Crocodylus johnstoni in a Controlled-Environment Chamber: a Raising Trial

Abstract

Crocodylus johnstoni hatchlings were raised in a constant-environment chamber of the type used for Alligator mississippiensis by Joanen and McNease. Minced marine fish with vitamin and mineral supplements appeared an adequate diet for growth, but growth rates were highly variable. Density was an important determinant of mortality and food conversion rates. No significant variation in growth rate was attributable to sex, but mortality in low-density pens was slightly higher for males than for females; samples were too small to determine whether or not this was significant. Daily feeding resulted in higher conversion rates and a greater intake of food per pen than feeding 5 days per week, but within the period tested significant differences in linear growth were not apparent. This could reflect excessive fat deposition, which is known to result in chronic obesity. No significant difference in growth was attributable to chopped or minced food. Food intake and conversion rates dropped during the dry season, when feeding and growth in the field are also retarded. The application of constant-environment chambers for testing variables likely to influence raising success is discussed; however, C. johnstoni may not be as suited to this style of raising as are some other crocodilians. At all densities tested fighting was a problem, and even minor disturbances were associated with reduced food intake and defensive behaviour.