The importance of avian egg components in the determination of hatchling size and quality has yet to be fully evaluated. In the first experiment, 20% of the albumen and/or the yolk was removed from chicken eggs to determine the impact of each egg component on metabolism and various size measures in near-term embryos. Results show that metabolic rate, dry body mass, and internal organ mass are largely independent of egg composition. Removal of albumen resulted in a decrease in wet body mass corresponding to decreases in water content in the body and the yolk sac, and decreased tibiotarsus length. Removal of yolk resulted in no change in body mass, but decreases in both wet and dry yolk sac mass. In a second experiment, removal of 15% of either egg component led to reductions in hatchling mass similar to those observed in whole near-term embryos. Albumen, as the primary source of water in the egg, is the primary determinant of hatchling size and may influence hatchling success through size-related limiting factors. Differences in yolk content may influence neonatal quality as a nutritional supplement, but seem not to result in greater tissue formation during embryonic development.

The effects of water availability during incubation on the water contents of neonatal snapping turtles at hatching were examined, along with the influence of hatchling water content on desiccation tolerance and terrestrial locomotor performance. The water contents of hatchlings from eggs incubated on wet substrates were both absolutely and proportionally greater than were those of hatchlings from eggs incubated on dry substrates. Hatchlings with greater water contents at hatching were able to survive longer and to lose more water before physiological performance was adversely affected by desiccation. Increased water contents in hatchlings with greater water availability during incubation may enhance survival by increasing the amount of water the animal can afford to lose before dehydration begins to adversely affect whole animal performance.

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Although many authors have used thread trailing to monitor movements of turtles and other vertebrates, most have evaluated only a portion of the information contained in these pathways. We describe ways of extracting information from thread trails by determining length of trail, mean distance moved per unit time, net displacement, area encompassed by the trail, mean turning angle, and mean vector length. We further describe and compare four measures of trail sinuosity, the ratio of greatest distance to length of path (d/L), the square root of the ratio of area to path length [Formula: see text], fractal dimension (D), and sinuosity (S); we then applied these methods to the trails of a population of ornate box turtles (Terrapene ornata) from the Nebraska Sand Hills. Though preliminary, these data suggest that vegetation cover affects the sinuosity of turtle trails (based on D), that temperature affects the mean distance moved per day, that T. ornata ordinarily show little or no directional bias, and that injury can affect distance moved, trail sinuosity, and mean turning angle. Among these measures of trail sinuosity, D and S are highly correlated and provide similar information. Though less closely correlated with D and S, or with each other, [Formula: see text] and d/L also reflect trail sinuosity; of these indices, however, d/L best reflects trail directionality. This analysis suggests that a more comprehensive evaluation of pathways at this fine scale will provide new insights into the routine movements of animals.

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