People may spot dead bumblebees on sidewalks during the summer for a few different reasons, according to ScienceDaily. Some are linked to natural colony behavior, while others are tied to weather and human activity.
Bumblebee workers live only about four to six weeks, so older bees die off fairly quickly. To help keep disease from spreading, healthy bees in the colony remove the dead and carry them away from the nest.
Extreme heat is another factor. ScienceDaily notes that very hot weather can cause thermal stress in bees, affecting their development, reproduction, flight ability and foraging. Bees can use cooling behaviors such as fanning their wings, but those defenses have limits in severe heat.
Pesticides, herbicides and habitat loss also contribute to bee declines. The article says some chemicals can directly harm bees or remove plants they depend on for food, while development, intensive agriculture and roads reduce the habitats they need.
ScienceDaily also points to climate-related timing mismatches between bees and the plants they rely on. With wild bee species under growing threat in Europe, the article says people can help by supporting nature-friendly farming, planting native flowers, leaving some lawn unmown and offering a struggling bee sugary water and a shady spot if it is safe to do so.
