Chapter 13 Opener: Weaver ants form superbly cooperative societies

13.1 The energy budget of “helpers” in Neolamprologus pulcher (Part 1)

13.1 The energy budget of “helpers” in Neolamprologus pulcher (Part 2)

13.2 Effect of removal of the top-ranked subordinate helper in a cooperatively breeding group

13.3 Reproductive interference in a social animal

13.4 Competition for food is a cost of sociality in the fieldfare

13.5 Effect of parasites on cliff swallow nestlings

13.6 Social living with defensive benefits?

13.7 Mutual defense in a society of bluegills

13.8 The different categories of helping behavior

13.9 Cooperation among competitors

13.10 Cooperative courtship of the long-tailed manakin

13.11 Cooperation with an eventual payoff

13.12 A meerkat sentinel on the alert for approaching predators

13.13 Reciprocity in a social primate

13.14 Experimental demonstration of reciprocity in cotton-top tamarins (Part 1)

13.14 Experimental demonstration of reciprocity in cotton-top tamarins (Part 2)

13.15 The prisoner’s dilemma

13.16 The components of selection and fitness

13.17 A Belding’s ground squirrel gives an alarm call after spotting a terrestrial predator

13.18 Altruism and relatedness in pied kingfishers

13.19 Cooperation among scrub jay relatives

13.20 Seasonal changes in prolactin concentrations in breeders and nonbreeding helpers (Part 1)

13.20 Seasonal changes in prolactin concentrations in breeders and nonbreeding helpers (Part 2)

13.21 Helpers at the nest help parents raise more siblings in the Florida scrub jay

13.22 Conditional reproductive tactics of female white-fronted bee-eaters (Part 1)

13.22 Conditional reproductive tactics of female white-fronted bee-eaters (Part 2)

13.23 Haplodiploid sex determination in Hymenoptera (Part 1)

13.23 Haplodiploid sex determination in Hymenoptera (Part 2)

13.23 Haplodiploid sex determination in Hymenoptera (Part 3)

13.24 Conflict within ant colonies over reproduction

13.25 A test of a hypothesis based on transactional theory

13.26 The effect of relatedness on equality of reproductive opportunities

13.27 Eusocial insects have sterile castes

13.28 Suicidal sacrifice by a worker bee

13.29 Eusociality has an evolutionary history

13.30 Haplodiploidy and the evolution of eusociality in the Hymenoptera (Part 1)

13.30 Haplodiploidy and the evolution of eusociality in the Hymenoptera (Part 2)

13.31 A sterile thrips soldier (right) next to a reproductive foundress female (left)

13.32 Altruism in aphids

13.33 Selfish behavior of aphid clone invaders

13.34 A mammal with an effectively sterile caste

13.35 Fortress living space may provide an incentive against dispersal in many eusocial insects