Jumping spiders, members of the family Salticidae, represent the largest family of spiders in the world. These common arachnids are easily recognizable by their four pairs of eyes, especially the two large, forward-facing eyes that grant them exceptional vision among arthropods. Throughout the warmer months, these active predators use their sharp eyesight for navigation, courtship, and their characteristic agile hunting style, which often involves a quick, precise leap onto prey. Their vibrant activity ceases when the cold arrives, leading many to wonder how such mobile, warmth-dependent creatures manage to survive the harsh conditions of winter.
The Winter Survival Strategy
As autumn progresses and the days shorten, jumping spiders begin preparing for a state of metabolic arrest known as diapause. Diapause is a predetermined developmental and physiological state timed by environmental cues like decreasing photoperiod and temperature, rather than being triggered solely by cold. This strategy allows the spider to proactively prepare its body for the impending low temperatures.
During this prolonged period of dormancy, the spider’s metabolism slows drastically to conserve energy. Feeding and active movement cease almost entirely, allowing the spider to survive for months without food until warmer weather returns. This state is a critical phase of their life cycle, particularly for sub-adults who will often enter diapause and emerge in the spring to undergo their final molt and reach maturity.
Physiological Mechanisms of Cold Tolerance
To withstand temperatures that often drop below freezing, jumping spiders employ a cold tolerance strategy known as freeze avoidance. This means they cannot survive if ice crystals form within their body fluids, so their internal chemistry is adapted to prevent freezing altogether. This avoidance is achieved by lowering the supercooling point (SCP), the temperature at which the body fluids spontaneously freeze.
The physiological mechanism involves the synthesis of specialized compounds, referred to as cryoprotectants, which act like natural antifreeze. These can include polyols like glycerol or specialized sugars, which are concentrated in the hemolymph (spider blood) and other body fluids. The accumulation of these solutes lowers the freezing point of the water inside the spider’s body, allowing them to survive chilling temperatures.
Jumping spiders have been observed to reduce their supercooling point significantly between fall and winter. This “cold hardening” process is an adaptation to avoid the mechanical damage to cells that occurs when ice crystals form. In addition to cryoprotectants, some spiders may produce antifreeze proteins that inhibit the growth of any small ice crystals, further stabilizing the supercooled state.
Choosing Winter Shelters
Before entering diapause, the jumping spider must select a suitable microhabitat that will help mitigate the worst of the environmental fluctuations. They seek out locations that offer protection from wind, precipitation, and the most extreme temperature drops, often finding a sheltered, insulated spot close to the ground. Common outdoor choices include tucking themselves under loose tree bark, within rock crevices, deep inside leaf litter, or beneath logs.
The spider then constructs a specialized physical retreat for the winter, known as a hibernaculum. This structure is a dense, multi-layered silken sac that is far more robust than their usual resting hammocks. The dense silk provides a crucial layer of insulation, creating a microenvironment that remains slightly warmer and more stable than the outside air.
This silk shelter is carefully attached to the chosen substrate, offering protection from predators and the damaging effects of harsh weather. The hibernaculum physically shields the metabolically slowed spider until the increasing daylight and warmth of spring signal the end of their long winter dormancy.