Abstract
Mother-offspring communication is especially crucial for social species in order to synchronize activities essential for early survival including nursing, resting, maintaining proximity during group movements between food or water sources, and locating one another if separated in a large social group. One of the most social ungulate species in North America is the American Bison (Bison bison), formerly known as buffalo. Adult female bison associate with their young for over a year and communication between mother and offspring is likely essential for establishing and maintaining a bond upon which the life of a calf depends. One goal of this study was to quantify and compare the acoustic form of vocalizations of adult female, subadult, and calf bison and to determine how age classes differed in call structure. The other goal was to identify the contexts in which bison vocalized. Vocalizations of 101 bison (53 adult females, 15 subadults, 33 calves) in a semi-free-ranging herd in Montana were analyzed and found to be pulsatile sounds, unlike vocalizations of bison bulls or domestic cows and calves. Vocalizations of bison cows, subadults, and calves differed significantly in total duration, numbers of pulses, pulse duration, and pulse rate. Seven distinct call contexts were identified. The majority of calls were "moving-on calls" (39%), when a cow called and her calf ran to her side and the 2 moved on together, and "contact calls" (21%) when a cow called and her calf called back but neither changed their location. "Imprinting calls" and "nursing calls" were also identified. Mother-offspring acoustic communication in bison appears especially critical for coordinating movements. Understanding the role of acoustic communication in maintaining the bond between bison mothers and their offspring can contribute to the humane management and welfare of this iconic species.
The American Bison, the national mammal of the United States, teetered on the brink of extinction in the 1800s. Today, efforts to reestablish populations of bison are increasing. However, bison are not domestic cattle and we lack an understanding of bison behavior, which can lead to bison and bison managers being injured. Bison cows and their offspring numerically dominate a bison herd and this study focused on the vocalization of bison cows and their offspring. Using 4 acoustic variables, bison vocalizations could be correctly classified to age class of the individual calling in 85% of cases, indicating the potential for individual identification. Bison mothers uttered calls, to which their calves responded, in 7 distinct contexts. In the majority of cases, mothers called to their calves in the contexts of moving to a new location and when locating the position of the calf in the herd (39% moving-on calls and 21% contact calls). Mother-offspring acoustic communication in bison appears critical for coordinating movements. Understanding the role of acoustic communication in maintaining the bond between bison mothers and their offspring can contribute to the humane management and welfare of this iconic species.
La comunicaci & oacute;n madre-cr & iacute;a es especialmente crucial para especies sociales, debido a que permite sincronizar actividades esenciales para la supervivencia temprana, como la lactancia, el descanso, el mantenimiento de proximidad durante los movimientos de los grupo entre las fuentes de alimento o agua y la localizaci & oacute;n mutua en caso de separaci & oacute;n dentro de un grupo social grande. Una de las especies de ungulados m & aacute;s sociales de Am & eacute;rica del Norte es el bisonte (Bison bison). Las hembras adultas de bisonte se asocian con sus cr & iacute;as durante m & aacute;s de un a & ntilde;o y la comunicaci & oacute;n entre madre el becerro es probablemente esencial para establecer y mantener un v & iacute;nculo en el que depende la vida de la cr & iacute;a. Uno de los objetivos de este estudio fue cuantificar y comparar la forma ac & uacute;stica de las vocalizaciones de hembras adultas, subadultas y cr & iacute;as de bisonte, y determinar c & oacute;mo difer & iacute;an las clases por edad en la estructura de las llamadas. Otro objetivo fue identificar los contextos en los que se emit & iacute;an las vocalizaciones. Se analizaron las vocalizaciones de 101 bisontes (53 hembras adultas, 15 hembras subadultas, 33 cr & iacute;as) en un reba & ntilde;o semi-libre en Montana. Se encontr & oacute; que estas vocalizaciones eran sonidos puls & aacute;tiles, completamente diferentes a los emitidos por los bisontes machos adultos o las vacas y becerros dom & eacute;sticos. Las vocalizaciones difer & iacute;an significativamente entre las tres clases de edad en su duraci & oacute;n total, n & uacute;mero de pulsos, duraci & oacute;n de los pulsos y ritmo de los pulsos. La mayor & iacute;a de las llamadas se dieron en dos contextos: "llamadas de avance" (39%), cuando una hembra adulta llamaba y su cr & iacute;a corr & iacute;a a su lado y ambas avanzaban juntas, y "llamadas de contacto" (21%), cuando una hembra adulta llamaba y su cr & iacute;a respond & iacute;a, pero ninguna cambiaba su ubicaci & oacute;n. Tambi & eacute;n se identificaron "llamadas de impronta" y "llamadas de amamantamiento," as & iacute; como otros tres contextos de llamada. La comunicaci & oacute;n ac & uacute;stica madre-cr & iacute;a en bisontes parece especialmente cr & iacute;tica para coordinar los movimientos. Entender el papel de la comunicaci & oacute;n ac & uacute;stica en el mantenimiento del v & iacute;nculo entre las madres y sus cr & iacute;as puede contribuir al manejo humanitario y al bienestar de esta especie ic & oacute;nica. Este trabajo representa el primer estudio que investiga cuantitativamente las se & ntilde;ales ac & uacute;sticas de hembras adultas, subadultas y cr & iacute;as de bisontes Norte Americanos mientras se desplazan en condiciones de semi-libertad.