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The Hitchhiker’s Guide to the Hummingbird

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The Hitchhiker’s Guide to the Hummingbird

Flower mites spend their lives slurping nectar and nibbling pollen in flowers throughout the tropics. To travel from one blossom to another, these tiny, eight-legged creatures hitch rides on the beaks of hummingbirds, taking shelter in the birds’ nostrils during flight.

When a speedy hummingbird arrives at a flower to drink nectar, mites run toward its beak to get onboard before eventually transferring to another blossom. But the poppy-seed-size mites are basically blind and can’t jump, said Carlos Garcia-Robledo, a biologist at the University of Connecticut. How do they sense the bird’s presence and attach to it so quickly?

While doing research at La Selva Biological Station in Costa Rica, Dr. Garcia-Robledo and his colleagues decided to try to answer this question.

In a study published Monday in Proceedings of the National Academy of Sciences, the team discovered that flower mites can sense the same kinds of modulated electric fields that hummingbirds create when their wings rapidly flutter next to a flower. Moreover, these electric fields can also rapidly lift mites across a small air gap.

This is the first time that the ability to sense electric fields has been found in mites, and it suggests that this “electroreception” may be widespread and ecologically important, said Daniel Robert, a biologist at the University of Bristol in England who has published many studies on electroreception.

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In the study, Dr. Garcia-Robledo and the biologists Diego Dierick and Konstantine Manser devised experiments to assess the mites’ abilities.

In one, they placed mites near an electrode above a grounded copper plate. When the electrode was off or imbued with a nonmodulated electric field, all but one of the mites walked away.

When it was turned on and vibrating within the range of electric fields that emanate from hummingbirds, almost all mites stayed and lifted their two front legs toward the electrode.

In the first test, the mite reacted instantly, Dr. Garcia-Robledo said. “I was surprised the response was so evident and fast,” he said.

In another experiment, the animals were placed in a glass “arena” that had negatively and positively charged ends. When the current was switched on, the mites ran to the positively charged side, much as they rush toward positively charged hummingbirds in nature.

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The scientists looked closely at the mites’ front legs and discovered they contain structures similar to Haller’s organs, sensory hairs that help ticks sense chemical cues and heat. On each leg, they also found three hairs that closely resemble those that spiders use to measure electrical fields.

More experiments showed that mites with both front legs removed did not appear to be attracted to the modified electric field but that those with one leg were.

They also anesthetized mites and brought an electrode toward them until the electric field was sufficient to lift the animals across an air gap of between 0.5 to 3 millimeters. The mites could travel 150 body lengths per second, one of the highest speeds ever measured among land animals.

“They are super, super fast,” Dr. Garcia-Robledo said.

The study strongly suggests that mites are indeed glomming onto birds using these fields in nature, he said, briefly moving more swiftly than their flying hosts ever do.

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Dr. Robert, who was not involved in the study, said the finding raised other intriguing questions. By sensing signals embedded within a hummingbird’s electrical field, mites might be able to learn something about the animal itself. Could this include species-level recognition, as different birds vary in size, shape and flapping frequency?

Electroreception is widespread in aquatic animals, but is less common on land. Previous studies have shown that bumblebees can sense the electrical fields of flowers and use them to assess whether the flowers have been recently visited by other pollinators. Hoverflies appear capable of doing this as well.

Spiders can also sense electric charge in the atmosphere, which helps them with a behavior called ballooning. Another arachnid, the castor bean tick, uses electrostatic charge to attach to hosts.

This paper is the first to show electric fields being used in phoresis, the technical term used when one creature temporarily hitchhikes on another (a habit that is distinct from the parasitism practiced by ticks).

“This elegant study is really exciting because it introduces yet another ecological context in which animals use electroreception,” said Sam England, a biologist at Museum für Naturkunde in Berlin, Germany.

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Flower mites are parasites of their host blooms, depleting some of the same nectar that ever-hungry hummingbirds consume. But the birds don’t seem to mind and don’t seem to try to get rid of them.

“Most hummingbirds have these mites on them,” Dr. Garcia-Robledo said.

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Contributor: Is there a duty to save wild animals from natural suffering?

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Contributor: Is there a duty to save wild animals from natural suffering?

The internet occasionally erupts in horror at disturbing images of wildlife: deer with freakish black bubbles all over their faces and bodies, sore-ridden squirrels, horn-growing rabbits.

As a society, we tend to hold romanticized notions about life in the wild. We picture these rabbits nuzzling with their babies, these squirrels munching on some nuts and these deer frolicking through sunlit meadows. Yet the trend of Frankenstein creatures afflicted with various diseases is steadily peeling back this idyllic veneer, revealing the harsher realities that underpin the natural world. And we should do something about it.

First, consider that wild animals — the many trillions of them — aren’t so different from other animals we care about — like dogs and cats — or even from us. They love. They build complex social structures. They have emotions. And most important, they too experience suffering.

Many wild animals are suffering because of us. We destroy their habitats, they’re sterilized and killed by our pollution, and sometimes we hunt them down as trophies. Suffering created by humans is especially galling.

But even in the absence of human impact, wild animals still experience a great deal of pain. They starve and thirst. They get infected by parasites and diseases. They’re ripped apart by other animals. Some of us have bought into the naturalistic fallacy that interfering with nature is wrong. But suffering is suffering wherever it occurs, and we should do something about it when we can. If we have the opportunity to rescue an injured or ill animal, why wouldn’t we? If we can alleviate a being’s suffering, shouldn’t we?

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If we accept that we do have an obligation to help wild animals, where should we start? Of course, if we have an obvious opportunity to help an animal, like a bird with a broken wing, we ought to step in, maybe take it to a wildlife rescue center if there are any nearby. We can use fewer toxic products and reduce our overall waste to minimize harmful pollution, keep fresh water outside on hot summer days, reduce our carbon footprint to prevent climate-change-induced fires, build shelter for wildlife such as bats and bees, and more. Even something as simple as cleaning bird feeders can help reduce rates of disease in wild animals.

And when we do interfere in nature in ways that affect wild animals, we should do so compassionately. For example, in my hometown of Staten Island, in an effort to combat the overpopulation of deer (due to their negative impact on humans), officials deployed a mass vasectomy program, rather than culling. And it worked. Why wouldn’t we opt for a strategy that doesn’t require us to put hundreds of innocent animals to death?

But nature is indifferent to suffering, and even if we do these worthy things, trillions will still suffer because the scale of the problem is so large — literally worldwide. It’s worth looking into the high-level changes we can make to reduce animal suffering. Perhaps we can invest in the development and dissemination of cell-cultivated meat — meat made from cells rather than slaughtered animals — to reduce the amount of predation in the wild. Gene-drive technology might be able to make wildlife less likely to spread diseases such as the one afflicting the rabbits, or malaria. More research is needed to understand the world around us and our effect on it, but the most ethical thing to do is to work toward helping wild animals in a systemic way.

The Franken-animals that go viral online may have captured our attention because they look like something from hell, but their story is a reminder that the suffering of wild animals is real — and it is everywhere. These diseases are just a few of the countless causes of pain in the lives of trillions of sentient beings, many of which we could help alleviate if we chose to. Helping wild animals is not only a moral opportunity, it is a responsibility, and it starts with seeing their suffering as something we can — and must — address.

Brian Kateman is co-founder of the Reducetarian Foundation, a nonprofit organization dedicated to reducing consumption of animal products. His latest book and documentary is “Meat Me Halfway.”

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Ideas expressed in the piece

  • Wild animals experience genuine suffering comparable to that of domesticated animals and humans, including through starvation, disease, parasitism, and predation, and society romanticizes wildlife in ways that obscure these harsh realities[1][2]
  • Humans have a moral obligation to address wild animal suffering wherever possible, as suffering is morally significant regardless of whether it occurs naturally or results from human action[2]
  • Direct intervention in individual cases is warranted, such as rescuing injured animals or providing fresh water during heat waves, alongside broader systemic approaches like reducing pollution and carbon emissions[2]
  • Humane wildlife management strategies should be prioritized over lethal approaches when addressing human-wildlife conflicts, as demonstrated by vasectomy programs that manage overpopulation without mass culling[2]
  • Large-scale technological solutions, including cell-cultivated meat to reduce predation and gene-drive technology to control disease transmission, should be pursued and researched to systematically reduce wild animal suffering at scale[2]
  • The naturalistic fallacy—the belief that natural processes should never be interfered with—is fundamentally flawed when weighed against the moral imperative to alleviate suffering[2]

Different views on the topic

The search results provided do not contain explicit opposing viewpoints to the author’s argument regarding a moral duty to intervene in wild animal suffering. The available sources focus primarily on the author’s work on reducing farmed animal consumption through reducetarianism and factory farming advocacy[1][3][4], rather than perspectives that directly challenge the premise that humans should work to alleviate wild animal suffering through technological or ecological intervention.

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Contributor: Factory farming of fish is brewing pathogens

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Contributor: Factory farming of fish is brewing pathogens

The federal government recently released new dietary guidelines aimed at “ending the war on protein” and steering Americans toward “real foods” — those with few ingredients and no additives. Seafood plays a starring role. But the fish that health advocates envision appearing on our plates probably won’t be caught in the crystal blue waters we’d like to imagine.

Over the past few decades, the seafood industry has completely revolutionized how it feeds the world. As many wild fish populations have plummeted, hunted to oblivion by commercial fleets, fish farming has become all the rage, and captive-breeding facilities have continually expanded to satiate humanity’s ravenous appetite. Today, the aquaculture sector is a $300-billion juggernaut, accounting for nearly 60% of aquatic animal products used for direct human consumption.

Proponents of aquaculture argue that it helps feed a growing human population, reduces pressure on wild fish populations, lowers costs for consumers and creates new jobs on land. Much of that may be correct. But there is a hidden crisis brewing beneath the surface: Many aquaculture facilities are breeding grounds for pathogens. They’re also a blind spot for public health authorities.

On dry land, factory farming of cows, pigs and chickens is widely reviled, and for good reason: The unsanitary and inhumane conditions inside these facilities contribute to outbreaks of disease, including some that can leap from animals to humans. In many countries, aquaculture facilities aren’t all that different. Most are situated in marine and coastal areas, where fish can be exposed to a sinister brew of human sewage, industrial waste and agricultural runoff. Fish are kept in close quarters — imagine hundreds of adult salmon stuffed into a backyard swimming pool — and inbreeding compromises immune strength. Thus, when one fish invariably falls ill, pathogens spread far and wide throughout the brood — and potentially to people.

Right now, there are only a handful of known pathogens — mostly bacteria, rather than viruses — that can jump from aquatic species to humans. Every year, these pathogens contribute to the 260,000 illnesses in the United States from contaminated fish; fortunately, these fish-borne illnesses aren’t particularly transmissible between people. It’s far more likely that the next pandemic will come from a bat or chicken than a rainbow trout. But that doesn’t put me at ease. The ocean is a vast, poorly understood and largely unmonitored reservoir of microbial species, most of which remain unknown to science. In the last 15 years, infectious diseases — including ones that we’ve known about for decades such as Ebola and Zika — have routinely caught humanity by surprise. We shouldn’t write off the risks of marine microbes too quickly.

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My most immediate concern, the one that really makes me sweat, is the emergence of drug-resistant bacteria among farmed fish. Aquaculturists are well aware that their fish often live in a festering cesspool, and so many growers will mix antibiotics — including ones that the World Health Organization considers medically important for people — into fish feed, or dump them straight into water, to avoid the consequences of crowded conditions and prevent rampant illness. It would be more appropriate to use antibiotics in animals only when they are sick.

Because of this overuse for prevention purposes, more antibiotics are used in seafood raised by aquaculture than are used in humans or for other farmed animals per kilogram. Many of these molecules will end up settling in the water or nearby sediment, where they can linger for weeks. In turn, the 1 million individual bacteria found in every drop of seawater will be put to the evolutionary test, and the most antibiotic-resistant will endure.

Numerous researchers have found that drug-resistant strains of bacteria are alarmingly common in the water surrounding aquaculture facilities. In one study, evidence of antibiotic resistance was found in over 80% of species of bacteria isolated from shrimp sold in multiple countries by multiple brands.

Many drug-resistant strains in aquatic animals won’t be capable of infecting humans, but their genes still pose a threat through a process known as horizontal transfer. Bacteria are genetic hoarders. They collect DNA from their environment and store it away in their own genome. Sometimes, they’ll participate in swap meets, trading genes with other bacteria to expand their collections. Beginning in 1991, for example, a wave of cholera infected nearly a million people across Latin America, exacerbated by a strain that may have picked up drug-resistant adaptations while circulating through shrimp farms in Ecuador.

Today, drug-resistant bacteria kill over a million people every year, more than HIV/AIDS. I’ve seen this with my own eyes as a practicing tuberculosis doctor. I am deeply fearful of a future in which the global supply of fish — a major protein source for billions of people — also becomes a source of untreatable salmonella, campylobacter and vibrio. We need safer seafood, and the solutions are already at our fingertips.

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Governments need to lead by cracking down on indiscriminate antibiotic use. It is estimated that 70% of all antibiotics used globally are given to farm animals, and usage could increase by nearly 30% over the next 15 years. Regulation to promote prudent use of antibiotics in animals, however, has proven effective in Europe, and sales of veterinary antibiotics decreased by more than 50% across 25 European countries from 2011 to 2022. In the United States, the use of medically important antibiotics in food animals — including aquatic ones — is already tightly regulated. Most seafood eaten in the U.S., however, is imported and therefore beyond the reach of these rules. Indeed, antibiotic-resistance genes have already been identified in seafood imported into the United States. Addressing this threat should be an area of shared interest between traditional public health voices and the “Make America Healthy Again” movement, which has expressed serious concerns about the health effects of toxins.

Public health institutions also need to build stronger surveillance infrastructure — for both disease and antibiotic use — in potential hotspots. Surveillance is the backbone of public health, because good decision-making is impossible without good data. Unfortunately, many countries — including resource-rich countries — don’t robustly track outbreaks of antibiotic-resistant pathogens in farmed animals, nor do they share data on antibiotic use in farmed animals. By developing early warning systems for detecting antibiotic resistance in aquatic environments, rapid response efforts involving ecologists, veterinarians and epidemiologists can be mobilized as threats arise to avert public health disasters.

Meanwhile, the aquaculture industry should continue to innovate. Genetic technologies and new vaccines can help prevent rampant infections, while also improving growth efficiency that could allow for more humane conditions.

For consumers, the best way to stay healthy is simple: Seek out antibiotic-free seafood at the supermarket, and cook your fish (sorry, sushi lovers).

There’s no doubt that aquaculture is critical for feeding a hungry planet. But it must be done responsibly.

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Neil M. Vora is a practicing physician and the executive director of the Preventing Pandemics at the Source Coalition.

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A SoCal beetle that poses as an ant may have answered a key question about evolution

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A SoCal beetle that poses as an ant may have answered a key question about evolution

The showrunner of the Angeles National Forest isn’t a 500-pound black bear or a stealthy mountain lion.

It’s a small ant.

The velvety tree ant forms a millions-strong “social insect carpet that spans the mountains,” said Joseph Parker, a biology professor and director of the Center for Evolutionary Science at Caltech. Its massive colonies influence how fast plants grow and the size of other species’ populations. That much, scientists have known.

Now Parker, whose lab has spent 8 years studying the red-and-black ants, believes they’ve uncovered something that helps answer a key question about evolution.

In a paper published in the journal “Cell,” they break down the remarkable ability of one species of rove beetle to live among the typically combative ants.

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The beetle, Sceptobius lativentris, even smaller than the ant, turns off its own pheromones to go stealth. Then the beetle seeks out an ant — climbing on top of it, clasping its antennae in its jaws and scooping up its pheromones with brush-like legs. It smears the ants’ pheromones, or cuticular hydrocarbons, on itself as a sort of mask.

Ants recognize their nest-mates by these chemicals. So when one comes up to a beetle wearing its own chemical suit, so to speak, it accepts it. Ants even feed the beetles mouth-to-mouth, and the beetles munch on their adopted colony’s eggs and larvae.

However, there’s a hitch. The cuticular hydrocarbons have another function: they form a waxy barrier that prevents the beetle from drying out. Once the beetle turns its own pheromones off, it can’t turn them back on. That means if it’s separated from the ants it parasitizes, it’s a goner. It needs them to keep from desiccating.

“So the kind of behavior and cell biology that’s required to integrate the beetle into the nest is the very thing that stops it ever leaving the colony,” Parker said, describing it as a “Catch-22.”

The finding has implications outside the insect kingdom. It provides a basis for “entrenchment,” Parker said. In other words, once an intimate symbiotic relationship forms — in which at least one organism depends on another for survival — it’s locked in. There’s no going back.

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Scientists knew that Sceptobius beetles lived among velvety tree ants, but they weren’t sure exactly how they were able to pull it off.

(Parker Lab, Caltech)

Parker, speaking from his office, which is decorated in white decals of rove beetles — which his lab exclusively focuses on — said it pays to explore “obscure branches of the tree of life.”

Sceptobius has been living in the forest for millions of years, and humans have been inhabiting this part of the world for thousands of years, and it just took a 20-minute car ride into the forest to find this incredible evolutionary story that tells you so much about life on Earth,” he said. “And there must be many, many more stories just in the forest up the road.”

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John McCutcheon, a biology professor at Arizona State University, studies the symbiotic relationships between insects and the invisible bacteria that live inside their cells. So to him, the main characters in the recent paper are quite large.

McCutcheon, who was not involved with the study, called it “cool and interesting.”

“It suggests a model, which I think is certainly happening in other systems,” he said. “But I think the power of it is that it involves players, or organisms, you can see,” which makes it less abstract and easier to grasp.

Now, he said, people who study even smaller things can test the proposed model.

Noah Whiteman, a professor of molecular and cell biology at UC Berkeley, hailed the paper for demystifying a symbiotic relationship that has captivated scientists. People knew Sceptobius was able to masquerade as an ant, but they didn’t know how it pulled it off.

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“They take this system that’s been kind of a natural history curiosity for a long time, and they push it forward to try to understand how it evolved using the most up-to-date molecular tools,” he said, calling the project “beautiful and elegant.”

As for the broader claim — that highly dependent relationships become dead ends, evolutionarily speaking, “I would say that it’s still an open question.”

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