It has been found that discarded bottles often contain the remains of small mammals. The phenomenon is of widespread occurrence in the British Isles and involves at least ten species.
Mammals appear to be trapped in bottles because of their differential abilities to enter and exit through the neck. Entry is probably in response to feeding or exploratory drives, exit is prevented by a number of different factors. While shrews tend to occur in all bottle sizes, rodents are found more often in those bottles with the wider necks.
The practice of examining discarded bottles is indicated as an important tool in the collection of mammal distribution records.