Science was not giving us a huge amount of good news these days. We are accelerating towards the climate catastrophe, for example. We have ruined the environment so badly, it is hard to even define it as an environment. And this is coming back to bite (or sting) us: the bee populations, which we are counting on pollinating our crops, are collapsing.
But science is coming to the rescue, gluing the QR codes to the backs of the bumblebees and following their movements with a robotic camera. Researchers have created a system that monitors the individual bees and dynamics of entire colonies exposed to ididacloprid, a neurotoxin belonging to the notorious neonicotinoid pesticide group. The discoveries are not beautiful, but they can do a lot to tease the way the neonicotinoids are devastating bees and how we can save these flyers.
Neonicotinoids are the most widespread class of insecticides globally. "When we started using them in agriculture in particular, have they passed the initial tests of Oh are they safe for bees at concentrations they might encounter on the field?", Says Harvard biologist James Crall, lead author of a new paper in Science which describes the tracing technique of the hornet.
But those tests were not accurate enough. "You may not see a dead bee in 24 or 48 hours, but you will continue to see important behavioral changes over time that lead to impaired colony function and long-term growth," adds Crall.
Although a neonicotinoid such as imidacloprid, a common insecticide, does not permanently kill a bee, it can cause other changes. Previous research shows, for example, that in the field the neonicotinoids may compromise the ability of a bee to navigate and find flowers. This has implications for how bees feed on themselves and their colonies in general. What happened within a colony exposed to neonicotinoids, however, was more difficult to analyze.
Here's where Crall and his team's research resume. In the laboratory they set up a dozen hornet colonies, each contained in a transparent acrylic box. The researchers fed some colonies of imidacloprid to levels equal to those that the bees would have exposed in the field, while they held other control colonies free of imidacloprid. A system of robotic cameras runs on tracks above the head, scanning each nest below. "So we monitor for about 5 minutes what happens in each colony 12 times a day," says Crall. "And we can manage it completely independently for almost two weeks". Because each bee has a QR code on its back, a computer vision system can follow day and night movements.
The differences that researchers have discovered between exposed and normal colonies are affecting. "Bees are less active, so they spend more time resting," says Crall. "They are a little farther from the nest center", where the larvae require care, "and interact even less with the nest partners." And behavioral changes are more pronounced at night. "Sometimes the eye colony looks totally functional during the day, and then you see these heavy incidents at night."
Lower activity levels are particularly problematic when one considers that bumbles have those larvae to cuddle. Healthy bees actively heat young people with their bodies by making their muscles vibrate. What Crall and his colleagues have discovered is that the colonies exposed to ididacloprid are not as good at maintaining the temperature of the larvae as normal bumbles do, which could have implications for the development of young people.
"If this is one of the main ways these compounds are affecting growth, which could be more extreme in some environments than others, or under different conditions than others," says Crall. If the outside temperature is adorable for bumblebees, this may not be a big deal. But if you have temperature changes and imidacloprid is affecting people's ability to control the nest, young people may not prosper.
This was not the only difference in the way the bees cultivate their young. Normally bumblebees build a canopy of wax that sits like a blanket over the developing hatch, again for warmth. Almost all the control colonies Crall was experimenting with did this, but none of the colonies exposed to ididacloprid did. "It's probably upsetting not only these short-term direct behaviors, but these long-term changes in the nest architecture," says Crall.
Most species of bees, however, are solitary, not social. So what happens to solitary bees exposed to neonicotinoids? The females are largely alone in these species: they will mate with a male and the male will take off. "So that female has to do all these different activities to create the nest, forage, lay eggs and continue that cycle for weeks or in some cases months until death," says Nigel Raine of the University of Guelph, who studies bees and exposure to pesticides and who wrote a comment on this new study. "So we could imagine that the exposure to pesticides for that individual could have more serious consequences for their reproductive production."
At the other end of the spectrum are the bees, whose colonies are thousands. (The species that Crall studies falls in the middle: the hornet Bombus impatiens with about 200 to a colony.) Neonicotinoids cause subtle behavioral changes even for honey bees, but this may not be as consequential as it would be for a small colony of bumblebees or a solitary bee. "A relatively small impact on an individual's foraging performance can be masked by more individuals who go out and perform this task," says Raine.
Good news for honey bees, but here is a problem. Researchers and regulators have relied largely on bees as a model for studying exposure to the neonicotinoid: they are easy to find, for example. But when it comes to pesticides, what happens to bees is probably not for solitary bumbles or bees because of the size of societies. Raine says she is working with colleagues and regulators to consider these potentially more vulnerable species.
Also, we're talking about a single stress factor here: Crall and his colleagues have looked at a single pesticide of seven neonicotinoids. But the idea is that researchers can use this technique to test other pesticides in bee colonies.
Bees are in trouble, yes. But with new techniques like this, scientists can better understand what puts them at risk. A bit of good news, perhaps, on a crazy planet.
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