Spiders are widespread predators found in nearly every terrestrial habitat. Their global presence is due in part to their profound physiological resilience and ability to endure periods of extreme resource scarcity. Spiders are well-known for surviving extended fasts, but the timelines for survival vary greatly across the vast diversity of species.
The Physiology of Endurance
A spider’s long-term survival is rooted in biological machinery designed for unpredictable prey availability. Spiders are ectotherms; their internal body temperature and metabolic rate fluctuate with the external environment. This results in a significantly lower resting metabolic rate compared to mammals, drastically reducing the energy needed to sustain life.
Since spiders do not expend energy to generate internal body heat, they conserve fat reserves stored in their abdomen. When food is scarce, they can further depress their metabolism, entering a state of torpor or reduced activity to minimize energy use. This allows them to stretch a single meal’s energy content for weeks or even months.
Water conservation is managed primarily by the spider’s external covering, the cuticle or exoskeleton. This specialized outer layer is highly efficient at preventing water loss through evaporation. Spiders also possess physiological adaptations around their breathing structures, called spiracles, which help regulate air exchange while minimizing moisture escape.
Key Environmental and Species Variables
The ultimate survival time for any spider is modulated by its surrounding environment and biological traits. Temperature is a major factor; higher heat accelerates the spider’s metabolism, forcing it to burn energy reserves more quickly. A faster metabolism also increases the rate of water loss, which rapidly shortens the time a spider can survive without water.
Humidity levels also play a direct role in dehydration risk, as low humidity increases evaporative water loss through the cuticle. A spider in a dry, warm attic will dehydrate faster than one in a cool, humid basement. To counteract harsh conditions, many species instinctively seek microenvironments like burrows or shaded crevices to maintain a stable, cooler, and more humid zone.
Species size and prior nutritional status are major determinants of survival. Larger spiders, such as tarantulas, possess greater body mass and larger fat reserves, allowing them to endure longer fasts than smaller species. A spider that has recently consumed a large meal will naturally outlast one that was already lean when the food supply disappeared.
Typical Survival Timelines (Food vs. Water)
Survival time must distinguish between food and water, as water is the more immediate limiting factor for nearly all species. While a spider can survive long periods of starvation, it cannot survive long without hydration, especially in dry air. Small, common house spiders may only last a few days without water in dry conditions before succumbing to dehydration.
In contrast, small house spiders, such as the American house spider or wolf spiders, can typically go four to eight weeks without food when water is available. Larger web-building species often show greater endurance, capable of surviving one to three months between meals. This ability is necessary for species that rely on inconsistent prey capture in their webs.
The champions of fasting are large, heavy-bodied mygalomorphs, such as tarantulas, which leverage their massive fat stores and low metabolic rates. Many adult tarantulas can fast for six months to a year without ill effect; some documented cases show survival for up to two years without eating. Despite this resilience to starvation, even these large spiders still require water every few weeks to months to maintain basic cellular function.