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Catching the Buzz

As bee populations decline, so do their pollination services. Researchers have developed a new acoustic monitoring method to measure bees' productivity.
A bumblebee hovers past a red poppy flower on June 1st, 2017.

A bumblebee hovers past a red poppy flower on June 1st, 2017.

In a study published last month, Nicole E. Miller-Struttmann and a research team from the University of Missouri tested a new method to study bees–through acoustics.

Pollinator species are in decline as habitat loss, climate change, and exposure to pesticides affect their health and access to food resources. Studies have concluded that 87.5 percent of flowering plants and 75 percent of commodity crops are pollinated by animal species, of which 200,000 are wild bees.

With the decline of bee populations, the most effective pollinators, loss of their production services will be costly to native flowering plants and agriculture.

To help combat the decline in bee populations, scientists and policymaking bodies, such as the Pollinator Health Task Force, are working toward methods for thorough and extensive population monitoring.

According to the 2015 National Strategy to Promote the Health of Honey Bees and Other Pollinators, pollinators are responsible for the production of one in every three bites of food that we take and increase the value of agriculture in the United States by over $15 billion annually.

"Unabated, these losses of our pollinators threaten agricultural production, the maintenance of natural plant communities, and the important services provided by those ecosystems, such as carbon cycling, flood and erosion control, and recreation," the task force states in the Strategy document.

Traditional vs. Acoustic Pollinator Monitoring Methods

Traditional, field-based methods of surveying bee populations provide delayed data, can be affected by weather and population sizes, and are limited to certain areas.

According Miller-Struttmann, bees are visually observed or collected through netting or traps in other studies, which could potentially kill the bee. Collecting data using these methods requires substantial time and expert knowledge.

Acoustic monitoring has been used to monitor various animal groups, including bats, birds, and whales. Because foraging bees can create vibrations, or "buzzes," of between 120 and 400 hertz in flight, the researchers found that they could also apply acoustic monitoring to bee populations on Pennsylvania Mountain, Colorado.

The data collected by harnessing a bee's vibrations and using that to hone in on its location as well as its activity correlates to the bee's productiveness in its natural environments.

The research team collected the acoustic data using the Awesome Voice Recorder application on iPad minis, amplified by microphones that Miller-Struttmann says cost five dollars to build.

Using these iPads, the research team used an algorithm created based on Computational Auditory Scene Analysis to cut out background noise that wasn't of interest and bring the buzzes to the foreground so that they could be counted.

Acoustics allow for real-time monitoring over an entire foraging range, and the cost of the method is low enough to eventually be available to the common farmer or beekeeper in even the most remote locations. The method is also non-invasive and less harmful to the bees.

Counting the Bee's Buzzes: What Do They Mean?

To get an idea of what most impacts pollination services, the researchers first looked at the bee's physical traits. The researchers collected individual bees, measured their wing length to estimate the body size and buzz frequency data, and released the bees back into their collection location. They also collected tongue length data from published records.

They found that both tongue length and body size influence which flowers a particular bee visits.

Bees with longer tongues tend to visit long-tubed flowers, while short-tongued bees robbed nectar by feeding from holes in the flower without pollinating it, rather than entering into the flower's natural bloomed openings. The bees with longer tongues have larger bodies and greater contact with the plant, so they will be more successful at pollinating.

These traits that most affect bee pollination efficiency also result in unique acoustic signatures that can be deciphered to understand and monitor the bee's activities.

Miller-Struttmann and her team studied the relationship between physical characteristics and frequency of buzzes in flight of queen and workers of the bumblebees Bombus balteatus and B. sylvicola. Once they identified and counted the number of buzzes recorded at each location, the results were compared to the manually collected visual and auditory estimates and were found to match up.

"Our results indicate that acoustic signals capture diversity in traits that mediate pollination success," the study said. "Specifically, bee body size and tongue length predict characteristic frequency reflecting the phenotypic landscape of the community."

Real-Life Application

The acoustic monitoring method to study the productiveness of pollinating bees is inexpensive, time-efficient, and could be used by beehive managers to measure their bees' productivity.

"We consider [this method] to be most cost effective in the amount of human hours, and although we don't have a product that is readily available in stores, we're trying to make it as inexpensive as possible," Miller-Struttmann said.

Miller-Struttman said that the team's next step is to test their acoustic monitoring method in an agricultural setting, where the environment could differ from that of the wild populations that were monitored in the Colorado mountains. For example, the buzzing of increased fly populations in agricultural settings could displace the bees' vibrations from the monitors.

"Farmers or managers can actually get real-time information about bee activity in their farms or wherever they're monitoring," Miller-Struttmann said. "It can tell them if they need to bring in more bees or if their bees are performing well."

Acoustic monitoring technology could also eventually allow scientists and farmers to detect and respond to bee population declines quickly or to enhance the success of wild pollinators with landscaping methods such as cover crops and no-till practices.

This story originally appeared at the website of global conservation news service Get updates on their stories delivered to your inbox, or follow @Mongabay on Facebook, Instagram, or Twitter.