EFFECTS OF RELATIVE HUMIDITY AND ATMOSPHERIC OXYGEN ON HATCHING SUCCESS OF AMERICAN ALLIGATOR Alligator mississippiensis
Alligator producers in Louisiana obtain their farm stock by collecting eggs from nests on public and private lands under a permit system managed by the Louisiana Department of Wildlife and Fisheries. Eggs are available only once per year (May-June), so it is critical that farmers maximize egg-hatching success. Some farmers maintain higher than normal oxygen concentrations during egg incubation to improve hatching success, though it is not known if this practice is effective. This study was conducted to determine the effects of relative humidity and normal (21%) oxygen vs. elevated oxygen concentration on egg hatching success.
Two-hundred-sixteen alligator eggs collected at Rockefeller Wildlife Refuge (Grand Chenier, Louisiana) were distributed among 12 incubators (18 eggs per incubator) and maintained at 31.13 ± 0.05 °C (88.0 ± 0.1 °F) for 55 days under one of four treatments involving two levels of relative humidity (RH) and two atmospheric oxygen (O2) concentrations: (1) 80% RH and 21% O2; (2) 80% RH and 28% O2; (3) 93% RH and 21% O2; or (4) 93% RH and 28% O2. Three incubators were assigned to each of the four treatments.
Relative humidity averaged 79.9 ± 0.1% and 93.5 ± 0.4% in the low humidity and high humidity treatments, respectively. Hatching success of eggs in the 93/21 and 93/28 treatments averaged 83.3 ± 5.5% with no significant difference (P > 0.05) between treatments (Fig. 1A). Hatching success of eggs in the 80/21 and 80/28 treatments, combined, totaled 1.8% — only two of 108 eggs in the six low-humidity incubators hatched. Body weights (Fig. 1B) and body lengths (Fig. 1C) of hatchlings in the 93/21 and 93/28 treatments also were not significantly different (P > 0.05).
Results indicated that 80% relative humidity reduced egg hatching success to nearly zero, regardless of atmospheric oxygen concentration, while 93% relative humidity produced good hatching success. Elevated atmospheric oxygen concentration (7% above ambient) had no effect on egg-hatching success under the conditions of this study.