Lecture 15. Foraging Behavior and Optimality

Foraging refers to the behavior of searching for and exploiting food resources.
Different species exhibit unique strategies based on environmental factors and food availability.

Optimal Mussel Selection:
- Oystercatchers maximize caloric intake by choosing the most profitable mussels, not necessarily the largest.
- Study by Meire and Ervynck observed that larger mussels provided more calories per minute despite taking longer to open.
Key Prediction:
- Researchers predicted oystercatchers would select larger mussels based on caloric content. However, this prediction was proven incorrect.
- Initial model (Model A) was rejected due to prolonged opening times for large, barnacle-encrusted mussels.
Model Revision:
- Revised Model B presented a more accurate depiction of mussel selection by oystercatchers.
- It emphasized efficiency in foraging strategies over mere caloric value.

Foraging behavior can be influenced by various non-food factors:
- Predation Risk: Garden skinks decrease movement in the presence of snake odors.
- Dietary Preferences:
- Howler monkeys select leaves low in toxins and high in protein.
- Red grouse choose heather leaves rich in nutrient content (nitrogen, phosphorous).
Fitness and Dietary Oddities:
- Some species (e.g., macaws) consume clay possibly due to zinc deficiency or to alleviate diarrhea.
- Spice consumption (e.g., garlic, oregano) is tied to reducing bacterial contamination in diets.

Search Image Concept:
- Developed by Luuk Tinbergen; refers to a predator's ability to form mental images of specific prey types to enhance foraging success.
- Observations showed parent birds returning with prey in greater proportions than expected.
Impact of Prey Crypticity:
- Studies by Gendron, Goss-Custard, and Smith indicated that a predator's search speed decreases when searching for cryptic (camouflaged) prey.
Improvement of Search Images:
- Blue Jays improved their search images after repeated exposure to a specific prey type, enhancing foraging efficiency.

Communication in Bees:
- Bees communicate food locations through round and waggle dances, where they gauge distance traveled using optic flow.
- Optic flow is the perception of the movement of nearby objects relative to distant ones, influencing how bees find resources.
Ravens as Information Centers:
- Ravens (Corvus corax) utilize communal roosts to share information about food locations.
- Experimental studies with sheep carcasses showed that spatial distribution of food information was influenced by roost dynamics.

Some predators (e.g., certain spiders) mimic non-prey species to lure in unsuspecting victims, showcasing a complex foraging strategy.
Visual deceptions enhance predator success rates.

Not Always Optimal:
- It's important to recognize that not all foraging behavior results in optimal outcomes, particularly in environments impacted by human activity or climate change.
- Adaptation and flexibility in foraging strategies are critical for survival in changing habitats.

Overview of how observing animal behaviors enhances understanding of biological processes.

Objective: Investigate how crows utilize tools to access food.
Observation: Crows drop whelks (a type of seafood) from a height to break the shells and access the food inside.
Experiment Details: Reto measured the size of whelks and the height needed for effective shell opening.
Findings:
- Data Table: Relationship between whelk size, drop height, and number of drops required.
- Larger whelks require higher drop heights and multiple drops to crack open.
- Smaller whelks can be cracked with lower heights and fewer drops.
- Indicates that energy expenditure in flying high affects foraging strategies.

Crows and their choice of food based on size and energy efficiency.
Not all animals prefer the largest prey; efficiency in foraging is crucial.
Comparative Studies: Mary and Ebernik researched oyster catchers, birds that also open mussels and varied their selections.
Key Finding: Animals adapt foraging behavior based on food availability; middle-sized prey often preferred due to abundance.

Foraging Theory: Models suggest animals aim for profit maximization in food gathering.
The availability of food types (medium vs._large) affects the foraging choices and strategies employed by animals.

Energy Needs and Habitat Structure: The physical environment impacts how and where animals forage.
Predator Presence: Predation risk alters foraging behavior.
Learned Behaviors: Individuals adapt foraging tactics based on experiences and environmental cues.
Food Location: Search images are formed—mental representations that help identify prey.

Animals develop a search image based on food preferences, which enhances hunting efficiency.
Examples from bird behaviors illustrating the concept of search images and learning outcomes in foraging success.

Waggle Dance in Bees: Method of communication that informs hive members about food source direction and distance.
- Demonstrates social dynamics in foraging behavior.
Group Foraging: Animals might share information on food sources post-roosting, leading to collective foraging success.

Animals exhibit behavioral plasticity in response to predation, food availability, and habitat structures.
Learning from experience shapes their foraging behaviors.
The intersection of instinct and experience plays a critical role in survival and optimizing food acquisition strategies.

Clay Eating in Animals: Consuming clay for nutritional benefits like obtaining zinc.
Use of Spices by Humans: Reflects on the historical significance of spices in food preservation and safety from microbial growth.

Foraging behavior is complex and influenced by ecological factors, energy needs, and interspecies interactions.
Optimal foraging involves trade-offs between energy expenditure and food availability, evolving strategies based on environmental conditions.