Egg-eating behaviour in laboratory squirrel monkeys (Saimiri scuireus)

The present study aimed to clarify an individual character of squirrel monk ey by analysing a complicated behaviour, the egg-eating behaviour series (E S), of laboratory-reared squirrel monkeys. Eight types of unit movements we re observed in the ES: the initial taking of the egg by hand; rolling it be tween the fingers; sniffing it in its shell; biting it in its shell; pressi ng or rubbing it against a surface of the cage; opening or peeling it; eati ng it; or putting it down without eating. In the first experiment, the beha viour of 72 monkeys was recorded by direct observation or by a video camera , following which the sequences of the movement from a total of 378 ES were analysed. Three statistically significant ES were detected (Ta-Bi-Op/Pe-Ea , Ta-Ro-Bi-Op/Pe-Ea and Ta-Pr/Ru-Bi-Op/Pe-Ea. In the second experiment, eig ht squirrel monkeys were selected at random from the same group and 31 to 3 6 ES for each monkey were observed and analysed. These monkeys were classif ied into a pressing/rubbing (Pr/Ru) group and a no-Pr/Ru group. PriRu appea red to have no relationship to the monkey's age or sex. Furthermore, the Pr /Ru group monkeys contained individuals always exhibiting Pr/Ru in their ES and others sometimes lacking Pr/Pu in their ES. In short, the monkeys coul d be divided into two groups tie., PriRu and no-Pr/Ru) and they displayed t heir own individual characteristic ES. We concluded that the ES observed in this experiment suggest that the squirrel monkeys acquired individual char acteristics in their ES in the laboratory environment.