One of the oddest little animals in existence is the Californian wood-rat, better known as the “trade-rat.” It owes the latter name to the fact that though it is a great thief, it never steals anything without putting something else in its place. Rather more than a year ago a photograph appeared among The Strand Curiosities of a paste-pot which had been left overnight in the assay office at the Silver Queen Mine, and which was found in the morning filled with the oddest collection of rubbish. This was the work of trade-rats. They had stolen the paste and left in exchange a piece of stick, a length of rope, some odds and end’s of wire, and an unbroken glass funnel.
The object of the trade-rat in so scrupulously paying for what he takes is something of a mystery. But these same rats certainly take the greatest pleasure in the odds and ends which they steal and collect. In Lindsay’s “Mind in Lower Animals,” a description is given of a trade-rat’s nest found in an unoccupied house. The outside was composed entirely of iron spikes laid in perfect symmetry, with the points outwards. Interlaced with the spikes were about two dozen forks and spoons and three large butcher-knives. There were also a large carving-fork, knife, and steel, several plugs of tobacco, an old purse, a quantity of small carpenters’ tools, including several augers, and a watch, of which the outside casing, the glass, and the works were all distributed separately, so as to make the best show possible. Altogether the oddest collection! None of these things were of any earthly use to the rats. They must have collected them just in the same way that a child hoards up odds and ends to play with.
—The Strand Magazine Vol. XXXII, No. 88 (September 1906)
Also: “Dusky-footed woodrats of California have been found to selectively place California bay leaves (Umbellularia) around the edges of their nest within their stickhouses to control levels of ectoparasites such as fleas. The leaves contain volatile organic compounds which are toxic to flea larvae.” (source)
Image: Illustration from The Dusky-footed Wood-rat by Jean M. Linsdale and Lloyd P. Tevis, Jr. (1951).