Health and Chemistry

Last Updated on August 11, 2026 by Staff

Environmental change does not always make life harder in obvious ways.
Sometimes the important difference is that familiar signals stop being reliable, leaving animals to adjust their behavior even when food remains available.

A new experiment with bumblebees suggests that this kind of instability can have effects that are easy to miss at first.

Bees exposed to flowers that repeatedly changed orientation adjusted how they foraged, and although they largely maintained their short-term pollen collection, they later collected less pollen when placed back into a common environment.

The finding points to an important lesson about animal behavior: coping with change in the moment does not necessarily mean that there are no costs afterward.

Flowers can affect bumblebees

For a foraging bee, experience can be useful.

When a flower, its location, and the way it must be handled remain predictable, past visits can help the bee decide where to go and how to collect food.

The researchers focused on one physical feature that can change in nature: the direction a flower faces.

Flowers can point upward, downward, or sideways, and their orientation can shift because of plant growth, movement, weather, or physical disturbance.

The experiment used workers of the buff-tailed bumblebee, Bombus terrestris, that had not previously encountered the artificial flowers used for testing.
The researchers created blue artificial flowers with a yellow structure carrying pollen, and each flower could be positioned upward, downward, or sideways.

The bees were divided into two groups

One group always encountered the same flower orientation during three foraging trips, while the other encountered a different orientation on each trip, with the flowers switching among upward, downward, and sideways positions, and the number of flowers, their locations, and the amount of pollen available stayed the same.

The experiment included 32 bees, with 16 assigned to each treatment.
After the three foraging trials, 31 bees completed a final test in which all three flower orientations were available at the same time, along with more abundant pollen rewards.

Bees changed their routines

The first clear differences appeared in how the bees moved among flowers.
Bees experiencing stable conditions continued to revisit flowers at fairly similar rates during all three trials, while bees encountering changing orientations became less likely to return to flowers they had already visited.

Among the unstable group, the estimated proportion of visits that were revisits fell from 0.42 in the first trial to 0.35 in the second and 0.22 in the third.
The stable group remained near the same level, moving from 0.44 to 0.44 and then 0.48.

That change did not mean the bees simply stopped exploring.

The number of different flowers each bee visited remained similar between the treatments and across trials.

This distinction matters because revisiting and exploring are not the same thing.
The bees facing unstable conditions appeared to reorganize their routes rather than simply becoming less active, suggesting that repeated changes may have reduced the usefulness of information gathered during earlier visits.

The bees also changed how they handled flowers.

Bumblebees can use a behavior called sonication, sometimes known as buzz pollination, in which they produce vibrations that help release pollen from certain flowers.

The probability of this behavior was substantially higher under stable conditions.
Researchers estimated a sonication probability of 0.388 for the stable group, compared with 0.137 for bees exposed to changing flower orientations.

Short-term costs were limited

Despite these behavioral changes, the unstable environment did not produce a large immediate drop in pollen collection.

Bees exposed to changing flower orientations were no less likely to return with pollen during the three treatment trials.

They did show a tendency to collect smaller pollen loads, but the evidence for that difference was only marginal.

By the third trial, bees that successfully collected pollen under unstable conditions were actually more efficient than successful bees in the stable group because they completed their foraging bouts more quickly.

The results therefore do not show that changing flower orientation immediately prevented bees from finding or collecting food.

Instead, the bees appeared able to adjust their behavior enough to keep their short-term performance relatively stable.

That apparent resilience became more complicated in the final test.

The effects appeared later

After the three treatment trials, both groups entered the same environment.
All three flower orientations were available, and each flower contained enough pollen that a bee could theoretically collect a full pollen load from flowers of just one orientation.

Yet the bees that had previously experienced changing flower orientations collected significantly less pollen overall than the bees that had experienced stable flowers.

They were also less likely to return with any recoverable pollen at all.

The difference was not caused by successful bees carrying smaller loads.
When the researchers looked only at bees that did return with measurable pollen, the amount collected did not differ significantly between the two groups.

The researchers also could not explain the difference through the other behaviors they measured.

Revisiting, the number of flowers visited, total visitation, sonication, foraging time, body size, and preferences for particular flower orientations did not account for the reduced pollen collection in the previously unstable group.

What caused the lasting effect?

The experiment cannot answer that question yet.

The researchers suggest several possibilities, including changes in the bees’ motivation or persistence while collecting pollen, or finer details of pollen handling that were not captured by their observations.

The experiment also did not directly measure learning, memory, or cognition, so it cannot establish that changing flower orientation altered any particular mental process.

The results are instead consistent with the possibility that repeated instability changed how bees used information from their previous experiences.

Important limits to the findings

The experiment involved a relatively small number of bees, used artificial flowers, and changed only one feature of the environment under controlled laboratory conditions.

It remains unknown whether the same delayed effects occur in more complex natural settings or after other kinds of environmental instability.

Still, the results offer a useful way to think about how animals respond to changing environments.

A behavior that looks successful when measured immediately may hide consequences that become visible only after conditions return to normal.

For these bumblebees, flexibility helped preserve short-term foraging performance while flowers kept changing.

But the same experience was followed by a lower chance of successful pollen collection later, showing why understanding environmental change may require looking beyond what animals do while the disturbance is happening.

Source: BiorXiv