﻿338 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loo 



THE SOUTH AMERICAN COTTONTAIL 



SYLVILAGUS FLORIDANUS (Allen) 



(Synonymies given under subspecies headings) 



Distribution (map, fig. 42). — Islands of Aruba, Cura9ao, Margarita, 

 Los Testigos, and arid and semiarid savannas and scrublands of 

 Caribbean coastal plains and highlands of Colombia and Venezuela. 

 Some cottontails have penetrated southward into valleys of the upper 

 Rio Orinoco, Venezuela, and the upper Rio Magdalena, Colombia; 

 altitudinal range to approximately 1,000 meters above sea level. 



Characters. — Larger than S. brasiliensis but ear averaging propor- 

 tionately shorter; base of ear on outer side thinly haired, the median 

 anterior portion well defined from crown ; gray inner side of ear sharply 

 defined from brownish outer surface by a fine white edging. Tail 

 comparatively long, grayish to brownish above, cottony white to 

 grayish brown beneath, and always distinguishable from rump. 

 Dominantly white upper surface of hind foot often marked with spots 

 or patches of ochraceous to tawny. A well-defined white to buff 

 circumorbital band nearly always present. Nuchal patch ochraceous 

 to black. Rump hke back or paler, grayer. IVlammae, eight: one 

 pair pectoral, two pairs abdominal, one pair inguinal. Skull com- 

 paratively large and relatively narrow, the rostrum broad; nasals long, 

 between 82 and 107 percent of zygomatic breadth. Supraorbital 

 process comparatively heavy, posterior wing thick and broad with 

 posterior edge of inner border nearly always fused with frontal, some- 

 times entire inner border fused. Least length of palatal bridge 

 usually less than one-third greatest distance across outer border of 

 maxillary plates of molar rows. Bulla comparatively large. 



Remarks. — Most cranial differences between Neotropical ^on(/an'MS 

 and brasiliensis are largely dependent upon over-all differences in size. 

 There is some overlapping in actual cranial measurements between 

 smaller races of jloridanus and larger ones of brasiliensis. In these 

 extremes there is usually a narrower average difference in some cranial 

 proportions. As a rule, however, the relatively longer nasal and 

 larger bulla distinguish the skull of any one individual of Neotropical 

 Jloridanus from an otherwise similar skull of brasiliensis. In addition, 

 the posterior angle of supraorbital process in Jloridanus is never so 

 delicate and widely separated from frontal as in many individuals and 

 even entire populations of brasiliensis. 



Variation. — South American cottontails vary individually, locally, 

 sexually, and to a certain extent seasonally, as described by Nelson 

 (1909, pp. 26-37) for their North American relatives. A slightly 

 larger average size noted among females may be attributable to the 

 greater number of old females than old males in collections. Seasonal 

 change in pelage among Neotropical cottontails follows the same cycle 

 as that of Boreal forms but shows less strongly contrasted differences 



