21. Pair-bonede species: Gibbons and siamangs Males are attentive to mates Sing duets in territorial displays Females have priority of access Males help care for infants
30. Intense male-male competition can also lead to sperm competition….and larger testes…in species where females mate promiscuously Monogamous 1- ♂, Multi-♀ Multi- ♂, Multi-♀ Observed/Expected Size 0.5 1.0 1.5 2.0
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35. 1. Infanticide is associated with changes in male status: Males don’t kill unless they GAIN reproductive access they did not have before
36. 1. Males begin to kill infants soon after they join group Hanuman langurs, Borries & Koenig 2000
37. 2. Males kill unweaned infants Probability of surviving presence of infanticidal male Langurs Howlers 0-3 3-6 6-9 > 9 Age (mos)