The influence of behavioral context on the vocalizations of Mallard ducklings (Anas platyrhynchos)

Date of Completion

January 1998

Keywords

Psychology, Behavioral|Biology, Zoology

Degree

Ph.D.

Abstract

Acoustic properties of duckling vocalizations differ based on the social context of the duckling. Vocalizations from 18 broods of socially-reared, maternally-naive mallard ducklings were recorded across four contexts that varied in the type of contact (visual, auditory and tactile) between the focal duckling and its broodmates. Additional vocalizations from field tapes of 3 broods of ducklings were included in the discriminant analyses. Vocalizations in contexts where the focal duckling is visually isolated from broodmates contain more notes per call, have higher dominant frequencies, have a slower repetition rate and longer note duration than the vocalizations in contexts where visual contact with siblings is maintained. Note duration and repetition rate are related since the longer the individual notes, the fewer notes that can be given in a specified time period. These findings are important because repetition rate is a key acoustic property for mother-offspring communication. Ducklings respond differentially to maternal assembly calls than to maternal alarm calls with repetition rate being the salient difference between these two types of maternal calls.^ In summary, ducklings vocalized significantly more in the opaque barrier and arena contexts than in the clear barrier context. Based on repetition rate, more than 95% of the notes recorded in both the opaque barrier and arena contexts, but less than 10% of the notes recorded in the clear barrier context, were categorized as distress notes. The combination of four variables: note duration, repetition rate, dominant frequency and number of notes per call, maximally discriminated recording contexts from one another in each of four discriminant analyses. Frequency of vocalizations, classification of notes via the derived discriminant functions, and group means on both the discriminant variables and the first discriminant function all substantiated that the opaque barrier and arena contexts formed a set of contexts that is different from a set consisting of the brooder, clear barrier and field tape contexts. The most obvious difference between these two sets of contexts is whether or not the focal duckling is able to maintain visual contact with siblings. ^

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