Location: Pollinating Insect-Biology, Management, Systematics Research
Project Number: 2080-21000-019-018-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jul 31, 2019
End Date: Jan 31, 2024
Objective:
Study Rusty Patched Bumble Bee (RPBB) nesting habitat needs to inform captive programs, habitat management, and future reintroductions. Study nesting habitat at three extant RPBB locations.
Approach:
At three locations where we have established the presence of RPBB, we will employ a combination of strategies in order to track bees from foraging sites back to their nests. First, we will use mobile and static methods of nest identification following Osborne et al. (2008). In the mobile approach, we will visually observe the direction and distance of bees approaching and leaving floral patches, and will follow bees on foot in an iterative fashion to ascertain potential colony locations at a coarse scale. In the static approach, a fixed area will be observed for 20 minutes to search for bumble bee activity near the ground. In the event that tracking results in the location of only a few nest locations, we will explore additional methods for locating nests. This will include capturing foraging individuals and marking them with a temporary, non-toxic fluorescent dye. Using black lights at night, we will scan for dye traces left in the field by workers returning to their nests. At all candidate nesting areas identified by these two methods, we will then conduct thorough walking transects across the landscape during peak foraging hours to search for flight activity at or near ground level. Nest locations will be recorded when three or more RPBB individuals are observed entering or leaving the same entrance. The location of each nest will be mapped in GIS with 10 cm accuracy. These will be mapped onto detailed vegetation maps available for some of the sites, or coarse land cover maps available for all sites (e.g., NASS CDL, WiscLand 2.0). For all verified nests, we will record information on the habitat characteristics in which the nest is found Quantitative analysis of general site characteristics, such as density of vegetation, plant species diversity, thatch layer depth, amount of exposed soil, and landscape diversity (from GIS databases of sites), as well as soil characteristics (texture analysis) will be measured. Active nests will then be monitored from late August through early October to determine when all reproductive individuals have left and colonies are no longer producing offspring. At this point, we will excavate nests to further understand features of the burrow and comb (e.g., nest lining material, evidence of cohabitation by other species, depth below ground, entrance length, pollen and nectar stores, colony size, and parasite load). We will establish a list of shared characteristics among nests, in terms of micro and macro-habitat associations, and within-nest characteristics, that can be used to identify future like nest site locations or areas of conservation priority. Depending on the number of nests located over the two years, different types of analyses will be performed to help inform RPBB nesting habitat needs. An interim report will be provided at the end of the first year after project initiation, outlining the field activities and information on nests. In the second year, we will repeat the field observations approach, modifying the protocol as needed to improve efficiency. A final report will be submitted following data analyses for both field seasons by the end of the second year of funding.
