A new paper published in the journal, Coral Reefs, ‘Tool use in the tuskfish Choerodon schoenleinii?’ by A. M. Jones, C. Brown and S. Gardner, opens up a debate about tool use in fishes.
Jane Goodall describes tool use as the use of an external object as a functional extension of mouth or hand in the attainment of an immediate goal (van Lawick-Goodall 1970). Tool use is often observed in a foraging context in a wide range of species, such as primates, birds, dolphins, elephants and recently octopuses, and complex feeding behaviours are not uncommon among marine fishes. For instance, wrasses crunch sea urchins against corals and use anvils to smash food into more manageable pieces (Pas´ko 2010, reviewed in Brown et al. 2006). In spite of the anecdotal evidence for the use of tools in marine fishes, there are few documented cases, particularly those based on observations in the wild. In this paper the authors present evidence of a Black Spot Tuskfish, Choerodon schoenleinii, using a rock as an anvil to open a cockleshell that conforms to Goodall’s definition of tool use.
On 12 November 2006, Scott Gardner, a professional diver, was returning from an 18-m dive in the Keppel region of the southern Great Barrier Reef when he heard a cracking noise and saw a Tuskfish hovering just above a sand patch near a rock grasping a cockle in its mouth. Gardner, having his camera with him, recorded the fish and its apparent tool use, the photographs span 75 s and show the fish grasping the shell in its jaws and rolling onto its side to land alternate blows on the rock until the shell fractured (Fig. 1a–f) and the fish ate the bivalve inside.
Fig. 1 a–f Series of six photographs of the Black Spot Tuskfish, Choerodon schoenleinii using a rock as an anvil to open a cockle shell. Broken shells can be seen lying on the sand near the rock.
The use of a rock as an anvil rather than a hammer could be considered a sign of intelligence considering the ineffectiveness of manipulating a freely suspended tool in water. The images certainly provide an interesting starting point for further comparative studies on tool use in fishes.
Culum Brown, a behavioural ecologist from Macquarie University in Australia, co-author of the paper, says that the pictures taken by Gardner show that this fish was quite skilled at this behaviour. Evidence around the rock show this was not the first crushed shell and believes that with more exploration, more fish species will be found to use tools.
This opens up a debate as to exactly what defines tool use. While the Tuskfish is clearly using the rock to break the shell, it is never really “holding” the tool itself. Some scientists argue that this is essentially not tool use. However, Brown argues that this definition of tool use would restrict any possibility to only animals with an anatomy similar to humans. Lacking hands, fish use the resources available to them.
Brown C, Laland K, Krause J (2006) Fish cognition and behaviour. Blackwell Publishing, Cambridge
Pas´ko (2010) Tool-like behavior in the sixbar wrasse, Thalassoma hardwicke (Bennett, 1830). Zoo Biol 29:767–773
van Lawick-Goodall J (1970) Tool-using primates and other vertebrates. In: Lehrman D, Hinde R, Shaw E (eds) Advances in the study of behavior. Academic Press, New York, pp 195–249
Author’s note: This does not seem dissimilar to the avian behaviour of dropping snails onto rocky ground to break open the shell. The use of the mouth to grasp the cockle is in accordance with Goodall’s definition of tool use. TMH.