• Comparing traits among species
• Without phylogeny
– Relate behavior to ecological factors across spp. or populations
• E.g., Eggshell removal
– Problems
• Causation?
• “Cherry picking” examples that support hypotheses
• Confounds, like size, phylogeny

• Body size is an important confound in comparative studies
• Scaling one body part against another is tricky
• Allometry is the study of the relationship between body measurements
• log(Y)= b log (X) + log (a)
• Slope (b) > 1 means Y increases faster than X
– “positive allometry”
• Comparing residuals is informative

• Phylogenetic inertia
• Homology
– Common descent
• Homoplasy
– Convergence
• Determining ancestral characters
– Maximum parsimony
• Problem of equal parsimony

• Looks for relationship between two continuous variables while controlling for phylogeny
–Examples
• Assumes random change, independent changes in different branches

• Discrete variables
– E.g., duetting and monogamy
• 1 st model: State changes in two variables are independent (a)
• 2 nd model: State changes are interdependent (b)
• Can find most likely direction, order

• Chemical messengers secreted in one part of an organism that affect a relatively distant part of that organism
– Work in conjunction with neurotransmitters
– Work in concert with nervous system to control behaviour
• Relative to nervous system, slower and more general

• Negative feedback
– Like a thermostat
– The male hypothalamic-pituitarygonadal (HPG) axis
• Gonadotropin (GnRH) in hypothalamus  follicle-stimulating hormone (FSH) and leuteinizing hormone (LH) in pituitary  sperm and testosterone (T) in testes  rising T reduces output of GnRH
• Positive feedback
– Oxytocin release during labor
• Pressure on cervix  Oxytocin release  Stronger contractions…

• Transported in the blood
• Affect remote cells by binding dynamically to receptor molecules
– Protein hormones bind to surface receptors
• Rapidly alter cellular behavior
– Steroids (lipid hormones) pass through the membrane, bind to a receptor and affect transcription
• Generally slow, but fast-acting steroids challenge model
– Mountain chickadees and CORT

• Hormone levels in blood
• Binding protein concentration
• Receptor density
─ Up- / down-regulation in response to concentration
─ Pulsatile hormone release limits receptor regulation
• Hormone conversion by enzymes
• T  oestrodiol in brain by P450 aromatase
• Chaperones that modify effects of hormones on receptors

• Radioactively labeled sex steroids accumulate at similar brain regions in rats, frogs, and chaffinches
• Preoptic, limbic, & hypothalamus
• Neural firing rates correspond to hormone presence
• T injected directly into male mouse brains
• Median preoptic area
• + vocalization
• + urine marking
• + mounting
• Hypothalamus
• + urine marking
• Other regions
• No increase in sexual behaviour

• Hormone secretion is dynamic
– Responds to environmental cues
• The “challenge hypothesis”
– Male green tree frogs
• Human males, coin flips, and T

• Gonads (testes and ovaries) develop from bipotential tissues
– The gonads mediate further differentiation
• In most mammals
– XX  Female, XY  Male
– SRY region on Y is major gene for sex determination
• SRY product leads to a cascade that results in testes
– Otherwise, ovaries
• Other genes on Y involved in spermatogenesis
• Snakes, birds, and some lizards and turtles
– ZZ  Males, ZW  Females

• Incubation temperature influences the expression of cytochrome-P450
• Cytochrome-P450 converts testosterone and androstenidone into oestrogen hormones
• The amount oestrogens in the gonad directly influence differentiation

• Critical regulatory pathway
– Growth, stress, sexual behavior, etc.
• Generally, cascade runs
H  P  G
• Develops in reverse
– Lower levels control development of higher levels
• Brains pretty well shuts down
HPG in infancy
• HPG kicks in at puberty

• As they relate to sex and the brain
–Organizational effects of hormones in early life differentiate male and female brains
–Activational effects later in life facilitate expression of sex-specific behaviours

• SDN-POA in hypothalamus is up to 5 x larger in males
– Lesions disrupt copulatory behavior in males
– Lesions + female sex hormones cause males to exhibit lordosis
• Dominant female hyenas pass more androgens to their offspring
– Early androgens  aggression
– Masculanization of females http://www.eurekalert.org/multimedia/ pub/web/716_web.jpg

• Tree lizards exhibit permanent organizational effects and reversible activational effects
– Males plain orange dewlap are non-territorial
– Males with orange dewlap & blue spot are territorial
• Higher T and progesterone as juveniles
– Critical period
• Adrenal origin suggests association with stress
– Activational effects on spotless males
• When stressed, they go nomadic
– Low T, high Cort
• When not stressed, they are sedentary
– High T, low Cort
• Can go back and forth

• Stress in rats
– Daughters of mothers stressed during pregnancy secrete more Cort when stressed response relative to controls
• Their HPA axis has been sensitized during development
• Potentially adaptive maternal effects in birds
– T helps male offspring grow faster

• Embryonic rats are exposed to their sibs hormones
– Females b/t males mount more, have different genital structure
– Males b/t females are more active, less sexual, and respond with less aggression to T injections in adulthood

• T stimulates male to court
– Interacting with female increases his T
• Courtship stimulates female to release FSH, stimulating follicle development
– Female’s own “coos” necessary
• Interacting with the nest stimulates progesterone in females
• Increasing LH stimulates female to lay
• Progesterone maintains incubation in both sexes
• Incubation stimulates secretion of prolactin
– Inhibits FSH and LH
– Stimulates crop milk production
• Prolactin decreases while feeding young
– Allows FSH and LH to rebound for next mating