Week 1: 02 Behavior Flashcards
House finch
A moderately-sized finch
Found in North America
Males are more brightly coloured than females
Male coloration varies in intensity with the seasons
The colours range from pale yellow through bright orange to intense red.
Dr. Geof Hill
Professor & Curator of Birds
Auburn University
Geoff leads an integrative research program investigating the function and evolution of animal ornamentation.
The Hill group addressed the nature of differential plumage coloration in male and female house finches.
Cartotenoids
Lipophilic biochemical
reflected colours: yellow, orange, red and pink
Animals lack the ability to synthesise carotenoids from precursors
they must obtain them from their diet
In males,
Cartenoid-rich diet leads to….
Cartenoid-poor diet leads to….
Males with bright coloration
Males with drab coloration
Hill’s work demonstrated that at the proximate level, differences in male plumage were correlated with the amount of carotenoids in their diet.
In females
Cartenoid-rich diet leads to….
Cartenoid-poor diet leads to….
Females with brighter plumage
Females with drab plumage
- Females in the carotenoids treatment developed much brighter plumage.
- There is between-population differences in female plumage coloration.
- The more such food is present in the environment, the brighter the average females is in a population.
Females vs Males in regards to diet.
Males actively search for and ingest catenoid-based foods, where females eat carotenoid-based foods, but they don’t actively search for such food.
So the sexual differences in plumage coloration does not result from the availability of cartenoid-based foods.
Rather, the differences in foraging strategies explain the sexual differences in plumage coloration at the proximate level.
Ultimate questions for differences in plumage coloration
Why do males, but not females, actively search for carotenoid-based foods?
Hill hypothesized that males receive significant benefits for having colorful plumage, but females do not.
But what exactly were these benefits?
Plumage manipulation experiments
Males that had their color experimentally brightened were much more likely to get a mate than males whose color had been experimentally lightened.
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Bright males are more attractive to females than drab males.
Ultimate question: Are there benefits for females that choose males with brighter plumage coloration?
Plumage is an indicator of male quality
Brighter males are good fathers with respect to feeding young
Brighter males are good foragers and produce sons that are good foragers.
Pathogen inoculation experiments
Males with more elaborate plumage coloration were able to rid themselves of the pathogen more quickly than drab-colored males.
Colorful males that had been selected as mates had lower levels of bacteria that degrade the quality of feathers.
Male feeding statistic
The mean number of times a male fed a chick at his nest was positively correlated with the intensity of his plumage coloration.
Brighter males fed chicks more than twice as often as drabber males.
Plumage coloration inherited or acquired?
Coloration can’t be inherited, its diet dependent.
Proximate perspectives/causes
“how” or “what”
related to the immediate causation (stimulus and mechanism) for the behavior
address the genetic, physiological, and anatomical mechanisms underlying a behavioral act.
Ultimate perspectives/causes
“why”
related to the survival and reproductive success of the animal.
address the evolutionary significance of a behavior.
Levels of questions: proximate vs ultimate
Proximate questions:
- What causes the variation in male plumage in the house finch?
- What causes differences in plumage coloration between males and females?
Ultimate questions:
- Why do males, but not females, actively search for carotenoid-based foods?
- Why females prefer males with bright plumage?
Both levels of analysis are equally important
Proximate and ultimate explanations complement each other.
