Winter survival strategies of cave-adapted amphipods in the Ice Caves of Sam’s Point area of Minnewaska State Park Preserve, NY, USA

The Allegheny Cave Amphipod ( Stygobromus allegheniensis Holsinger, 1967) is a troglobiotic crustacean native to caves in the northeastern United States, including the unique tectonic ice caves of New York’s Shawangunk Ridge. These caves act as natural cold air traps, retaining ice even through summer, creating an extreme environment for aquatic cave-adapted stygobionts. A key question is how these amphipods survive winters when the caves freeze, encasing floors and walls in ice. While past lab studies suggested they can survive freezing, our research shows limitations: individuals fully encased in ice do not survive beyond four hours. However, when surrounded by ice but buffered by a thin layer of liquid water at 0.5 °C, amphipods can endure prolonged exposure to near-freezing temperatures. Field observations confirmed that live specimens persist in the liquid layer beneath the ice and remain active during winter, displaying movement and foraging for food in baited traps. Additionally, specimens varied widely in size, suggesting the presence of multiple reproductive cohorts rather than a single annual reproductive cycle triggered by spring thaw. These findings indicate that reproduction and mortality occur year-round and that adults are capable of surviving the ice cave’s extreme winter conditions.