Imagine being a bumblebee, with the ability to see a vibrant world of colors and scents. Bumblebees possess a keen sense of sight, allowing them to distinguish UV and most colors except red, and three separate simple eyes for detecting polarized light. In addition, their sense of smell is approximately 100 times more sensitive than humans, enabling them to detect illegal drugs or explosives, confirm pregnancy in women, or even identify cancers and diabetes in early-stage patients.
Recently, researchers have discovered that bumblebees employ their sense of smell to locate their nest, particularly when landscapes go through sudden changes that render visual landmarks ineffective. This discovery was published in Frontiers in Behavioral Neuroscience.
“Our research demonstrates that bumblebees rely on their own scent markings, which they leave behind at their nest exits when heading out foraging, to navigate back when visual cues are unreliable,” explains Sonja Eckel, the study’s lead author and a Ph.D. candidate at Bielefeld University’s Department of Neurobiology in Germany.
Visual Landmarks
Eckel and her colleagues observed the homing behavior of the buff-tailed bumblebee Bombus terrestris in the lab. In nature, these bumblebees typically nest in abandoned mouseholes concealed beneath grass or leaves. In the lab, the bees learned to locate their nest entrance using visual orientation against two sets of landmarks inside a round, enclosed flight arena measuring 150 cm across and 85 cm high. The first set of landmarks included three vertical black stripes, each 12 cm wide and 85 cm long, set against the arena’s white background. The second set featured three cylinders, each 2.5 cm wide and 15 cm high, arranged in a triangle around the entrance hole.
The arena floor offered no visual cues, simply presenting a random red-and-white pattern that appeared black and white to the bumblebees. After some practice, the worker bees flew straight back to the entrance when returning from the polle and nectar foraging chamber.
Bumblebees possess multiple scent glands throughout their bodies, and passive scent marking occurs whenever they touch any surface, including their nest entrances. The researchers collected scent marks by placing a glass ring around the entrance, which the bees would walk across when returning to the nest after foraging.
Deceiving the Bumblebees
Eckel and the research team then deceived the bumblebees by quickly shifting the locations of both sets of visual landmarks, releasing conflicting information about the entrance’s location. The bees had no visual cues that accurately marked the true entrance because it was concealed.
The researchers measured the returning foragers’ hover time and distance around each false location based on conflicting landmarks. They assumed that the longer the bees hovered in a particular location and the shorter their average flight distance, the more accurate that location was to the entrance’s real location.
Overall, the bumblebees appeared equally focused on both false locations, indicating that they used both sets of visual landmarks to figure out the nest’s location unsuccessfully. Once the researchers placed the glass ring, carrying the bumblebee scent marks, around either location, the bees became fixated on the false location suggested by the scent marks.
The researchers concluded that bumblebees rely on their sense of smell and vision to find their way home, particularly when visual information is conflicting.
Bouquet of Scents
“Visual information is used to perceive the approximate location of the nest, covering a larger distance, while scent marks are employed to pinpoint the nest entrance’s exact location in the immediate proximity. The identification of the scent likely requires physical contact,” Eckel shared.
Eckel’s team conducted chemical analyses, indicating that bumblebee scent consists of hydrocarbons, fatty acids, and other substances like esters and alcohols. Many of these substances are employed by bumblebees in other behavioral contexts and other insect species. In subsequent research, Eckel and her team plan to study how bumblebees analyze and combine different sensory cues to differentiate different behaviorally relevant goals, such as nest holes and food sourcing.
More information: Nest-associated scent marks help bumblebees localize their nest in visually ambiguous situations, Frontiers in Behavioral Neuroscience (2023). DOI: 10.3389/fnbeh.2023.1155223. www.frontiersin.org/articles/1 … eh.2023.1155223/full
Citation: Slightly lost bumble bees use scent to find their way home (2023, June 14) retrieved 14 June 2023 from https://phys.org/news/2023-06-slightly-lost-bumble-bees-scent.html
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