A warming climate poses a fundamental problem for embryos that develop within eggs because their demand for oxygen (O 2 ) increases much more rapidly with temperature than their capacity for supply, which is constrained by diffusion across the egg surface. Thus, as temperatures rise, eggs may experience O 2 limitation due to an imbalance between O 2 supply and demand. Here, we formulate a mathematical model of O 2 limitation and experimentally test whether this mechanism underlies the upper thermal tolerance in large aquatic eggs. Using Chinook salmon ( Oncorhynchus tshawytscha ) as a model system, we show that the thermal tolerance of eggs varies systematically with features of the organism and environment. Importantly, this variation can be precisely predicted by the degree to which these features shift the balance between O 2 supply and demand. Equipped with this mechanistic understanding, we predict and experimentally confirm that the thermal tolerance of these embryos in their natural habitat is substantially lower than expected from laboratory experiments performed under normoxia. More broadly, our biophysical model of O 2 limitation provides a mechanistic explanation for the elevated thermal sensitivity of fish embryos relative to other life stages, global patterns in egg size and the extreme fecundity of large teleosts.

Shifting suitable range limits under global warming will threaten many species. Modeling and mapping these potential range shifts is important for conservation. As global warming will introduce new sets of abiotic conditions, predictive empirical niche models may not perform well and the best method to model a specie's projected range shifts may be to model their fundamental niche with a biophysical mechanistic niche model. However, this class of model requires many physiological parameters that are difficult to measure for species not easily kept in captivity. It is also difficult to estimate these parameters for marine species given the interactions among their in-water motion, metabolism, and heat transfer. To surmount these difficulties, we use our previously verified novel technique combining 3D digital design, computational fluid dynamics, and finite volume heat transfer modeling to find animal core temperatures. We then use this method to build a fundamental niche map for internesting and nesting leatherback sea turtles (Dermochelys coriacea). With these niche maps we analyze three main nesting areas. We show that global warming poses a large overheating risk to leatherbacks in Southeast Asia, a slight risk to leatherbacks in the West Atlantic and a low risk to leatherbacks in the East Atlantic. We also show that the impact may be less on leatherbacks that shift their nesting location or who are smaller. Methods such these are important to produce efficiently and economically accurate maps of regions that will become inhospitable to species under global warming conditions.

Animal momentum and heat transfer analysis has historically used direct animal measurements or approximations to calculate drag and heat transfer coefficients. Research can now use modern 3D rendering and computational fluid dynamics software to simulate animal-fluid interactions. Key questions are the level of agreement between simulations and experiments and how superior they are to classical approximations. In this paper we compared experimental and simulated heat transfer and drag calculations on a scale model solid aluminum African elephant casting. We found good agreement between experimental and simulated data and large differences from classical approximations. We used the simulation results to calculate coefficients for heat transfer and drag of the elephant geometry.