The ocean depths hold many mysteries, and among the most captivating is the behavior of certain octopus species that appear to arrange objects around their homes. This phenomenon sparks curiosity, prompting questions about whether these intelligent creatures truly cultivate “gardens” in the traditional sense. Exploring the science behind this intriguing behavior offers a glimpse into the complex lives of octopuses and their interactions with their marine environment.
Unpacking the Octopus “Garden”
What marine biologists call an octopus “garden” is not a botanical arrangement but an accumulation of objects around an octopus’s den. These collections are often referred to as middens, essentially piles of discarded materials. An octopus midden typically consists of items like rocks, shells, and sometimes prey bones. Near human activity, these middens can also include discarded items like bottles or glass fragments.
These curated piles conceal the entrance of the octopus’s den, typically a crevice in rocks or other hard structures. The appearance of these “gardens” can vary, from simple heaps of shells to more structured arrangements. Some octopuses have been observed building distinctive “walls” of rocks and shells extending outward from their den entrances. The composition of these middens often reflects the octopus’s diet, as many species bring their prey back to the den to eat, leaving behind the hard, uneaten parts.
Why Octopuses Arrange Objects
The reasons for this object-arranging behavior are diverse, rooted in survival and adaptation. One primary theory suggests octopuses accumulate objects to fortify and protect their dens from predators. By creating barriers with shells and rocks, they make their homes more secure, deterring animals like moray eels. This defensive strategy is particularly evident in species inhabiting sandy environments with limited natural shelter, where octopuses collect more substantial items.
Beyond defense, object arrangement also serves as territorial marking. Some octopuses create visual perimeters around their dens, signaling ownership to other octopuses. These territorial displays can incorporate chemical signals, as octopuses secrete compounds onto frequently handled objects. Discarded shells and other materials also function as refuse disposal, as the octopus tidily pushes unwanted items out of its living space. Some observations suggest a possible aesthetic motivation, with octopuses rearranging colorful objects without apparent survival benefit.
Species Known for Accumulation
Several octopus species are recognized for their object-collecting habits, each with unique approaches. The Veined Octopus, also known as the Coconut Octopus (Amphioctopus marginatus), is notable for its sophisticated use of discarded coconut and large bivalve shells. This species uses these items to create mobile protective shelters, a behavior considered tool use. They have been observed carrying these shells while “stilt-walking” across the seafloor, providing immediate refuge.
The Common Octopus (Octopus vulgaris) is frequently observed building and maintaining middens around its den. These middens are often composed of marine plant life, algae, shells, and rocks. The Gloomy Octopus (Octopus tetricus) also exhibits this behavior, collecting scallop shells and other marine debris to fortify den entrances. The aggregation of these decorated dens can create modified habitats that attract other marine species, forming small ecosystems centered around the octopuses’ collections.