o hai octopi | tool use in cephalopods
Bio 342 Fall 2011
Because this complex behavior has not yet been studied extensively, there is no data reporting the ages of the organisms that engage in coconut-carrying behavior. However, since related behaviors, such as home modification, become more sophisticated as the animal grows , it is reasonable to assume a similar ontogenic pattern for coconut-carrying. This section is sub-divided into learning and physiological development because those explain the behavior’s higher prevalence in adults than in juveniles.
Learning can be subdivided into three categories: visual and tactile discriminative capabilities, spatial learning, and observational learning. It is not known which of these learning behaviors are employed in this coconut-carrying behavior, but a brief discussion of these three learning-related possibilities will show the potential involvement of each.
Visual and Tactile Discrimination
Octopus' visual and tactile discriminatory capabilities far exceed what is necessary to discriminate a coconut shell from, say, a rock. For example, Muntz (1970) trained octopuses to successfully discriminate between the following shapes after four days . See Figure 1 below.
Figure 1. O. vulgaris learned to successfully discriminate between these shapes after four days of training using classical conditioning .
While studying octopuses’ navigation using landmarks, Mather (1991) found that “octopuses can and do use a long-term memory of a visual landmark array” . This is significant for coconut-carrying behavior because 1) individuals repeatedly engage in the behavior over time which indicates that it requires long-term memory and 2) depending on the availability and range of the coconut halves, the octopi may have to navigate back to the coconut-laden sites.
Despite the fact that octopi are typically solitary animals, they do have the capability to utilize information gathered by observing conspecifics . In Fioritto and Scotto’s experiment, the octopi were able to learn more quickly by observation than by trial-and-error or classic conditioning. The fact that their learned behavior was stable for five days after observation is taken to be indicative of long-term retention.
(Also see Cognitive Mechanisms under Mechanism.)
Although the veined octopus’ particular lifespan has not been studied, it is probably somewhere between 6 months and 1 year based on the lifespans of related species A. aegina (6-9 months) and O. Vulgaris (12-24 months) [19, 18]. During this time, they grow to be only 8cm, or ~15cm including their arms. Because stilt walking requires the octopuses to wrap their arms around the coconut shell and still be able to walk, young octopuses would be unable to engage in coconut-carrying behavior on the basis of size alone, regardless of cognitive capacity. Due to a lack of information on the veined octopus’ development and the size of the coconuts, it is difficult to pinpoint an exact size or age at which the octopuses would physically be able to stilt walk. See figure 2 below to get an idea A. marginatus' size.
Figure 2. Small Amphioctopus marginatus (4-6cm) using nut shell and clam shell as shelter.