Primate Infanticide: Outline
Background
Primate infanticide, the killing of young by an individual of the same species, can be explained by a series of five hypotheses: exploitation, resource competition, parental manipulation, sexual selection, and social pathology (Hrdy, 1979).
Outside/external/non-related/non-familial
Resource Competition
o Overall occurrence of feticide and infanticide is higher / increases when resource competition is high / availability of resources is lower (Zipple 2017)
o When other groups invade a social structure, resource competition increases, and infanticide rate is higher (Zipple 2017)
o Easy to eliminate infants because they are mostly defenseless, and entire social group is to benefit from the infant’s death if resources are scarce enough (Hrdy 1977)
o Sometimes this involves cannibalism; killing the infant not only leaves more resources for group but is also a food source on its own (this is seen in gorillas) (Hrdy 1977)
o More infanticide when it is xenophobic (from an invading group) because a foreign infant is easiest to eliminate when resources are scare (Hrdy 1977)
Role of Social Organization
· In mammals, interaction between the sexes is usually limited to the female estrous or copulation. However, in non-human primates, these male-female bonds persist past the estrous. These social relationships are hypothesized to protect from male infanticide (Palombit, 1999).
· It is hypothesized that this year- round association serves to lower the probability of infanticide by other males (Van Schaik and Kappeler, 1997).
· Many primates live in multifemale groups, and it has been proposed that these females live together to reduce the risk of infanticide through paternity confusion ( Van Schaik and Kappeler, 2002).
Sexual Competition
· Infanticide can be used by males to increase reproductive success when a male takes over a troop of females. This behavior has been observed in langurs. The females whose infants were killed exhibited estrous behavior and copulated with the new leader. (Hrdy S, B, Male-Male Competition and Infanticide Among the Langurs (Presbytis Entellus) of Abu, Rajasthan. Folia Primatol 1974;22:19-58)
· Infanticide by a male taking over a female group in one-male breeding units has also been observed in red-tailed monkeys (Struhsaker 2010) and blue monkeys (Butynski 1982).
· This has also been observed in species that live in multimale breeding groups, the red howler and the mantled howler.(Parmigiani and vom Saal 2016)
Familial/internal/intra/related
Sibling
· A lack of research on infanticide among siblings in primates may infer that it has never been observed.
Maternal Infanticide
· Maternal infanticide is rare in non-human primates, and has been reported less than a handful of times.
· Maternal infanticide has been reported once in S. fuscicollis and once in Callicebus nigrifrons, and four times in Saguinus mystax (Culot, 2011).
· It is proposed that maternal infanticide occurs when the mother assesses the probability for infant survival based on previous infant deaths (Culot, 2011).
Paternal Infanticide
· DNA analysis of wild Japanese macaques study showed males wouldn’t attack their own offspring or offspring of a female they mated with, only non familial (Soltis 2000)
· Females form bonds with males so they will not kill offspring, because male primates will not commit infanticide of their own offspring (Palombit 1999)
· Opie (2013) also says monogamy is so paternal infanticide will not occur
Counter Adaptations
· Many primate species have developed counter strategies to reduce the likelihood of infanticide from male-female sexual competition in accordance with the Red Queen Hypothesis.
· Defense: social and physical
· Female “friendships” with males in chacma baboons may serve to protect infants from infanticidal individuals (Palombit et al., 1997)
· Social monogamy: Males remain with mated females through weaning in order to protect their offspring from infanticidal males
· Territoriality: females actively defend territory from potentially infanticidal females, seen in chimpanzees (Agrell et al., 1998)
· Paternity Confusion: Females and males utilize paternity confusion to reduce the chance of a male she has mated with from killing her offspring.
· Concealed ovulation: female catarrhine primates such as Hanuman langurs have evolved an extended estrous state with variable ovulation in order to conceal which mating likely resulted in fertilization (Hestermann et al., 2001).
· Promiscuous mating: females mate with multiple males (mating patterns such as polyandry, promiscuous in multi-male multi-female) (Clarke et al., 2009)
· Female chacma baboons prefer polyandry when threat of intragroup infanticide is low (Clarke et al., 2009)
· Post-conception mating: similar to promiscuous mating, in some primate species females are proceptive during first and second trimester in order to increase paternity confusion (Engelhardt et al., 2007)
· Female synchrony: when many females are fertile at the same time it becomes impossible for one male to monopolize all females (Henzi et al., 2010)
· Males utilize paternity confusion: Mating concessions: high ranking males will allow lower ranking males access to receptive females in order to protect his own offspring from immigrant males (Henzi et al., 2010)
· Reproduction suppression:
· Bruce Effect: Female primates may abort the pregnancy when presented with a new male as seen in langurs, baboons, and gibbons possibly in order to avoid any added investment when infanticide is likely (van Schaik & Janson, 2000).
· Counter to the counterstrategies:
· Counter to paternity confusion:
· Mate-guarding, consortships, pair-bonding, all of which increase paternity certainty often in the case of mate-guarding and consortship through physical coercion or intimidation.
See Also
· Infanticide (zoology)
· Infanticide in humans
[1][2][3][4] [5] [6] [7] [8] [9] [10] [11] [12][13] Sroivas (talk) 02:37, 17 February 2017 (UTC)
Bibliography
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- ^ Butynski, Thomas (8 December 1981). "Harem-male replacement and infanticide in the blue monkey (Cercopithecus mitus stuhlmanni) in the Kibale Forest, Uganda". American Journal of Primatology. 3 (1–4): 1. Retrieved 17 February 2017.
- ^ Zipple, Matthew (25 January 2017). "You have access Conditional fetal and infant killing by male baboons" (PDF). Proceedings of the Royal Society B. 284 (1847). Retrieved 17 February 2017.
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- ^ Hrdy, SB (1977). "Infanticide as a primate reproductive strategy". American scientist. 65 (1): 40–9. PMID 402873.
- ^ Opie, C.; Atkinson, Q. D.; Dunbar, R. I. M.; Shultz, S. (29 July 2013). "Male infanticide leads to social monogamy in primates". Proceedings of the National Academy of Sciences. 110 (33): 13328–13332. doi:10.1073/pnas.1307903110.
- ^ Soltis, J.; Thomsen, R.; Matsubayashi, K.; Takenaka, O. (24 August 2000). "Infanticide by resident males and female counter-strategies in wild Japanese macaques ( Macaca fuscata )". Behavioral Ecology and Sociobiology. 48 (3): 195–202. doi:10.1007/s002650000224.
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