Presentation on theme: "Uroplatus Gecko This has nothing to do with today’s lecture but speaking of cryptic critters…"— Presentation transcript:
Uroplatus Gecko This has nothing to do with today’s lecture but speaking of cryptic critters…
We all got to eat: Foraging behaviors (cont)
Spider webs: Crypsis for hunting or predator avoidance or both?
Evolution produces an array of web specializations
Orb weaver spiders produce an array of web specializations called stabilimentum Orb weavers use non UV reflecting silk for their orbs but UV reflecting silk for stabilimentum.
Orb weaver spiders: stabilimentum and behavior
Stabilimentum increase prey capture but at a cost
Foraging and web-building in Dictyinidae Costa Rican net casting spiders Diversity of web specializations Nursery web spider
Bolas spider: uses a pheromone- like lure to attract moths
Generalist: Species that sacrifice some profitability in exchange for less energy and time searching for prey. Specialist: Pursue items with high profitability but must spend more time and energy searching for prey. Different species exhibit a variety of strategies along the continuum from generalist to specialist. The optimal foraging strategy for a species will be that which maximizes net energy intake. Foraging strategies:
Optimal foraging theory Eenergy content of a prey item (kJ) hhandling time for a prey item ithe "next most-profitable item" ssearch time for a given prey item The profitability of the "next most-profitable item type" (the ith item) search for a more profitable item (type) already in diet
Prey TypeDensity (zone M) Density (zone A) Density (zone L) Search Time (s i ) Handling Time (h i ) Energy per Prey E i (kJ) Energy Gain (kJ/hour) urchins chitons mussels Foraging behavior of Glaucous-winged Gulls in rocky intertidal habitats of the Aleutian Islands. **In nature gulls consistently selected sea urchins over chitons, but mussels were still the least preferred despite their high abundance. What would explain these preferences Irons et al. (1986) Three prey items of gulls: Muscles Chitons Urchins Prey preference experiments, in which both search and handling times of the different prey items were zero, showed that gulls chose chitons over urchins and mussels Three tidal zones: M (muscle) A (Alaria) L (Laminaria)
Foraging behavior of Glaucous-winged Gulls in rocky intertidal habitats of the Aleutian Islands. Discontinuity between predictions and nature are the result of a model that does not consider foraging zone preference Prey TypeDensity (zone M) Density (zone A) Density (zone L) Search Time (s i ) Handling Time (h i ) Energy per Prey E i (kJ) Energy Gain (kJ/hour) urchins chitons mussels Energy gain when considering zones A and L only: Urchins: kJ/h Chitons: kJ/h