Octopuses, creatures commonly associated with the depths of the ocean, possess a surprising capability. While their natural habitat is underwater, certain species temporarily leave the water and navigate terrestrial environments. This unexpected behavior raises questions about how these soft-bodied invertebrates move on land and the reasons behind such unusual excursions.
The Mechanics of Terrestrial Movement
Octopuses are uniquely equipped to move outside of water due to their flexible anatomy. Their eight powerful arms, covered with hundreds of suckers, provide grip and propulsion to navigate solid surfaces. These suckers allow them to adhere and detach, enabling a coordinated push-and-pull motion.
Unlike animals with rigid skeletons, octopuses possess a hydrostatic skeleton, supported by muscle and fluid, allowing them to deform their shape and squeeze through tight spaces. Their lack of bones contributes to flexibility, enabling them to contort and maneuver across uneven terrain.
When out of water, an octopus can retain water within its mantle cavity, which helps keep its gills moist and facilitates brief respiration. The movement is less of a “walk” and more of a “slithering” or “crawling” action, effective for short distances. Some species, like the Abdopus aculeatus, are adept at these land-based maneuvers, moving efficiently between tide pools.
Reasons for Land Ventures
Octopuses venture onto land for adaptive reasons, primarily driven by survival and foraging opportunities. One common motivation is hunting, as they pursue prey like crabs and shellfish trapped in tide pools or on exposed rocks during low tide. This allows them to access food sources unavailable in deeper waters.
Temporarily leaving the aquatic environment allows an octopus to evade immediate danger from predators like sharks or seals. They also move between tide pools or relocate to new den sites if their current habitat becomes unsuitable due to changing tides or food scarcity. These movements are typically short and purposeful.
Survival Limits on Land
Despite their ability to move on land, octopuses face physiological constraints limiting their time out of water. Their primary respiration method involves gills, designed to extract oxygen from water. Exposed to air, these gill structures can collapse, severely reducing oxygen absorption and leading to suffocation.
While limited oxygen absorption can occur through their skin, this is insufficient for prolonged survival. Dehydration is another major threat, as their permeable skin rapidly loses moisture. High temperatures and dry conditions accelerate this desiccation, shortening their survival time. Cooler, humid conditions can extend this period.
Out of water, octopuses also become more vulnerable to terrestrial predators like birds. Without water’s buoyancy, their soft bodies are more susceptible to gravity’s effects and injury on rough surfaces. Most octopus species can only survive out of water for a brief period, typically a few minutes to about an hour, depending on species, size, and conditions. Voluntary excursions are often even shorter, lasting just minutes.