Biology subjects

Negron-Del Valle, J.

Publications and source records attributed to Negron-Del Valle, J..

4 recordsLinked to original sources

bioRxiv2025

The influence of captivity on cardiac structure and function across age, in rhesus macaques

BackgroundCaptive non-human primates are widely used as models of human aging, yet the conditions they live in differ markedly from their naturalistic environment. Differences between captive and free-ranging environments may impact how the cardiovascular system adapts with age, potentially confounding studies of natural aging. This study characterized age-related cardiac phenotypes in free-ranging rhesus macaques and compared these patterns with their captive-housed counterparts to assess the influence of living environment on cardiac health across the lifespan. MethodologyWe performed transthoracic echocardiography in a cross-sectional cohort of 133 free-ranging rhesus macaques (Macaca mulatta, aged 7 - 25 years, 41 % female) living on Cayo Santiago, Puerto Rico. First, we compared structural and functional cardiac parameters between young (7 - 12 years; n = 48, 60% female) and old (18-26 years, n = 33, 42% female) free-ranging macaques. We then performed an ANCOVA, with age as a covariate, to compare cardiac structural and functional parameters between free-ranging and captive-housed macaques (n = 347, aged 7 - 32 years, 71% female). ResultsIn our free-ranging cohort, older macaques had greater interventricular septal thickness and relative wall thickness (RWT) than young. Males exhibited larger left ventricular (LV) internal dimensions, wall thickness, LV mass, and LV volumes than females, but these differences were attenuated when indexed to body mass. Diastolic function was lower with advanced age in both sexes, reflected by a lower E/A ratio, reduced myocardial tissue velocities during early diastole (e') and greater myocardial tissue velocities during atrial contraction (a). Compared with captive macaques, free-ranging animals exhibited better diastolic function, including a significantly higher E/A ratio, greater e, and lower a. Captive macaques also had significantly greater relative wall thickness across age and between sexes. Conclusions and implicationsOur study provides the first comprehensive characterization of age-related cardiac differences in free-ranging rhesus macaques, which show structural and functional cardiac differences similar to those observed with human aging. Captive macaques exhibited a more pronounced age-related cardiac phenotype than their free-ranging counterparts, including thicker left ventricular walls and lower diastolic function for a given age. These findings highlight the importance of considering the ecological context when interpreting animal models of cardiovascular aging.

physiology↗

bioRxiv2023

Socioecological drivers of injuries in female and male rhesus macaques (Macaca mulatta)

Competition over access to resources, such as food and mates, is believed to be one of the major costs associated with group living. Two socioecological factors suggested to predict the intensity of competition are group size and the relative abundance of sexually active individuals. However, empirical evidence linking these factors to injuries and survival costs is scarce. Here, we leveraged 10 years of data from free-ranging rhesus macaques where injuries inflicted by conspecifics are associated with a high mortality risk. We tested if group size and adult sex ratio predicted the occurrence of injuries and used data on physical aggression to contextualise these results. We found that males were less likely to be injured when living in larger groups, potentially due to advantages in intergroup encounters. Females, instead, had higher injury risk when living in larger groups but this was not explained by within-group aggression among females. Further, male-biased sex ratios predicted a weak increase in injury risk in females and were positively related to male-female aggression, indicating that male coercion during mating competition may be a cause of injuries in females. Overall, our results provide insights into sex differences in the fitness-related costs of competition and empirical evidence for long-standing predictions on the evolution of group living.

evolutionary biology↗

bioRxiv2023

Natural disaster alters the adaptive benefits of sociality

Weather-related disasters can radically alter ecosystems. When disaster-driven ecological damage persists, the selective pressures exerted on individuals can change, eventually leading to phenotypic adjustments. For group-living animals, social relationships are believed to help individuals cope with environmental challenges and may be a critical mechanism enabling adaptation to ecosystems degraded by disasters. Yet, whether natural disasters alter selective pressures on patterns of social interactions and whether group-living animals can, as a result, adaptively change their social relationships remains untested. Here, we leveraged unique data collected on rhesus macaques from 5 years before to 5 years after a category 4 hurricane, leading to persistent deforestation which exacerbated monkeys exposure to intense heat. In response, macaques increased tolerance for and decreased aggression toward other monkeys, facilitating access to scarce shade critical for thermoregulation. Social tolerance predicted individual survival for 5 years after the hurricane, but not before it, revealing a clear shift in the adaptive function of social relationships in this population. We demonstrate that an extreme climatic event altered selection on sociality and triggered substantial and persistent changes in the social structure of a primate species. Our findings unveil the function and adaptive flexibility of social relationships in degraded ecosystems and identify natural disasters as potential evolutionary drivers of sociality. One-Sentence SummaryTestard et al. show that a natural disaster altered selection on sociality in group-living primates triggering persistent changes in their social structure.

animal behavior and cognition↗

bioRxiv2023

Social responses to a hurricane drive greater epidemic risk

Climate change is intensifying extreme weather events, with severe implications for ecosystem dynamics. A key behavioural mechanism whereby animals may cope with such events is by increasing social cohesion to improve access to scarce resources like refuges, which in turn could exacerbate epidemic risk due to increased close contact. However, how and to what extent natural disasters affect disease risk via changes in sociality remains unexplored in animal populations. By modelling disease spread in free-living rhesus macaque groups (Macaca mulatta) before and after a hurricane, we demonstrate doubled pathogen transmission rates up to five years following the disaster, equivalent to an increase in pathogen infectivity from 10% to 20%. Moreover, the hurricane redistributed the risk of infection across the population, decreasing status-related differences found in pre-hurricane years. These findings demonstrate that natural disasters can exacerbate and homogenise epidemic risk in an animal population via changes in sociality. These observations provide unexpected further mechanisms by which extreme weather events can threaten wildlife health, population viability, and spillover to humans.

ecology↗