Data from: Luck in food-finding affects individual performance and population trajectories

Energy harvesting by animals is important because it provides the power
needed for all metabolic processes. Beyond this, efficient food-finding
enhances individual fitness [1] and population viability [2], although
rates of energy accumulation are affected by the environment and food
distribution. Typically, differences between individuals in the rate of
food acquisition are attributed to varying competencies [3] even though
food encounter rates are known to be probabilistic [4]. We used
animal-attached technology to quantify food intake in four disparate
free-living vertebrates (condors, cheetahs, penguins and sheep) and found
that inter-individual variability depended critically on the probability
of food encounter. We modelled this to reveal that animals taking rarer
food, such as apex predators and scavengers, are particularly susceptible
to breeding failure because this variability results in larger proportions
of the population failing to accrue the necessary resources for their
young before they starve, and because even small changes in food abundance
can affect this variability disproportionately. A test of our model on
wild animals indicated why Magellanic penguins have a stable population
while the congeneric African penguin population has declined for decades.
We suggest that such models predicting probabilistic ruin can help predict
the fortunes of species operating under globally changing conditions.