Tool Academy

15 December 2009

The mainstream corporate science media is, to paraphrase Keith Olberman, going “cuckoo for coconut octopodes.”  A new paper in Current Biology shows how the cephalopod Amphioctopus deliberately carries debris (shells, coconuts, garbage) for later use as building material to construct makeshift hideouts:

Many of the news stories about this paper imply, or state outright, that this marks the first observed case of “tool use” in an invertebrate.  It’s not.  In fact, it is not even the first purported case of tool use by an octopus.

Jones (1968) described an encounter with a weaponized Tremoctopus:

Among the frequent visitors to the submerged light were a number of immature female octopods, Tremoctopus violaceus. I dip-netted one of these from the water and lifted it by hand out of the net. I experienced sudden and severe pain and involuntarily threw the octopod back into the water. To determine the mechanism responsible for this sensation 10 or 12 small (40 to 72 mm total length) octopods were captured and I purposely placed each one on the tender areas of my hands. The severe pain occurred each time, but careful observation indicated that I was not being bitten by the octopod…Subsequent examination of one of these female octopods, 72 mm long, which had been preserved, revealed fragments of Physalia [n.b. the not-quite-a-real-jellyfish better known as the Portuguese Man O’war] tentacles attached in an orderly fashion to each row of suckers of each of its four dorsal arms. (Jones 1968).

Crustaceans are also known to employ stinging cnidarians (jellyfish, anemones and the lot) for defense, both by placing them on their body as a passive defense and by directly wielding them as weapons held in their appendages.  Jones speculated that the octopus might use the Physalia tentacles to aid in prey capture as well as defense, but I’m not sure if that speculation has been confirmed by observation.

More reminiscent of the new Amphioctopus case is the report by Mather (1993) of careful selection of stones by Octopus vulgaris which were then carried back to an existing shelter and used to fortify the entrance.  The line between construction behaviors (which are well known in many invertebrates) and “tool use” is blurry, but the Octopus vulgaris case seems to show the same kind of advance planning that is so striking in the coconut octopus shenanigans.  Cephalopods are complex, intelligent even creative creatures and in retrospect these incidents are perhaps not all that surprising though no less impressive.

Another group of putative invertebrate tool users are more surprising from a cognitive standpoint.  Compared to cephalopods, insects are pretty dumb at least one the individual level.  However, ants are known to use tools in a variety of ways.  Ants will drop small bits of debris (sticks, grains of sand) into liquid food sources then carry the soaked objects back to the nest.  These makeshift vessels allow individual ants to increase their foraging efficiency by transporting larger volumes of food than they could carry in their crop alone.  Ants are also known to drop small stones in their lairs of rival insects such as burrowing wasps as an apparent tactic to impede competition (Pierce 1985).

Again, if you know something about the astonishing behavioral repertoire of ants (e.g. domesticating aphids, constructing enormous underground fungus farms, building living bridges and rafts to cross bodies of water) these cases aren’t actually that surprising – but they do serve to highlight that depending on how you define it (which is a whole other kettle of fish I won’t go into here) “tool use” does not require as much cognitive complexity as one might expect.

Some other cases of purported arthropod tool use include “sand throwing” by ant lions, corpse camouflage by assassin bugs, and the construction of special sound amplification systems from leaves by singing katydids (Pierce 1985).  Corolla spiders place stone rings around their lair.  When a potential prey item bumps into the stones, the spider can sense the vibration and leap out to capture the prey (Henschel 1995).  This is pretty clearly a modification of the prey capture strategies used by other ambush predator spiders that use systems of silken trip wires to detect prey.

You might quibble with any (or all) of these examples as representing the same sort of “tool use” as seen in Amphioctopus. But they do show a spectrum of specialized use of inanimate objects to further the biological goals of individuals and social aggregations.  In the past, we often had to rely on somewhat unsatisfactory (though often enjoyable to read) written anecdotal accounts of behavior observed in the field.  As the new paper shows, the ability to easily incorporate video in scientific communication–something that has only really taken off in the last few years–is fueling a much more sophisticated and well-documented record of animal behavior.  To put it in a coconut-shell: the evolution of human technology is transforming our understanding of the evolution of animal technology.

Cool.  Here’s a coconut octopus in a beer bottle, not really relevant, but too good to pass up.

2 Responses to “Tool Academy”

  1. […] Neil notes in a comment below that he’s summarized several other cases of putative tool use by […]

  2. […] Biology paper here. // Visit Microecos for more examples of invertebrate tool […]

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