Behavioral Ecology Flashcards
behavioral ecology
study of ecological pressures that impact evolution of behavior
Four ways evolution has been used to study behavior
- Historical/phylogenetic approach
- Testing adaptive value through experimentation
- Comparative approach
- Predictive approach
Historical/phylogenetic approach
involves reconstructing evolutionary history of behavior –> find behavioral “homologies”
ex. Kettlewell Peppered moth
Testing adaptive value through experimentation
involves determining adaptive value of behavior
Comparative approach
relies on comparing species w/ similar ancestry but living in different environments AND/OR comparing species with different ancestries but living in similar environments
ex. Darwin’s finches
Predictive approach
involves setting up hypotheses derived from evolutionary theory –> testing them with behavioral data from extant species (ex. optimality models)
Peppered moth (Kettlewell)
- trend since early 19th century –> peppered moth once mostly light-gray individuals –> now dark gray in industrial areas (light-gray in rural)
- place moths on trunks in both environments –> mark-recapture across 2 nights –> crypsis (camoflauge advantage)
Crypsis
camoflage or protective appearence of an animal
Of Moths and Men (2002)
- implied Kettlewell comitted fraud, popular with opponents of evolution
- ignores much subsequent research confirming Kettlewell’s results
Blue jay (Pietrewicz & Kamil)
- peck if see moth on video, can be trained
Convergent evolution
similar selection pressures despite different lineages
Divergent evolution
different selection pressures despite same lineage
Darwin’s finches
natural selection shaped bills in accordance to diet
Cactus & Ground Finches (Peter & Rosemary Grant)
- studied Darwin’s finches for 40+ years
- noticed changes in adaptive success of finches based on environmental changes
- Medium ground finch: 4% increase in beak size across 2-year period due to drought affecting food availability
Who said “nature red in tooth?”
Weiner
1982 Medium vs. Large Ground Finch
- larger species arrives in Daphne Island –> eats most of the larger, thorny seeds of puncture vine plants – pushing medium finches to rely on smaller seeds
- medium ground finch that did not compete with larger species performed better + more likely to have surviving offspring –> overall smaller beaks
Adaptive value of mobbing in gulls (Kruuk)
- Bank swallow & other colonial smallows + Ground nesting gulls: distinct ancestry, shared mobbing behavior (both lay eggs on ground)
- Ground-nesting gulls + Kittiwakes: shared ancestry, divergent behavior (Kittiwake nests on cliffs)
Principle of Parsimony
Simpler scenarios involving fewer transitions preferred
African Weaver Birds (Crook 1964)
- found that they could be divided into two groups:
GROUP 1 : forest, insectivorous, solitary nests, feed alone in large territories, drab color, monogamous
GROUP 2 : savannah, seed eaters, nest in colonies, feed in flocks, males brightly colored, polygamous
- food abundance and distribution thought to be main selective pressure
African ungulates (Jarman 1974)
- divided ungulates into 5 classes (dikdik, reedbuck, gazelle, wildebeest, buffalo)
- organized based on :
- body weight (low –> high)
- habitat (forest –> grassland)
- diet (browsing –> grazing)
- group size (solitary –> herd)
- reproductive unit (pair –> male dominance hierarchy in herd)
- antipredator behavior (hide –> defense)
- Gut size is important component to efficient digestion of foliage
- as body mass increases, volume of gastrointestinal tract increases
Kieft (2017)
abundance and diversity of animal-associated microbes scale with individual animal mass
Ungulate videos
Plants
* ungulates able to consume with head up to watch for predators
* ungulates form unique niches to reduce competition for resources
* elephants able to reach top of akashia trees with few thorns, stomachs allow for long digestion
Predators
* ears can be rotated to hear sounds from all directions
* noses and sense predators
* head down –> eyes can swivel to see in fron tand behind to sense danger
* predators’ eyes pointed ahead to sense range
* prey stalk predator –> taunt hunter to prevent surprise attack
* North American pronghorn fastest animal for long distances
* jumping use to distort predators
* slim legs –> easy to trip
Older hypotheses on egg shape
- clutch size (shapes optimized for sharing warmth in)
- calcium conservation (spherical eggs have less surface area –> conserve calcium where mineral is rare)
- roll factor (conical eggs less likely to roll off cliff)
Caswell (2017)
- looked at asymmetry and ellipticity of eggs –> partitioned egg variation among avian orders (largest is Charadriiformes)
- most Charadriiformes live near water + eat invertebrates/small animals
- found that:
length of egg correlates with bird body size
shape of egg (asymmetry/elliptical) relates to flying habits
stronger bird’s flight –> more asymmetrical/elliptical eggs (likely due to pressure on pelvis –> round eggs require wider pelvis)
HWI
- “hand-wing index”
- measure of wing shape (wing length to width)
- high HWI linked to long distance flight ability
Spotted Hyenas (Kruuk)
- Serengeti usually nomadic and scavengers
- Ngorongoro Crater live in large groups to defend + hunt prey
- When prey high in Serengeti, hyenas form social groups + hunt (facultative behavior)
Flexible social systems: hamadryas and gelada baboons
- gelada =/= actually baboons
- hamadryas part of genus Papio
- Papio: social groups, maintain similar social organizations
- Hamadryas: large social groups –> split into smaller groups to forage (1 male, many females)
- environment influences social structure
Testes size and primate mating systems
- correlate body weight w/ testes weight
- multi-male reproductive systems tend to overperform (larger testes than projected trend)
Correlation between brain size and intelligence: model species
Dolphins, baleen whales
* Baleen whales: mouth type enables filtration, low effort
* Dolphins: body shape enables herding, requires strategy and coordination
Dorsal stripe morphology as an adaptation to predation in Timema walking stick insects (Sandoval & Crespi)
- 2 species, feed on two different leaf types –> white stripe adopted by needle-feeders to blend in
- comparative study on all 21 species –> Timema walking sticks evolved dorsal stripe 5-6 times independently (each time associated with shift to needle-like plants)
- ecological experiment tests selction w/ & w/o stripes in diff environments –> striped has higher survival on needle leaves
Predictive method
setting up hypotheses derived from evolutionary theory –> test with behavioral data from extant spcies
natural selection should, over time, make animals efficient at tasks critical to survival & reproduction –> “optimality models” of behavior
Behavioral ecology and optimality approaches: animal economics
- currency of fitness (& its proxies)
- “decisions” by animals
- constraints on decisions
- competition
- social behavior
- predation
- sex & mating
- reproduction & parental care
- costs of adornment & signaling
Crows & whelks (Zach)
- coastal crows feed on whelks by dropping them from air onto rocks below –> do the birds use a dropping height that minimizes the total energy expenditure in upward flight?
- in general, largest size possible chosen –> break @ lower heights
- all eventually plateau at around 5m in # of drops
Animal Behavior (Alcock)
“This seems adaptive. Case closed.” –> assumes must be about genes –> must see differences between environmentally separated groups of crows (exposed to whelks and not) to determine genetic role
–> “At first, this behavior appears to be adaptive.”
Starlings @ the nest (Kacelnik)
- “economics” of foraging
- How many items should the parent bring on each trip in order to maximize the rate of delivery of food to the nestlings?
- central place foraging (nest)
- “Marginal value theorem” - diminishing returns –> plateau
Dungfly copulation time (Parker)
- problem of the second male (want to guard to increase chance of parenting offspring)
- consider guarding time in optimizing copulation time (before pursuing another female)
- predicted: 41 min, observed: 36 min –> lead to issues regarding optimality models’ accuracy
Critics of Optimality Approaches
- Pierce & Ollason: problem of seeking agreement to models –> poorer data more likely to support models, many fits to predictions might disappear if more data were available
Scientific principle of falsifiability (Popper)
- scientific hypotheses can only be empiracally tested by trying to disprove them
- however, seeking agreement w/ predicting rather than challenging –> confirmation bias
African Golden-Winged Sunbirds: nectar & territoriality (Gill & Wolf)
- undefended flowers –> less nectar for birds/flower
- if undefended foraging time = territory foraging time –> no benefit –> sunbirds abandon territorial behavior completely if it becomes uneconomical to defend flowers
Evaluating optimality models: advantages
- generate testable, quantitative predictions
- assumptions need to be made explicit (ex. starlings optimize rate of delivery)
Evaluating optimality models: disadvantages
- what if behavior does not fit prediction?
- what if animals are not optimally adapted? (environmental changes, insufficient genetic variation)
- “good enough” vs. optimal
- assumption of genes “for the behavior”
- constraints on optimality
