Abstract
ABSTRACTWe study a discrete time, structured population dynamic model that is motivated by recent field observations concerning certain life history strategies of colonial-nesting gulls, specifically the glaucous-winged gull (Larus glaucescens). The model focuses on mechanisms hypothesized to play key roles in a population's response to degraded environment resources, namely, increased cannibalism and adjustments in reproductive timing. We explore the dynamic consequences of these mechanics using a juvenile–adult structure model. Mathematically, the model is unusual in that it involves a high co-dimension bifurcation at which, in turn, leads to a dynamic dichotomy between equilibrium states and synchronized oscillatory states. We give diagnostic criteria that determine which dynamic is stable. We also explore strong Allee effects caused by positive feedback mechanisms in the model and the possible consequence that a cannibalistic population can survive when a non-cannibalistic population cannot.
Highlights
Cannibalism is a life history trait found in a wide variety of animals, ranging from protozoans and invertebrates to all major vertebrate classes [15]
While egg and chick cannibalism occurs commonly among colonial-nesting gulls, a recent study demonstrated that egg cannibalism among glaucous-winged gulls (Larus glaucescens) and glaucouswinged × western gull (L. glaucescens ×occidentalis) hybrids increased in response to impoverished food supplies resulting from El NiñoSouthern Oscillation (ENSO)-related high sea surface temperature (SST) events [17]
Before we investigate the interplay of juvenile cannibalism by adults and reproductive synchrony (Section 4), we consider an example model that illustrates the mathematical issues involved in the model with regard to reproductive synchrony alone
Summary
Cannibalism is a life history trait found in a wide variety of animals, ranging from protozoans and invertebrates to all major vertebrate classes [15]. These theorems provide diagnostic quantities that determine which of these bifurcating states is stable/unstable as well as their direction of bifurcation.
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