Learning from play in octopus

Introduction to the book: The brain of cephalopods rivals that of the vertebrates in relative size, being as large as or larger than the brains of many fish, although smaller than those of birds and mammals (Hochner, 2008). The elaborate sensory and neural system in many extant cephalopods enables them to exhibit complex types of adaptive behaviour (Wells, 1978; Hanlon & Messenger, 1996; Nixon & Young, 2003; Hochner, 2008, 2010). Of the many kinds of such complex behaviour, we focus here on exploration, play and cognition.

To adequately study exploration, or playful interaction, in cephalopods, we need to know a good deal about their behaviour, especially ‘normal’ or ethotypic behaviour, and have sufficient time and opportunities to observe changes to their behaviour across time and settings. This requires keeping animals in good condition in captivity or observing them in the wild in natural environments. This being said, most cephalopods live in the open waters of the deep sea and the majority are unavailable for systematic observation. Furthermore, most cephalopod species cannot be maintained regularly in laboratory conditions. For these reasons, most studies of the behaviour of individual cephalopods come from work on only three genera, Octopus, Sepia and Loligo, animals that live in coastal waters. These, and a few of their close relatives, are the only cephalopods that have been kept at all regularly in aquaria;Octopus, Sepia and, to some extent, Sepiotheuthis alone do sufficiently well under these conditions for their observed behaviour to be considered typical and natural (Wells, 1962; Sanders, 1975; Wells, 1978; Moynihan & Rodaniche, 1982; Hanlon & Messenger, 1996; Nixon & Young, 2003; Mather, Griebel & Byrne, 2010). Due to this lack of data on basic behaviours of these animals, it is often difficult to argue which observed playful behaviours might be considered exaggerations or modifications of normal behaviours. To date we are aware of only four papers, on two different species of octopus, dealing with exploration and play (Mather & Anderson, 1999; Kuba, Meisel, Byrne, Griebel & Mather, 2003; Kuba, Byrne, Meisel & Mather, 2006a, 2006b). In this chapter, therefore, we will focus on octopuses, probably the most studied group of all cephalopods.

Octopuses have fascinated observers for thousands of years and there is a wealth of anecdotal reports of their intelligence, cunning and curiosity. They are generalist predators and detect their prey both visually and by touch (Hanlon & Messenger, 1996). The loss of the external molluscan shell has been linked to their high behavioural plasticity for predator avoidance, an increase in brain size and the evolution of more effective sense organs, resulting in higher cognitive abilities (Packard, 1972; Hanlon & Messenger, 1996). The aim of the studies on octopus exploration and play is to describe the behavioural processes involved and to untangle the interplay between exploration, habituation and exploratory play in these animals. These studies show, for the first time, that an invertebrate does engage in playful interactions with objects (Burghardt, 2005).

Introduction to the book: The brain of cephalopods rivals that of the vertebrates in relative size, being as large as or larger than the brains of many fish, although smaller than those of birds and mammals (Hochner, 2008). The elaborate sensory and neural system in many extant cephalopods enables them to exhibit complex types of adaptive behaviour (Wells, 1978; Hanlon & Messenger, 1996; Nixon & Young, 2003; Hochner, 2008, 2010). Of the many kinds of such complex behaviour, we focus here on exploration, play and cognition.

To adequately study exploration, or playful interaction, in cephalopods, we need to know a good deal about their behaviour, especially ‘normal’ or ethotypic behaviour, and have sufficient time and opportunities to observe changes to their behaviour across time and settings. This requires keeping animals in good condition in captivity or observing them in the wild in natural environments. This being said, most cephalopods live in the open waters of the deep sea and the majority are unavailable for systematic observation. Furthermore, most cephalopod species cannot be maintained regularly in laboratory conditions. For these reasons, most studies of the behaviour of individual cephalopods come from work on only three genera, Octopus, Sepia and Loligo, animals that live in coastal waters. These, and a few of their close relatives, are the only cephalopods that have been kept at all regularly in aquaria;Octopus, Sepia and, to some extent, Sepiotheuthis alone do sufficiently well under these conditions for their observed behaviour to be considered typical and natural (Wells, 1962; Sanders, 1975; Wells, 1978; Moynihan & Rodaniche, 1982; Hanlon & Messenger, 1996; Nixon & Young, 2003; Mather, Griebel & Byrne, 2010). Due to this lack of data on basic behaviours of these animals, it is often difficult to argue which observed playful behaviours might be considered exaggerations or modifications of normal behaviours. To date we are aware of only four papers, on two different species of octopus, dealing with exploration and play (Mather & Anderson, 1999; Kuba, Meisel, Byrne, Griebel & Mather, 2003; Kuba, Byrne, Meisel & Mather, 2006a, 2006b). In this chapter, therefore, we will focus on octopuses, probably the most studied group of all cephalopods.

Octopuses have fascinated observers for thousands of years and there is a wealth of anecdotal reports of their intelligence, cunning and curiosity. They are generalist predators and detect their prey both visually and by touch (Hanlon & Messenger, 1996). The loss of the external molluscan shell has been linked to their high behavioural plasticity for predator avoidance, an increase in brain size and the evolution of more effective sense organs, resulting in higher cognitive abilities (Packard, 1972; Hanlon & Messenger, 1996). The aim of the studies on octopus exploration and play is to describe the behavioural processes involved and to untangle the interplay between exploration, habituation and exploratory play in these animals. These studies show, for the first time, that an invertebrate does engage in playful interactions with objects (Burghardt, 2005).

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