The fascinating abilities of bumblebees

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In the animal kingdom, a wide variety of species achieve amazing things time and time again. When you think of these super talents, you probably don't think of bumblebees first. But these fluffy-looking little creatures have a lot going for them.

"Insects are among the most successful creatures on the planet," explains Christoph Kurze, whose research at the University of Regensburg includes bumblebees, which belong to the family of true bees (Apidae). "The ability to fly has contributed significantly to this."

Too heavy to fly?

However, the assumption that bumblebees should not be able to fly at all due to their body shape and weight persists. This is a myth, which is probably the brainchild of Antoine Magnan. The professor studied animal mechanics for use in aviation in 1935, Kurze explains. Instead, the striped buzzers are amazingly good flyers: With an extremely high wing beat rate of 140 to 220 Hertz, the energy expenditure for the bumblebees when flying is extremely high. "The metabolic rate is 50 to 200 times that of the resting state," says the bumblebee researcher.

A study by scientists from Berkeley University (USA) also demonstrates the amazing abilities of the sympathetic fliers. The research team simulated the pressure conditions of the air at an altitude of 9000 meters. "The males of a mountain bumblebee species from the Himalayas were still able to fly even under these extreme pressure conditions," reports Kurze enthusiastically. "Not even a high-performance helicopter can do that."

No training effect

However, the biologist knows that flying itself is quite strenuous for bumblebees. Unlike birds, they cannot make use of thermals. The energy expenditure is extremely high. Nevertheless, the insects are real powerhouses. "They can carry up to 90 percent of their body weight and still take off," Kurze emphasizes. If a bumblebee is so heavily laden, the buzzing noise it makes when flying is also louder, as it has to flap its wings more intensively.

However, there is no known muscular training in bumblebees as there is in humans, says Kurze – at least there is no data to suggest a training effect. This means that nothing changes in the insects' body size or exoskeleton in adulthood: their talent for flight is fixed from the beginning of their lives. However, Kurze and his team have discovered that Adult workers can fly at different speeds depending on their body size. And age apparently also plays a role: "Young bumblebee workers don't fly as far – at two weeks old, they fly six times further than they did a week earlier." Kurze cannot conclusively say why this is the case. "Maybe they can't do it, but maybe they're just not ready yet."

Bumblebee queens raise their first brood alone

At the end of the season, it all comes down to the bumblebee queens: A few days after they hatch, they leave the nest. "The males then first have to find the queens via chemical communication in order to mate," explains Kurze. Once this has happened, each of the young queens looks for a place to spend the winter alone – usually underground.

"Worker bees only live for a few weeks to around three months, the males for one to two months," explains Kurze. However, the queen bumblebee lives for a good year. After hibernation, she builds her own colony. "When it gets warmer in March or April, you often see particularly large bumblebees – these are the queens looking for a new nest," says the entomologist. "They collect nectar and pollen to raise the first brood on their own." Once the first brood has hatched, the workers take over the care. The queen continues to lay eggs instead.

Excellent sense of direction

The fluffy insects cover astonishing distances in search of food. "There are 41 known species of bumblebee that live or have lived in Germany, compared to around 250 worldwide," says Kurze. "Some of them differ significantly from one another." While the dark ground bumblebee, which is particularly well researched in Germany, flies around one to three kilometers around the nest, there is a bumblebee species on the west coast of the USA that searches for nectar up to twelve kilometers from its nest. "This depends heavily on environmental factors, especially the food supply."

Despite the great distances, the bumblebees find their way back home. They rely primarily on their compound eyes to do this. "For visual orientation, bumblebees pay attention to the position of the sun, but can also see polarized light," says Kurze. "The principle is known from polarized sunglasses, for example, which make it easier to see through reflections."

The sense of smell also plays a major role in orientation. "Bumblebees can smell with their antennae and have specific receptors that enable them to detect odor molecules very well," explains the scientist. "They can even be conditioned to certain odors."

Another guide is path integration. Here, the animals benefit from their good memory. "Put simply, bumblebees have a sense of how far they have flown and in which direction," explains the biologist. "The fascinating thing about path integration is that they can fly the most direct route back." There are also indications that they may have a kind of magnetic compass.

Communication via vibrations

Once in the nest, they can give other workers clues as to where the search for food is particularly lucrative. To do this, they use vibrations to communicate on certain frequencies. Chemical communication based on pheromones also plays an important role, says Kurze. However, the exact directions that honeybees can give with the help of a waggle dance are not yet known for bumblebees.

If you find bumblebees on the sidewalk in late summer or fall, there is usually not much you can do for them – except put them in a nicer environment. "Most of them are at the end of their lives," explains Kurze. Sometimes, however, the animals don't find enough food and starve to death. "If you want to do something good for bumblebees and other insects, don't just plant short-cut grass in your garden, but also let clover grow, at least in parts, or give wild flowers a chance." According to Christoph Kurze, Provence lavender, common viper's bugloss, catmint, cranesbill "Spinners" and Byzantine woolly bugloss are particularly popular with bumblebees.

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