Age and Litter Effects on Testosterone Levels in Young Water Snakes
To test whether a pulse of testosterone reported in young male garter snakes also occurs in related snakes, testosterone levels were measured in 18 male water snakes (Nerodia sipedon) belonging to four litters at 5–6, 16–17, 29–30, and 250–267 days of age. Testosterone levels were uniformly low over the first 30 days of life but increased significantly by 250–267 days of age; there were also significant differences among litters in levels of this hormone by that time.Abstract
Changes in testosterone levels with age in young water snakes. Shown are means and standard errors for males from four families (n = 4–6 per families). Separate symbols and line styles distinguish families. Testosterone levels were measured in pg/ml and are plotted on a log scale
Relationship between snout–vent length and testosterone levels in 250–267-day-old male water snakes belonging to four families. Testosterone levels were measured in pg/ml, and snout–vent length was measured in millimeters; both variables are plotted on log scales. Separate symbols and line styles distinguish families as in Figure 1 (squares are associated with the dotted line, circles with the dashed line, upward pointing triangles with the dot-dashed line, and downward pointing triangles with the solid line. Regression lines are drawn to reflect differences in intercept but not in slope (see text)