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Week 6: Reproductive Strategies in Animals By: Randi Scott, Cat Alvarado, and Sanan Mehserdjian Fall 2014.

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Presentation on theme: "Week 6: Reproductive Strategies in Animals By: Randi Scott, Cat Alvarado, and Sanan Mehserdjian Fall 2014."— Presentation transcript:

1 Week 6: Reproductive Strategies in Animals By: Randi Scott, Cat Alvarado, and Sanan Mehserdjian Fall 2014

2 Video: Weird Animal Mating Habits LdSHyXO-Q

3 Article: Infanticide Among Animals: An Examination of Reproductive Strategies d323127fe66f?AccessKeyId=EFCDB7266BB382D CA111&disposition=0 Sarah Blaffer Hrdy (1979). “Infanticide Among Animals: A Review, Classification, and Examination of the Implications for the Reproductive Strategies of Females.” Ethology and Sociobiology:

4 Introduction Purpose: to explain and categorize instances of infanticide Perpetrators: adult males, adult females, even other young Members of own group, outsiders, and parents 5 Classes of Infanticide Sarah Blaffer Hrdy (1979). “Infanticide Among Animals: A Review, Classification, and Examination of the Implications for the Reproductive Strategies of Females.” Ethology and Sociobiology:

5 Exploitation When perpetrators benefit from consumption or use of their victim Infant becomes a food resource, protective buffer against third parties, or a prop for gaining maternal experience Cannibalism: Squirrels, lions, some fish and insects Starvation: Female primates kidnapping and “aunting” by non- lactating females Sarah Blaffer Hrdy (1979). “Infanticide Among Animals: A Review, Classification, and Examination of the Implications for the Reproductive Strategies of Females.” Ethology and Sociobiology:

6 Resource Competition Competition for food or nest sites Death of infant  increased access to resources for killer/ killer’s offspring Wild dogs, elephant seals, large primates Xenophobia

7 Parental Manipulation Death of infant  improved survival of mother or other offspring Imperfect infant  unlikely to carry on genes Humans, Kangaroos, Norway rats

8 Sexual Selection Most popular kind Competition between one sex for reproductive investment of the other sex  advantageous to kill another animal’s offspring Eliminating infant increases infanticidal male’s chance at reproducing Occurs during lactation usually Females: quails, Lions, rarely in Humans

9 Social Pathology Only kind that does not assume infanticide is adaptive Pathological; random Child abuse in humans

10 Hanuman langurs Highest recorded case was 83% in on troop Sexual selection Species where male takeover is short Some groups do it, some do not – Why? Best guess is population and human interference

11 Female Reproductive Strategies Social organization: female gorillas move between groups Males protect females after takeover Ability to conceive soon after losing infant  evolution is for good of individual In primates, there is a trend away from hormonal signs of receptivity

12 Critical Review If infanticide is a male reproductive strategy how would males avoid killing their own offspring? Hrdy answers with a study on langurs: it is the female, rather than the infant, who provides males with the cue to attack or tolerate her infant. Difficulty in interpreting captive observations Difficult to discern whether an act of infanticide is pathological or an evolved tactic

13 Works Cited Sarah Blaffer Hrdy (1979). “Infanticide Among Animals: A Review, Classification, and Examination of the Implications for the Reproductive Strategies of Females.” Ethology and Sociobiology:


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