Number of Young per Litter
Records of from one to 16 young per litter have been reported (Ditmars, 1945:330; Clark, 1949:259), but the average is probably between six or seven. Most accounts in the literature present information on number of ova or embryos per female rather than the number of young. Size and age of the mother (Table 9) influence the number of ova produced. Allen and Swindell (1948:11) recorded three to 12 embryos in 31 cottonmouths varying in total length from 26 to 44 inches. An average of 6.5 embryos per female was found.
TABLE 9.—Number of Ova Produced by Fecund Cottonmouths.
| Snout-vent length in millimeters | Number in sample | Number of ova, average and extremes |
| 450-549 | 10 | 4.1 (2 to 7) |
| 550-649 | 11 | 4.9 (1 to 8) |
| 650-749 | 4 | 6.3 (4 to 8) |
| 750-849 | 1 | 5 |
| 850-949 | 1 | 14 |
Mortality at birth has been recorded for almost every litter born in captivity (see Allen and Swindell, loc. cit.; Conant, 1933:43; Wharton, 1960:125). A female that I kept in captivity gave birth to seven young. Three never ruptured their sacs, and another died soon after leaving the sac. The effects of captivity on females may result in higher rates of deformity and mortality in young than is common in nature. Klauber (1956:699-700) estimated that the defects brought about by conditions of captivity on rattlesnakes eliminate about three young per litter.