A cat bell is a

bell A bell is a directly struck idiophone percussion instrument. Most bells have the shape of a hollow cup that when struck vibrates in a single strong strike tone, with its sides forming an efficient resonator. The strike may be made by an inte ...

attached to the

collar Collar may refer to: Human neckwear *Clerical collar (informally ''dog collar''), a distinctive collar used by the clergy of some Christian religious denominations *Collar (clothing), the part of a garment that fastens around or frames the neck ...

of a

cat The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...

to prevent the cat from harming local wildlife. The bell can warn potential

prey Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...

of the cat's approach. Cats eventually learn to walk without ringing the bell and pet owners are therefore encouraged to regularly change the bell or attach two bells on the collar. Attaching a bell on a cat's collar has been shown to reduce the amount of captured birds by 30–40%. With one collar, birds were found to be hunted 2.7 times less than without the collar. However, some animal care organizations also claim that cat bells are irritating to cats due to their sensitive hearing, and may just confuse birds by interfering with their natural defense mechanisms. Some owners worry that as well as alerting prey, a bell could alert large predators to a cat’s presence, given most predators' acute hearing. However, the acute hearing of predators is good enough that it is unlikely to make a difference in practice.{{Cite web , title=Should I Attach a Bell to My Cat’s Collar? , url=https://www.mcgill.ca/oss/article/general-science/should-i-attach-bell-my-cats-collar , access-date=2022-11-01 , website=Office for Science and Society , language=en

References

Jasper Copping.
Change your cat's bell to save birds
, telegraph.co.uk, 30 May 2010. Retrieved 13 March 2016. Anton Karis.
Katter dödar 16 miljoner fåglar om året
(at 8 min), ''Studio Ett'', Sveriges radio, 28 June 2016. Retrieved 28 June 2016. (In Swedish) Cat equipment