Water provisioning increases caged worker bee lifespan and caged worker bees are living half as long as observed 50 years ago

Abstract

The high loss rates of honey bee colonies drive research for solutions aimed to mitigate these losses. While honey bee colonies are superorganisms, experiments that measure the response to stressors often use caged individuals to allow for inference in a controlled setting. In an initial experiment, we showed that caged honey bees provisioned with various types of water (deionized, 1%NaCl in deionized, or tap) have greater median lifespans than those that did not. While researching the history of water provisioning in cage studies, we observed that the median lifespan of caged honey bees has been declining in the US since the 1970’s, from an average of 34.3 days to 17.7 days. In response to this, we again turned to historical record and found a relationship between this trend and a decline in the average amount of honey produced per colony per year in the US over the last 5 decades. To understand the relationship between individual bee lifespan and colony success we used an established honey bee population model (BEEHAVE) to simulate the predicted effects of decreased worker lifespans. Declines in downstream measures of colony population, overall honey production, and colony lifespan resulted from reduced worker bee lifespans. Modeled colony lifespans allowed us to estimate colony loss rates in a beekeeping operation where lost colonies are replaced annually. Resulting loss rates were reflective of what beekeepers’ experience today, which suggests the average lifespan of individual bees plays an important role in colony success.