Purr
A purr or whirr is a tonal fluttering sound made by some species of
Although true purring is exclusive to
]Animals purr for a variety of reasons, including to express happiness or fear, and as a defense mechanism. It has also been shown that cats purr to manage pain and soothe themselves.[2] Purring is a soft buzzing sound, similar to a rolled 'r' with a fundamental frequency of around 25 Hz.[3] This sound occurs with noticeable vibrations on the surface of the body, varies in a rhythmic pattern during breathing and occurs continuously during inhalation and exhalation. The intensity and length of the purr can also vary depending on the level of arousal of the animal.[3]
Mechanism
The mechanism by which cats purr is an object of speculation, with different hypotheses proposed. An early idea was that purring is a hemodynamic process where sound is produced as the blood runs through the thorax.[4]
There is a unique "neural oscillator" in the cat's brain of uncertain significance.[5] Although the mechanism has not yet been fully explained, recent studies have inferred it could be the result of oscillatory mechanisms in the central nervous system.[6] Studies have also shown that purring can be caused through electrically stimulating the infundibular region of the cat's brain, suggesting central control.[7]
Vocal folds/laryngeal muscles
One hypothesis, backed by
Degree of hyoid ossification
No cat can both purr and
The "roaring cats" (lion, Panthera leo; tiger, P. tigris; jaguar, P. onca; leopard, P. pardus) have an incompletely ossified hyoid, which, according to this hypothesis, enables them to roar but not to purr. However, the snow leopard (Uncia uncia, or P. uncia), as the fifth felid species with an incompletely ossified hyoid, purrs.[13]
All remaining species of the family Felidae ("purring cats") have a completely ossified hyoid, which enables them to purr but not to roar. Based on a technical acoustic definition of roaring, the presence of this vocalization type depends on specific characteristics of the vocal folds and an elongated vocal tract, which is rendered possible by an incompletely ossified hyoid.
Frequency, amplitude, and respiratory variation
- Domestic cats purr at a frequency of 20 to 30 vibrations per second.[2]
- Eklund, Peters & Duthie, comparing purring in a cheetah (Acinonyx jubatus) and a domestic cat (Felis catus) found that the cheetah purred with an average frequency of 20.87 Hz (ingressive phases), while the much smaller domestic cat purred with an average frequency of 21.98 Hz (egressive phases) and 23.24 Hz (ingressive phases).[14]
- Schötz & Eklund studied purring in four domestic cats and found that the fundamental frequency varied between 20.94 and 27.21 Hz for egressive phases and between 23.0 and 26.09 Hz for ingressive phases. Schötz & Eklund also observed considerable variation between the four cats as regards relative amplitude, duration and frequency between egressive and ingressive phases, but that this variation occurred within the same general range.[15]
- In a follow-up study of purring in four adult cheetahs, Eklund, Peters, Weise & Munro found that egressive phases were longer than ingressive phases in all four cheetahs. Likewise, ingressive phases had a lower frequency than egressive phases in all four cheetahs. Mean frequency were between 19.3 Hz and 20.5 Hz in ingressive phases, and between 21.9 Hz and 23.4 Hz in egressive phases. Moreover, the amplitude was louder in the egressive phases in four cheetahs.[16]
- Eklund & Peters compared purring in adult, subadult and juvenile cheetahs and reported that while there was considerable variation across most of the parameters analyzed (amplitude, phase duration, cycles per phase and fundamental frequency) – mainly attributable to degree of relaxation/agitation in the animals resting or playing– previously reported observations that ingressive phases tend to be lower in frequency were largely confirmed. There were no major differences in these parameters as a function of age.[17]
Purpose
In domestic cats, many signals that occur when interacting with humans seem to originate from when the animal was dependent on the mother. Cats have been observed to purr for most of their lifespan, starting from when they were young and suckling from their mother.[18] Purring may be a signaling mechanism of reassurance between mother cats and nursing kittens. Post-nursing cats often purr as a sign of contentment when being petted, becoming relaxed or eating. Some purring may be a signal to another animal that the purring cat does not pose a threat.
Cats have been shown to have different types of purrs depending on situations. For example, purring appears to be a way for cats to signal their caretakers for food. This purring has a high-frequency component not present in other purrs. These are called solicitation purrs (when the cat is seeking a result) and non-solicitation purrs, and the two are distinguishable to humans. In a study, 50 humans were subjected to playbacks of purrs recorded in solicitation and non-solicitation situations at the same amplitude. Humans regularly judged the solicitation purrs as less pleasant and more urgent than the non-solicitation purrs.[18] This variety of purring seems to be found more frequently in cats in a one-to-one relationship with a caretaker. Similarities have been drawn between an infant's cry and the isolation cry of domestic cats. The high-frequency aspect of the purr may subtly exploit humans' sensitivity to these cries. Using sensory biases in communication between species provides cats with a productive means of improving the care that they receive.[18]
Cats often purr when distressed or in pain, such as during the three stages of
There is also some evidence that the frequency at which cats purr can help promote bone density and hasten healing.[20]
See also
References
- ISSN 1365-2907.
- ^ a b "What Makes A Cat Purr". purina.com.au. Retrieved 18 November 2019.
- ^ S2CID 32350871.
- )
- ^ "Why and how do cats purr?". Library of Congress. Retrieved 10 April 2011.
- PMID 4644061.
- S2CID 84375344.
- ^ K.M. Dyce, W.O. Sack and C.J.G. Wensing in Textbook of Veterinary Anatomy 3rd Ed. 2002, Saunders, Philadelphia; p156
- ^ "How A Puma Purrs". Archived from the original on 22 January 2013.
- .
- .
- PMID 12363272.
- JSTOR 3503882.
- ^ Eklund, Robert, Gustav Peters & Elizabeth D. Duthie. 2010. An acoustic analysis of purring in the cheetah (Acinonyx jubatus) and in the domestic cat (Felis catus), Proceedings of Fonetik 2010, 2–4 June 2010, Lund University, Lund, Sweden, pp. 17–22.
- ^ Schötz, Susanne & Robert Eklund. 2011. A comparative acoustic analysis of purring in four cats. Proceedings of Fonetik 2011, 8–10 June 2011, Royal Institute of Technology, Stockholm, Sweden, pp. 9–12.
- ^ Eklund, Robert, Gustav Peters, Florian Weise & Stuart Munro. 2012. A comparative acoustic analysis of purring in four cheetahs, Proceedings of Fonetik 2012, 30 May–1 June 2012, Gothenburg University, Gothenburg, Sweden, pp. 41–44.
- ISBN 978-91-7519-579-7, ISSN 1403-2570, pp. 25–28.
- ^ S2CID 10972076.
- ^ "Birth Difficulties Symptoms - Cats | petMD". www.petmd.com. Retrieved 18 November 2019.
- ^ Lyons, Leslie A. (3 April 2006). "Why do cats purr?". Scientific American. Archived from the original on 30 May 2023. Retrieved 30 September 2022.
Further reading
- Peters, G. (2002). "Purring and similar vocalizations in mammals". Mammal Review. 32 (4): 245–271. .
- Stogdale L, Delack JB. Feline purring. Compendium on Continuing Education for the Practicing Veterinarian 1985; 7: 551–553.
- Reprinted in: Voith VL, Borchelt PL (eds). Readings in Companion Animal Behavior. Trenton: Veterinary Learning Systems, 1996; 269–270.
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