Polyphony of domestic dog whines and vocal cues to body size

Abstract

In domestic dogs Canis familiaris, vocal traits have been investigated for barks and growls, and the relationship between individual body size and vocal traits investigated for growls, with less corresponding information for whines. In this study, we examined the frequency and temporal traits of whines of 20 adult companion dogs (9 males, 11 females), ranging in body mass from 3.5 to 70.0 kg and belonging to 16 breeds. Dog whines (26-71 per individual, 824 in total) were recorded in conditioned begging contexts modeled by dog owners. Whines had 3 independent fundamental frequencies: the low, the high and the ultra-high that occurred singly as monophonic calls or simultaneously as 2-voice biphonic or 3-voice polyphonic calls. From the smallest to largest dog, the upper frequency limit varied from 0.24 to 2.13 kHz for the low fundamental frequency, from 2.95 to 10.46 kHz for the high fundamental frequency and from 9.99 to 23.26 kHz for the ultra-high fundamental frequency. Within individuals, the low fundamental frequency was lower in monophonic than in biphonic whines, whereas the high fundamental frequency did not differ between those whine types. All frequency variables of the low, high, and ultra-high fundamental frequencies correlated negatively with dog body mass. For duration, no correlation with body mass was found. We discuss potential production mechanisms and sound sources for each fundamental frequency; point to the acoustic similarity between high-frequency dog whines and rodent ultrasonic calls and hypothesize that ultra-high fundamental frequencies function to allow private, "tete-a-tete" communication between members of social groups.

Keywords: Canis familiaris; acoustic communication; companion dogs; high-frequency calls; nonlinear phenomena; vocalization.

Figure 1.

Spectrograms (below) and waveforms (above) of different whines of domestic dogs: f-whines—the whines with the low fundamental frequency f0 alone; g-whines—the whines with the high fundamental frequency g0 alone; f&g-whines—the whines with both low f0 and high g0 fundamental frequencies, combinatory frequency bands between f0 and g0 are labeled with asterisk; h-whines—the whines containing the ultra-high (h0) fundamental frequency, combinatory frequency bands between g0 and h0 are labeled with asterisk. (a) f-whine of Caucasian shepherd #6; (b) f-whine of spaniel mix #14; (c) f-whine of toy dachshund #7; (d) g-whine of spaniel mix #14; (e) g-whine of toy terrier and pincher #9; (f) g-whine of husky #16; (g) f&g-whine of dachshund #11; (h) f&g-whine of East European shepherd #20; (i) f&g-whine of husky #16; (j) f&g-whine of Weimar hound #18; (k) h-whine of dachshund #10; (l) h-whine of greyhound hortaya #15; (m) h-whine of toy terrier #8. The spectrograms were created with Hamming window, 48 kHz sampling rate, FFT 1024 points, frame 50% and overlap 93.75%. The audio file with these calls is provided in Supplementary material Audio S3.

Figure 2.

Measured acoustic variables in domestic dog whines. (A) h-whine of Weimar hound #18; (B) f&g-whine of dachshund #3. Designations: call-dur—total duration of a call; f-dur=f-dur1+f-dur2—duration of low-frequency call part; g-dur=g-dur1+g-dur2+g-dur3—duration of high-frequency call part; h-dur—duration of ultra-high-frequency call part; h0max—maximum ultra-high fundamental frequency; h0min—minimum ultra-high fundamental frequency; g0max—maximum high fundamental frequency; g0min—minimum high fundamental frequency; f0max—maximum low fundamental frequency; f0min—minimum low fundamental frequency. The spectrograms were created with Hamming window, 48 kHz (A) and 22.05 kHz (B) sampling rate, FFT 1024 points, frame 50%, and overlap 96.87%.

Figure 3.

Plots illustrating the differences in (A) f0max between the monophonic f-whines and the biphonic f&g-whines; (B) f0min between the monophonic f-whines and the biphonic f&g-whines.

Figure 4.

Plots illustrating the differences in (A) g0max between the monophonic g-whines and the biphonic f&g-whines; (B) g0min between the monophonic g-whines and the biphonic f&g-whines.

Figure 5.

Plots illustrating the differences in (A) f0max and g0min of the monophonic f- and g-whines; (B) f0max and g0min of the biphonic f&g-whines.

Figure 6.

Plots illustrating differences between (A) g0max in monophonic g-whines and h0min in h-whines; (B) g0max in biphonic f&g-whines and h0min in h-whines.

Figure 7.

Scatterplots illustrating the relationships between acoustic variables of different categories of whines and log body mass of the study dogs. (A) f-whines; (B) g-whines; (C) f&g-whines; (D) h-whines. For decoding the abbreviations of measured acoustic variables, see Table 2. Linear regression lines with 95% confidence intervals are shown. P-values indicate the Pearson correlation results.