Figure 4. A total of 110 eggs (N = 14 clutches) of the water snake were incubated in the exact position they were laid, including 77 top embryos (located at the top of the egg) and 33 bottom embryos (located at the bottom) and eggs regularly surveyed for their heart rates (i.e. metabolic rate).

Heart rates were consistently higher throughout the incubation period in top (85.23 ± 3.33 bpm) compared to bottom embryos (83.04 ± 3.17 bpm—repeated measures Anova; interaction term F_{54, 324} = 1.14; P = 0.24; effect of embryo location F_{1, 54} = 7.29; P = 0.009). Means + SE are given.