Common herbicide impairs fertility but not survival in bumblebees, Bombus impatiens

Abstract

Insect declines have raised concerns over widespread agrochemical usage. Current environmental risk assessments (ERAs) focus on lethal effects, often neglecting fitness-relevant parameters. Here, we experimentally exposed male bumblebees (Bombus impatiens) to a field-realistic concentration of a glyphosate-based herbicide (GBH) under controlled laboratory conditions to assess potential effects on survival, consumption behavior, and reproductive physiology (i.e., spermatozoa traits). Our results demonstrate that chronic exposure of male bumblebees to GBH significantly enhanced their survival yet reduced living spermatozoa (~ 34%). This highlights a physiological shift, where resources appear prioritized toward survival mechanisms over reproductive investment. Such findings underscore critical false negative results in current ERAs and advocate for incorporating fitness endpoints to better understand and mitigate ongoing insect declines.