Biology subjects

Rutschmann, B.

Publications and source records attributed to Rutschmann, B..

4 recordsLinked to original sources

bioRxiv2024

Swarming rate and timing of unmanaged honeybee colonies (Apis mellifera carnica) in a forest environment

Investigating the life history of social insect colonies and the demography of their populations are important for their conservation, but data collection is challenging. There is a growing interest in understanding the population status of wild-living honeybee colonies across Europe, for which it is critical to collect data on survival and natality rates. Although survival rates can be investigated through regular inspections of wild nests, the accurate quantification of natality rates (i.e., the number of swarms produced per colony per year) remains a significant challenge. Using digital weight scales, we remotely monitored the natural swarming behavior of ten unmanaged Apis mellifera carnica colonies housed in static-volume hives (45L) in a forest region of southern Germany. During the 2019 season, between mid-May and late June, we recorded 17 swarming events, averaging 1.7 swarms per colony. Our observations offer a reference point for the timing, frequency, and size of honeybee swarms that helps us understand the natural reproductive patterns of wild-living honeybees in a temperate forest environment.

ecology↗

bioRxiv2024

Assessing nest sites, survival rates and population dynamics of free-living honeybee colonies in Germany: A comparative study using personally collected and Citizen Science data

Our understanding of the western honeybee (Apis mellifera) predominantly stems from studies conducted within beekeeping environments, leaving the presence and characteristics of honeybees outside managed settings largely unexplored. This study examined the habitats, nesting sites, and survival rates of free-living colonies through personal monitoring of nest sites in Munich (N=107) and the coordination of Citizen Science monitoring across Germany (N=423). Within seven years we collected 2,555 observations on 530 colonies from 311 participants. Nesting preferences differed between urban, rural, and forested areas. Overall, we found that 31% of the occupied nest sites were in buildings and 63% in mature trees, with clear preferences for specific tree species. On average, only 12% of the personal monitored colonies in Munich survived annually, a figure that aligns well with other published studies but contrasts sharply with the significantly higher survival rates reported by Citizen Science (29%). We found that Citizen Science yielded significantly fewer updates per colony, underreported abandoned sites, and that 46% of overwintering reports overlapped with the swarming season and had to be excluded. To gain reliable survival data in Citizen Science projects, consistency and timing of reports need particular attention and regional swarming should be monitored too. This study enhances our understanding of the ecological dynamics, liminal state, and conservation needs of free-living honeybee cohorts, addresses potential monitoring biases, and suggests standardized data collection protocols for future monitoring projects.

ecology↗

bioRxiv2022

Reduced parasite burden in feral honeybee colonies

Bee parasites are the main threat to apiculture, and since many parasite taxa can spill over from honeybees (Apis mellifera) to other bee species, honeybee disease management is important for pollinator conservation in general. It is unknown whether honeybees that escaped from apiaries (i.e., feral colonies) benefit from natural parasite-reducing mechanisms like swarming or suffer from high parasite pressure due to the lack of medical treatment. In the latter case, they could function as parasite reservoirs and pose a risk to the health of managed honeybees (spillback) and wild bees (spillover). We compared the occurrence of 18 microparasites among managed (N=74) and feral (N=64) honeybee colony samples from four regions in Germany using qPCR. We distinguished five colony types representing differences in colony age and management histories, two variables potentially modulating parasite prevalence. Besides strong regional variation in parasite communities, parasite burden was consistently lower in feral than in managed colonies. The overall number of detected parasite taxa per colony was lower, and Trypanosomatidae, chronic bee paralysis virus, and deformed wing viruses A and B were less prevalent and abundant in feral colonies than in managed colonies. Parasite burden was lowest in newly founded feral colonies, intermediate in overwintered feral colonies and managed nucleus colonies, and highest in overwintered managed colonies and hived swarms. Our study confirms the hypothesis that the natural mode of colony reproduction and dispersal by swarming temporally reduces parasite pressure in honeybees. We conclude that feral colonies are unlikely to contribute significantly to the spread of bee diseases.

ecology↗

bioRxiv2020

Do honey bee species differ in the odometer used for the waggle dance?

Honey bees estimate distances to food sources using image motion experienced on the flight path and they use this measure to tune the waggle phase duration in their dance communication. Most studies on the relationship between experienced optic flow and the dance-related odometer are based on experiments with Apis mellifera foragers trained into a small tunnel with black and white patterns which allowed quantifiable changes in the optic flow. In this study we determined the calibration curves for foragers of the two Asian honey bee species, A. florea and A. cerana, in two different natural environments with clear differences in the vegetation conditions and hence visual contrast. We found that the dense vegetation condition (with higher contrast) elicited a more rapid increase in the waggle phase duration with distance than the sparse vegetation in A. florea but not in A. cerana. Visual contrast did not affect the perception of the food reward, measured as the number of dance circuits produced per distance, in both species. Our findings suggest that contrast sensitivity of the waggle dance odometer, or other aspects of flight behaviour, might vary among honey bee species.

animal behavior and cognition↗