Structure and Function of the Vocalization of Japanese Squirrels, Sciurus lis

Although much research has accumulated on Sciuridae vocalizations, most of it has been on terrestrial squirrels, and there is still a significant knowledge gap regarding arboreal squirrels. Vocalizations of the Japanese squirrel, Sciurus lis, were investigated in the urban park of Iwate Prefecture, Japan. The Japanese squirrels produced “kuk” and “moan” in alert and “squeal” and “buzz” in social interactions. Of the “kuk” sounds, 58.2% were uttered toward cats, dogs, or observers, while 36.4% of the “moan” sounds were toward crows or hawks. In a playback experiment of two types of alarm calls, when the squirrels were on the ground, they immediately fled up the tree in response to the “kuk” sound but remained still in response to the “moan” sound. However, squirrels in the trees often responded to remain still for both sounds. These results indicated that “kuk” tends to be emitted against terrestrial mammals and “moan” against aerial birds, and the decision to flee or stay is more critical on the ground, where they are more vulnerable to predation. The two types of alarm vocalizations in the Japanese squirrel may function to ensure the rapid and appropriate escape behavior of nearby close relatives.