Article: Samuelson, A.E., Schürch, R., & Leadbeater, E. (2021). Dancing bees evaluate central urban forage resources as superior to agricultural land. Journal of Applied Ecology 59: 79-88. https://doi.org/10.1111/1365-2664.14011
The expansion and intensification of farmlands worldwide is reducing and fragmenting bee habitat, threatening bee populations. Pollinators in general, including bees, are also facing an increase in disease and threat of pesticides, all contributing to the decline of their populations. This decline has widespread implications for the environment, and for us, as many plants and animals depend on the pollination services that bees provide. Threats to pollination are threats to the sustainability of our food.
Bees collect pollen and nectar from flowers for food for their colonies, and in doing so, pollinate plants. Flower-rich areas in cities, such as gardens and local parks, can support bee populations, but comparing the suitability of flower-rich resources for bees in urban and agricultural landscapes can be difficult. Ash Samuelson at the Royal Holloway University in London, UK and their colleagues, however, recently compared the distance in which bees from both urban and agricultural hives need to travel to reach sufficient nectar and pollen sources. They accomplished this by “listening” to the bees themselves, decoding the messages that they send to each other through dance.
Dancing the Distance
When honey bees return to the hive with nectar, they perform what is known as a “waggle dance” to let the other bees know where to find the flowers they just visited. The duration of the “waggle” relates to the distance that the bees traveled to find the flowers, and the direction the bees are facing relative to the sun indicates the direction in which they traveled. Scientists in the past have come up with a way to decode these dances and estimate just how far and in what direction the bees found flowers.
Samuelson and their colleagues selected 20 existing hives near London, 10 in agricultural areas and 10 in urban areas within central London. In each of these hives, they videoed waggle dances once every 2 weeks for 24 weeks between April and September of 2017. With over 3,000 waggle dances to decode, they were able to estimate where the bees had gone to find flowers and use maps that subdivided the agricultural and urban land into seven more specific categories each to see where bees had gone to find flowers. For agriculture, categories included fruit crops, woodland, pasture land, other agricultural, non-agricultural, oilseed rape, and arable land. For urban areas, categories included woodland, water, sparse residential areas, dense residential areas, parks, railways, and amenity grass.
If bees from one type of land use (i.e., agriculture) are traveling farther on average than bees from another type, this could mean that there aren’t many flowers nearby in the first land-use type and the bees therefore have to travel farther to find nectar. Alternatively, this could mean that flowers located closer to the hive could have inferior nectar quality. To rule out this second possibility, the authors collected 10 of the returning bees, put them under anesthesia, and then massaged the bees’ abdomens with a stick to encourage them to regurgitate the nectar that they had recently consumed. They measured sucrose (i.e., sugar) concentrations in this nectar to evaluate its quality.
Thriving in the City
Samuelson and their colleagues found that bees from urban areas consistently flew shorter distances to find flowers; she also found no difference in nectar quality between agricultural and urban areas. This implies, then, that bees in agricultural areas needed to travel farther to find flowers for nectar. This is good news for urban gardeners; the flowers we plant in cities matter, especially native plants (as ornamental plants do not tend to attract insects as well), and they provide an incredibly important resource for pollinators that helps ensure the sustainability of our food supply. In particular, when they considered specific categories of urban land to which bees traveled, sparse and dense residential areas were visited most often, followed by parks and amenity grass, though these areas were visited much less frequently than residential areas. The authors note that suburban areas were not studied, and could potentially serve as even better sources of flowers for bees, given that there tends to be more green space in suburban areas.
Agricultural land is not devoid of flowers, however. Samuelson and their colleagues found that within agricultural areas, bees tended to travel to areas where fruit crops and oilseed rape were planted, but also pasture land, perhaps due to flowering weeds and field borders with flowering plants in pastures. These findings point that it is possible to support local honey bee populations by adding flowering plants to farmland where possible, such as planting borders or allowing weeds to grow in certain areas.
If you want to support healthy honey bee populations in your area, consider planting native flowers. Even small urban gardens can serve as important nectar sources for local honey bees.