When cold weather arrives, many wonder what happens to spiders. Most species have developed remarkable adaptations to survive the winter months. Their strategies range from physiological changes to seeking specific sheltered environments. Understanding these adaptations reveals how spiders successfully navigate freezing temperatures and scarce resources.
Spider Survival Strategies
Spiders are cold-blooded, so their internal temperature largely matches their surroundings. To cope with dropping temperatures, many species enter a state called diapause, which is a period of suspended development and reduced metabolic activity. This conserves energy, decreasing their need for food when prey is scarce. This slowdown is similar to hibernation in other animals, making spiders sluggish and less active.
A significant physiological adaptation involves the production of natural “antifreeze” compounds in their hemolymph, which is their version of blood. These cryoprotectants, like glycol and glycerol, lower the freezing point of their bodily fluids. Glycerol forms hydrogen bonds with water molecules, making it harder for ice crystals to form within cells, preventing cellular damage from freezing. This chemical change allows some spiders to withstand temperatures well below freezing, sometimes as low as -20 degrees Celsius.
Beyond internal chemistry, spiders also employ behavioral adjustments to regulate their body temperature. They often seek insulated microhabitats with more stable temperatures. Some species may even bask in sunlight to absorb warmth or orient their webs in a way that maximizes sun exposure. Spider silk can also provide insulation; some spiders construct silk “pods” or “tents” to enclose themselves, offering protection from cold winds.
While many adult spiders survive the winter, some species with shorter lifespans die as temperatures drop. In such cases, their survival is ensured by their eggs, which are laid in protective silk sacs. These egg sacs are placed in sheltered locations, allowing spiderlings to remain insulated and develop until they hatch in the spring.
Common Overwintering Locations
Spiders seek out various sheltered places to spend the winter, both outdoors and sometimes indoors, depending on their species and environmental conditions. Outside, common overwintering spots include under leaf litter, mulch, or rocks, which provide insulation from extreme cold. They also find refuge under loose tree bark, inside hollow plant stems, or within logs, utilizing the natural protection these materials offer.
Some spiders burrow into the soil or take shelter in rock crevices, where temperatures are more stable than on the surface. A particularly effective outdoor strategy involves the “subnivean zone,” which is the insulated space that forms between the ground and a layer of snow. This area can remain above freezing even when air temperatures are much colder, allowing some spiders to remain active or dormant beneath the snow.
For indoor-dwelling species, or those that opportunistically enter structures, homes and other buildings offer stable, warmer environments throughout the winter. Spiders commonly seek refuge in undisturbed indoor areas such as basements, attics, and garages. Wall voids, crawl spaces, and even small cracks around windows and doors can also serve as sheltered locations. Many spiders observed indoors during winter are often species that live exclusively within human structures year-round, rather than outdoor spiders migrating in for warmth.