Existing models of attachment do not explain how death of offspring affects maternal behavior. Previous descriptions of maternal responsiveness to dead offspring in nonhuman anthropoids have not expounded the wide variation of deceased-infant carrying (DIC) behavior. Through the current study, we attempt to (a) identify determinants of DIC through a systematic survey across anthropoids, (b) quantitatively assess behavioral changes of mother during DIC, and (c) infer death perception of conspecifics. Firstly, we performed phylogenetic regression using duration of DIC as the dependent variable. Secondly, we undertook case studies of DIC in the bonnet monkey and the lion-tailed monkey through behavioral sampling. Results of phylogenetic Generalized Linear Mixed Model (Nspecies = 18; Ncases = 48) revealed a strong homology (H2 = 0.86). We also obtained a high intraspecific variation in DIC and found DIC to be affected by mother’s age, context of death, habitat condition, and degree of arboreality. We found bonnet mothers to carry their deceased offspring for 3.56 ± 4.03 SD days (N = 7) with diminished feeding, enhanced passivity, and social isolation during DIC and progressive decline in protection/attentiveness of corpse and attachment. Following Anderson (2016)’s framework of death perception, we interpreted repeated sensory investigation of corpses by mothers as comprehending causality of death, inanimate handling of corpse and its defense as comprehension of non-functionality, and a progressive disinterest of mothers in them as perceiving irreversibility of death. Lastly, we integrated DIC with mother-infant attachment theories and proposed a conceptual model characterizing DIC with causal determinants.
Primates exhibit laterality in hand usage either in terms of (a) hand with which an individual solves a task or while solving a task that requires both hands, executes the most complex action, that is, "hand preference," or (b) hand with which an individual executes actions most efficiently, that is, "hand performance." Observations from previous studies indicate that laterality in hand usage might reflect specialization of the two hands for accomplishing tasks that require maneuvering dexterity or physical strength. However, no existing study has investigated handedness with regard to this possibility. In this study, we examined laterality in hand usage in urban free-ranging bonnet macaques, Macaca radiata with regard to the above possibility. While solving four distinct food extraction tasks which varied in the number of steps involved in the food extraction process and the dexterity required in executing the individual steps, the macaques consistently used one hand for extracting food (i.e., task requiring maneuvering dexterity)-the "maneuvering" hand, and the other hand for supporting the body (i.e., task requiring physical strength)-the "supporting" hand. Analogously, the macaques used the maneuvering hand for the spontaneous routine activities that involved maneuvering in three-dimensional space, such as grooming, and hitting an opponent during an agonistic interaction, and the supporting hand for those that required physical strength, such as pulling the body up while climbing. Moreover, while solving a task that ergonomically forced the usage of a particular hand, the macaques extracted food faster with the maneuvering hand as compared to the supporting hand, demonstrating the higher maneuvering dexterity of the maneuvering hand. As opposed to the conventional ideas of handedness in non-human primates, these observations demonstrate division of labor between the two hands marked by their consistent usage across spontaneous and experimental tasks requiring maneuvering in three-dimensional space or those requiring physical strength.
Group territory defence poses a collective action problem: individuals can free-ride, benefiting without paying the costs. Individual heterogeneity has been proposed to solve such problems, as individuals high in reproductive success, rank, fighting ability or motivation may benefit from defending territories even if others free-ride. To test this hypothesis, we analysed 30 years of data from chimpanzees ( Pan troglodytes ) in the Kasekela community, Gombe National Park, Tanzania (1978–2007). We examined the extent to which individual participation in patrols varied according to correlates of reproductive success (mating rate, rank, age), fighting ability (hunting), motivation (scores from personality ratings), costs of defecting (the number of adult males in the community) and gregariousness (sighting frequency). By contrast to expectations from collective action theory, males participated in patrols at consistently high rates (mean ± s.d. = 74.5 ± 11.1% of patrols, n = 23 males). The best predictors of patrol participation were sighting frequency, age and hunting participation. Current and former alpha males did not participate at a higher rate than males that never achieved alpha status. These findings suggest that the temptation to free-ride is low, and that a mutualistic mechanism such as group augmentation may better explain individual participation in group territorial behaviour. This article is part of the theme issue ‘Intergroup conflict across taxa’.
Introduction: Treatment toxicities are common in older adults with cancer and consequently, treatment modifications are sometimes considered. We evaluated the prevalence and factors associated with treatment modifications at the first cycle in older patients receiving palliative systemic treatment. Methods: Patients (n = 369) from the GAP 70+ Trial (NCT02054741; PI: Mohile) usual care arm were included. Enrolled patients were aged 70+ with advanced cancer and ≥ 1 Geriatric Assessment (GA) domain impairment. Treatment modification was defined as any change from National Comprehensive Cancer Network guidelines or published clinical trials. Baseline variables included: 1) sociodemographic factors; 2) clinical variables; 3) GA domains; and 4) physician beliefs about life expectancy. Bivariate analyses and multivariable cluster-weighted generalized estimating equation model were conducted to assess the association of baseline variables with cycle 1 treatment modifications. Results: Mean age was 77.2 years (range: 70-94); 62% had lung or gastrointestinal cancers, and 35% had treatment modifications at cycle 1. Increasing age by one year (odds ratio (OR) 1.1, 95% confidence interval [CI] 1.0-1.2), receipt of ≥second line of chemotherapy (OR 1.8, CI 1.1-3.0), functional impairment (OR 1.6, CI 1.1-2.3) and income ≤$50,000 (OR 1.7, CI 1.1-2.4) were independently associated with a higher likelihood of cycle 1 treatment modification. Conclusion: Treatment modifications occurred in 35% of older adults with advanced cancer at cycle 1. Increasing age, receipt of ≥second line of chemotherapy, functional impairment, and lower income were independently associated with treatment modifications. These findings emphasize the need for evidence-based regimens in older adults with cancer and GA impairments.
Vocal learning, the ability to voluntarily modify the acoustic structure of vocalizations based on social cues, is a fundamental feature of speech in humans (Homo sapiens). While vocal learning is common in taxa such as songbirds and whales, the vocal learning capacities of nonhuman primates appear more limited. Intriguingly, evidence for vocal learning has been reported in chimpanzees (Pan troglodytes), for example in the form of regional variation ('dialects') in the 'pant-hoot' calls. This suggests that some capacity for vocal learning may be an ancient feature of the Pan-Homo clade. Nonetheless, reported differences have been subtle, with inter-community variation representing only a small portion of the total acoustic variation. To gain further insights into the extent of regional variation in chimpanzee vocalizations, we performed an analysis of pant-hoots from chimpanzees in the neighboring Kasekela and Mitumba communities at Gombe National Park, Tanzania, and the geographically distant Kanyawara community at Kibale National Park, Uganda. We observed group differences only among the geographically isolated communities and did not find any differences between the neighboring communities at Gombe. Furthermore, we found differences among individuals in all communities. Hence, the variation in chimpanzee pant-hoots reflected individual differences, rather than group differences. The limited evidences for vocal learning in Pan suggest that extensive vocal learning emerged in the human lineage after the divergence from Pan.
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