Showing papers by "Sarah A. Boyle published in 2021"

The disappearing Dry Chaco, one of the last dry forest systems on earth

Abstract: The Dry Chaco spans more than 87 million hectares across Argentina, Bolivia, and Paraguay. This unique forest system has experienced extensive loss and fragmentation due to land-use change, with different land-use histories in the three countries. This forest loss has altered landscape connectivity for the Dry Chaco’s associated biota. We compared patterns of deforestation-induced fragmentation and concomitant changes in structural landscape connectivity between 2000 and 2019 in the three countries to identify consistent patterns that might facilitate biome-wide conservation. We quantified forest cover in the Dry Chaco of Argentina, Bolivia, and Paraguay for the years 2000 and 2019 at 30 m resolution. We analyzed structural connectivity at three scales. Then, we identified and visualized the most important stepping stones per country per year. Between 2000 and 2019, the overall extent of Dry Chaco forest cover decreased by 20.2% (9.5 million ha). All three counties experienced substantial reductions, with Paraguay undergoing the greatest loss and fragmentation relative to 2000. Most of the overall network metrics decreased from 2000 to 2019 for Paraguay and Bolivia, but Argentina experienced increased coalescence distance and average nodal connectance. Dispersal-level metrics showed clustering threshold distances between 1000 and 2000 m for each country in both years. The large number of forest fragments and distances between them suggest that some mammals characteristic of the biome may be experiencing negative impacts from this fragmentation. Contemporary and future challenges of uncoordinated national conservation and management policies, land speculation, and increased human infrastructure will accelerate the rate of deforestation.

Small mammal glucocorticoid concentrations vary with forest fragment size, trap type, and mammal taxa in the Interior Atlantic Forest

Abstract: Species that live in degraded habitats often show signs of physiological stress Glucocorticoid hormones (eg, corticosterone and cortisol) are often assessed as a proxy of the extent of physiological stress an animal has experienced Our goal was to quantify glucocorticoids in free-ranging small mammals in fragments of Interior Atlantic Forest We extracted glucocorticoids from fur samples of 106 small mammals (rodent genera Akodon and Oligoryzomys, and marsupial genera Gracilinanus and Marmosa) from six forest fragments (2–1200 ha) in the Reserva Natural Tapyta, Caazapa Department, Paraguay To our knowledge, this is the first publication of corticosterone and cortisol levels for three of the four sampled genera (Akodon, Oligoryzomys, and Marmosa) in this forest system We discovered three notable results First, as predicted, glucocorticoid levels were higher in individuals living withing small forest fragments Second, animals captured live using restraint trapping methods (Sherman traps) had higher glucocorticoid levels than those animals captured using kill traps (Victor traps), suggesting that hair glucocorticoid measures can reflect acute stress levels in addition to long-term glucocorticoid incorporation These acute levels are likely due to urinary steroids diffusing into the hair shaft This finding raises a concern about the use of certain trapping techniques in association with fur hormone analysis Finally, as expected, we also detected genus-specific differences in glucocorticoid levels, as well as cortisol/corticosterone ratios

Fermented food consumption in wild nonhuman primates and its ecological drivers

Abstract: OBJECTIVES: Although fermented food use is ubiquitous in humans, the ecological and evolutionary factors contributing to its emergence are unclear. Here we investigated the ecological contexts surrounding the consumption of fruits in the late stages of fermentation by wild primates to provide insight into its adaptive function. We hypothesized that climate, socioecological traits, and habitat patch size would influence the occurrence of this behavior due to effects on the environmental prevalence of late-stage fermented foods, the ability of primates to detect them, and potential nutritional benefits. MATERIALS AND METHODS: We compiled data from field studies lasting at least 9 months to describe the contexts in which primates were observed consuming fruits in the late stages of fermentation. Using generalized linear mixed-effects models, we assessed the effects of 18 predictor variables on the occurrence of fermented food use in primates. RESULTS: Late-stage fermented foods were consumed by a wide taxonomic breadth of primates. However, they generally made up 0.01%-3% of the annual diet and were limited to a subset of fruit species, many of which are reported to have mechanical and chemical defenses against herbivores when not fermented. Additionally, late-stage fermented food consumption was best predicted by climate and habitat patch size. It was more likely to occur in larger habitat patches with lower annual mean rainfall and higher annual mean maximum temperatures. DISCUSSION: We posit that primates capitalize on the natural fermentation of some fruits as part of a nutritional strategy to maximize periods of fruit exploitation and/or access a wider range of plant species. We speculate that these factors contributed to the evolutionary emergence of the human propensity for fermented foods.

Food availability, plant diversity, and vegetation structure drive behavioral and ecological variation in Endangered Coimbra-Filho's titi monkeys.

Abstract: There is wide variability in primate behavior and ecology Understanding how frugivorous primates behave under different habitat fragmentation levels is key for effective conservation and management of species and their habitats We evaluated the seasonality in activity budget, diet, and ranging behavior of two groups of Endangered Coimbra-Filho's titi monkeys (Callicebus coimbrai) One group inhabited a 14-ha forest fragment, whereas the other lived in a 522-ha fragment We measured the monthly density of trees and lianas available as food sources over 8 months We also collected behavioral and group location data every 5 min, from dawn to dusk, using the scan sampling method The two forest fragments differed seasonally in the number of fruiting food-resource available In the 14-ha fragment, we found that the time spent by titi monkeys feeding, foraging, resting, and traveling differed seasonally In the 522-ha fragment, titi monkeys exhibited seasonal differences in time spent sleeping, socializing, foraging, and revisiting food sources In both titi monkey groups, diets varied seasonally Our findings indicate that Coimbra-Filho's titi monkeys can exhibit behavioral flexibility in their activity budgets, diets, and movement patterns Such flexibility is important for this species to survive in fragmented habitats and may be linked to three key factors: species-specific resource availability, plant species diversity, and the vegetation structure of each forest fragment

Identifying structural connectivity priorities in eastern Paraguay's fragmented Atlantic Forest.

Abstract: The Atlantic Forest of eastern Paraguay has experienced extensive recent deforestation. Less than one-third of the region is forested, and the remaining forest largely consists of isolated remnants with potentially disrupted connectivity for forest fauna. We used a graph theory approach to identify those forest remnants that are important in maintaining landscape structural connectivity for mammals in this fragmented forest. We quantified structural connectivity for forest remnants over the period 2000–2019 at three levels: the entire network of Atlantic Forest remnants in eastern Paraguay; at 10 smaller, nested spatial scales (40–10,000 m) encompassing a range of potential mammalian dispersal abilities; and at the level of individual remnants. We used 10 graph theory metrics to assess aspects of network complexity, dispersal-route efficiency, and individual remnant importance in supporting structural connectivity. We identified forest remnants that serve as important structural connectivity roles as stepping stones, hubs, or articulation points and that should be prioritized for connectivity conservation. Structural connectivity was constrained for organisms incapable of travelling at least 9–12 km (farthest distances between nearest-neighboring forest remnants depending on whether smaller remnants were included or not) and was particularly limited for area-sensitive forest-specialist mammals. With the increased forest loss and fragmentation that is occurring, the connectivity of this system will likely be further compromised, but most of the remnants that we identified as playing important roles for structural connectivity were outside of the country’s proposed “green corridor,” indicating additional areas where conservation action can be directed.

Throat-to-Chest Behavior in Coimbra-Filho’s Titi Monkeys (Callicebus coimbrai) Is Potentially Associated with Olfactory Communication

Abstract: Despite the evident socioecological importance, knowledge of olfactory communication in Neotropical primates is in its infancy. Thus, to aid our understanding, we report on and describe olfactory communication behavior in Endangered Coimbra-Filho’s titi monkey (Callicebus coimbrai) in two Atlantic Forest fragments in northeastern Brazil. We discuss our data using intragroup (communication and sexual attraction) and intergroup (territoriality) contexts. We systematically observed two titi monkey groups, one at Fazenda Trapsa (21 mo: 1513 h) and another at Mata do Junco (11 mo: 683 h). We recorded data on olfactory signals via all-occurrence sampling. We registered 14 olfaction-linked events in which the titi monkey pressed the right hand against the gular and sternal body regions and then wiped the palm repeatedly on the nearby branch. Adult males performed 11 events, whereas adult females performed the remaining 3. Most events associated with intragroup encounters had a sexual context. The events related to intergroup encounters appeared to be related to territorial defense. Our study provides the first evidence that Coimbra-Filho’s titi monkey uses olfactory communication for both intragroup and intergroup communication. Dominance, mate attraction, and territorial defense functions shown by Coimbra-Filho titi monkeys in their olfactory behaviors provide new insights into the socioecology of Callicebusand potential themes for future research.