﻿MAMMALS OF NORTHERN COLOMBIA — ^HERSHKOVITZ 329 



Panama and northwestern Colombia, These savannas may have been 

 more numerous and more extensive than is indicated at present time. 



Primary forests are natural barriers to the spread of cottontails in 

 South America. Thus, the northern Colombian cottontail (S. jiori- 

 danus superciliaris) is abundant along the base and cleared foothills 

 of the Sierra Nevada de Santa Marta but is absent from savannas in 

 the Sierra Nevada at 1,000 meters and more above sea level. These 

 montane savannas, apparently affording ideal habitats for cottontails, 

 are separated from lowland savannas by a continuous belt of forest. 

 On the other hand, the same cottontail has penetrated clearings on 

 the opposing slope of the Sierra de Perijd, to as high as 1,000 meters 

 above sea level where these clearings are continuous with those of the 

 lowlands. 



Cottontails have spread over cleared banks of the Rio Magdalena 

 and those of many of its tributaries but have not gained access to true 

 highland savannas, or paramos, on the crests of the Andes. These 

 paramos are isolated from the largely artificially created savannas 

 lower down, by belts of primary forest. Nothing impedes a continuous 

 distribution of cottontails from the Rio Cesar Valley, Colombia, into 

 the arid Guajira Peninsula, thence eastward into arid and semiarid 

 savannas and scrub countries of northern Venezuela. The llanos of 

 the Orinoco Basin again provide suitable and accessible habitats. 

 The cottontails on a few islands off the Venezuelan coast must have 

 been introduced relatively recently by man. 



Cottontails are active only at night unless some disturbing circum- 

 stance compels them to emerge from their retreats in daytime. The 

 savamia dog, Dusicyon thous, is their most persistent enemy. 



Tapitis {Sylvilagus brasiliensis) inhabit the remainder of South 

 America exclusive of high altitudes above snow line and the Patago- 

 nian region south of the Argentine Chaco. They live in Tropical and 

 Temperate Zone forests and in swamps, savannas, scrublands, and 

 deserts. Their presence is most evident in forest clearings and natural 

 grasslands. Tapitis nest in brush heaps, in hollow trunks of trees, at 

 the base of trees, and amid tangled roots. They sometimes iind refuge 

 in burrows made by other animals. In lowlands tapitis are active 

 only at night. In the highland paramos they are active from late in 

 the afternoon to early in the morning. Principal enemies of tapitis 

 are members of the cat and dog families. 



In northwestern South America habitats of tapitis and cottontails 

 are mutually exclusive. Tapitis cling to d%\dndliug forests and the 

 clearings therein and to natural savannas of the Andean crests, while 

 cottontails are replacing them in artificial savannas cutting through 

 the original forests. No doubt introduction of the larger, more prolific, 

 and more aggressive cottontail, together with the train of predators 

 following it, is the most important factor contributing to the exclusion 



