Mexico and Central America 



INTRODUCTION 



The poisonous snakes of northern Mexico and 

 of tlie Mexican plateau southward to ^fexico City 

 are very similar to those of the United States. 

 Tliese liinfh and arid rep;ions are inhabited mainly 

 (speaking in teiins of poisonous snakes) by vari- 

 ous species of rattlesnakes. However, the Ari- 

 zona coral snake (MJcniroides eurj/.rrnifhiix) also 

 is found along the northern border of the western 

 states of Chihuiduui, Sinaloa, and Sonera, and the 

 coral snake, Micriiriix ffzingeri. is found in the 

 south. 



As one descends from the plateau to the coastal 

 plain, however, even as far north as Tamaulii)as 

 and Xayarit, a strange tropical snake fauiux is 

 found. Included in this are many kinds of coral 

 snakes, the cascabel (tro])ical rattlesnake), Crotn- 

 Juft dur/s.siis. ami various members of the Ameri- 

 can lanceheads, the genus Bothropx. 



The coral snakes are a negligible source of 

 danger although they are highly venomous and 

 the case fatality rate is high (approaching 50 per- 

 cent). Because they are such secretive animals, 

 however, they are seldom encountered. Almost 

 every coral snake bite is inflicted on a person that 

 is attempting to catch or kill the reptile. If jieo- 

 ple would but leave the bright -coloi-ed snakes 

 with red, black, and yellow (or whitish) rings 

 alone, this group would otl'er little danger. It is 

 the absence of a broad head and vertically ellipti- 

 cal pupils (characteristic of pit vipers) that 

 causes the unknowledgeable man to mistake a 

 coral snake for a nonvenomous species. 



The other poisonous species are all pit vipers 

 and are easily identified by the loreal pit, the 

 broad head, eyes with vertical pupils, and the 

 rough-scaled body. Most of the species of rattle- 

 snakes are northern and western in distribution. 

 Those along the Mexican-United States border 

 are the same as those which occur in the United 

 States. 



However, the cascabel {Crofahis durissus) 

 ranges through the grasslands and other dry and 

 open areas of the tropical lowlands throughout 

 the region as far north as southern Tamaulipas. 

 It attains a length of 6 feet and has a large store 

 of a vei-y toxic venom. Apj)arently, too, its 

 venom does not cause the formation of antibodies 

 in horses to the extent that most venoms do ; and, 



therefore, the antivenin is only weakly etfective. 

 This makes it one of the most dangei"ous snakes 

 of the region and one of the most dangerous 

 snakes on earth. 



Most of the bites through the tropical areas of 

 Central America are inflicted by members of the 

 American lanceheads {Bothi'ops). Many of the 

 bites are by bush and tree vipei's such as the eye- 

 lash vij^er {Botlifops schhgelU). These often 

 cause serious injury to the affected part but sel- 

 dom cause death. The major killer of man 

 throughout the region is tlie barba amarilla, 

 Bothrops afrox (often miscalled fer-de-lance). 

 This 5 to 8 foot snake has an unpredictable 

 temperament; it is easily irritated to strike and 

 carries a large supply of powerful venom. It 

 causes a large inimber of deaths each year. 



The huge bushmaster {Laches/s mufufi), on the 

 other hand, which grows to a length of 9 to 12 

 feet, is seldom encountered due to its purely noc- 

 turnal haliits. It causes relatively few bites, and 

 these appear to be no more serious than those of 

 the barba amarilla. 



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Map 3. — Section 2, Me.xico and Central America. 



49 



