Can Bees Follow Floral Scents after Heat and Dryness?

Can bees that have spent time in hot, dry conditions immediately resume searching for flowers once they return somewhere cooler? Detecting a floral scent and beginning to move toward it may not be the same ability.

In 2026, Zoltán Tóth and colleagues exposed buff-tailed bumblebees (Bombus terrestris) to high temperature and low humidity, then examined movement toward a floral scent and electrical responses of their antennae. The study investigated which stages of scent-based communication between flowers and pollinating insects may be disrupted by extreme heat.

From dry conditions at 40°C to testing after a 15-minute rest

The bees came from three commercially supplied colonies. Beginning five days before the experiments, a floral scent comprising ten compounds was added to sugar syrup, giving the bees an opportunity to associate the odor with food.

Bees in the heat-treatment group were placed individually in containers for two hours and 45 minutes at 40°C and an average relative humidity of approximately 15%. Control bees also spent the same period individually confined without food, but at 26–28°C and 60–67% humidity. The comparison therefore differed in humidity as well as temperature.

After treatment, the bees rested for 15 minutes before being transferred to an experimental apparatus at 26–28°C. The experiment thus examined whether the effects of hot, dry conditions persisted afterward, not behavior while at 40°C. Four bees died during treatment, and 68 survivors participated in the behavioral experiment.

Leaving a small cage, not departing from the nest

The behavioral experiment used a long, narrow wind tunnel with a gentle airflow. At two upwind locations were the floral scent used during learning and a mineral-oil control. Both had blue disc markers, and their left–right positions were alternated.

Each bee was placed in a small release cage 65 centimeters from the scent sources. For ten minutes after the cage was opened, video recorded whether it began moving, when it left, and which source it first approached. This did not directly measure bees leaving a nest and searching for real flowers outdoors.

Examination after the experiment showed that 49 of the 68 bees were workers and 19 were males. Because most males came from one colony, workers and males were analyzed separately.

Nearly half the treated workers did not leave the cage

All 26 control workers left the cage. In contrast, only 12 of the 23 workers exposed to hot, dry conditions did so. This difference was statistically significant.

Even among workers that emerged, departure was slower in the treated group. However, body size was also related to this timing difference. The study used the length of a portion of the wing as a proxy for body size.

Among males, all ten controls emerged, compared with two of nine treated bees. No treated male approached a scent source, so detailed analyses of directional choice and related outcomes were not performed.

The clearest result was that more bees failed to initiate exploration-related behavior after experiencing heat and dryness.

Whether scent choice deteriorated remains uncertain

Among workers, 32 approached one of the scent sources: 23 controls and nine treated bees. For these individuals, the researchers compared whether the first approach was to the floral scent or mineral oil.

The statistical model estimated the probability of first approaching the floral scent at approximately 78% in controls and 56% in treated bees. Controls were more likely to choose the floral scent than expected from a 50:50 chance distribution, whereas the treated group did not differ significantly from 50:50.

However, the direct difference between the two groups was also not significant. A significant departure from 50:50 in only one group does not itself prove a difference in choice ability between groups. Few treated individuals moved, leaving substantial uncertainty in the estimates.

The authors discuss the possibility of disrupted scent-guided orientation, but evidence here is less clear than the reduction in the proportion initiating movement. Among bees that approached a scent source, treatment also had no significant effect on time to reach the first source.

Antennal responses did not weaken uniformly

After the behavioral experiment, the researchers removed the bees’ antennae and measured electrical responses to brief presentations of floral scent. This measures the antenna’s response to odor stimulation, not memory in the brain or motivation to move toward flowers directly.

In the analysis of 49 workers, increasing the scent dose increased responses in both groups. There was no result showing a uniform overall weakening of responses following the hot, dry treatment.

However, the relationship with body size differed. Larger individuals tended to show stronger antennal responses in the control group, but this relationship was absent in treated bees. The treatment-by-body-size interaction was statistically significant.

This does not establish that smaller bees tolerate heat better. It is a finding about post-treatment antennal responses to one particular odor blend.

Detecting an odor does not necessarily mean going out to find it

The authors emphasize that more bees failed to initiate behavior even though antennal responses were not substantially reduced. Heat may affect not only the initial detection of odor but also movement, motivation to forage, or the process of using a learned scent.

Bees may also have avoided energy-demanding activity while cooling or recovering. However, the study did not directly measure motor neurons, brain function, or thermoregulatory mechanisms, and cannot identify a single cause.

Furthermore, the treated bees included in the directional-choice analysis were only the small subset that began moving. More strongly affected individuals may have been excluded, leaving relatively less affected bees in the analysis. This is one reason to consider each behavioral stage separately.

How far do these findings extend to flowers and bees in the wild?

The study showed that activity needed for foraging can remain reduced after hot, dry conditions. The authors point to potential consequences of repeated heat waves for individuals’ food acquisition, colonies, and pollination. They also call for investigating effects on male foraging and reproduction.

In the wild, however, bees can choose shade or change the time of day when they are active. Unlike continuous exposure in containers, actual pollination, colony growth, and male mating success were not measured. The results concern three colonies, one high-temperature, low-humidity treatment, and a short recovery period.

Flowers may also change their emission of aroma compounds under heat, but this study used no plants, instead releasing a synthetic ten-compound scent from a standardized apparatus. Because many bees remained inactive even with an undiluted blend in the behavioral test, the authors argue that increased floral emissions alone would be unlikely to substantially compensate for reduced activity under similar heat stress. However, this was not tested by increasing plant emissions or stimulus concentrations. Whether longer rest allows recovery, and what happens when other environmental factors overlap, remain questions for future work.

The research received support from the British Ecological Society, the Hungarian Academy of Sciences, the German Research Foundation, and other sources. The authors declared no competing interests.

Summary

After high-temperature, low-humidity treatment, buff-tailed bumblebees were much less likely to leave the cage and begin exploring. Meanwhile, the between-group difference in directional choice among bees that moved remained unresolved, and antennal responses did not decline uniformly.

Receiving a floral scent and using it to move toward food are separate processes. This study shows why understanding climate effects requires examining not only scent detection but also the initiation of movement and directional choice. Understanding which stages are disrupted can help reveal the effects on relationships between flowers and their pollinators.

References

Tóth, Z., Juhász, B., Kárpáti, Z., Schultheiss, P., & Nooten, S. S. (2026). Heat waves impair foraging initiation and directional movement toward a floral scent in the buff-tailed bumblebee (Bombus terrestris). Scientific Reports, 16, 21196. DOI: 10.1038/s41598-026-53492-6. Full original article. © The Author(s) 2026. The original article is available under CC BY 4.0.