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Predator and prey interact antagonistically, and theory predicts that prey density tends to decay when predators are present. Considering this prediction, efforts made to conserve a prey species can have the opposite effect, as the increase in prey density leads to an increase in predator consumption, resulting in decreased prey density. In this sense, field studies describing species interactions and resulting effects of conservation efforts are essential to both to validate theoretical predictions and conservational concerns. California sea otter (Enhydra lutris nereis) regardless of being super cute, are also voracious predators who really like to eat abalones (Haliotis cracherodii). As it turns out, humans also really like to eat abalone, and human harvesting and sea otter predation are important factors decreasing abalone densities. Both species (sea otter and black abalone) are listed as endangered species and are protected in California coast. A recent study (Raimondi et al. 2015) investigated local abundances of sea otters and black abalones at 12 different sites. The authors found a positive relation between the predator's and prey density. Along with that, the presence of the predator also correlated with prey's pattern of habitat use. In sites with greater sea otter densities, black abalone where found in places conferring greater refuge, which can difficult illegal human harvest.

The interaction between predator and prey can go far beyond the model proposed by Lotka-Volterra. Describe the essential components needed to understand the dynamics between sea otters and black abalone and how conservation efforts targeting one or both species would affect their population densities.

• One interesting (and perhaps counterintuitive) result found by the authors is that the increase in predator population density leads to a positive relation with prey density. The authors propose three hypothesis to explain this pattern. Considering each hypothesis, select one of them, understand the mechanisms supporting the hypothesis and test the hypothesis using a model of population dynamics.
• Sea otter density is correlated with black abalone density. How habitat use of prey (refuge value) affects the result found by the authors?

• Raimondi et al (2015) Evaluating potential conservation conflicts between two listed species: sea otters and black abalone Ecology 96(11): 3102-3108 link