Book's revised definition expands animal tool use

Robert Shumaker, vice president of Life Sciences at the Indianapolis Zoo, led a discussion Friday in the Student Building on his new book, “Animal Tool Behavior: The Use and Manufacture of Tools by Animals.” The book, Shumaker said, is a summary and review of all reported cases of nonhuman tool use.

The book was written with Kristina Walkup and Ben Beck, and it is a revision of a 1980 version of the same book. The original version was written by Beck.

There are two differences between the new and old version of “Animal Tool Behavior.” First, there are simply more cases of tool use documented in the new version.

“There are many more researchers for every animal group nowadays,” Shumaker said. While the first edition has 670 different known examples of tool use, the new edition has about 1,750.

“Many animals, not just primates, make tools,” Shumaker said. He showed pictures of several examples, like spiders that throw globs of sticky silk at passing
insects and an octopus that was photographed using a coconut as a shelter and carrying the coconut with it wherever it went.

The second difference between the editions was the definition of “tool use.” The three authors modified the original book’s definition.

First, they said a tool can be both unattached and attached to the animal’s environment, where in the first book, only unattached tools were counted. For example, a vine that is pulled down by an animal to get its fruit would be a tool only in the second version.

Second, the authors said a tool can be manipulated at any time relative to the use of the tool, where the first book said an animal must manipulate the tool just before it is used. For example, say an ape carries a rock to a fruit, leaves for an hour and then comes back and smashes the fruit with the rock. It is using a tool only by the second definition because the time between manipulation and use is too long for the first definition.

“We have yet to find a definition of tool use that is as useful and appropriate,” Shumaker said of the new definition.

Shumaker ended the presentation with the subject of orangutan tool use.

“There is no reliable trend to predict which types of animals will use tools,” he said, “but the most frequent use of complex tool use is by great apes.” Among the great apes, he said, orangutans use the most tools.

Of the 22 modes of tool use, wild orangutans use 16, but both captive orangutans and those that were taken out of the wild — often illegally by poachers — use all 22 modes. Shumaker said he thinks this difference is partly due to the difficulty of documenting orangutans in the wild and hopes to see further wild tool use in future studies.