Study of the interactive effect of prey toxin and optimal foraging strategy on a predator–prey model

The optimal foraging theory predicts that predators choose prey with more net rate of energy intake and less energy costs if there are multiple food sources available. Toxins are found in many species in nature. Those toxins may be produced by prey as self-protection from predatory animals, or come from other sources such as pesticide residue. Therefore, it requires a balance between energy intake and toxicity damage. In order to study the interactive effect of prey toxin and optimal foraging strategy, we construct a predator–prey model with toxin-induced functional response and optimal foraging property. Dynamical analysis shows that the optimal strategy system presents more complex dynamical behavior than the fixed preference system. We conclude that optimal foraging strategy might play a key role in stabilizing or destabilizing the coexistence states of the species in the system, depending on the level of prey toxins.

Traits for predator selection on Pentaclethra macroloba seeds

Pentaclethra macroloba (Fabaceae: Mimosoidea) is a dominant species of canopy tree in Costa Rica’s Caribbean lowlands, constituting up to 40% of the local tree population in some areas. It has been suggested that P. macroloba’s dominance is due in part to low post-dispersal seed depredation, as few terrestrial seed predators can tolerate the high concentration of toxic alkaloids and free amino acids. Seeds are not immune from depredation, however. Several species of parrots and squirrels have been observed depredating pre-dehiscent legumes and may present selective pressure on P. macroloba recruitment. In this study, we assessed depredation patterns in P. macroloba to (1) determine if predators use legume and seed traits to select food items, (2) determine if such patterns represent an optimal foraging strategy for vertebrate predators, and (3) explore potential consequences of depredation on P. macroloba. Seed depredation was not correlated with legume valve side, legume size, seed number, or seed compartment size, though seeds at the distal end of legumes were more often extracted. Depredation patterns do not indicate that seed predators are foraging optimally and may be quickly satiated due to their low toxicity tolerance the abundance of seeds. Despite a lack of predator selection of various legume and seed characteristics, legume damage caused by depredation may interfere with the explosive dehiscence of P. macroloba and constitute a significant recruitment barrier.

Prestige, taboo, and sustainability: predicting wildlife population trajectories in indigenous commerce

Commercial traffic in plants and animals has led to severe declines for some species, while others have experienced few if any negative impacts. Given the uncertainty regarding which species are likely to be adversely affected by monetized trade, it would be useful to have a model that could predict wildlife population trajectories of wild-gathered species subsequent to commercialization. We suggest that the indigenous conservation strategy of "taboo" offers important insights into identifying species that are susceptible to over-exploitation through commercial traffic. We describe an economic conservation/extinction model based on the dual concepts of taboo and optimal foraging strategy and examine the model through a detailed case study of vulnerability to perturbation in the case of commercial traffic in Pacific island flying foxes. We suggest that tile virtual eradication of flying foxes from the island of Guam during the Twentieth Century resulted from a cultural predilection among the indigenous Chamorro people for consuming flying foxes coupled with the cultural loss of the traditional taboo conservation system on the island.