BIO 240 Chapter 1, Spring 2014

Animal Behavior Introduction Purposes of studying animal behavior • Utilitarian: for dealing with: – Animal production p – Hunting and fishing – Pest control • Environmental: – Dealing with conservation issues – Understanding ecological relationships • Scientific – Understanding evolutionary processes – Relating behavior to neurobiology • Social and psychological: – Understanding human behavior How is the study of animal behavior approached? We can illustrate this using examples. Monogamy in The prairie vole • Monogamy = staying with one mate for an entire reproductive cycle, or lifetime ) • The prairie vole (Microtus ochrogaster) is monogamous. • Many other species of voles are polygynous (mating with many females) Q ti Wh i th i i l Question: Why is the prairi vole monogamous? This Question could be approached from more th ti than one perspective; Neurophysiological Basis (Larry Young, Emory University) • When a vole copulates, some brain cells � vassopressin in bloodstream • � ventral pallium Parts with many vassopressin‐ binding cells appear black in binding cells appear black in this brain section treated in a certain way . • Pallium: anatomically distinct brain “center” containing vassopressin‐binding centers. • (Pallium = structure found at base of brain in various species; responds to hormonal signals.) Neurophysiological Basis (Larry Young, Emory University) • Receptor proteins in the ventral pallium, (called Vl‐a receptors), bond with vasopressin receptors), bond with vasopressin �chemical events � trigger activity in the receptor‐rich cells �affecting neural pathways in brain �positive feedback for the vole (rewards) �Male encouraged to remain in the company of his mate �a long‐term social bond with her • V1‐a receptors not as numerous in other polygynous voles. (not as much reward � move to another mate.) Genetic Basis (Larry Young, Emory University) • V1‐a receptor protein, encoded by V1‐aR gene. • One segment of the DNA is lacking in polygynous voles • One segment of the DNA is lacking in polygynous voles. • Inserting prairi vole’s V1‐aR gene in polygynous voles’ brain cells � genetically modified voles � pair‐ bonding. Significant preferences for familiar partner when given V1aR Choices of partners by male voles Cp = caudate putamen, VP= ventral pallium. LacZ=gene different from V1aR Therefore, V1‐aR � monogamous behavior. Evolutionary Basis: 1. Selective processes (Jerry Woolf, Memphis State Univ.) • Monogamous males leave more offspring than others? • Benefits; Benefits; – Keep females from copulating with other males. • 55% of females copulate with other male, if males prevented experimentally from pair‐bonding. – More reproductive success – Males with this behavior will sire most of the female’s off‐spring off spring – � selective advantage � more voles with this behavior. • Costs: losing mating opportunities. Evolutionary Basis: 2. History • Requires tracing sequence of events � monogamy. – Examining ancestry of vole species. – Most probably ancestors were not monogamous (most mammals are not)� evolution of monogamy – Tracing ancestry via phylogenetic tree. • e.g. Comparing DNA sequences in various species � phylogenetic tree. Evolutionary Basis: 2. History • Vole phylogenetic tree. Shifting back to polygyny Origin of monogamy Levels of analysis Researchers had the following approaches: 1) how a gene contributes to the development of the behavior 1) how a gene contributes to the development of the behavior in male voles, 2) the physiological foundation for the behavior in terms of the operation of the male vole's brain, 3) the adaptive value of the behavior in terms of its contribution to male reproductive success, and 4) the transformation of a polygynous ancestor into the monogamous modern prairie vole Levels of analysis Proximate Causes Proximate Causes Ultimate Causes Ultimate Causes 1. Genetic‐developmental mechanisms Effects of heredity on behavior Development of sensory‐motor systems via gene‐environment interactions 2. Sensory‐motor mechanisms – Nervous systems for the detection of 1. Historical pathways leading to a current behavioral trait – Events occurring over evolution from the origin of the trait to the present 2. Selective processes shaping the history of a behavioral trait – Past and current usefulness of the behavior in promoting lifetime – Nervous systems for the detection of environmental stimuli – Hormone systems for adjusting – responsiveness to environmental stimuli – Skeletal‐muscular systems for carrying out responses be a o p o ot g et e reproductive success Evolution Evolution e factors e factors ve reproductive success ve reproductive success Natural Natural Selection Selection Ultimate Ultimate Need to improv Need to improv - Selection for improved Selection for improved reproductive success reproductive success - Usefulness of the behavior Usefulness of the behavior Animal’s lifetime Animal’s lifetime Adaptation Adaptation Proximate factors Proximate factors Use of Use of adaptation adaptation Establishing pair bond Establishing pair bond Genetic mechanism Genetic mechanism Sensory Sensory--motor motor mechanism mechanism Scientific Study of Animal behavior •Theory and Hypothesis •Proximate and Ultimate Hypotheses Theory and hypothesis • Theory = a statement of cause not directly tested by • Theory = a statement of cause not directly tested by experiment. • Hypothesis = a statement of cause that can be directly tested by experiment. – Could be formulated as “if..then..”. Inductive Inductive method method Inductive Inductive method method Hypothetico Hypothetico-- deductive deductive method method Hypothetico Hypothetico-- deductive deductive method method Theory Theory Theory Theory Hypothesis Hypothesis 11 Hypothesis Hypothesis 11 Hypothesis Hypothesis 22 Hypothesis Hypothesis 22 Hypothesis Hypothesis 33 Hypothesis Hypothesis 33 Testing Testing Testing Testing Testing Testing Testing Testing Testing Testing Testing Testing Experiment or Experiment or observation observation Experiment or Experiment or observation observation Experiment or Experiment or observation observation Experiment or Experiment or observation observation Experiment or Experiment or observation observation Experiment or Experiment or observation observation g Proximate hypothesis • Example: How could we state this hypothesis? Ultimate hypothesis Darwinian Theory Ultimate Hypotheses Darwinian Evolution Evolution will occur given the following conditions: 1. Variation: members of a species differ in some of their characteristics. 2. Heredity: parents able to pass on some of their distinctive characteristics to their offspring 3. Differences in reproductive success: some individuals have surviving offspring > others in their population, thanks to their distinctive characteristics Genetic variation • Occurs when a given gene exists in 2 or more alleles, • species' gene pool = Various alleles • genetically different individuals � different alleles � diff. proteins • If some alleles are more successful than others � make individuals reproductively successful, � those alleles will get themselves passed on from generation to generation � more common over time � gradually displace other "competitors" over the course of evolution. Genetic variation + differential reproduction = evolutionary change at p y g the genetic level • alleles will spread in proportion to how well they make their bearers good at reproducing. Natural Selection • E.g. Ladybirds Natural Selection Darwinism and Behavior • Darwinian evolution could account for many problems in the evolution of behavior. • Evolutionary explanations do not seem to account for other behaviors. • Infanticide: – Behavior found in many species Infanticide e.g. Hanuman langurs Ad l • Advantages: male gets exclusive access to females in group that bear his offspring. Infanticide • Disadvantages I l ti d – Involves time and energy expenditure – Involves risk to infanticidal male (females fight back) – Might not endear male to female. Infanticide: 3 possible explanations 1. Pathological inclinations due to stress caused by overcrowding 2. Darwinian selection: l b h i d i stress caused by overcrowding and shortage of food. Males boost their reproductive success, where females have no choice but to mate with them. 3. as a means of population regulation, to prevent overpopulation . p p p i.e. for the good of the group?? (Group Selection?) Group Selection • Selection between groups rather than individuals. • Groups (or species) with infanticide have a better • Groups (or species) with infanticide have a better chance of survival than groups without infanticide, because they would regulate their densities in harmony with resources. • Problems of group selection: – Individual (Darwinian ) selection is stronger. Group selection can occur in limited circumstances that – Group selection can occur in limited circumstances that involve keeping group integrity for long periods, i.e. not be invaded by ‘selfish” alleles which will replace group‐oriented individuals. Infanticide: 3 possible explanations 1. Social pathology hypothesis: 2. Quicker reproduction hypothesis (Darwinian selection) If true, infanticide would occur only in crowded situations NOT TRUE (Darwinian selection) 3. Population regulation hypothesis If true, infanticide would occur only in crowded situations NOT TRUE Infanticide: possible explanations 2. Quicker reproduction hypothesis (Darwinian selection) (cannibalism might be an explanation but not observed) Implications of Quicker reproduction hypothesis 1. Males should not kill their own young: DNA testing proves this. 2. Females would resume reproductive cycle, and mate with the infant‐killer: Observations show this is true. infant killer: Observations show this is true. Infanticide Anthropomorphism Anthropomorphism ("of human form") Att ib ti f h liti t h thi = Attribution of human qualities to non‐human things. e.g. in animal behavior. Uncritical anthropomorphism: Uncritical anthropomorphism: ==> Purposeful behavior ==> Purposeful behavior e g caring for young as if "knowing" the purpose e g caring for young as if "knowing" the purpose e.g. caring for young as if knowing the purpose. e.g. caring for young as if knowing the purpose. Problems: Problems: ‐ Observations Observations � animal behavior is purposeful animal behavior is purposeful ‐ Animals respond to stimuli; absence of stimulus inhibits Animals respond to stimuli; absence of stimulus inhibits behavior e.g. maternal behavior. behavior e.g. maternal behavior. ‐ Even human behavior includes poorly Even human behavior includes poorly‐understood understood compulsive behavior (e.g. Alcoholism, overeating, odd compulsive behavior (e.g. Alcoholism, overeating, odd sexual behavior) sexual behavior) Rejected Anthropomorphism Rejected Anthropomorphism ‐ There is a tendency to reject anthropomorphism completely There is a tendency to reject anthropomorphism completely ‐ i.e. an animal is viewed as a machine with senses and pre i.e. an animal is viewed as a machine with senses and pre‐ i.e. an animal is viewed as a machine with senses and pre i.e. an animal is viewed as a machine with senses and pre programmed responses programmed responses ‐ Even humans can be viewed as not much different from other Even humans can be viewed as not much different from other animals (but more advanced). animals (but more advanced). ‐ “anthropomorphism is dead” because it constrains the formulation “anthropomorphism is dead” because it constrains the formulation of well informed theories and hypothesis. of well informed theories and hypothesis. Critical anthropomorphism • Bridge between two extremes • One Could use human thoughts and feelings, imagining being the animal, g g g g g observations of human subjects � understanding animal behavior. • The debate continues 23:45 39