Chapter 6

7 Pages
Unlock Document

Biological Sciences
Maydianne Andrade

Chapter 6 Darwinian Puzzles • Some species make it known to themselves to predators o Traits that seem to exceed their benefits are darwnian puzzles • Monarch butterfly: orange and black spots make it easy to spot o Monarch larvae feed on poisonous milkweed o Dead individuals educate predators so genetically similar monarchas pass on shared genes to the next generation o Alternative hypothesis: monarchs are so bad tasting that birds will release monarch after grabbing it • Ephritid fly: waves banded wins as if trying to catch the attention of predators o Wing markings resemble the legs of jumping spiders (fly predators)  Wing movement produces a similar effect to spides o Test hypothesis o Swap wings with clear-winged houseflies  Clearwinged mutants got eaten  Houseflies got eaten – combo of pattern and wing movement • Thomson’s gazelle – stotting: leap into the air o To scan ahead for unseen enemies lying in ambush o Anti-ambush hypothesis: stotting does not occur in short grass but reserved for tall grass habitats  However, short grass gazelles stott o Alarm signal hypothesis: warn others that predator is near o Social cohesion: stotting enables gazelle to form groups and flee in a coordinated manner to make it hard to cut them o Confusion effect: individuals confuse and distract following predators o Pursuit deterrence: announce to predator individual is in good health and is unlikely to be captured o Single gazelles stott – eliminate signal hypothesis – no need to warn  Eliminate confusion hypothesis: does not confuse  Social cohesion theory: should head towards other gazelles, but the rump is towards predators • Announce to predator they are hard to capture o Comparative method: look at other species that stot o Honesty of method of uncatchability  Anolis lizard: push up display when it spots a snake • Time spend running was correlated with push ups done • Moth – produces loud ultrasonic clicks when the muscles pull the tymbals in o Bats can hear ultrasound o Other moths are poisonous  Bats associate clicking with poison o Egle does not have to invest in metabolic equipment to store toxic but can still educate bats with acoustic deception • Birds and rabbits – calls while in crutches of predator o Perhaps product of ability to feel pain o Scream may startle a predator to release its prey  However birds continue to scream long after caught o Screams may warn of danger  However, members of species ignore – if predator is occupied, then no risk for others o Capture animals scream to attract other predators to the scene  Confusion model – to enable prey to escape  Attract-competing predator hypothesis predict that birds in dense cover give more screams than open habitats • Dense cover require calls for others to locate  Sounds convey health and condition of the caller • Distress call show health to suggest whether recapture is likely to reevaluate catching it in the first place Optimality Theory and Antipredator Behaviour • Fitness costs and benefits o Net benefit of a trait rather than whether or not a trait provides a benefit  Adaptation has more to do than merely confer a benefit o Adaptation is better than alternatives – better = net benefit is greater than nonadaptive features • Optimality Theory o Adaptation = greatest benefit  Optimal trait o Strongly used in foraging behaviour since it is possible to measure both costs and benefit in the same units – calories from food vs. calories expended • Antipredator behaviour o Bobwhite quail in groups of coveys 2-22 – peak at 11  Covey are safer from attack (higher overall group vigilance)  Benefits are offset by competition for food • Large group move more than groups of 11 o Small groups move even more to find groups of 11 Chapter 7 • Animals are good at postponing their demise, so predators have to overcome a series of obstacles to get to food o Hunting skills are the product of pretty defenses Optimal Foraging Behaviour • Crows: clam, snail, mussel, whelk – picks it up into the air and drops it to eat exposed eat o Foraging crows have certain behaviours  Whelks only 3.5-4.4 cm long  Fly up to about 5 meters  Kept with chosen whelk until it broke o Predictions for observed behaviour  Large whelks are more likely to shatter  Drops less than 5 meters yield a reduce break rate  Probability of whelk breaking is independent of the times it has already dropped o Predictions tested  Large whelks required less 5 meter drops before breaking vs. medium or small ones  Probability of whelk improves as the height dropped, but beyond 5 meter does not increase  Probability of breaking a whelk is not better after on next attempt – finding new pray requires more energy  Net calorie gain of big whelk – 1.5 kilocalories, medium whelk is a net loss of 0.3 kilcalories • Fitness as a function of energy gained per unit time • Zebra finches: highest daily net caloric gains survived best o Decrease seed intake take longer to lay their first egg • Sandpiper: need horseshoe crab for food o Over harvest of horseshoe crab led to decline of population  Those that survive the migration are heavier to start to secure fat stores for later How to Choose an Optimal Mussel • Oystercaster: optimal calculation: bigger mussels should provide more net caloric gain – but they do not prefer the really large ones o Hypothesis 1: profitability of large mussel is reduced because some cannot be opened which reduces average return  However, optimization should be at 50mm mussels but 30-45 is more preferred. o Hypothesis 2: large mussels are covered with barnacles which makes them impossible to open  Larger mussels has higher chance to acquire impenetrable coats of barnacle • Prey opening time
More Less

Related notes for BIOC54H3

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.