First record of leucism in Mantled Howler Monkeys Alouatta palliata (Gray 1849)

The existence of chromatic aberrations such as leucism or albinism is the result of inbreeding in isolated populations of wild local fauna and is associated with environmental stressors. This anomaly may reduce survival rates. There are many cases of leucism in wildlife, but overall, it is considered very rare. In neotropical primates, there have been records of leucism but previously, in howler monkeys was unknown. In this article, we report for the first time leucistic young individuals of Mantled howler monkeys Alouatta palliata, subspecies A. p. aequatorialis in an isolated remanent of tropical dry forest in southwestern Ecuador, namely Cerro Blanco Protective Forest. In total, we found two individuals, we named them Albita (a female) and Japu (a male). We also include a spatial analysis of the covert forest loss between 2000 to 2020. The report of individuals with leucism, may imply inbreeding because of isolated populations. Thus, immediate management strategies must be considered to significantly increase connectivity with other populations of howler monkeys.

Co-structure analysis and genetic associations reveal insights into pinworms (Trypanoxyuris) and primates (Alouatta palliata) microevolutionary dynamics

Background In parasitism arm race processes and red queen dynamics between host and parasites reciprocally mold many aspects of their genetics and evolution. We performed a parallel assessment of population genetics and demography of two species of pinworms with different degrees of host specificity (Trypanoxyuris multilabiatus, species-specific; and T. minutus, genus-specific) and their host, the mantled howler monkey (Alouatta palliata), based on mitochondrial DNA sequences and microsatellite loci (these only for the host). Given that pinworms and primates have a close co-evolutionary history, covariation in several genetic aspects of their populations is expected. Results Mitochondrial DNA revealed two genetic clusters (West and East) in both pinworm species and howler monkeys, although population structure and genetic differentiation were stronger in the host, while genetic diversity was higher in pinworms than howler populations. Co-divergence tests showed no congruence between host and parasite phylogenies; nonetheless, a significant correlation was found between both pinworms and A. palliata genetic pairwise distances suggesting that the parasites’ gene flow is mediated by the host dispersal. Moreover, the parasite most infective and the host most susceptible haplotypes were also the most frequent, whereas the less divergent haplotypes tended to be either more infective (for pinworms) or more susceptible (for howlers). Finally, a positive correlation was found between pairwise p-distance of host haplotypes and that of their associated pinworm haplotypes. Conclusion The genetic configuration of pinworm populations appears to be molded by their own demography and life history traits in conjunction with the biology and evolutionary history of their hosts, including host genetic variation, social interactions, dispersal and biogeography. Similarity in patterns of genetic structure, differentiation and diversity is higher between howler monkeys and T. multilabiatus in comparison with T. minutus, highlighting the role of host-specificity in coevolving processes. Trypanoxyuris minutus exhibits genetic specificity towards the most frequent host haplotype as well as geographic specificity. Results suggest signals of potential local adaptation in pinworms and further support the notion of correlated evolution between pinworms and their primate hosts.

Social correlates of variation in urinary oxytocin concentrations of mantled howler monkeys Alouatta palliata (Gray, 1849) (Primates: Atelidae): A preliminary assessment

There is growing evidence that non-human primate sociality is linked to proximate neuroendocrine mechanisms. Arginine vasopressin, endorphins, and oxytocin may be involved in such mechanisms. Here, we perform a preliminary analysis of the social correlates of variation in urinary oxytocin concentrations in mantled howler monkeys (Alouatta palliata). From January to December 2017, we studied 13 adult mantled howler monkeys belonging to two groups. We recorded the occurrence of social interactions (547.5 observation hours); assessed proximity among group members (2,194 instantaneous recordings); and collected 172 urine samples. Urine samples were assayed (ELISA) for oxytocin concentrations, which were corrected for specific gravity, resulting in 54 analyzed samples. Hormone concentrations increased by approximately 62% when individuals were involved in affiliative interactions. With respect to when no affiliative interactions occurred, urinary oxytocin concentrations were higher when dyads with a low-quality social relationship affiliated. These results agree with previous contentions that this hormone is linked to participation in affiliative interactions. Convergence between these and results from other taxa supports the hypothesis that the biological mechanisms that allow for primate sociality are shared among species.

A preliminary assessment of allostatic load in male mantled howler monkeys

Allostatic load refers to the wear and tear of the organism associated with the repeated activation of mechanisms that allow for homeostasis. Although allostasis (i.e., maintaining stability through change) is achieved through the orchestration of multiple systems, assessments of allostatic load in wildlife have usually relied on the measurement of single or few physiological mediators. In the present study, we aimed at constructing an allostatic load index (ALI) for male mantled howler monkeys (Alouatta palliata) based on seven physiological mediators (C-peptide, triiodothyronine, glucocorticoids, testosterone, amount of activity, foraging effort, and participation in agonistic interactions). We then examined if variation in this ALI was associated with social, ecological, and abiotic challenges. For five years, we studied ten adult males belonging to two groups. We assessed physiological mediators via behavioral observations (3,364 hours of samplings), and both urine (1,500 assayed samples) and fecal (1,500 assayed samples) sampling. We calculated an ALI based on mediator specific risk scores. Seasonality, encounters with extragroup males, mating, and centrality were positively related with male allostatic load, though only the first two had significant effects on ALI. ALI reflected the physiological and behavioral responses of males to social, ecological, and abiotic challenges. It remains for future research to determine if the observed trends correspond to normal fluctuations in mechanisms that allow male mantled howler monkeys to cope with their environment.

Abnormal pelage color in mantled howler monkey (Alouatta palliata mexicana) in Veracruz, México

El leucismo es una despigmentación total o parcial del pelaje, mientras que el albinismo es la pérdida total de pigmentos en el cuerpo entero; las condiciones anormales de la carencia del pigmento se deben a la expresión de genes recesivos. Se realizó una expedición ad libitum en el Ejido Álvaro Obregón, al suroeste de Nuevo Cantón, municipio de Uxpanapa, Veracruz en diciembre de 2019. Presentamos el primer registro de un individuo de mono aullador de manto (Alouatta palliata mexicana) con coloración no convencional (probablemente leucismo o albinismo), observado en una tropa silvestre en la región del Valle de Uxpanapa, Veracruz, México. La coloración de la mucosa oral y palpebral no muestran pigmentación y pueden ser resultado de la expresión de genes recesivos en el individuo, por lo que realizar estudios más profundos sobre la expresión de genes recesivos ampliaría la comprensión del fenómeno.