Worcestershire Record No. 18 April 2005 p. 28


John Dodgson

It is well-known that discarded bottles are a good place to look for small mammals but in today’s world of the screw cap suitable bottles are a rarity. Discarded drinks cans have become the place to look.

The can needs to be is such a position that the mammal can get in but not out, fixed in the vegetation with the opening upwards. Examining well-positioned cans only get a hit rate of one in four or five. The losers may be empty or have a watery soup of insects or slugs. The winners have one of more small mammals in various stages of decay, from a complete corpse to just fur and bones.

The mammal gets trapped in the can, dies within a few hours and may be discovered by Burying Beetles Nicrophorus sp. The Burying Beetles and their larvae eat the flesh leaving fur and bones. Often Burying Beetles are unable to escape.

If there is a complete corpse the usual characteristics can be noted (shape of head, length of head and body, length of hind foot, length and hairiness of tail) If Burying Beetles have done their work then the skull and lower jaws can be extracted easily from the gunge – not to be recommended after a heavy lunch!

My records for the past winter (2004-2005) in Worcestershire VC37 are shown in table 1

Species Number of 1x1 km squares % of squares with records
Bank vole 63 48.9
Common shrew 27 20.9
Wood mouse 13 10.0
Field vole 11 8.5
Water shrew 7 5.4
Pygmy shrew 6 4.6
House mouse 1 0.9
Harvest mouse 1 0.9

Table 1. Records of small mammals in cans winter 2004-5.

The results give some indication of distribution but are biased towards hedges and ditches near roads. Bank vole, Common shrew and Wood Mouse are widespread, with Water Shrew near water and Pygmy Shrew liking sandy areas.

The most popular can I have found contained six Bank Voles and four Common Shrews with lots of Burying Beetles – some party, but it was a Guinness can … …

Why do they enter cans? Horizontal cans have nests in them or have been used as refuges and contain the uneatable remains of hawthorn berries.

Well-positioned drinks cans are a good source of mammal records and fun once you have overcome the initial disgust.

A key to the remains of small mammals found in drink cans  - due to the detail in the image this is a file of 180Kb

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