Time flies when you’re bumblin’: Bumble bees focus of survey in Roaring Fork Valley

Aspen-Sopris Forest Service technicians survey local bumble bee populations for the fourth year

Maggie Moline and Ellen Peterson, wildlife technicians with the Aspen-Sopris Ranger District of the U.S. Forest Service, spent Wednesday surveying the bumble bee populations near Fourmile Park and Baylor Park.
Josie Taris/The Aspen Times

When a bumble bee emerges from torpor, it repeatedly rubs its arms over its head and flexes its abdomen. It’s a half-stretch, half-dance move that warms the bee up and out of the state of decreased physiological activity. 

It almost mimics the way they collect pollen in a flower, by “combing” their legs through the pollen and buzzing to shake it off and collect it in “pouches” on their legs. 

“That’s why it always looks like they’re brushing their hair,” joked Maggie Moline, a wildlife technician with the U.S. Forest Service Aspen-Sopris District.  

A few dozen bees found themselves doing that dance on Wednesday morning after wildlife technicians from the district conducted a bumble-bee survey on forest land between Carbondale and Glenwood Springs. 

The Aspen-Sopris Ranger District started surveying bumble bees about four years ago to get a better idea of the species of bumble bees that inhabit their lands. 

“The time is now to start surveying, even if it’s just for knowledge,” said Moline. 

The data set they have now is relatively small, but in 10 to 20 years, the district might be able to glean insight on areas of the forest popular with sensitive bumble-bee species — like the Western Bumble Bee. 

“If we found a bunch of Western Bumble Bees (or an endangered species), then maybe we’d make a land-management decision,” said Ellen Peterson, another wildlife technician. The bumble-bee data set might inform a decision to close an area of the forest during the peak activity of a sensitive species.

A bumble bee in torpor sits on the guide packet while Moline confirms its species.
Josie Taris/The Aspen Times

Bumble bees differ from honey bees in they don’t produce as much honey and congregate in much smaller colonies. Still, they are one of the region’s — and world’s — most important pollinators. 

The Aspen-Sopris district comprises approximately 700,000 acres. Choosing where to survey is almost random and largely based on the presence of wildflowers, but Peterson is looking ahead to the fall, hoping to collect “before and after” data at Lime Park near Basalt. 

The site is tentatively scheduled for a prescribed burn this fall, so she surveyed the bees there earlier in the year. Some time after the burn, they will go back to see if they can record any difference in the bee population. 

They estimate they conduct about a dozen separate surveys a year but hope to do more. 

The data is all internal, for now, but Moline said she’s thinking about passing it along to a larger, bee-focused organization. Some districts within the White River National Forest conduct bumble bee surveys, others do not. 

“I want to get our data to larger organizations that are looking at bumble bees across the West and across the country,” she said. 

How to conduct a bee survey 

The technicians headed out with nets, those little plastic to-go containers for sauces at restaurants, and a lunchbox full of ice packs with pictorial guides stuffed in the pockets. It’s not an ultra sophisticated operation, but it provides a data set of the region’s bumble bees. 

Moline first parked the truck next to a field near Fourmile Park between Carbondale and Glenwood Springs. It had once been flooded with wildflowers, but in late August many of the flowers were past their peak blooms. Still, the buzzing of the bees was audible crunching through the grass. 

Peterson lifts the net to trap the bumble bee at the top before securing it in a container that will fit in the cooler.
Josie Taris/The Aspen Times

To catch a bumble bee, Moline and Peterson lowered a net around the flower with the bee. Bumble bees tend to fly upward, so they’d lift the netting up as high as it could go to isolate the bee at the tip of the net. With a fist closed around the net to keep the bee at the tip, they walked back to the truck. 

Set up in the truck bed were the mini to-go containers and the insulated lunchbox. Relocating the bee from the net into the little container is tricky — the bees are always looking for an opportunity to fly away.

“You give a bee a chance to escape, it probably will,” Moline warned. 

Once they’re in the container, emitting a high-pitched buzz of distress and annoyance, they get tucked between ice packs in the cooler to enter torpor. 

Torpor is a state of rest in cold temperatures, with decreased physiological activity to conserve energy. The bees appear “asleep” when in torpor, which makes them much easier to identify. 

Depending on the size of the bee, it can take anywhere from 5-20 minutes for them to go from angrily buzzing to docility. Once calm, Moline and Peterson popped the bees out of their containers to identify its sex and species. 

Moline gets up close to determine the species of bumble bee sitting, while in torpor, on her guide packet.
Josie Taris/The Aspen Times

Female bumble bees do all the work. They collect pollen for the colony and can be quickly identified by “pouches” of pollen that they collect on their legs. Males buzz about looking to mate. They visit flowers as needed to sustain themselves, but they never collect pollen on their legs to contribute to a colony. 

The more tedious way to identify the sex of a bumble bee is the number of stripes on its abdomen. Males have one more than females. 

Moline and Peterson brought the bees extremely close to their faces to count the number of abdomen stripes, usually resulting in a coo of adoration from one or both of the technicians.

“Hey, little buddy,” Moline whispered to one bumble bee. “You’re so cute!”

And to identify the species, of which 24 live in Colorado, the technicians compared the bee’s coloring and fuzz to the illustrations in “The Bumble Bees or Colorado: A Pictorial Identification and Information Guide.” Colorado is high in bumble-bee diversity, she said, likely because they’ve adapted to cold weather better than honey bees. 

This yellow head bumblebee (B. flavifrons) is notable for its fuzzines and mix of black and yellow hairs behind its head.
Josie Taris/The Aspen Times

They recorded 21 bees in total among these species:

Central bumblebee (Bombus centralis)

Yellow head bumble bee (B. flavifrons)

White-shouldered bumble bee (B. appositus)

Two-form bumble bee (B. bifarius)

Red-belted bumble bee (B. rufocintus)

and an unconfirmed Western bumble bee (B. occidentalis)

Some species are marked by their “long, silky hairs” and others by the coloring of the fuzz on their head. The guide is detailed, with long overviews of each species to accompany a quick color 

To record the findings, Moline and Peterson photographed the bee to upload to their survey database on U.S. Forest Service-issued tablets or through an app on their cell phones. Location, elevation, the flower the bee was pollinating, sex, and more data points are all noted. If the techs are unsure of a species, they have an expert double-check. 

This female worker bee has a pouch of pollen on her rear leg.
Josie Taris/The Aspen Times

Bumble bee surveying is not just for USFS employees. For anyone interested in citizen-science, organizations like the Xerces Society for Invertebrate Conservation and BumbleBee Watch offer informational material and the opportunity to submit your own bumble bee survey data. 

And to support bumble bees in the Roaring Fork Valley, Moline and Peterson said planting native, flowering plants in your yard or garden is best — especially outside of peak wildflower season when the bees have less to choose from out in the wilderness.