Alejandro Estrada

Nearly 70% of all primate species with available data are threatened with extinction. Hunting (i.e., wild animals either killed or live‐captured) is a major contributor to primate population decline, impacting ~70% of all species. Using a large dataset of species' hunting status and body mass, we evaluated the spatial and phylogenetic patterns of hunting and threat status. We modeled both hunting and extinction risk as predicted by body mass and evolutionary distinctiveness (ED). We found that the subset of hunted primates is not random taxonomically or across biogeographic regions, and that the likelihood of a species being hunted increases with body mass, particularly in the American Tropics. Globally, extinction risk increased with body mass and ED. Within biogeographic regions, body mass was also related to extinction risk, and in the American Tropics evolutionarily distinct species had higher likelihoods of being threatened with extinction. In the American Tropics, 54% of species were reported to be threatened by hunting, whereas this was 70% for Africa and 89% for Asia, indicating geographic disparity in hunting patterns that could bias our results. We encourage researchers to consider the intricate relationships among species' body mass, life history traits, and hunting in conservation planning, and recommend incorporating information on local cultural hunting patterns and purposes in developing place‐based conservation initiatives.

Conservation funding is currently limited; cost‐effective conservation solutions are essential. We suggest that the thousands of field stations worldwide can play key roles at the frontline of biodiversity conservation and have high intrinsic value. We assessed field stations’ conservation return on investment and explored the impact of COVID‐19. We surveyed leaders of field stations across tropical regions that host primate research; 157 field stations in 56 countries responded. Respondents reported improved habitat quality and reduced hunting rates at over 80% of field stations and lower operational costs per km ² than protected areas, yet half of those surveyed have less funding now than in 2019. Spatial analyses support field station presence as reducing deforestation. These “earth observatories” provide a high return on investment; we advocate for increased support of field station programs and for governments to support their vital conservation efforts by investing accordingly.

Long‐term land‐use change impacts tropical bird communities through population‐level and functional diversity effects from habitat loss, degradation and fragmentation, leading to land management and conservation challenges. Assessing the temporal impacts of land‐use change on occupancy patterns, population change and functional traits of bird species in tropical areas is limited by the treatment of nondetections as true absences or artefacts of low sampling effort during and throughout years. With this in mind, we developed a novel Bayesian species occupancy framework to account for species absences to evaluate bird community changes in Palenque, Chiapas, Mexico, where there is opportunity for study given exceptional records of change across habitats from rainforest to urban centres. We created a novel dataset of population trends for 244 bird species over the years 1900 to 2020 from published short‐term field studies, expert field notes and community science pages. Our results show that open area species had higher population increases than forest specialists over time, represented most evidently by the turnover of rainforest specialists for urban species. Modelled influence of functional traits displayed the importance of main habitat types, body mass and habitat and dietary breadth as factors that associated with bird population trends. On average, species with body masses 948.4 g showed decreasing trends, while all other species showed increasing or stable trends. Our findings illuminate the value of accounting for species absences from several data sources to discover long‐term species population trends and affiliated functional traits whose preservation requires conservation and land management action to protect bird ecosystem services. Primary forest conservation is key to maintaining populations of habitat and dietary specialists, such as small understorey insectivorous and large frugivorous species. Protecting rare natural savanna patches from conversion to cattle pasture is vital to prevent further extirpation of native granivores and to slow colonization by exotic and invasive species.

Primates, represented by 521 species, are distributed across 91 countries primarily in the Neotropic, Afrotropic, and Indo-Malayan realms. Primates inhabit a wide range of habitats and play critical roles in sustaining healthy ecosystems that benefit human and nonhuman communities. Approximately 68% of primate species are threatened with extinction because of global pressures to convert their habitats for agricultural production and the extraction of natural resources. Here, we review the scientific literature and conduct a spatial analysis to assess the significance of Indigenous Peoples’ lands in safeguarding primate biodiversity. We found that Indigenous Peoples’ lands account for 30% of the primate range, and 71% of primate species inhabit these lands. As their range on these lands increases, primate species are less likely to be classified as threatened or have declining populations. Safeguarding Indigenous Peoples’ lands, languages, and cultures represents our greatest chance to prevent the extinction of the world’s primates.

Nonhuman primates are facing an impending extinction crisis with over 65% of species listed as Vulnerable, Endangered, or Critically Endangered, and 93% characterized by declining populations. Primary drivers of primate population decline include deforestation, principally for industrial agriculture and the production of food and nonfood commodities, much of which is exported to wealthy consumer nations, unsustainable bushmeat hunting, the illegal pet trade, the capture of primates for body parts, expanding road and rail networks, mining, dam building, oil and gas exploration, and the threat of emerging diseases. Over the next several decades, human population increase, agricultural expansion, and climate change are expected to contribute significantly to the loss of additional suitable habitat and a reduction in the viability of local primate populations. If we are to avoid this impending extinction crisis, primate researchers must prioritize projects designed to mitigate the effects of habitat change on ecosystems health and biodiversity, and play a greater role in conservation and environmental policy by educating global citizens and political leaders. In addition, the international community will need to work with governments in primate habitat countries to expand the number of protected areas that contain primate species (94 primate species have < 10% of their range in protected areas). In this special issue of the International Journal of Primatology, we bring together researchers from a wide range of disciplines to examine the current and future threats to primate population persistence, and present local, country, and regional solutions to protect primate species.

When navigating, wild animals rely on internal representations of the external world – called ‘cognitive maps’ – to take movement decisions. Generally, flexible navigation is hypothesized to be supported by sophisticated spatial skills (i.e. Euclidean cognitive maps); however, constrained movements along habitual routes are the most commonly reported navigation strategy. Even though incorporating metric information (i.e. distances and angles between locations) in route-based cognitive maps would likely enhance an animal's navigation efficiency, there has been no evidence of this strategy reported for non-human animals to date. Here, we examined the properties of the cognitive map used by a wild population of primates by testing a series of cognitive hypotheses against spatially explicit movement simulations. We collected 3104 h of ranging and behavioural data on five groups of black howler monkeys (Alouatta pigra) at Palenque National Park, Mexico, from September 2016 through August 2017. We simulated correlated random walks mimicking the ranging behaviour of the study subjects and tested for differences between observed and simulated movement patterns. Our results indicated that black howler monkeys engaged in constrained movement patterns characterized by a high path recursion tendency, which limited their capacity to travel in straight lines and approach feeding trees from multiple directions. In addition, we found that the structure of observed route networks was more complex and efficient than simulated route networks, suggesting that black howler monkeys incorporate metric information into their cognitive map. Our findings not only expand the use of metric information during route navigation to non-human animals, but also highlight the importance of considering efficient route-based navigation as a cognitively demanding mechanism.

Animal communication has long been thought to be subject to pressures and constraints associated with social relationships. However, our understanding of how the nature and quality of social relationships relates to the use and evolution of communication is limited by a lack of directly comparable methods across multiple levels of analysis. Here, we analysed observational data from 111 wild groups belonging to 26 non-human primate species, to test how vocal communication relates to dominance style (the strictness with which a dominance hierarchy is enforced, ranging from ‘despotic’ to ‘tolerant’). At the individual-level, we found that dominant individuals who were more tolerant vocalized at a higher rate than their despotic counterparts. This indicates that tolerance within a relationship may place pressure on the dominant partner to communicate more during social interactions. At the species-level, however, despotic species exhibited a larger repertoire of hierarchy-related vocalizations than their tolerant counterparts. Findings suggest primate signals are used and evolve in tandem with the nature of interactions that characterize individuals' social relationships.

Currently, ~65% of extant primate species (ca 512 species) distributed in 91 countries in the Neotropics, mainland Africa, Madagascar, South Asia and Southeast Asia are threatened with extinction and 75% have declining populations as a result of deforestation and habitat loss resulting from increasing global market demands, and land conversion for industrial agriculture, cattle production and natural resource extraction. Other pressures that negatively impact primates are unsustainable bushmeat hunting, the illegal trade of primates as pets and as body parts, expanding road networks in previously isolated areas, zoonotic disease transmission and climate change. Here we examine current and future trends in several socio-economic factors directly or indirectly affecting primates to further our understanding of the interdependent relationship between human well-being, sustainable development, and primate population persistence. We found that between 2001 and 2018 ca 191 Mha of tropical forest (30% canopy cover) were lost as a result of human activities in the five primate range regions. Forty-six percent of this loss was in the Neotropics (Mexico, Central and South America), 30% in Southeast Asia, 21% in mainland Africa, 2% in Madagascar and 1% in South Asia. Countries with the greatest losses (ca 57% of total tree cover loss) were Brazil, Indonesia, DRC, China, and Malaysia. Together these countries harbor almost 50% of all extant primate species. In 2018, the world human population was estimated at ca 8bn people, ca 60% of which were found in primate range countries. Projections to 2050 and to 2100 indicate continued rapid growth of the human populations in these five primate range regions, with Africa surpassing all the other regions and totaling ca 4bn people by the year 2100. Socioeconomic indicators show that, compared to developed nations, most primate range countries are characterized by high levels of poverty and income inequality, low human development, low food security, high levels of corruption and weak governance. Models of Shared Socioeconomic Pathway scenarios (SSPs) projected to 2050 and 2100 showed that whereas practices of increasing inequality (SSP4) or unconstrained growth in economic output and energy use (SSP5) are projected to have dire consequences for human well-being and primate survivorship, practices of sustainability-focused growth and equality (SSP1) are expected to have a positive effect on maintaining biodiversity, protecting environments, and improving the human condition. These results stress that improving the well-being, health, and security of the current and future human populations in primate range countries are of paramount importance if we are to move forward with effective policies to protect the world’s primate species and promote biodiversity conservation.

For wild primates, demography studies are increasingly recognized as necessary for assessing the viability of vulnerable populations experiencing rapid environmental change. In particular, anthropogenic changes such as habitat loss and fragmentation can cause ecological and behavioral changes in small, isolated populations, which may, over time, alter population density and demographic structure (age/sex classes and group composition) in fragment populations relative to continuous forest populations. We compared our study population of Endangered black howler monkeys (Alouatta pigra) in 34 forest fragments around Palenque National Park (PNP), Mexico (62 groups, 407 individuals), to the adjacent population in PNP, protected primary forest (21 groups, 134 individuals), and to previous research on black howlers in fragments in our study area (18 groups, 115 individuals). We usedχ²and Mann–WhitneyUtests to address the questions: (a) what is the current black howler demographic population structure in unprotected forest fragments around PNP? (b) How does it compare to PNP's stable, continuous population? (c) How has it changed over time? Compared to the PNP population, the fragment populations showed higher density, a significantly lower proportion of multimale groups, and significantly fewer adult males per group. The population's age/sex structure in the fragmented landscape has been stable over the last 17 years, but differed in a higher proportion of multifemale groups, higher density, and higher patch occupancy in the present. In the context of conservation, some of our results may be positive as they indicate possible population growth over time. However, long‐term scarcity of adult males in fragments and associated effects on population demographic structure might be cause for concern, in that it may affect gene flow and genetic diversity. The scarcity of adult males might stem from males experiencing increased mortality while dispersing in the fragmented landscape, whereas females might be becoming more philopatric in fragments.

Background: Although navigating along a network of routes might constrain animal movement flexibility, it may be an energetically efficient strategy. Routinely using the same route allows for visually monitoring of food resources, which might reduce the cognitive load and as such facilitate the process of movement decision-making. Similarly, locating routes in areas that avoid costly landscape attributes will enhance their overall energy balance. In this study we determined the benefits of route navigation in an energy minimiser arboreal primate, the black howler monkey (Alouatta pigra).Methods: We monitored five neighbouring groups of black howler monkeys at Palenque National Park, Mexico from September 2016 through August 2017. We recorded the location of the focal group every 20 m and mapped all travel paths to establish a route network (N = 1528 travel bouts). We constructed linear mixed models to assess the influence of food resource distribution (N = 931 trees) and landscape attributes (slope, elevation and presence of canopy gaps) on the location of routes within a route network.Results: The number of food trees that fell within the visual detection distance from the route network was higher (mean: 156.1 ± SD 44.9) than randomly simulated locations (mean: 121.9 ± SD 46.4). Similarly, the number of food trees found within the monkey’s visual range per meter travelled increased, on overage, 0.35 ± SE 0.04 trees/m with increasing use of the route. In addition, route segments used at least twice were more likely to occur with increasing density of food resources and decreasing presence of canopy gaps. Route segments used at least four times were more likely to occur in elevated areas within the home ranges but only under conditions of reduced visual access to food resources.Conclusions: Route navigation emerged as an efficient movement strategy in a group-living arboreal primate. Highly used route segments potentially increased visual access to food resources while avoiding energetically costly landscape features securing foraging success in a tropical rainforest.