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Researchers have demonstrated the neighbor effect for affiliative and agonistic neighbor vocalizations in captive chimpanzees. We extend the investigation of the neighbor effect to New World monkeys, Callithrix jacchus. We collected data on vocalizations and behaviors of 31 focal individuals and concurrent neighbor vocalization within three behavioral categories: intragroup and intergroup aggression and intragroup affiliation. We investigated whether there was an influence of neighbor vocalizations on focal behavior within the same behavioral category. For data analysis we used approximate randomization of paired-sample t-tests. We found that marmosets performed intergroup aggressive behavior (bristle, anogenital present for neighbor loud shrill only) for significantly longer, and emitted significantly more intergroup agonistic vocalizations (twitter, loud shrill), at a high frequency of intergroup agonistic neighbor vocalizations (twitter, loud shrill) than at low. The marmosets were also significantly more likely to engage in bristle behavior immediately after hearing a neighbor intergroup aggressive call (twitter, loud shrill) than directly beforehand. High neighbor intragroup agonistic calls (chatter) were associated with significantly longer spent in related behavior (composite of: attack, chase, steal food). Affiliative behaviors (share food, grooming invite) were engaged in by marmosets for significantly longer at higher frequencies of affiliative neighbor chirp calls than at low. Marmosets were also significantly more likely to perform food sharing and active affiliative contact immediately after rather than before hearing a neighbor chirp call. Our findings suggest that neighbor vocalizations influence marmoset behavior through social contagion and indicate that the neighbor effect for affiliation and aggression generalizes to the marmoset. Am. J. Primatol. 72:549–558, 2010. © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

In comparative thanatology, most reports for nonhuman mammals concern mothers' behavioural responses to their dead offspring: most prominently, dead-infant carrying (sometimes of extended duration); but also inspection, proximity, maternal care such as grooming, protective behaviours and filial cannibalism. Documented across many primate species, these behaviours remain poorly understood in all. The literature is dominated by relatively brief qualitative descriptions of isolated anecdotal cases in apes and monkeys. We argue for quantitative coding in case reports, alongside analyses of longitudinal records of such events to allow objective evaluation of competing theories, and systematic comparisons within and across species and populations. Obtaining necessary datasets depends on raised awareness in researchers of the importance of recording occurrences and knowledge of pertinent data to collect. We review proposed explanatory hypotheses and outline data needed to test each empirically. To determine factors influencing infant-corpse carriage, we suggest analyses of deaths resulting in 'carry' versus 'no carry'. For individual cases, we highlight behavioural variables to code and the need for hormonal samples. We discuss mothers' stress and welfare in relation to infant death, continued transportation and premature removal of the corpse. Elucidating underlying proximate and ultimate causes is important for understanding phylogeny of maternal responses to infant death.This article is part of the theme issue 'Evolutionary thanatology: impacts of the dead on the living in humans and other animals'., (© 2018 The Author(s).)