Grossmann: The Bumblebee – The Possible Return of the Hive-Less Bee

29 August 2013

In the summer of 2012, bee enthusiast Megan O’Donald encountered a bumblebee in her mother’s garden in Briar, Washington.  In the distant past, this would have hardly been noteworthy, but after the disappearance of bumblebees from Washington state, almost ten years ago, the sighting was an event. [1]  In 2013, O’Donald saw another bumblebee in a goldenrod in the same garden.

When Will Peterman, a freelance writer and photographer, heard about O’Donald’s sightings, he decided to “launch an expedition.”  He identified several “patches of habitat” in small parks and unmown lots.  Investigation of the first three sites yielded nothing but, at the fourth, he struck gold. [2]

In Briar, Washington‘s Briar Park, he found and photographed several bumblebees.  Several days later, Peterman returned to the park with a group of bee experts (entomologists) and, together, they located and photographed several bumblebee queens.

It is estimated that the United States has lost almost half of its honeybee population in just the last seven years.  However, the many species of the relatively petite honeybee differ in appearance, behavior, and habitat from that group of species called bumblebees.

The relatively large and, somewhat, rotund bumblebee has also suffered a substantial disappearance in North America.  Not long ago, the bumblebee was common throughout the Western United States and Canada.  However, beginning in the late 1990’s, its numbers declined until it all but vanished from a vast area of its range extending from the Pacific Coast of California north into British Columbia.  Mysteriously, bumblebee populations remained relatively unaffected in the mountainous portions of this same range.

Unlike honeybees, bumbles are wild bees.  They are not kept by beekeepers.  However, their wild status makes them no less important to the agricultural industry.  These bees are specially suited to pollinate a variety of cash crops including tomatoes, cranberries, almonds, apples, zucchinis, avocados, and plums and their unique style of pollination accounts for about 3 billion dollars in produce each year.

Bumblebees are known for their characteristically loud buzz.  However, unlike hive-dwelling honeybees, bumblebees don’t just buzz when they’re flying.  They can, and do, produce that same buzz without moving their wings.  And it is just the vibration from this flightless buzz that makes them uniquely valuable pollinators of certain crops.

After landing in a blossom, the large bumblebee grabs the blossom and holds it tightly.  While maintaining this tight grip, it strongly vibrates while remaining stationary.  Nothing less than the bumblebee’s strong vibration will assure pollination by shaking loose sufficient quantities of the thick pollen produced by certain species of plants.  No other bee could do this job as consistently or successfully.

While the sighting of a few bumblebees in Washington state may not seem like much, Biologist Rich Hatfield, of the Xerces Society, believes that these few sightings hold the promise of a possible bumblebee repopulation of the their abandoned Western Range. [3]

Also, these sightings came at a time when bee watchers needed some good news.  Just a few weeks earlier, 50,000 bumblebees died, in mass, in an Oregon parking lot.  The cause of the die-off remains unexplained.  Even worse, these deaths came only one week before the beginning of the newly declared “National Pollinator Week.”

The challenges to bumblebee survival grow out of its peculiar lifestyle.  Unlike the petite honeybee, the bumblebee doesn’t maintain the familiar hive.  Bumble queens locate their 12-inch wide nests rather opportunistically, in “clumps of dry grass, old bird nests, abandoned rodent burrows, old mattresses, car cushions or even in or under old abandoned buildings.” [4]  Each bumblebee nest will be used for only a single year.  And a colony will begin and end within that same year’s time.  Each year, a new nest will be built and a new colony developed in a different location.  Most colonies number only a few hundred bees, though rarely, numbers can reach as high as 2,000.

The wild bumble’s nomadic lifestyle disburses its population.  This works to their advantage by protecting them from the rapid, plague-like spread of diseases so common in the perennial and densely populated hives of the honeybee.  Also, the freestyle foraging of this wild bee limits its exposure to systematically applied pesticides.

Bumbles certainly suffer some collateral damage from pesticides and are vulnerable to certain diseases.  However, pesticides and disease, the “usual suspects” in the disappearance of the honeybee, are less prominent contributors to the decline in bumble populations.

Inspired by the honeybee colonies, human attempts to create similar domesticated bumble colonies led to one of the few documented disease outbreaks among these bees.  When a few of the experimental, domesticated queens were imported from Europe to American, they brought with them a new fungal disease, which spread among some American bumblebees.

In spite of this incident, and the plentiful speculation about the possible role of disease in declining American bumble populations, there is little evidence that any disease played a significant role in the massive North American disappearance.  In fact, the healthy bumble population levels in the Western mountainous areas of North America and Canada argue against the disease theory.  These unaffected populations suggest another cause — one more often associated with animals than insects: loss of habitat.

Certain human activities have tremendously reduced the bumble’s natural habitat.  Modern land management, agricultural and aesthetic, continues to eliminate the open, unmown grasslands and areas of brush that bumbles need for nesting.

Over the past 40 years, agricultural planning and land-use have been revolutionized to provide maximum yields.  But these modifications have destroyed vast areas of potential habitat — especially those close to sources of honey and, therefore, locations in need of pollinators.

In the past, the typical farm included a substantial number of fallow tracts of land in which wild brush and unmown grass were allowed to grow.  These areas provided breaks between fields to slow or prevent the spread of disease.  Other uncultivated areas were buffers between different types of crops.  This separation was intended to prevent bleed-over of one type of crop into fields dedicated to another.  However, the practice of planting different types of crops was, again, a kind of insurance against the spread of disease.  While one type of crop might fall victim to disease, another would be less susceptible and survive to produce a much-needed yield at harvest.  And, finally, there was crop rotation.  Some fields were periodically left fallow to prevent a loss of fertility.  All of these uncultivated areas of the typical farm were ideal habitat for the bumblebee.

However, advances in pesticides and herbicides have so reduced the incidence of crop damage and disease that a new style of agriculture, sometimes called “monoculture,” dominates farm planning and geography.  The modern farm is a study in intensive land use and specialization.  All lands are cultivated and, often, with a single crop.  Any creeping wild brush or grass growth is eliminated, quickly and thoroughly, with extremely effective herbicides.  Chemical soil fertilization is just as effective and has made crop rotation a thing of the past.  The result is a modern farm with no place for bumbles.

Beyond our farms, today’s increasingly urban world is also working to eliminate unsightly brush and unmown lands.  Even road embankments and open park areas are regularly mowed.  This creates a more pleasing cosmetic effect, but at the expense of bumblebee habitat.

In notable contrast, the bumble’s habitat remains relatively intact in the less farm-friendly mountainous areas of the Western United States and Canada.  And it is in just these areas, less touched by modern farming or systematic public landscaping, that bumble populations remain strong.

At least one organization, the Xerces Society, named for the extinct California butterfly, Xerces Blue, is currently working to advance conservation of bumblebee habitat.  The society focuses on several conservation issues including the preservation of native pollinators.  In 2010, the society’s scientists developed a bee-friendly conservation strategy, the Yolo Natural Heritage Program, operated in Yolo County California.


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