Did you know that a single bumble bee colony can contain up to 500 individuals? This remarkable fact underscores the complex social dynamics and intricate behavioral repertoires of these fascinating pollinators. A recent study has revealed that bumble bees not only learn from each other but also develop distinct “trends” in their foraging behaviors, challenging the long-held belief that their actions are purely instinctual.
The research, conducted by scientists at Queen Mary University of London, provides strong evidence that social learning plays a significant role in shaping the behaviors of bumble bees, particularly in how they forage for food. This discovery suggests that these insects may possess culture-like phenomena akin to what has been observed in primates and birds, opening up new avenues for understanding the evolution of their behavior.
Key Takeaways
- Bumble bees can pick up new behavioral “trends” by observing and learning from other bees in their colony.
- A single form of a behavior can spread rapidly through a bumble bee colony, even when a different version is discovered.
- Social learning appears to be a key driver in the spread of foraging behaviors among bumble bees.
- Bumble bees exhibit culture-like phenomena, similar to what has been observed in primates and birds.
- The complexity of bumble bee behaviors may be more influenced by social learning than previously thought.
Bumblebees: Fascinating Social Learners
The research, led by Queen Mary University of London and published in PLOS Biology, provides strong evidence that social learning drives the spread of bumblebee behaviors. A variety of experiments were set up to establish this. The researchers designed a two-option puzzle box that could be opened either by pushing a red tab clockwise or a blue tab counter-clockwise to reveal a 50 per cent sucrose solution reward. ‘Demonstrator’ bees were trained to use either the red or blue tabs, with ‘observer’ bees watching. When it was the observers’ turn to tackle the puzzle, they overwhelmingly and repeatedly chose to use the same method that they had seen, even after discovering the alternative option. This preference for the taught option was maintained by whole colonies of bees, with a mean of 98.6% of box openings made using the taught method.
Social Learning Drives the Spread of Behaviors
The importance of social learning to the acquisition of puzzle box solutions was also illustrated through the control group, which lacked a demonstrator. In this group, some bees managed to open the puzzle boxes, but did so far fewer times than those who benefitted from seeing another bee do it first. The median number of boxes opened in a day by the observer bees with a demonstrator was 28 boxes a day, whereas it was only 1 for the control colony. This demonstrates how bumblebees can observe and imitate foraging techniques from other bees.
Observing and Imitating Foraging Techniques
In an additional experiment, the researchers put both ‘blue’ and ‘red’ demonstrators into the same populations of bees. In the first population, 97.3% of the 263 incidents of box-opening by observers by day 12 used the red method. In the second population, observers preferred the blue method over the red on all days except one. This demonstrated how a behavioral trend might emerge in a population, for the most part, due to experienced bees retiring from foraging and new learners arising, rather than any bees changing their preferred behavior.
Bumble Bee: Cumulative Culture and Innovations
Culture refers to behaviors that are socially learned and persist within a population over time. Increasing evidence suggests that animal culture can, like human culture, be cumulative: characterized by sequential innovations that build on previous ones. However, human cumulative culture involves behaviors so complex that they lie beyond the capacity of any individual to independently discover during their lifetime. To determine whether bumblebees could acquire a behavior through social learning that they could not innovate independently, researchers developed a novel two-step puzzle box.
Social Learning Allows Acquisition of Complex Behaviors
Their hypothesis was that this degree of temporal and spatial separation between performing the first step of the behavior and the reward would make it very difficult, if not impossible, for a naive bumblebee to form a lasting association between this necessary initial action and the final reward.
Demonstrating the Two-Step Puzzle Box Task
The two-step puzzle box relied on the same principles as a previous single-step, two-option puzzle box, but this new design required bees to first push a blue tab out of the path of a red tab, which could then be pushed in turn to rotate a clear lid around a central axis to access a sucrose-solution reward. The researchers found that while naive bees failed to open the box despite extended exposure for up to 24 days, a third of naive observer bees learned to open the two-step box from trained demonstrator bees, without ever being rewarded after the first step. This suggests that social learning might permit the acquisition of behaviors too complex for bumblebees to innovate independently.
Traits and Characteristics of Bumblebees
Bumblebees are excellent pollinators, much more efficient than honeybees. They mainly forage for pollen rather than nectar, and transfer more pollen to the pistils of the flowers with each visit. Many crops are well suited to natural pollination by bumblebees, including cucumbers, peppers, tomatoes, seed crops, strawberries, blueberries, raspberries, melons, and squash. Bumblebees perform a unique service called “buzz pollination” by grabbing the pollen-producing part of the plant in their jaws and vibrating their wing muscles to loosen trapped pollen. Bumblebees’ wings beat more than 130 times per second, making them highly effective pollinators.
Flower Preferences and Attracting Bumblebees
Bumblebees are not fussy; they will visit any flowers that produce nectar and pollen. However, they are especially attracted to tube-shaped flowers, and some flowers have evolved to be pollinated almost exclusively by these beefy bees. The bottle gentian (Gentiana andrewsii), for example, has developed bottle-shaped flowers that never open fully, which means that a strong bee must pry its way into the flower to pollinate it. To attract bumblebees and other native bee species, consider planting native plants such as asters, coneflowers (Echinacea spp.), lupines, bee balm (Monarda spp.), and spring ephemerals. Bumblebees are able to fly in cooler temperatures and lower light conditions than other bees, making them among the first pollinators you’ll see in the spring and the last ones flying in the fall.
Unique Flight Mechanism and Warming Up
You have to wonder how these big round bees fly so well. A recent study showed how the tiny wings keep the bumblebees aloft: Bumblebees flap their wings back and forth rather than up and down, making their wings more similar to a helicopter propeller than an airplane. Bumblebees also have to warm up before they can fly. Ever noticed how bumblebees just “bumble around” in the early morning, moving slowly? Their Teddy-bear fur and their ability to regulate body temperature allows them to be out and about on cold mornings, but they can’t fly until they have warmed up.
Bumblebee Colonies and Life Cycle
Bumblebees have small nests, between the size of a baseball and a softball. Unlike a honeybee hive, bumblebees usually nest close to the ground or even underground, in stone walls, under clumps of grass, or in hollow trees and stumps. Abandoned mouse holes are a favorite since they come complete with a warm fur lining. Colonies may contain between 50 and 500 individuals, whereas honeybee hives may have 50,000. After foraging at various flowers, bumblebees carry their collected pollen and nectar back to the nest to feed.
Queen’s Role and Overwintering
Unlike honeybees, the bumblebee colony dies in late fall. The queen (who rules the colony) is the only member of a bumblebee colony who can survive the winter! She hibernates underground during the winter months and starts a new colony in the spring. Male bees will also sleep outside, after they leave the nest (never to return). Sometimes, it’s the female who’s caught outside the nest because the temperature cooled so rapidly that she couldn’t fly back; she’ll wait until morning to bring her pollen back to the nest.
Threats and Conservation Efforts
Many bumblebees are listed as endangered, vulnerable, or near threatened. A few years ago, the rusty patched bumblebee (Bombus affinis) was the first bee listed as an endangered species in the continental U.S., and it is thought to be extinct here in New Hampshire—the last recorded sighting of it was in 1993. According to the Dept. of Agriculture, the decline in bumblebee populations can be blamed on the 5 “P’s”—parasites, pests, pathogens, poor nutrition, and bumblebee pesticides.
Decline in Bumblebee Populations
If you notice a lack of bees in your yard, consider whether your neighborhood uses a lot of pesticides in their lawns and gardens. A group of insecticides called neonicotinoids have been shown to have a devastating effect on all types of bees. It is a systemic insecticide that can come from pre-treated seeds or sprays applied to bedding plants. The chemical is present in every part of the treated plant—flowers, stems, leaves, etc. Bumblebee habitat loss is also a major factor in the decline of bumblebee populations.
Creating Bee-Friendly Gardens
To provide nesting sites, leave some part of your yard a little wild and brushy. Don’t mow or rake there, and leave some plant stems standing over the winter to give the new queens places to hibernate and spots to establish new colonies in the spring. To attract bumblebees and other native bee species, consider planting native plants—such as asters, coneflowers (Echinacea spp.), lupines, bee balm (Monarda spp.), and spring ephemerals. Buy organic whenever possible or ask your local nursery to make sure that no systemics were used on the plants you are purchasing.
Conclusion
The research on bumblebees’ social learning and complex behavior acquisition sheds new light on the intricacies of these fascinating insects. Bumblebees have demonstrated remarkable capabilities in observing, imitating, and spreading behaviors within their colonies, challenging the previous notion that their behaviors were solely instinctive. This discovery of culture-like phenomena in bumblebees suggests that social learning has played a significant role in the evolution of their behavioral repertoire.
As efficient pollinators, bumblebees play a crucial role in maintaining the health of ecosystems and supporting agricultural productivity. However, the decline in bumblebee populations due to factors such as pesticide use, habitat loss, and disease is a growing concern. Conservation efforts that focus on creating bee-friendly gardens, reducing pesticide use, and preserving natural habitats are vital to ensuring the survival of these essential pollinators.
By understanding the complexity of bumblebee behaviors and the threats they face, we can take meaningful steps to protect these remarkable creatures. Continued research and public awareness can help guide policies and individual actions that support the thriving of bumblebee populations, ultimately benefiting the broader ecosystem and our own well-being.
