Critically Endangered Species of the Week: Franklin's Bumble Bee!

About:

        The 'disappearance of the bumble bees' is a common concern, with sightings of many species drastically down in the last decade. Franklin's Bumble Bee (Bombus franklini) may be one of those species in the greatest peril, with one of the smallest distributions of the genus Bombus.

        Bumble bees are necessary pollinators of many crop and wild plant species, and for this reason are essential for reproduction of commercial plants, and to many natural food webs. Like other bees, the species is eusocial, living in colonies with specific roles, and has a flight season from end-Spring to Summer [4].

        Franklin's Bumble Bee can be identified by its extended yellow colouration in the middle of the body, forming an inverted U-shape and extending beyond the wing bases, a lack of yellow on the abdomen, a predominantly black head with yellow at the top and white colouration at the abdomen tip [1; 4].

Franklin's Bumble Bee, Bombus franklini, showing the
distinctive colouration.
Photo by Robbin Thorp.

Number left in existence:



       The species is classified as critically endangered, however it may already be extinct! This is based on the research and expertise of Dr R.W. Thorpe, who has extensively surveyed populations since 1998. These supported a drastic population decrease from numerous new sites in 1998 (94 individuals; 4) -2000 to only one sighted individual in 2006, with a lack of any definate sightings since then [2; 3].



Map of Bombus franklini sightings; red dots from
2003, the single red star the last locality from 2006.
Image from The Xerces Society [4].



       Exact numbers are hard to determine, as with most species, but appear to be at dangerously low levels.

Geographical Range in the wild:

       Occuring only in the USA, Bombus franklini inhabits a tiny area 190 miles N-S and 70 miles E-W in Southern Oregan to Northern California [1; 3; 4]. This is possibly the most limited geographical distribution of a bumble bee in the world.

Why they are endangered:

• Human introduction of commercial bumble bee species for crop pollination has caused exotic diseases to devastate wild populations [3; 4].
• Intensified human agriculture has resulted in habitat destruction and degradation that may threaten or fragment any developing populations [4].
• Agricultural pesticides can be toxic, accumulate in colonies or kill plants required by the bees [4].

What can we do to help?

       Unfortunately, there are currently no conservation measures in place to protect Bombus franklini. Methods of protection should be developed and enacted, such as managing the movement of alien, commercial species to limit the spread of exotic diseases [3]. Further research is also necessarily to determine the need for habitat protection [4], or whether Franklin's Bumble Bee is already extinct.

References:

1. U.S. Fish and Wildlife Service.

2. http://ucanr.edu/blogs/bugsquad/index.cfm?tagname=Bombus%20franklini (also photo).

3. IUCN Red List.

4. The Xerces Society.