Behavioural Biology of the Collared Lemming [Dicrostonyx groenlandicus (Trail)]: An Analysis of Acoustic Communication

Abstract The acoustic behaviour of collared lemmings was investigated in a laboratory study. Observations were conducted on behaviour of lemmings in a variety of test situations including: paired intraspecific male-male, male-oestrous female and male-dioestrous female encounters in an arena unfamiliar to both animals; paired intraspecific male-oestrous female encounters in the female's home cage; groups of lemmings in large enclosures; isolated, adult lemmings exposed to several stimulus situations; isolated pups subjected to a series of tests during development and mother-neonate interactions. A repertoire of the acoustic behaviour of lemmings was established and catalogued according to both physical and auditive properties of the several calls described, as well as the behavioural context in which the calls occurred. Physical analysis was accomplished using spectrographic and oscillographic measurements of calls recorded on tape. Ontogeny of the vocalizations was traced from birth to maturity. Sexual and individual variation in the sounds was also investigated. An attempt was made to determine the communicative function of each sound by correlating its occurrence with twenty previously defined non-vocal acts and postures and by observing responses of other lemmings to the calls. Detailed quantitative analysis was applied to the data, but interpretation of results of this analysis was limited by lack of knowledge concerning the perceptual capabilities of lemmings. The following results were obtained: 1. (1) Six distinct types of sounds were recognized; ultrasonic chirp, ultrasonic mating twitter, huh-huh call, tooth-chatter, squeal-squawkgrind complex and a group of less defined sounds classified into four sub-types: peeps, whines, mechanically produced sounds and an assortment of snorts, chuckles, pops and snarls. 2. (2) The first three types listed above were associated with relatively specific behavioural contexts. Ultrasonic chirps were given exclusively by pups less than 15 days old in response to cold stress and brief, non-painful tactile stimuli. This vocalization apparently aided the dam in noticing and locating pups which had fallen out of the nest. 3. (3) The ultrasonic mating twitter was emitted only by adults performing male-like sexual behaviour such as mounting, chasing and allogrooming. This call indicated that the caller was sexually aroused. 4. (4) Huh-huh calls were given by adult lemmings when they detected the presence of a predator. The call accompanied an erratic, explosive leaping behaviour which apparently served to distract the predator and allow the lemming more time to escape. 5. (5) Tooth-chatter was associated with threat behaviour and increased excitation. 6. (6) Squeals, squawks and grinds were distinct calls but intergraded along a continuum for frequency, duration, intensity, harmonic structure and various other physical parameters. These calls were associated with agonistic behaviour, specifically fear motivated actions. The graded system for these calls apparently was based upon small variations in motivation and the existence of this system suggests there is some selective advantage in communicating these variations. As a lemming became more frightened, calls of this type became shorter, louder and shriller (squeal). These calls were given by subordinates, in male-male encounters and by females in male-oestrous female encounters. 7. (7) Squeals were the only calls given at all ages. It was suggested that such sounds when given by very young pups inhibited the dam from injuring them. 8. (8) All calls displayed considerable variation in physical properties. 9. (9) The interaction of behavioural and ecological factors was discussed in terms of the evolution of age-related changes in various properties of the ultrasonic chirp. 10. (10) It was concluded that the communicative role of the calls could only be understood in the context of simultaneous non-vocal behaviour. Meaning of each signal or message probably varies with this context and the precise configuration of the total display will need to be known fully to appreciate the communicative significance of each call. Emission of a particular call reflected the underlying physiological state of the animal. When this relationship becomes better established vocal behaviour may be a useful tool in the study of motivation and in assessing physiological state and various thresholds in the vocalizing animal.