Can music relax pets too?
The relaxing effects of music on humans has been well documented. Listening to music has been shown to reduce levels of the stress hormone, cortisol, and trigger the release of the neurotransmitter, dopamine, which is associated with feelings of pleasure. It is thought that music also calms parts of the autonomic nervous system, leading to physiological changes such as slower breathing, a lower heart rate and reduced blood pressure. Further, music can act as a distraction from troubling thoughts or disturbing noises. As a result of all this, music can help us to fall asleep quicker, boost our sleep efficiency and optimise the quality of our sleep.
But, researchers have begun to wonder whether music affects animals in a similar way, particularly those captive animals living in human environments. Emerging evidence suggests that while music can improve the wellbeing of captive animals through environmental enrichment, stress relief and behavioural changes, the psychological and physiological benefits of listening to music depend on the species of animal, the type of music and the context, among other factors.
This article will consider the ways in which listening to music elicits a relaxing response in captive animals by reference to the current scientific evidence, and it will explore some of the key factors that influence this effect.
How does music relax captive animals?
There is some evidence that animals find listening to music a rewarding experience in a similar way to humans. Unfortunately, no animal studies have used the same imaging techniques to measure the activation of reward-related areas of the brain as those used in human studies. However, one study has found that chicks presented increased dopamine levels after listening to music. This indicates that animals may find listening to music rewarding or pleasurable.
Music also has the potential to decrease indicators of stress, such as heart rate and blood pressure, in some animals. Listening to Mozart compositions produced significant reductions in the blood pressure of rats within 30 minutes. This effect continued for up to 2 hours after the music was stopped. It is thought that the music causes increases of dopamine in the brain, which inhibits the activity of the sympathetic nervous system, which then causes a decrease in blood pressure.
By measuring the ‘heterophil:lymphocyte ratio’, an indicator of stress in chickens, another groups of researchers found that layer strain chicks reared with music enrichment were less stressed than those reared without music enrichment. As will be explored below, listening to music can have no calming effect or increase stress in some situations. More research is needed to investigate which types of music are best suited to which types of animals and in which contexts.
Studies have found that music can change the behaviour of animals. Rats and some non-human primates have indicated that they prefer to listen to music when given the choice. In some cases, this preference for music was associated with positive behavioural changes, such as less abnormal behaviour, pacing and aggressive activity.
However, there are some problems with this. Firstly, a preference for listening to music is not necessarily always an indication of relaxation and enhanced wellbeing. Secondly, the ability to vary music may have simply given some of the animals in these studies a greater sense of control over their environment. Whether the animals are calmed by this exertion of control, as opposed to the activity of listening to music, is up for debate. And finally, studies of non-human primates have demonstrated that the effect of music on animal behaviour varies significantly and appears to be largely unpredictable.
So, what varying factors have been observed from studies focused on the calming influence of music on animals?
The species of the animal matters
Experts have consistently found variations in the effects of music on different species of animals. For example, the heart rate of African green monkeys was not affected while they listened to harp music. Baboons, on the other hand, showed reduced heart rates when they were listening to radio music. Researchers suggested that this difference in the physiological effects of music between the two species was down to the fact that African green monkeys are naturally more calm in captivity.
There have also been variations in the effects of music within one species. For example, layer strain chicks presented lower stress levels when they were reared with music, but adult laying hens showed no significant reduction in stress when exposed to either background noise or classical music and background noise. This suggests that the age of the species can have an impact on how calming they find listening to music.
The health of individual animals could also influence the effect of music on a species. Rats with high blood pressure were found to experience significant decreases in blood pressure after listening to a Mozart composition. In another study, rats with normal blood pressure experienced no reduction in blood pressure or heart rate after listening to a Mozart composition.
In one study, the sexual biology of individual animals appeared to influence the physiological effects of music on mice. Listening to music only had an anti-anxiety effect for female mice with intact ovaries and mice with removed ovaries and progesterone supplementation.
The type of music matters
The genre, composer and frequency of the music is also a factor that influences the calming effect of music on animals. Researchers found that ‘new age’ music has a calming effect on mice, compared to classical music, pop music or the absence of music. In the case of ponies, however, classical music appeared to have a more calming effect than classical, jazz or rock music.
Classical music increased behaviours associated with relaxation in rescue dogs, compared to heavy metal and pop music. When listening to heavy metal music, dogs barked more, showing that some types of music can increase stress for some animals. This is why it’s important to further explore which types of music benefit which types of animals.
It may even be the case that different genres of music encourage different forms of relaxation. Instrumental music seemed to be more effective than vocal music in encouraging affiliative behaviours amongst captive chimpanzees. Whereas, vocal music was more effective at decreasing aggressive encounters in the group.
Within musical genres, animals can react differently to different composers or compositions. One study compared the effect of music by Mozart with that of Ligeti. The Ligeti composition was actually associated with an increase in blood pressure amongst rats with high blood pressure. Although the Mozart composition had no effect on the blood pressure of these rats in this study, blood pressure was reduced amongst rats with high blood pressure in a different study where a different Mozart composition was used.
The differences in the physiological effects of different Mozart compositions on rats with high blood pressure may be due to the difference in frequencies used in those compositions. One study found that higher frequencies of music produced the most significant physiological benefits in rats.
The context matters
Studies have also revealed that the context in which animals are listening to music can affect the extent to which music is relaxing for animals. The duration of time in which animals are exposed to music may account for the differences found in the stress levels of layer strain chicks and adult laying hens. While the chicks presented lower stress levels when reared with musical enrichment for 8 weeks, the hens presented no change in stress levels when exposed to music for 3 days.
In studies exploring animals’ preference for music, the type of music that some animals preferred was informed by the music they had previously heard. In some circumstances, animals seemed to prefer silence, indicating that animals can find music beneficial in some situations but not in others.
There is still much that we need to find out about the psychological and physiological impact of music on animals. However, the Institute for Laboratory Animal Research in the US has provided parameters around the exposure of laboratory animals to noise in light of the auditory and physiological effects on animals. The Guide for the Care and Use of Laboratory Animals specifically warns that radios should be turned off at the end of the working day in animal rooms and emphasises that music should be controlled as it can impact study results.
