Abstract-Siberian chipmunks were presented with snakes and 4 control animals (tortoises, frogs, eels, quails) in a large outdoor pen to examine whether the snakedirected behavior of the chipmunk is a response to identifying the snake or simply an exploratory behavior toward generally strange objects. The animals were presented to chipmunks in 3 manners; tethered, anesthetized, and in perforated opaque boxes and in wire netting boxes. In "tethered" and "anesthetized", chipmuhks responded significantly more intensively to snakes than to other animals. When the animals were presented in the boxes, that is, when chipmunks could perceive only olfactory stimulus from the animals, they also showed the strongest response to snakes. The results suggest that 1)snake-directed behavior of chipmunks is not a general exploratory response toward strange objects but a response to identifying the snakes, and that 2)olfaction is an important cue for the chipmunks to identify snakes.
--The signal effect of mobbing of snakes (a signal effect alerts conspecifics of the presence of a predator) by Siberian chipmunk Eutamias sibiricus asiaticus was examined. A pair of chipmunks, familiar with each other, were moved from their rearing pen into a test box, where they were kept undisturbed for acclimatization. Then the anterior portion (or head) of an anesthetized Japanese rat snake was exposed in a corner of the box. Several minutes later, one of the chipmunks discovered the snake and began mobbing it. This was followed by the discovery of the snake by the other chipmunk. Although the time span from the introduction of the snake to its discovery by the first chipmunk was quite different between trials, the time elasped from the snake discovery by the first chipmunk to that by the other chipmunk was relatively constant and significantly shorter than the former time span in all trials. These results strongly support the premise that the mobbing has a signal effect.
Some rodents assault live snakes by mobbing. Another snake‐directed behaviour is shown by Siberian chipmunks, Eutamias sibiricus asiaticus, when encountering a dead snake. They approach the carcass cautiously, gnaw the snake skin, and chew and apply the gnawed bits to their body fur. We have termed this behaviour “Snake‐Scent Application” (SSA). SSA behaviour is also elicited by snake urine and feces. Chemicals in snake skin and rectal and cloacal sacs release SSA. Snake urine applied to dead mice tends to suppress ingestion by snakes.
--The functions of snake mobbing by Siberian chipmunks were studied in the context of potencial benefit to the mobbers themselves. In experiment I, the threatening effect of the mobbing was examined, and following results were obtained. The snake retreated almost always into a shelter box when it was mobbed, and the time span from the beginning of the mobbing until the completion of the snake's retreat into the box was shorter when the snake was mobbed by 2 chipmunks than when mobbed by a single one. These results indicate that mobbing has a threatening effect against the snake that increases when more chipmunks mob. In experiment II, I examined whether chipmunks get information about the snake during the mobbing. The experiment showed that the chipmunks performed tail shakings after the mobbing more frequently at large snakes than at small ones, and also indicated that mobbing functions to obtain useful information about snakes. This study clarified that the snake mobbing by Siberian chipmunks provides benefits to the mobbers themselves.
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