The Migration of Mammals' 



By L. Harrison Matthews 



Director and Permanent Secretary, Zoological Society of London 



[With 1 plate] 



When I was asked to write of the migration of mammals my first 

 thought was, "Hardly any of them do" — and compared with birds, 

 the proportion of the 8,000 different sorts of mammals that have regu- 

 lar migrations is certainly very small. In fact the characteristic thing 

 about the majority of mammals is not that they migrate but how near 

 home they stay. Many mammals have a home range — a "territory" — 

 in which they spend practically the whole of their lives, and from 

 which they seldom or never wander. This applies particularly to those 

 small mammals that live in burrows, or nests, which form the center 

 of their territories. The normal range of the common long-tailed field 

 mouse, for example, covers only a trifling area, and it is unusual for an 

 individual to travel more than a hmidred yards from the center of its 

 territory. Eabbits usually live their whole lives in the warren in 

 which they are born, and do not go more than two or three hundred 

 yards away for their daily grazing. This attaclmient to territory also 

 applies during the breeding season to the more nomadic kinds as well, 

 for many animals that may be considerable wanderers for part of the 

 year have to become static when their young are born, and have to 

 make a home in which they can be reared. 



Carnivorous mammals usually have a hunting territory centered 

 upon a home, a den of some sort. They work this territory but do not 

 need to go beyond its bounds. Their food is concentrated high-grade 

 protein, and they may need to make a kill only at intervals of several 

 days. Unlike the herbivorous mammals they are not compelled to be 

 always feeding. 



The larger herbivorous mammals — the grazers and the browsers — 

 must feed on and otf all day, because the green herbage they eat has 

 a comparatively low food value. So the larger sorts must have a wide 

 grazing range, and in consequence their territory is often not well 

 marked. In Africa, for instance, many of the grazing mammals follow 

 the rains and the new grass that springs up afterward ; they thu? un- 

 dertake an irregular sort of migration through an extensive but ill- 

 defined territory, 



* Reprinted by permission from Discovery, vol. 15, No, 5, May 1954. 



277 



