Lecture 3: Selection and Domestication

What Shapes the Behavior of Animals?

-wild animals=forces of evolution=selection (natural), random drift, mutation, gene flow between populations

-domestic animals=forces of evolution+selection (natural, artificial, relaxed)

Artificial Selection

-controlled by humans, not nature

-is “goal-oriented”, whereby animals with a desirable phenotype are bred

-effects can be extremely rapid

-unintentional artificial selection=turkeys being unable to naturally breed (unintentional traits that become a part of a breed/species)

Relaxed Selection

-in domestic animals, certain behavioral adaptations important in nature are no longer relevant

-relaxed pressure drives these traits in the opposite direction

-ex=anti-predator behavior, response to novelty, foraging

Domestication

-a process whereby populations of animals change genetically and phenotypically

-driven by selection pressure based on human-desired traits

-an evolutionary process driven by selection pressures

Domesticated

-a permanent genetic modification that can lead to predisposition to associating with humans

applies to whole species

Tame

-a conditioned behavioral modification at the individual animal level

Why Domesticate Animals?

-economic=income, financial asset, social value (dowries)

-food and fiber production

-draft work

-hunting and/or sporting

-control of another species

-religious ceremonies

-war

-guide and working animals

-human companions

-scientific research

-protection

Desirable Features of Domestic Animals

-useful to humans

-adaptability (comfort-loving)

-hardiness

-inborn liking for man=mutually understandable social behaviors

-ability to breed freely in captivity

-ease of tending

Behavioral Traits That Facilitate Domestication

-social behavior=live in groups, have dominance hierarchies, territorial behavior is minimized, regular social grooming activities (allows humans to function as group members and take a dominant role)

-juvenile characteristics=temperament, dependency, curiosity in novel situations, quick learning, willingness to associate with other species

-adaptability and activity=wide environmental tolerance, absence of specialized dietary needs, limited agility, small home range

-sexual behavior=promiscuous matings, clear sexual signaling behaviors between males and females to indicate reproductive status, able to breed freely in captivity

-precocial development=young are relatively mature and mobile from the moment of birth or hatching (some exceptions in predator species), initial rapid, strong bonding of dam and young, young can be separated from parents at early age

-response to humans=tame-able/readily habituated, short-flight distance from man, non-aggressive toward humans, readily controlled, attention seeking

Physiological and Physical Changes From Domestication

-increased variation in coat color, horns, hair coat

-decrease in ratio of brain size to body size

-change in body size

-skeletal changes

-faster growth rate and changes in pattern of fat deposition=surplus fat tends to be deposited throughout muscle in domestic species and around internal organs in wild species

-increased muscle, milk production, or other economically favorable changes

Neoteny

-the retention of juvenile characteristics in the adult

-a major genetic change of domestication

Behavioral Changes From Domestication

-loss of self sufficiency

-less adaptable to changes in environment

-loss of pair bonding

-loss of broodiness in chickens and turkeys

-reduced flightiness and aggressiveness

-increased juvenile characteristics