Animals as Neighbors: The Past and Present of Commensal Animals

Chapter 5 - Rats, Mice, and Other Rodents

81 5 rats, mice, and other rodents explain “commensal animals” to many people and their first response is “oh, like rats and mice?” These species are all too familiar to urbanized Western societies, but perhaps their familiarity leads us to neglect and underrate them. The association of rodents with people goes back over the millennia, extends all over the world, and includes species other than the familiar house mouse and common rat. rats and mice are biologically highly successful, and their prevalence today is something of a monument to their versatility, and to the cozy niche that they constructed thousands of years ago. rats and mice are rodents of the zoological family muridae, a family that is originally eurasian but is now worldwide in distribution—in part because its many species have successfully adapted to a wide range of environments from the wet tropics to the arid middle east, and in part because a few murid species have hitched a ride with people, using our homes and food stores as places to raise an abundance of offspring, and co-opting our means of transport to follow us all over the globe.1 Although a great many rodents have been deliberately or accidentally transported by people, it is the murids that have been most successful in this regard, and four species in particular deserve close attention: the house mouse (Mus musculus, M. domesticus); the ship rat, black rat, or roof rat (Rattus rattus); the common rat, brown rat, or norway rat (R. norvegicus); and the kiore, maori rat, or Pacific rat (R. exulans). A couple of other taxa will be mentioned in passing: the spiny mouse Acomys cahirinus, and the Australian swamp rat Rattus lutreolus. The African giant rat, or pouched rat (Cricetomys gambianus) is neither a murid nor a commensal within the terms of this book, though its increasing popularity as a pet and its valuable role in land-mine detection almost earn it a place. People’s attitudes to rats and mice vary culturally and individually , ranging from acute, almost phobic revulsion, to the affection that many people in europe and north America feel for pet common rats. The murids have become iconic in Western cultures, from mickey mouse to the altogether more streetwise and sardonic roland rat.2 This chapter will review what we know of the long history of murids and men, beginning with house mice, moving on to rats, then reviewing the current situation for the group as a whole. 82| Chapter 5 hoUse miCe: From The FerTile CresCenT To AnTArCTiCA First a word regarding nomenclature: the animals that we call house mice have been subject to a complex history of taxonomic revision.3 linnaeus started the ball rolling by naming the species Mus musculus (the little mouse). That name held until 1943, when schwarz and schwarz4 tackled the diversity of house mice around europe and southwest Asia and proposed splitting them into a series of species. in particular, they argued that a clear distinction could be drawn within europe between an eastern species and a western species. As linnaeus had named M. musculus on the basis of a specimen from an eastern population, the western species needed a name of its own. The earliest published candidate, and therefore the one to take priority, was M. domesticus, based on specimens from Dublin described by rutty in 1772. some authors regard the eastern and western forms as subspecies, hence M. musculus domesticus and M. m. musculus. Two other M. musculus subspecies should be noted. M. musculus castaneus occurs throughout southeast Asia, where it is closely associated with people’s dwellings, and M. musculus bactrianus is described from iran to northern india—though of uncertain validity, as it is known from relatively few specimens and seems to be genetically remarkably diverse. For our present purposes, we can call them all house mice, and deal with their past and present on those terms. so successful have house mice been in spreading around the globe that it is quite difficult to decide where they originally called home. genetic studies place their center of divergence in southwest Asia: indeed, the diversity of modern M. m. bactrianus populations may indicate the region from which other house-mouse stocks have dispersed. As we have seen with foxes and perhaps cats, archaeological records indicate that our association with mice began in the middle east at the end of the last climatic cold stage, some 11,000 years ago.5 People were beginning to settle...