Abstract <p>Life-history theory proposed that animals will produce fewer, larger offspring in response to environmental stress, and that there is a litter size-number of offspring trade-off to cope with further stress. Understanding how this reproductive strategy—the trade-off between clutch size and egg volume—is modified along elevational gradients is central to understanding life-history evolution. In this study, we evaluated the reproductive strategies of three populations of <i>Heremites vittatus</i> from different elevations in Türkiye. We found that female body size was not significantly different across the three elevational groups. However, when we compared egg volume with elevation, we found that egg volume showed a significant increase with elevation. At higher elevations, which have more stressful and less stable conditions, this pattern may reflect an adaptive reproductive strategy favouring larger offspring size. However, despite the increase in elevation and egg volume, we did not find a significant difference in clutch size. Additionally, our findings showed that reproductive activity was delayed at higher elevations, while it begins faster at lower elevations, possibly because of better environmental conditions. Environmental factors like temperature and food availability may cause variations in egg volume and reproductive timing between elevations.</p>