CRANIAL AND BRACHIAL BIOMETRY OF DESMODUS-ROTUNDUS (CHIROPTERA, PHYLLOSTOMIDAE) IN FRENCH-GUIANA

During an ecological study of the Common Vampire, Desmodus rotundus, in French Guiana, a large sample of specimens was collected and measured (forearm : N = 389, skulls : N = 146). These biometric data are analysed in respect of the main variation sources, and then, according to the systematics of the species. Females are generally bigger than males; this is obvious for the forearm length,and is also statistically significant for most of the cranial measurements (length and breadth of the skull zygomatic breadth, length of the mandible,... p < 0,001). Some discriminant functions are calculated; with the forearm length, as many as 90% of the specimens can be rightly assigned to one sex (75% with only skull measures); males are statistically below 59,5mm, but eight of them are larger while two adult females are smaller than expected. This significant sexual dimorphism is the only clear biometric variation, more particularly it appears relevant that all the common vampires of the French Guiana coast, from Cayenne region to Saint-Laurent-du-Maroni region, belong to a sole population. According to their weight and their forearm length these Desmodus rotundus could be assigned to the northern subspecies; but can these measurements be reliable criteria for this identification, and are there several subspecies? Beyond a large amount of individual variation, bibliographic data from various countries of the whole range of the species exhibit some clear differences between samples. A comparative morphometric and genetic study including large samples from differenciated populations (Mexico, Trinidad and Argentina for example) is needed for delimiting possible subspecies.