1～3週齢および6～8週齢における子羊とその母羊の音声構造

Abstract

In this study we examined the fundamental frequency, formants, and vocal structure at the time of onset in 1 to 3 week-old and 6 to 8 week-old lambs and ewes. We found that fundamental frequency between ewes with open mouths at 1 to 3 weeks was higher than in lambs with closed mouths, while the first formant (F1) in ewes was higher between ewes with a closed mouth than with an open one. We took this as an indication of vocalization based on a low tongue position and suggestive of maternal attention displayed by ewes to their care. We further found that fundamental frequency was higher in 1 to 3 week-old male lambs compared to females of the same age group, and that vocalization duration was also longer in males than in females, suggesting gender differences being already developed at this stage of lamb development. Fundamental frequency was also higher in both the 1 to 3 week-old and 6 to 8 week-old lamb groups than between ewes, suggesting a number of distinctive features between lamb and ewe vocalization structure. Our study revealed that the F 1 among 6 to 8 week-old lambs was higher between males than in female lambs, and that the Fl was higher overall between lambs than in ewes. Both of these findings are thought to be as a result of a low tongue position in lambs. We also found that the second formant (F2) in 6 to 8 week-old lambs was higher between lambs than in ewes, indicating that vocalization in these cases was based on the forward location of the tongue. Through this study we were able to establish that the fundamental frequency between ewes and lambs was higher in 6 to 8 week-old lambs than in 1 to 3 week-old lambs, indicating a diversity in sound and development processes among the subjects. In both male and female lambs the F2 was higher in 6 to 8-week old lambs than in 1 to 3 week-old subjects a result of vocalization for both male and female 6 to 8 week-old lambs being based on the more forward location of the tongue in this group compared to 1 to 3-week old lambs. The Fl in 6 to 8 week-old lambs was higher in males than in females, thought to be as a result of vocalization in male lambs being based on a lower tongue position than that of females. Our study also found that vocalization duration was longer in 1 to 3 week-old lambs compared to their 6 to 8 week-old counterparts, indicating a demand for attention and care on ewes between lambs. F1 between males and F2 between females were both higher in 6 to 8-week old lambs than in 1 to 3 week-old lambs, which we took as being dependant on a separation between the high and low and forward and rear positioning of the tongue that accompanies the vocalization developmental stage in both male and female 6 to 8 week-old lambs. We also witnessed differences in developmental structures in 4 different varieties of ewes in particular the breed characteristics of fundamental frequency, formant construction, and duration of vocalization of the Finnish Landrace breed.