bumblebee-queens-hibernate-pesticide-soil

Researchers Uncover Bumblebee Queen's Preference for Pesticide-Laden Soil During Hibernation

Introduction

New research form the University of Guelph raises serious concerns about bumblebee health and reproductive viability. Drs. Nigel Raine and Sabrina Rondeau have found that bumblebee queens prefer to hibernate in pesticide-contaminated soil, an unexpected soil, an unexpected behaviour that remains poorly understood.

Research Objective

Investigating Bumblebee Queen's Behaviour

'We aimed to explore whether bumblebee queens demonstrate avoidance behaviours to lessen their risk of pesticide exposure, as some behaviours are still not well understood,' Raine states. 'The findings, however, were alarming.'

Methodology

Field Experiments Conducted

The research team carried out field experiments, allowing newly emerged queens of the common eastern bumblebee (Bombus imptiens) to fly freely in outdoor enclosures, mate, and select a hibernation site for the winter.

The queens were given a choice between clean soil and soil contaminated with one of five commonly used pesticides, including insecticides and fungicides, at varying concentrations.

Key Findings

Surprising Preferences

Researchers from the School of Environmental Sciences meticulously examined the soils for hibernating bumblebee queens. Surprisingly, they discovered that the queens avoided pesticide-free soil and were nearly twice as likely to prefer pesticide-contaminated soil.

Implications for Colony Health

While most bees in the study survived, the research-published in Science of the Total Environment-emphasizes additional consequences for the colony.

The findings were unexpected for both Raine and Rondeau, now a post-doctoral researcher at the University of Ottawa. This study, part of Rondeau's Ph.D. research at U of G's Ontario Agricultural College, was recently highlighted in The New York Times.

Concerns Raised

Risks to Bumblebee Health

Raine expresses concern, stating. 'This poses significant risks to bumblebee health, especially as this essential group of insect pollinators is already facing numerous challenges.'

During winter, bumblebee queens usually hibernate beneath the ground and then emerge in spring to find new colonies.

The Pesticide Puzzle

Unexpected Outcomes

The researchers aimed to investigate how these bees respond to contaminants at this pivotal yet vulnerable of development.

Previous investigations revealed that pesticides on crops can either lure or deter bees, depending on factors such as the specific pesticide, environmental context, and its concentration.

Surprising Preferences

Raine and Rondeau initially theorized that bumblebee queens would simply opt to avoid pesticide residues in the soil.

Rondeau expresses surprise, stating. "We did not anticipate this outcome. It implies that queens might actually favor these contaminated soils, although we still do not fully comprehend the reasons behind it."

Pesticides may make soil more attractive, but further investigation is needed

Potential explanations

Altered Soil Properties

One potential explanation is that pesticides modify the soil properties, making it more attractive to the queens.

For example, the fungicides applied in this research might have eliminated soil fungi and nematodes, causing queens to steer clear of fungal-rich soils, as they can be detrimental during hibernation.

Acquired Taste for Pesticides

As alternative possibility is that the queens might have cultivated an 'acquired taste' for pesticides, as the researchers indicate, as a result of prior exposure in their habitat.

It is possible that they are seeking out new opportunities, given that novelty-seeking behaviour is typical for bees and often results in the discovery of new resources for the colony.

Need for Further Research

Understanding Queen Behaviour

More investigations are essential to fully elucidate the mechanisms behind this unanticipated behaviour of the queens. Yet, the findings point to the necessity of rethinking pesticide usage and management in farming practices.

Pesticides in soil must be factored into environmental risk evaluations

Environmental Risk Evaluations

Pesticides in Soil

Pesticide exposure is playing a significant role in the global decline of insect populations.

In addition to occasionally causing death, pesticide exposure can disrupt bees' movement and their ability to forage for nectar and pollen, which may have significant consequences for the global food supply.

Future Questions

Questions linger about whether bumblebee queens might be attracted to contaminated soil in broader areas than those tested in the experiments, where real-world scents and environmental features could conceal the presence of pesticides. Further investigation is also needed to evaluate if these results are applicable to other bee species.

Recommendations for Pesticide Risk Assessments

Incorporating Soil Exposure

Current pesticide risk assessments overlook soil as a significant pathway of exposure for bees. This study advocates for enhancements in these assessments to incorporate this newly identified behaviour.

Examining Agricultural Exposure

Rondeau emphasizes that moving forward, it is essential to examine how agricultural practices-such as the types of pesticides used, application methods, and vegetation management-affect the built up of pesticide residues in soils where queens are likely to hibernate.

Conclusion:

"By enhancing our knowledge of the accumulation of pesticide residues in soil and their effects on bees, we can develop methods to protect these crucial pollinators."

Source

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