Is the Lion’s Mane a Signal?Is this a “signal”? “What” might it signal? Is it “honest”? & if so, how is that “honesty” regulated?-> Manes are Sexually Dimorphic, Develop at Puberty,& are Highly Variable in color1Hypothesis? Mane indicates Male Quality• How would you test this?• What would your predictions be in terms of Female and Male response towards Stimuli with different Mane Color/Length?• What is causing this variation in signal (mane color/length) and how is it linked to male quality? (IS this signal honest?)• How would you test whether the variation in mane color/length was genetically/environmentally determined? (a product of Nature or Nurture?)2• Manes lengthen and darken coincidentally with age-related rises in serum testosterone.Analyzing 568 Photographs from subadult and adult malesMane DarknessMane LengthSerum TestosteroneAGE (yrs)West & Packer, 20023Predictions? Females:1) 9/10 Females approached models with:Darker colored Manes2) (no sign diff withSignificant Difference Between Male and FemaleResponse to ModelsMane Darkness P = 0.002Mane Length= P. 0.018(Fisher’s Exact Test)4Movies• SCIENCE vol 297 (23 August 2002): pp 1339-1343 West & Packer• http://www.cbs.umn.edu/lionresearch/research/mane.shtml• Use HIGH WIRE PRESS (option)• Supporting Online Material• www.sciencemag.org/cgi/content/full/297/5585/1339/DC15Why (ultimately) would females want Darker-Maned Males?• Females can gain DIRECT Benefits from preferring superior males• Fathers protect their cubs from infanticide• Males can provision an entire pride by capturing large prey (Buffalo or Giraffe)• Dark-maned males have greater ‘staying’ power in the pride. This leads to higher survival rates for yearlings of dark-maned males.• **Annual Survival rates for yearlings were Higher for offspring of Dark-maned COALITIONS.6Infanticidehttp://www.lionresearch.org/behavior_guide/infant.htmlQuicktime video of male lion committing infanticide. WARNING: This video contains disturbing content.http://www.youtube.com/watch?v=17hGhaE0YgU&feature=relatedhttp://www.youtube.com/watch?v=T8cnEXIwjWAhttp://www.youtube.com/watch?NR=1&v=17hGhaE0YgU7What we know so far:• …the mane might have evolved to signal male quality• It appears to be an honest indicator of Testosterone level which regulates hair growth & melanin production & male aggression• Is this ‘signal’ genetically or environmentally determined?• How would you test this?8Looking for a genetic link:• With photos –they measured the correlation between father and son mane color/length• Limiting the analysis to Males over 4 yrs, Could find no measurable signs of heritability in either aspect of the mane (color or length)Slope of line is estimate of h2Father’s mane colorson’s mane color9IF Mane color was 100% geneticson’s mane colorFather’s mane colorIF Mane color was 100% environmentalHealthy Serengeti Male in March 1999same Male in Jan. 2000 after developing an infection post-injuryFound variations in length and color were associated with injury, testosterone, & Nutrition.10Is the Lion Mane color a signal & how is it regulated?• Mane color is physiologically linked to testosterone & conditional state• Both males and females display differential behavioral responses towards this conditional trait in ways that may increase their reproductive success• Current analysis suggests that there is no genetic regulation of mane signal…but are you convinced?11Questions• Are behaviors a product of Nature (innate/fixed) or Nurture (environment)?• How can single genes influence complex behaviors?• Why might some behaviors be regulated by environment for some species & regulated by genotype in another?• What are the mechanisms that regulate behavioral plasticity?• What are the molecular mechanisms by which the environment might alter behavioral phenoytpes?Table 10.1 Levels of analysis in the study of animal behavior(1) What is the mechanism producing this behavior?&(2) What is the basis of its development?(Nature vs Nurture)Nature vs Nurture• What has more influence on trait development?• ALL Traits are really a combination of the Two • Even for physiological traits that develop early on where the environment is considered the womb• But some traits are more affected by the environment then othersNature • Konrad Lorenz was one of the First Ethologist to propose that behaviors resulted from Innate (fixed) and acquired (environmental) elements• What do we mean by the term Innate?• Bateson (1999) identified 7 meanings:• Present at birth• Genetically determined• Unchangeable throughout development; not influenced by environment• Present before the behavior serves a function• Not learned• Adapted over the course of evolution• Shared by all members of a speciesHow to measure the effects of genetic variation on behavioral variation1) Cross-Fostering Experiments 2) Hybrid experiments3) Common Garden Experiments4) Selection Experiments 5) Single Gene Effects/Knockouts6)Transgenic experiments161) Cross-Fostering ExperimentsGreat tits & Blue Tits• Examined male’s ability to successfully pair with a conspecific in a cross-fostering experimentIs mate selection driven by genetic or environmental factors?-------------------------The Nature vs Nurture Continuum(mate selection)<----Mate Preference----Nurture• Great Tits• Males reared by Another species try to Find mates of that ‘foster parent’ speciesNature • Blue Tits• Males reared byFoster parents seekout their Own speciesfor a mateCross-fostering has different imprinting effects in two related songbirdsWhat other Behaviors might have Influenced the outcome of this experiment?Different wintering sites:Are these migration routes heritable?Funnel cage for recording the migratory orientation of captive birdsMeasure migratory activityInk padPaper coneMeasure migratory activityF1Cross individualsHybrid Studies:BetweenPopn.Southern Germany PopulationAustrian Population2) Hybrid Experiments• Migration**Finding Hybrids thatShow Intermediate BehaviorIndicates that it is (a) genetic, (b) Only a few genes,(c) no dominant genesA coastal Californian garter snake about to consume a banana slug3) Common Garden Experiments• Prey Selection in Garter SnakesCommon GardenExperiments areUsed to test theNature vs NurtureQuestion. When differences PersistIndicates that genetics has major