Cultural Transmission, Evolution, and Revolution in Vocal Displays: Insights From Bird and Whale Song

Abstract

Culture, defined as shared behavior or information within a community acquired through some form of social learning from conspecifics, is now suggested to act as a second inheritance system. Cultural processes are important in a wide variety of vertebrate species. Birdsong provides a classic example of cultural processes: cultural transmission, where changes in a shared song are learned from surrounding conspecifics, and cultural evolution, where the patterns of songs change through time. This form of cultural transmission of information has features that are different in speed and form from genetic transmission. More recently, culture, vocal traditions, and an extreme form of song evolution have been documented in cetaceans. Humpback whale song "revolutions," where the single population-wide shared song type is rapidly replaced by a new, novel song type introduced from a neighboring population, represents an extraordinary example of ocean basin-wide cultural transmission rivaled in its geographic extent only by humans. In this review, we examine the cultural evolutions and revolutions present in some birdsong and whale song, respectively. By taking a comparative approach to these cultural processes, we review the existing evidence to understand the similarities and differences for their patterns of expression and the underlying drivers, including anthropogenic influences, which may shape them. Finally, we encourage future studies to explore the role of innovation vs. production errors in song evolution, the fitness information present in song, and how human-induced changes in population sizes, trajectories, and migratory connections facilitating cultural transmission may be driving song revolutions.

Keywords: birdsong; cultural evolution; cultural revolution; cultural transmission; local dialect; sexual selection; vocal learning; whale song.

Figure 1

(A) Spectrograms illustrating the hierarchical structure of humpback whale song (from Garland et al., 2017b). A single unit (“trumpet”) and a single phrase from Theme 25a are shown in the top panel. Theme 25a units from the single phrase in the top panel are as follows: short ascending moan, grunt, grunt, grunt, grunt, grunt, grunt, short ascending moan, trumpet, squeak, trumpet, squeak, and trumpet. The repetition of phrases and the sequential singing of themes are shown in each of the subsequent panels. Spectrograms were 2048 point fast Fourier transform (FFT), Hann window, 31 Hz resolution, and 75% overlap, generated in Raven Pro 1.4. Reprinted with permission from Garland et al. 2017b (Copyright 2017, Acoustic Society of America). (B) Spectrograms illustrating the hierarchical structure of corn bunting song. The lower panel represents part of a bout of singing lasting several minutes. It shows two song types (song types differ mainly in the first part of the song; McGregor, 1986) sung in an eventual variety style: five repeats of song type 1, then four repeats of song type 2. A single song (top panel) is composed of units of grouped elements, where elements are single continuous sounds. Spectrograms produced with 20 kHz sampling rate and 160 Hz bandwidth.

Figure 2

Humpback whale song types identified in the South Pacific region from 1998 to 2008 (from Garland et al., 2011). Populations are listed from west to east across the region. Each color represents a distinct song type; song type colors are as follows: black, gray, pink, dark blue, blue, light blue, dark red, light red, yellow, dark green, and light green. Two colors within the same year and location indicate that both song types were present. In these cases, the seasons are broken into three periods (early, middle, and late) to indicate when a new song type was recorded. Crosshatching indicates no data available. Reproduced with permission.

Figure 3

Changes in song similarity (values are means ± SE) with distance between pairs of male great tits in five distance categories (100 m increments, 100 m ≈ 1 territory width). (A) The extent of repertoire sharing, expressed as the difference from the average yearly rate. n = 30 (five distance categories for each of 6 years). Details in McGregor and Krebs (1982). (B) The dissimilarity between songs of the same song type, expressed as a difference index (details in Falls et al., 1982). n = 150 comparisons.

Figure 4

Song of a color-ringed individual male corn bunting in 1987 (upper) and 1990 (lower). Colored boxes show examples of corresponding song elements that have changed between years. Scale bottom left indicates 0–4 kHz (y-axis) and 0–0.5 s (x-axis). Spectrograms produced by LSI Speech workstation, 16 kHz sampling rate and 160 Hz bandwidth. From original material after McGregor et al. (1997).