Spiders can starve to death, but they can survive without food for astonishingly long periods compared to mammals and many other animals. Their remarkable physiology allows them to endure prolonged periods of scarcity in unpredictable environments. A spider’s resilience is often measured in months, setting them apart as masters of metabolic efficiency.
The Biological Basis for Extreme Endurance
A spider’s ability to survive without food is rooted in its ectothermic nature, meaning its body temperature is regulated by the external environment. Unlike mammals, spiders do not constantly burn calories to maintain a high internal temperature. This absence of internal thermoregulation drastically reduces their base energy requirements for survival.
This low energy demand is amplified by an inherently low basal metabolic rate (BMR), the minimum energy required to keep their bodies functioning at rest. Spider BMRs are often significantly lower than predicted for their body size compared to other arthropods. Without food, spiders can enter a state of metabolic depression, slowing energy consumption further to a mere fraction of their normal resting rate.
Spiders store energy reserves almost exclusively as dense lipids, or fats, in their opisthosoma (abdomen). These fat reserves provide a highly concentrated source of fuel that can be metabolized slowly over time. When food is unavailable, the spider systematically taps into these lipid stores to maintain its low-level physiological processes.
Factors Determining Lifespan Without Food
The practical length of survival varies significantly based on several external and internal factors. Temperature acts as the primary control for the rate of metabolism, influencing how quickly stored lipids are depleted. A spider in a cool environment might survive for many months because its metabolism is slowed, while the same species in a warm environment will exhaust its reserves much faster.
Hydration is a more immediate and limiting factor than food scarcity. Spiders require water to facilitate metabolic reactions and manage waste, and they extract much of this water from their prey. Without a meal, they become highly susceptible to dehydration, which can be fatal in dry conditions sooner than starvation. Access to environmental moisture, such as condensation or high humidity, is important for prolonged fasting.
Survival time also depends heavily on the species and the spider’s size. Small, active hunters like jumping spiders might only endure a few weeks without food due to their higher activity levels and smaller storage capacity. Conversely, large, sedentary species like tarantulas, which have massive lipid stores, are known to survive for over a year, sometimes up to 18 months, without a meal. Adults generally survive longer than juveniles.
Physiological Decline and Outcome
As a spider exhausts its internal lipid stores, its physical condition declines visually and functionally. The most noticeable sign of prolonged starvation is the significant shrinkage of the abdomen, the primary energy storage location, as fats are metabolized. This loss of mass forces the spider to conserve energy by drastically reducing its activity, often becoming nearly immobile to preserve its reserves.
The body also sacrifices high-energy functions. The production of silk, a protein-intensive process, will cease as the spider redirects resources to basic survival. For hunting spiders relying on sight, prolonged starvation can lead to the degeneration of light-sensitive photoreceptor cells in the eyes, resulting in a loss of vision.
Death from starvation occurs when the spider’s systems fail due to the complete exhaustion of energy reserves. This manifests as a total inability to move or capture prey, organ failure, or the inability to successfully complete a necessary molt. The spider uses up all the fuel required to perform basic, life-sustaining functions.