Exam 4 Flashcards
Cryptic coloration
Reduces the ability of a predator to find it
Countershading, disruptive colors, background matching
Countershading
often aquatic, dorsal (backside) is darker, ventral side is brighter to match brightness of ocean floor and surface
Ponyfish Countershading Example
Bioluminescent organ that illuminates the bottom side of the fish’s body
Disruptive Coloration
High contrast makes it difficult to tell foreground from background or to distinguish an animal
Example: cannot tell zebras apart when they are in a pack
Background matching
pattern blends in with the environment, some can change color to camouflage. Squid can do this despite being unable to see color
Predator Avoidance in Crabs Example
Crabs on shell-hash have higher survival
Placed crabs with two types of tile, one with shell-hash and one white
Small crabs preferred the shell-hash more than the large crabs
Large crabs preferred the shell-hash when predation risk was high
Caterpillar Defensive Example
Squeezed by wasp predators
Measured parasitism
Drop and bite measures were most effective
Startle display
sudden movement that exposes conspicuous colors or a sound to reduce attack rate by predators
Great Tit & Butterfly Example
The butterfly’s movement is retrained
Resting position is usually closed
The dead butterfly is positioned with wings open
Live butterfly exhibited startle display 75% of the time
The bird attacks the dead butterfly more quickly (latency was longer for live butterfly)
Wolves and Elk Example
In Yellowstone, wolves were reintroduced to the park
Elk behavior changes with the presence of wolves
Female elk spent more time vigilant and less time feeding when the wolves were nearby
Male behavior didn’t differ
Food patch risk
Rich food patches are riskier, more prey aggregated for predators to attack
Redshank Bird Food Patch Example
Salt marsh is twice as abundant with food as the mudflat
Proportion of birds on the salt marsh is higher when the temperature is lower—birds are warm-blooded, and therefore have to eat more in order to maintain their body temperature
Fiddler Crab Food Patch Example
Hides in a burrow, but must leave in order to mate
Control: no female present
The recorded how long the males stayed in their burrow in response to (fake) bird attack
When female was present, they reemerged much more quickly
Song Sparrow Example
Do changes in perceived predation risk affect song sparrow life history?
Researchers protected the bird nests from predation
Then they played vocalizations of common predators, four days at a time
Predation treatment females laid fewer eggs, had less offspring, and nested in denser vegetation
She decides to save energy for the next breeding season in response to the predation risk
Relationship between perceived predation and reproduction
Group living: main purpose
reduce predation
Dilution effect
when swimming with many other fish, the chance of being caught is much lower than if the fish is swimming solo in open water
Confusion effect
it is easier for the predator to follow and catch one fish instead of multiple fish
Selfish herd theory
the predators are more likely to kill the members on the outside of the social group, so individuals can reduce predation risk by moving to the center of the group
Hamilton proposed this theory as an alternative explanation to the popular hypothesis—that evolution of animal aggregation is based on mutual benefits in the population
- Grouping is a result of selfish motivation, not for mutual benefits
- The group mutual benefits are merely a consequence
Group size effect
vigilance behavior of individuals declines as group size increases
Predator harassment
rapid movement around a predator, often coupled with loud vocalizations
Squirrels Harassing Snakes Example
the squirrel moves around and flaps its tail, the tail temperature of the squirrel is higher when harassing a rattlesnake to make the tail visible (rattlesnakes have pit organs), its tail doesn’t heat up when harassing gopher snakes (which can’t see infrared)
Chemical deterrence
release of a noxious repellant
Ex: Skunks
Bombardier Beetle Example
Creates a noxious hot chemical
Sprays it onto parasites / predators
Sprays quickly enough that it does not burn the beetle, creates steam
Escape Behavior
Some animals show themselves to predators by stotting or tail flagging
Stotting: jumping movements, makes itself more visible
Pursuit-deterrence hypothesis
advertisement behavior informs a predator that it has lost the element of surprise, so pursuit will not be successful
Alarm signal hypothesis
advertisement behavior is a warning signal to other members of the group
Cheetah and Gazelle Example
The cheetah can run faster than the gazelle
However, the gazelle can run for longer
Therefore, the cheetah stalks the gazelles until they gets close enough to catch them
The gazelle stotts to make itself more visible before attack attempt
Tail Flagging Deer Example
Researcher stalked a deer and measured the tail flagging based on researcher’s distance from the deer
No difference between solitary and social deer, so it doesn’t support the alarm signal hypothesis
As the distance shortens, there is less tail flagging
Competition hypothesis
dispersal functions to reduce competition for resources
Inbreeding avoidance hypothesis
dispersal function to reduce inbreeding depression
Inbreeding Avoidance Great Tit Example
Individuals that mated with close relatives had dispersed the shortest from the natal site
Dispersal behavior influences likelihood of inbreeding
Supports inbreeding avoidance hypothesis
Breeding Dispersal Dragonfly Example
Those who have a higher mating success return to the same mating spot
Factors that affect dispersal
Reproductive success and public information affect breeding dispersal behavior
Breeding dispersal vs. site fidelity
Many species exhibit site fidelity after a reproductive success and exhibit breeding dispersal after a reproductive failure (win-stay lose-shift pattern)
Kittiwake Dispersal Example
Experimental group: All birds have their eggs taken by the researchers
Control group: only focal birds lose their eggs
Return rate of focal birds was higher when neighboring birds succeeded (control group)
Costs of migration
Opportunity cost
Movement
Benefits of migration
Food/vegetation, longer days, water availability, avoidance from freezing, heat, dryness
Arctic Tern Example
Species of seabird
Round trip migration between the two polar regions covering up to 50,000 miles each year
Breeds only in the North while the day is 24/7 (sun does not set)
Gives them the opportunity to grow quickly because the parent bird can forage for the entire day
Migrate to Antarctica during the time where the sun doesn’t set in order to maximize foraging time
True monogamy species
They have a navigational ability
Common Green Darner Example
Migration takes three generations to complete
North, south, non-migratory
Is migratory behavior hereditary?
Yes
Positive correlation between migration date of parent and offspring
Biological Clocks
Endogenous: clocks are brain nuclei and other organs
Ubiquitous: all species
Stable: very accurate
Entrainment: adjustment is required for error correction
Hamster Endogenous Example
Hamsters are nocturnal
Example of endogenous clock
Put the hamster in a constantly dark condition, and the hamster will still have almost the exact same routine
Free running rhythm: clock is freely running without the influence of light
Hamster Entrainment Example
Shift the dark period by 6 hours, eventually they will shift their activity after many days
Monarch Example
Monarch migration, capture and then watch the direction they fly in
Use the sun (like honeybees) to orient when migrating
Clock is in the antennae
Can shift their clock using the dark period shift technique
Photoreceptors on the antennae, which look at the light in the sky separately from their eyes
When their antennae are removed, they cannot determine the direction to go in
When they painted the antennae black so that light cannot enter, the clock shifted by 8 hours over the course of 11 days. This is because the free running period is 23.3 hours.
With clear paint, they maintain the correct phase
Navigation Example
Desert Ant Example
Temperature becomes extremely high, and it is difficult to find food
Go out, find the food, then return straight back
Using the method of path integration
Able to determine the best path back by remembering their number of steps and the curve of their travel
Move the ant, it will still go in (internal) direction of home in relation to the sun
Cannot determine position when moved, only direction
Navigation example
Orientation vs. Navigation
Orientation: determination of the correct direction/angle
Navigation: determining a location and moving toward it
Bird Star Compass Example
Birds that migrate at night can use the constellations to navigate
Chicks must observe rotating constellations and learn
Adults use the learned star position of Polaris to determine north orientation
No biological clock is necessary
Emlen funnel: put the bird in a funnel and see which direction they try to go
The birds were placed in emlen funnels at sunset, and then put in a planetarium
No matter the time, they try to go in the same direction
Did not use the angle of the constellation pattern, only Polaris direction
They put up a wrong artificial constellation pattern, the bird will still know which is the center of the rotation and use it as a guide
Navigation example
Eurasian Reed Warbler Example
Not known how they navigate
Take the birds 1000 km east, they are able to still go to the correct migration spot, knew they were misplaced
Theory that one of their biological clocks is entrained to the new location, not fully known
Sea Turtle Example
Born in Florida, migration movement within the Atlantic Ocean
Use magnetic fields for orientation during migration
Treatment: altered magnetic field
Control: normal magnetic field
Measured movement and orientation
They try to go back to the path
Use both inclination angle and intensity
Purpose of sex
maintenance of genetic diversity and variation
Two-fold Cost of Sexual Reproduction
Only females bear offspring in sexual reproduction
With asexual reproduction, all organisms can produce offspring individually
intrasexual selection
Mate competition is intrasexual selection (compete with members of the same sex)
intersexual selection
Mate choice is intersexual selection (selection by one sex for members of the other sex)
Bateman’s Hypothesis
female reproductive success is most strongly limited by the number of eggs that she can produce, male reproductive success is limited by the number of mates
Results in male-male competition
Parental Investment Theory
The sex that has the greater investment (pays higher cost) in offspring production should be choosier when it comes to mates
Simultaneous hermaphrodite
produces eggs and sperm at the same time
Flatworm Example
Simultaneous hermaphrodite example
Ovary is not connected to the outside, body must be punctured by the other flatworm’s penis, a puncturing strike anywhere on the body can inseminate the eggs
Flatworms want to act as the male because it is more advantageous, don’t have to go through pregnancy
Sex role reversal
males invest more in reproduction and parental care, males are choosier
Male pregnancy
the male carries the offspring ex. Seahorses, pipefish
Pipefish Example
Male chooses brightly colored females
Sex role reversal
Dung Beetle
Mate competition
Female lays eggs on the dung ball
The males fight each other for the female
Sexual selection: peacocks
Tail length and number of spots correlate with mating success
Female choice benefits
get both direct (food, gifts, territory, etc.) and indirect benefits (genes)
Nuptial gifts
Male will sometimes try to steal back the nuptial gift
Spermatophore as a nuptial gift, fluid will be digested within her body and used for nutrients
Correlation where if she eats larger spermatophore, she produces larger eggs
Lizard Territory Example
Female prefers the male territory with more rocks, higher reproductive success
Exaggerated male traits derived from sexual selection
runaway process
Keeps becoming exaggerated until it develops negative consequences, natural selection selects starts to select against it
Female choice examples
Tadpole Example
Correspondence between growth rate and attractiveness
Guppie Example
Both good gene hypothesis and runaway process
Preexisting attraction to orange color
Good genes hypothesis
Females choose males with an exaggerated trait that accurately (honestly) indicates males’ genetic quality
Mate guarding
male prevents female from leaving and mating with another male and having extra-pair young
Damselfly Mating Example
Penis is designed to remove sperm from other males before mating with the female
Cryptic female choice
able to control the sperm’s success
Inbreeding depression avoidance
