TAYLOR, E.N.*; DENARDO, D.F.: Growth of juvenile western diamondback rattlesnakes (Crotalus atrox) raised on different diets

We examined the effect of food intake on growth parameters in juvenile western diamondback rattlesnakes (Crotalus atrox). Fifty snakes were captured from the wild shortly after birth and housed individually in the laboratory. Snakes were randomly assigned to “high intake” (i.e., fed one mouse per week) or “low intake” (i.e., fed one mouse every three weeks) groups. Exact masses of the mice were recorded, and snakes were measured every six weeks. Not surprisingly, high intake snakes grew more rapidly in mass and snout-vent length (SVL) than did low intake snakes. There were no overall differences in mass or SVL gain between sexes in either group. Production-ingestion (P-I) ratios, or the increase in the growth parameter divided by the mass of food consumed, were calculated for each group. Low intake snakes had higher P-I ratios for SVL than did high intake snakes, while high intake snakes had higher P-I ratios for mass than did low intake snakes. This suggests that juvenile rattlesnakes differentially allocate energy to growth and storage depending on food availability. Gender did not affect P-I ratios for either growth parameter. This latter result supports the hypothesis that as juveniles, male and female rattlesnakes grow at similar rates, and that sexual size dimorphism develops at some later point.