Part 11

"Head bobbing," more properly described as spastic contractions of the body, was observed in captives when food was introduced into a cage containing several individuals or when one of the snakes was returned to the cage after being handled. Reports in the literature also have connected these jerking movements with courtship. The response appears to be elicited whenever a nervous state is recognized in another individual and may serve to protect the jerking individual from aggressive advances of the former.

The relatively heavy appearance of the body, sluggish habits, and cryptic coloration are correlated with the development of venom and fangs. The poison apparatus has developed primarily as a means of causing rapid death in prey and secondarily, perhaps, to begin the digestion of small animals that are the usual prey, but it is also important as a defensive device. The venom contains at least eight constituents that aid in its action on prey. Toxicity of the venom is difficult to determine because of numerous variables, but cottonmouth venom is generally believed to be less potent than that of most rattlesnakes and more potent than that of the copperhead. Snakes in general are more resistant to snake venoms than other vertebrates of similar size, but there is no immunity even to their own venom.

About ten per cent of the approximately 5000 bites of poisonous snakes per year in the United States are attributable to cottonmouths, and about seven per cent of the approximately 14 deaths per year are caused by cottonmouths.

LITERATURE CITED

ALLEN, E. R.

1937. Florida snake venom experiments. Florida Acad. Sci., 2:7 pp.

ALLEN, E. R., and SWINDELL, D.

1948. Cottonmouth moccasin of Florida. Herpetologica, 4:1-16 (first supplement).

ALLEN, M. J.

1932. A survey of the amphibians and reptiles of Harrison County, Mississippi. Amer. Mus. Novit., 542:1-20.

ANDERSON, P.

1941. The cottonmouth in northern Missouri. Copeia, 1941(3):178.

1945. New herpetological records for Missouri. Bull. Chicago Acad. Sci., 7(5):271-275.

ANON.

1953. Snake collecting hobby of Colonial Heights lad. Virginia Wildlife, 14-24.

AUFFENBERG, W.

1963. The fossil snakes of Florida. Tulane Studies Zool., 10(3):131-216, 51 figs.

BAILEY, R. M.

1948. Winter mortality in the snake Storeria dekayi. Copeia, 1948(3): 215.

BARBOUR, R. W.

1956. A study of the cottonmouth, Agkistrodon piscivorus leucostoma Troost, in Kentucky. Trans. Kentucky Acad. Sci., 17(1):33-41, 1 fig.

BLANCHARD, F. N.

1922. The amphibians and reptiles of western Tennessee. Occ. Pap. Mus. Zool.; Univ. Michigan, 117:1-18.

BOGERT, C. M.

1943. Dentitional phenomena in cobras and other elapids with notes on adaptive modifications of fangs. Bull. Amer. Mus. Nat. Hist., 81(3):285-360.

BRATTSTROM, B. H.

1954. The fossil pitvipers (Reptilia: Crotalidae) of North America. Trans. San Diego Soc. Nat. Hist., 12(3):31-46, 2 figs.

BROWN, A. E.