Foraging as Economics
Every animal faces the same fundamental problem: how to extract maximum energy from the environment while minimizing costs. Optimal foraging theory applies economic reasoning to this biological challenge, treating prey items as commodities and foraging decisions as investment choices. The result is a powerful predictive framework that explains diet breadth, patch use, and movement patterns across the animal kingdom.
The Diet Breadth Model
Should a predator eat everything it encounters, or specialize on the most profitable prey? The diet breadth model shows that this depends on the encounter rate with preferred prey. When preferred prey is abundant, specialists win — the time saved by ignoring inferior items more than compensates. When preferred prey is scarce, generalists win because any energy source beats the cost of searching further.
Profitability and Handling Time
Prey profitability — energy gained divided by handling time — is the currency of foraging decisions. A large prey item with high energy but requiring extensive processing may be less profitable than a small, quickly consumed one. This explains counter-intuitive observations like shore crabs preferring medium-sized mussels over larger ones: the medium mussels offer the best energy-per-second-of-handling ratio.
Beyond Energy Maximization
Modern foraging theory extends well beyond simple energy maximization. Risk-sensitive foraging considers variance in intake rates — starving animals should be risk-prone (gambling for survival), while well-fed animals should be risk-averse. State-dependent models incorporate the animal's condition, reproductive status, and predation risk. Social foraging adds the complexities of group hunting, food sharing, and information parasitism.