1. Introduction
Our working assumption in writing this article is that the calls of cattle reflect the biological status of the animal as it interacts with its environment. Cattle emit vocaliza-
tions that are probably meaningful to other cattle. They may signal the physiological and emotional state, motivations and intentions of the calling animal. Increasingly, in applied
ethology, there has been interest in the development of objective measurements, and technologies that allow reliable quantification of behaviour without observer subjectiv-
Ž .
ity, bias or error e.g., Schwartzkopf-Genswein et al., 1997, 1998 . In studying cattle vocalization we are attempting to document an interpretive response to events, which is
a consequence of the perceptual, cognitive and emotional processes of the animal itself. It can be argued that vocalizations represent a form of commentary by an animal on it’s
own internal state. The study of vocal behaviour is therefore a useful means by which to investigate the physical and psychological functioning of that animal.
The vocalizations of cattle represent, potentially at least, acts of communication. That is, they may convey information about the calling animal, even if they seem to occur as
an involuntary response to environmental stimuli, or in contexts where conspecifics are not present. Communication can be defined as ‘‘The imparting of information from one
organism to another in a way that evokes a detectable response from the recipient at
Ž .
least some of the time’’ Wittenberger, 1981, pp. 613 . Where communication has occurred there should be an increase in the probability of some relevant response
Ž .
whether behavioural or physiological , being shown by the recipient. Therefore, if appropriate measures are employed, acts of communication should often be detectable.
Studies of communication in farm animals are not only practicable, they can make an important contribution to our understanding of the biology of the animals concerned.
However, in contrast to the extensive literature for wild vertebrates, particularly birds Ž
. Ž
See, for example, Kroodsma and Miller, 1996 and primates Cheney and Seyfarth, .
1990 , there has been limited research into auditory communication in domestic animals. Data on vocal behaviour of cattle are particularly sparse. It is surprising that they have
not received more attention, since vocal responses can be recorded noninvasively, and analysed using simple equipment. Yet, until recently, there has been little emphasis on
vocalization in cattle as a behaviour with potentially useful implications for animal production or welfare studies. One review of the use of behaviour studies in cattle
Ž .
production Stricklin and Kautz-Scanavy, 1984 did not mention vocal behaviour as an area of past or future interest in this regard. In their book ‘‘The behaviour of cattle’’,
Ž .
Albright and Arave 1997 did mention some aspects of vocal behaviour. However, their treatment was brief and did not deal with the questions raised in this article.
Recently, some researchers have become more interested in using vocal behaviour in farm animals as a way to evaluate their welfare. For example, the use of vocalizations
Ž .
Ž .
by swine as indicators of pain Weary et al., 1998 or need Weary and Fraser, 1995 . In cattle, the use of vocalization rate as a rule-of-thumb indicator of acceptable or
unacceptable welfare standards in a slaughter plant has recently been suggested by Ž
. Grandin 1998 .
Ž .
According to Griffin 1984, 1991 , the key to understanding the cognitive processes and subjective experiences, or consciousness, of animals lies in a careful study of the
Ž ways in which they communicate. By one widely accepted definition, Duncan and
. Ž
. Petherick, 1991 animal welfare is primarily perhaps solely dependent on how animals
feel. Cattle may have much to tell us about their neurophysiological, affective and cognitive processes if we can learn to interpret their vocal behaviour correctly. There-
fore, studies of cattle communication are relevant in discussions of welfare evaluation.
In this review we examine the existing evidence on vocal communication in cattle. With reference to this work and relevant studies on other species, mainly farm animals,
we ask what kinds of information cattle are likely to be able to exchange with each other, based on auditory cues. We discuss ways in which researchers may be able to
intercept some of this information and use it to obtain a better understanding of the animal and its responses to human management.
2. Evidence for the information content of cattle vocalizations
Kategori