’

by Ed Yong

On October 31, 1832, a young naturalist named Charles Darwin walked onto the deck of the HMS Beagle and realized that the ship had been boarded by thousands of intruders. Tiny red spiders, each a millimeter wide, were everywhere. The ship was 60 miles offshore, so the creatures must have floated over from the Argentinian mainland. “All the ropes were coated and fringed with gossamer web,” Darwin wrote.

Spiders have no wings, but they can take to the air nonetheless. They’ll climb to an exposed point, raise their abdomens to the sky, extrude strands of silk, and float away. This behavior is called ballooning. It might carry spiders away from predators and competitors, or toward new lands with abundant resources. But whatever the reason for it, it’s clearly an effective means of travel. Spiders have been found two-and-a-half miles up in the air, and 1,000 miles out to sea.

It is commonly believed that ballooning works because the silk catches on the wind, dragging the spider with it. But that doesn’t entirely make sense, especially since spiders only balloon during light winds. Spiders don’t shoot silk from their abdomens, and it seems unlikely that such gentle breezes could be strong enough to yank the threads out—let alone to carry the largest species aloft, or to generate the high accelerations of arachnid takeoff. Darwin himself found the rapidity of the spiders’ flight to be “quite unaccountable” and its cause to be “inexplicable.”

But Erica Morley and Daniel Robert have an explanation. The duo, who work at the University of Bristol, has shown that spiders can sense the Earth’s electric field, and use it to launch themselves into the air.

Every day, around 40,000 thunderstorms crackle around the world, collectively turning Earth’s atmosphere into a giant electrical circuit. The upper reaches of the atmosphere have a positive charge, and the planet’s surface has a negative one. Even on sunny days with cloudless skies, the air carries a voltage of around 100 volts for every meter above the ground. In foggy or stormy conditions, that gradient might increase to tens of thousands of volts per meter.

Ballooning spiders operate within this planetary electric field. When their silk leaves their bodies, it typically picks up a negative charge. This repels the similar negative charges on the surfaces on which the spiders sit, creating enough force to lift them into the air. And spiders can increase those forces by climbing onto twigs, leaves, or blades of grass. Plants, being earthed, have the same negative charge as the ground that they grow upon, but they protrude into the positively charged air. This creates substantial electric fields between the air around them and the tips of their leaves and branches—and the spiders ballooning from those tips.

This idea—flight by electrostatic repulsion—was first proposed in the early 1800s, around the time of Darwin’s voyage. Peter Gorham, a physicist, resurrected the idea in 2013, and showed that it was mathematically plausible. And now, Morley and Robert have tested it with actual spiders.

First, they showed that spiders can detect electric fields. They put the arachnids on vertical strips of cardboard in the center of a plastic box, and then generated electric fields between the floor and ceiling of similar strengths to what the spiders would experience outdoors. These fields ruffled tiny sensory hairs on the spiders’ feet, known as trichobothria. “It’s like when you rub a balloon and hold it up to your hairs,” Morley says.

In response, the spiders performed a set of movements called tiptoeing—they stood on the ends of their legs and stuck their abdomens in the air. “That behavior is only ever seen before ballooning,” says Morley. Many of the spiders actually managed to take off, despite being in closed boxes with no airflow within them. And when Morley turned off the electric fields inside the boxes, the ballooning spiders dropped.

It’s especially important, says Angela Chuang, from the University of Tennessee, to know that spiders can physically detect electrostatic changes in their surroundings. “[That’s] the foundation for lots of interesting research questions,” she says. “How do various electric-field strengths affect the physics of takeoff, flight, and landing? Do spiders use information on atmospheric conditions to make decisions about when to break down their webs, or create new ones?”

Air currents might still play some role in ballooning. After all, the same hairs that allow spiders to sense electric fields can also help them to gauge wind speed or direction. And Moonsung Cho from the Technical University of Berlin recently showed that spiders prepare for flight by raising their front legs into the wind, presumably to test how strong it is.

Still, Morley and Robert’s study shows that electrostatic forces are, on their own, enough to propel spiders into the air. “This is really top-notch science,” says Gorham. “As a physicist, it seemed very clear to me that electric fields played a central role, but I could only speculate on how the biology might support this. Morley and Robert have taken this to a level of certainty that far exceeds any expectations I had.”

“I think Charles Darwin would be as thrilled to read it as I was,” he adds.


By Michael Le Page

A recently discovered parasitic wasp appears to have extraordinary mind-controlling abilities – it can alter the behaviour of at least seven other species.

Many parasites manipulate the behaviour of their victims in extraordinary ways. For instance, sacculina barnacles invade crabs and make them care for barnacle larvae as if they were their own offspring. If the host crab is male, the parasite turns them female.

It was thought each species of parasite could manipulate the behaviour of only one host, or least only very closely related species. But the crypt-keeper wasp Euderus set is more versatile.

It parasitises other wasps called gall wasps. Gall wasps lay their eggs in plants, triggering abnormal growths – galls – inside which the wasp larvae feed and grow. Adult gall wasps chew their way out of the gall and fly off.

The crypt-keeper wasp seeks out oak galls and lays an egg inside them. The crypt-keeper larva then attacks the gall wasp larva. Infected gall wasps still start chewing their way out of the gall, but they stop chewing when the hole is still small and then remain where they are with their head blocking the exit and thus protecting the larva growing inside them – “keeping the crypt”.

How the crypt-keeper larva makes the gall wasp stop chewing at such a precise point is not clear. “I’d love to know how they do it,” says Anna Ward of the University of Iowa.

When the crypt-keeper larva turns into an adult wasp after a few days, it then chews through the head of the gall wasp to get out of the gall.

The crypt-keeper wasp, which was only described in 2017, was thought to parasitise just one species. But when Ward’s team collected 23,000 galls from 10 kinds of oak trees as part of a bigger study, they found at least 7 of the 100 species of gall wasp they collected were parasitised by the same crypt-keeper wasp. “What we found is that it is attacking different hosts that don’t seem to be closely related,” says Ward.

And there are likely many more extraordinary parasites out there. Ward thinks there are more species of parasitic wasps – most yet to be discovered – than there are species of beetle. So far 350,000 species of beetle have been described, the most of any group of animals. Parasitic wasps are small and hard to find, and hardly anyone looks for them, she says.

Journal reference: Biology Letters, DOI: 10.1098/rsbl.2019.0428

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The presence of people in remote areas of the Santa Cruz Mountains turns mountain lions into veritable fraidy-cats and strikes so much fear in bobcats, skunks and opossums that they change their behavior to avoid detection, a new study has found.

Rats and mice, on the other hand, actually forage more in areas where homo sapien voices are heard, probably because they know fewer rodent-eating predators are around, the UC Santa Cruz study concluded.

The paper, published Wednesday in the journal Ecology Letters, describes how humans create a “landscape of fear” among both large and small predators just by being around, a situation that is ripe for exploitation by rodents and, potentially, other pests like ticks.

“We already know that humans are incredibly lethal predators. We kill other predators at much higher rates than any other predator kills predators,” said Chris Wilmers, an associate professor of environmental studies who co-authored the paper with doctoral students. “What we didn’t know was the impact of just our presence in the forest.”

The findings, part of the university-managed Santa Cruz Puma Project, came two years after a previous study by Wilmers showed cougars on trail cameras abandoning deer carcasses and turning tail and running when recorded human voices suddenly started playing near them.

This time Wilmers wanted to find out the wider impact of the human presence, so his research team selected two remote locations closed to the public that some of the more than 40 cougars fitted with GPS and radio telemetry collars are known to frequent.

Twenty-five speakers were spaced evenly in five rows of five in each of the two square-kilometer grids, one inside the Sierra Azul Preserve, just south of Los Gatos, and the other in the San Vicente Redwoods, east of the coastal town of Davenport. There were about 200 meters between each speaker.

Between May 29 and Aug. 31, 2017, the speakers alternated broadcasts of human voices and Pacific tree frog vocalizations for five weeks each, with long silences in between. The researchers then compared the behavior and responses of the various animals.

The seven mountain lions they observed changed their behavior dramatically when the human voices were playing, becoming more cautious and avoiding the area where they perceived there was a human presence. The cougars increased their distance from the nearest speaker by 29% and were detected inside the test areas 30% less often when human voices were being broadcast.

“They both avoided the grid and changed their behavior,” said Justin Suraci, a post doctoral student in Wilmers’ lab and the lead author of the study. “They slowed down their movement speed, which we interpreted as increased caution.”

Bobcats reduced their daytime activity by 31%, skunk activity decreased 40%and opossums foraged 66% less when people were talking. All the medium-sized carnivores were detected less on camera at feed stations when the human voices were within earshot.

“All three of the meso predators were behaviorally suppressed by the presence of humans,” Suraci said. “As it turns out humans are sufficiently scary that it was better to be more cautious and avoid a risky human encounter.”

The opposite happened with mice and rats. Deer mice expanded their range by 45% when people were heard talking in the forest. Both mice and woodrats increased their foraging activities by 17% compared to times when human voices weren’t playing, according to the study.

None of the animals in the experiment changed their behavior or reacted in any noticeable way to the sound of tree frogs.

Wilmers said the sudden boldness of rodents is probably as significant to us as the fear displayed by the mountain lions. It could mean more tick and insect-borne diseases, like Lyme disease, are being spread by rodents and other prey species when predators aren’t around.

Previous studies of cougars in the Santa Cruz Mountains showed that they kill more deer in residential areas, but spend less time feeding when they are near humans. Researchers believe they abandon prey more often around people and then must kill more deer because they are hungry.

Wilmers said human-cougar encounters in the Bay Area mostly occur because mountain lion travel corridors have been blocked by development. One such incident occurred in May 2014 when a large male puma hid behind a small hedge on a busy street in Mountain View for nine hours as pedestrians and bicyclists passed only a few feet away.

The confused cat eventually was tranquilized amid a community furor and released in the hills, but he was later killed trying to cross Interstate 280.

by David Nield

Since the 1980s scientists have spotted a link between naval sonar systems and beaked whales seemingly killing themselves – by deliberately getting stranded on beaches. Now, researchers might have revealed the horrifying reason why.

In short, the sound pulses appear to scare the whales to death, acting like a shot of adrenaline might in a human, and causing deadly changes in their otherwise perfectly calibrated diving techniques.

By studying mass stranding events (MSEs) from recent history, the team found that beaked whales bring a sort of decompression sickness (also known as ‘the bends’ or ‘divers’ disease’) on themselves when they sense sonar. When panicked, their veins fill up with nitrogen gas bubbles, their brains suffer severe haemorrhaging, and other organs get damaged.

“In the presence of sonar they are stressed and swim vigorously away from the sound source, changing their diving pattern,” one of the researchers, Yara Bernaldo de Quiros from the University of Las Palmas de Gran Canaria in Spain, told AFP.

“The stress response, in other words, overrides the diving response, which makes the animals accumulate nitrogen.”

The end result is these poor creatures die in agony after getting the whale version of the bends – not something you would normally expect from whales that are so adept at navigating deep underwater.

Typically, these animals naturally lower their heart rate to reduce oxygen use and prevent nitrogen build-up when they plunge far below the surface. Tragically, it appears that a burst of sonar actually overrides these precautions.

The researchers weighed up the evidence from some 121 MSEs between the years 1960 and 2004, and particularly focussed on the autopsies of 10 dead whales stranded in the Canary Islands in 2002 after a nearby naval exercise.

It’s here that the decompression sickness effects were noticed, as they have been in other stranding events that the researchers looked at.

While the team notes that the effects of sonar on whales seem to “vary among individuals or populations”, and “predisposing factors may contribute to individual outcomes”, there does seem to be a common thread in terms of what happens to these unsuspecting mammals.

That’s especially true for Cuvier’s beaked whale (Ziphius cavirostris) – of the 121 MSEs we’ve mentioned, 61 involved Cuvier’s beaked whales, and the researchers say they appear particularly vulnerable to sonar.

There’s also a particular kind of sonar to be worried about: mid-frequency active sonar (MFAS), in the range of about 5 kilohertz.

Now the researchers behind the new report want to see the use of such sonar technology banned in areas where whales are known to live – such a ban has been in place in the Canary Islands since the 2002 incident.

“Up until then, the Canaries were a hotspot for this kind of atypical stranding,” de Quiros told AFP. “Since the moratorium, none have occurred.”

The research has been published in the Royal Society Journal Proceedings B.


In 1959, Soviet scientists embarked on an audacious experiment to breed a population of tame foxes, a strain of animals that wouldn’t be aggressive or fearful of people.

Scientists painstakingly selected the friendliest foxes to start each new generation, and within 10 cycles they began to see differences from wild foxes – fox pups that wagged their tails eagerly at people or with ears that stayed folded like a dog’s.

This study in animal domestication, known as the Russian farm-fox experiment, might be just a fascinating historical footnote – a quirky corner in the otherwise fraught scientific heritage of Soviet Russia.

Instead, it spawned an ongoing area of research into how domestication, based purely on behavioral traits, can result in other changes – like curlier tails and changes to fur color.

Now, the tools of modern biology are revealing the genetic changes that underpin the taming of foxes of Siberia.

In a new study, published Monday in Nature Ecology & Evolution, scientists used genome sequencing to identify 103 stretches of the fox genome that appear to have been changed by breeding, a first pass at identifying the genes that make some foxes comfortable with humans and others wary and aggressive.

The scientists studied the genomes of 10 foxes from three different groups: the tame population, a strain that was bred to be aggressive toward people and a conventional group bred to live on a farm.

Having genetic information from all three groups allowed the researchers to identify regions of the genome that were likely to have changed due to the active selection of animals with different behaviors, rather than natural fluctuation over time.

Those regions offer starting points in efforts to probe the genetic basis and evolution of complex traits, such as sociability or aggressiveness.

“The experiment has been going on for decades and decades, and to finally have the genome information, you get to look and see where in the genome and what in the genome has been likely driving these changes that we’ve seen – it’s a very elegant experimental design,” said Adam Boyko, an associate professor of biomedical sciences at Cornell University, who was not involved in the study.

While some genetic traits are relatively simple to unravel, the underpinnings of social behaviors aren’t easy to dissect. Behavior is influenced by hundreds or thousands of genes, as well as the environment – and typically behaviors fall on a wide spectrum.

The existence of fox populations bred solely for how they interact with people offers a rare opportunity to strip away some of the other complexity – with possible implications for understanding such traits in people and other animals, too, since evolution may work on the same pathways or even the same genes.

“We’re interested to see what are the genes that make such a big difference in behavior. There are not so many animal models which are good to study genetics of social behavior, and in these foxes it’s such a big difference between tame foxes compared to conventional foxes, and those selected for aggressive behavior,” said Anna Kukekova, an assistant professor at the University of Illinois at Urbana-Champaign, who led the work.

Kukekova and colleagues began studying one very large gene that they think may be linked to tame behavior, called SorCS1. The gene plays a role in sorting proteins that allow brain cells to communicate.

Kukekova is interested in determining what happens if the gene is deleted in a mouse and to search for specific mutations that might contribute to differences in behavior.

Bridgett vonHoldt, an assistant professor of ecology and evolutionary biology at Princeton University, said changes that occurred in foxes “overlap extensively with those observed in the transition of gray wolves to modern domestic dogs.”

She said the study may help dog and fox biologists determine if there are complex behavioral traits under the control of just a few genes.

Recent fox evolution in a domesticated population may seem to have little to do with understanding the genetics of human behavior, but interest in domestication has grown as an area of scientific interest in part because genes involved in behavior in one animal may play a similar role in another.

“One reason why it is interesting is it gives us some insights about us. Humans are domesticated themselves, in a way,” Boyko said.

“We’re much more tolerant of being around other humans than probably we were as we were evolving; we’ve had to undergo a transformation, even relatively recently from the agricultural revolution.”

Researchers found the first known hybrid between a rough-toothed dolphin and a melon-headed whale near Kauai, Hawaii.

Rough-toothed dolphins.

Melon-headed whales.

By Jessie Yeung

Scientists from the Cascadia Research Collective have discovered a rare dolphin-whale hybrid off the coast of Kauai, Hawaii, according to a report published last week.

The marine mammal monitoring program, funded by the US Navy, first spotted the animal in August 2017. The team tagged various species, including commonly seen rough-toothed dolphins and rarer melon-headed whales.
However, researchers soon noticed that one tagged animal that looked a little odd. Although it had a typical melon-headed whale’s dorsal fin shape and dorsal cape, it was also blotchy in pigmentation and had a sloping forehead, more reminiscent of a rough-toothed dolphin.

A genetic sample soon confirmed their suspicions: it was a hybrid of the two species, the first to ever be found.The cross-species hybridization may seem bizarre, but is made possible by the fact that melon-headed whales aren’t actually whales. They belong to the Delphinidae family, otherwise known as oceanic dolphins, which also includes orcas and two species of pilot whales.

It also isn’t the first discovery of hybridization in the family
— there have also been cases of bottlenose dolphin/false killer whale (Pseudorca crassidens) hybrids, known as Wolphins, and common/bottlenose dolphin hybrids.

This is the first confirmed hybrid between rough-toothed dolphins and melon-headed whales. However, though it’s an exciting discovery, researchers point out it is not, as commonly thought, a new species.

“While hybridization can at times lead to new species, most of the time this does not happen,” Cascadia researcher Robin Baird told CNN, pointing that there was only a single hybrid found this time.

Some hybrid animals, such as the mule — a hybrid of a male donkey and female horse — are mostly sterile and therefore cannot propagate easily.

The dolphin-whale hybridization is especially surprising in this region, as a sighting of melon-headed whales had never before been confirmed near the Pacific Missile Range Facility (PMRF) navy base.

The hybrid was only traveling with one companion — a melon-headed whale. This, too was unusual, given that melon-headed whales typically travel in groups of 200-300. The solitary pair were “found associating with rough-toothed dolphins,” the report read.

The odd pair and their closeness to the other dolphins have led the researchers to speculate that the accompanying melon-headed whale is the hybrid’s mother.
The research team will return to Kauai next week, hoping to confirm their theory.

“If we were lucky enough to find the pair again, we would try to get a biopsy sample of the accompanying melon-headed whale, to see whether it might be the mother of the hybrid, as well as get underwater images of the hybrid to better assess morphological differences from the parent species,” said Baird.

The US Navy is required to monitor these species as part of the Marine Mammal Protection Act and the Endangered Species Act.

They do so through the Cascadia Research Collective, which conducts photo identification, genetic analyzes, and acoustic monitoring to determine the abundance of odontocetes, also known as toothed whales.

Motion sensor “camera traps” unobtrusively take pictures of animals in their natural environment, oftentimes yielding images not otherwise observable. The artificial intelligence system automatically processes such images, here correctly reporting this as a picture of two impala standing.

A new paper in the Proceedings of the National Academy of Sciences (PNAS) reports how a cutting-edge artificial intelligence technique called deep learning can automatically identify, count and describe animals in their natural habitats.

Photographs that are automatically collected by motion-sensor cameras can then be automatically described by deep neural networks. The result is a system that can automate animal identification for up to 99.3 percent of images while still performing at the same 96.6 percent accuracy rate of crowdsourced teams of human volunteers.

“This technology lets us accurately, unobtrusively and inexpensively collect wildlife data, which could help catalyze the transformation of many fields of ecology, wildlife biology, zoology, conservation biology and animal behavior into ‘big data’ sciences. This will dramatically improve our ability to both study and conserve wildlife and precious ecosystems,” says Jeff Clune, the senior author of the paper. He is the Harris Associate Professor at the University of Wyoming and a senior research manager at Uber’s Artificial Intelligence Labs.

The paper was written by Clune; his Ph.D. student Mohammad Sadegh Norouzzadeh; his former Ph.D. student Anh Nguyen (now at Auburn University); Margaret Kosmala (Harvard University); Ali Swanson (University of Oxford); and Meredith Palmer and Craig Packer (both from the University of Minnesota).

Deep neural networks are a form of computational intelligence loosely inspired by how animal brains see and understand the world. They require vast amounts of training data to work well, and the data must be accurately labeled (e.g., each image being correctly tagged with which species of animal is present, how many there are, etc.).

This study obtained the necessary data from Snapshot Serengeti, a citizen science project on the platform. Snapshot Serengeti has deployed a large number of “camera traps” (motion-sensor cameras) in Tanzania that collect millions of images of animals in their natural habitat, such as lions, leopards, cheetahs and elephants. The information in these photographs is only useful once it has been converted into text and numbers. For years, the best method for extracting such information was to ask crowdsourced teams of human volunteers to label each image manually. The study published today harnessed 3.2 million labeled images produced in this manner by more than 50,000 human volunteers over several years.

“When I told Jeff Clune we had 3.2 million labeled images, he stopped in his tracks,” says Packer, who heads the Snapshot Serengeti project. “We wanted to test whether we could use machine learning to automate the work of human volunteers. Our citizen scientists have done phenomenal work, but we needed to speed up the process to handle ever greater amounts of data. The deep learning algorithm is amazing and far surpassed my expectations. This is a game changer for wildlife ecology.”

Swanson, who founded Snapshot Serengeti, adds: “There are hundreds of camera-trap projects in the world, and very few of them are able to recruit large armies of human volunteers to extract their data. That means that much of the knowledge in these important data sets remains untapped. Although projects are increasingly turning to citizen science for image classification, we’re starting to see it take longer and longer to label each batch of images as the demand for volunteers grows. We believe deep learning will be key in alleviating the bottleneck for camera-trap projects: the effort of converting images into usable data.”

“Not only does the artificial intelligence system tell you which of 48 different species of animal is present, but it also tells you how many there are and what they are doing. It will tell you if they are eating, sleeping, if babies are present, etc.,” adds Kosmala, another Snapshot Serengeti leader. “We estimate that the deep learning technology pipeline we describe would save more than eight years of human labeling effort for each additional 3 million images. That is a lot of valuable volunteer time that can be redeployed to help other projects.”

First-author Sadegh Norouzzadeh points out that “Deep learning is still improving rapidly, and we expect that its performance will only get better in the coming years. Here, we wanted to demonstrate the value of the technology to the wildlife ecology community, but we expect that as more people research how to improve deep learning for this application and publish their datasets, the sky’s the limit. It is exciting to think of all the different ways this technology can help with our important scientific and conservation missions.”

The paper that in PNAS is titled, “Automatically identifying, counting, and describing wild animals in camera-trap images with deep learning.”,-count,-describe-wild-animals.html