How Much Is Supper? Predator Diet and Prey Retaliation

This chapter focuses on the anaconda’s diet and the role it plays in the snake’s biology. Clearly, food intake is a critical aspect of any animal’s ecology for it determines how the animal obtains energy needed for survival and reproduction. Anacondas, with their strong build, are not fast enough to pursue prey on land. Although fast swimmers, an open mouth moving forward is not very hydrodynamic for catching fishes, which are often quite fast. However, anacondas can launch an extraordinarily fast attack on a prey out of the water when needed. In fact, the predatory strike of an anaconda can be so fast that it beats the eye. The anaconda’s preferred strategy is to wait in a place under the vegetation, with which they blend wonderfully, and wait for the right prey to come within range. This way, anacondas avoid being detected moving around looking for prey and save in locomotion energy. As reptiles, anacondas have a slow metabolism, which means they consume very little energy for metabolic maintenance. The chapter then looks at how anacondas kill their prey.

Predation Has Small, Short-Term, and in Certain Conditions Random Effect on the Evolution of Aging

The pace of aging varies considerably in nature. Historically, scientists focused mostly on why and how has aging evolved, while only a few studies explored mechanisms driving evolution of specific rates of aging. Here we develop an agent-based model simulating evolution of aging in prey subject to predation. Our results suggest that predation affects the pace of aging in prey only if young, vivid animals are not much more likely to escape predators than the old ones. However, even this effect slowly vanishes when the predator diet composition evolves, too. Furthermore, evolution of a specific aging rate, in our model, is driven mainly by a single parameter, the strength of a trade-off between aging and fecundity. Indeed, in absence of this trade-off the evolutionary impacts of predation on the prey aging rate appear random. Our model produces several testable predictions which may be useful for other areas of aging research.

Evolution of predator foraging in response to prey infection favors species coexistence

As acknowledged by Optimal Foraging theories, predator diets depend on prey profitability. Parasites, ubiquitous in food webs, are known to affect simultaneously host vulnerability to predation and host energy contents, thereby affecting profitability. In this work, we study the eco-evolutionary consequences of prey infection by a non trophically-transmitted parasite, with a simple lifecycle, on predator diet. We also analyze the consequences for coexistence between prey, predators and parasites. We model a trophic module with one predator and two prey species, one of these prey being infected by a parasite, and distinguish between two effects of infection: a decrease in host fecundity (virulence effect) and an increase in vulnerability to predation (facilitation effect). Predator foraging may evolve toward specialist or generalist strategies, the latter being less efficient on a given resource. We show that the virulence effect leads to specialisation on the non-infected prey while the facilitation effect, by increasing prey profitability, favors specialisation on the infected prey. Combining the two effects at intermediate intensities promotes either generalist predators or the diversification of foraging strategies (coexistence of specialists), depending of trade-off shape. We then investigate how the evolution of predator diet affects the niche overlap between predator and parasite. We show that facilitation effects systematically lead to a high niche overlap, ultimately resulting in the loss of the parasite. Virulence effects conversely favor coexistence by allowing a separation of the predator and parasite niches.