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River edge feeding: Howler monkey feeding ecology in a fragmented riparian forest
Abstract
Rivers are important components of animal habitats worldwide. The area near riparian edge (≤100m from the river) has different abiotic characteristics and vegetation than both forest interior and areas bordering human development, which may lead to differences in animal feeding behaviour. To better contextualize the impact of human-caused habitat destruction on animal feeding ecology, it is important to study both natural riparian and anthropogenic forest edges within the same habitat. We compared howler monkey (Alouatta palliata) feeding behaviour and tree use across four forest zones (riparian edge, anthropogenic edge, forest interior, and combined riparian and anthropogenic edge) in a fragmented riparian rainforest in Costa Rica, La Suerte Biological Research Station (LSBRS). We predicted that monkey feeding behaviour and tree use would differ across forest zones, and especially between riparian and anthropogenic edges due to higher vegetation quality near the river. We observed individual focal monkeys for 30-minute periods, collecting data on monkey feeding behaviour and tree use every 2 minutes. We recorded plant parts eaten and feeding tree taxonomy, and measured feeding trees. Monkeys ate more leaves in riparian edge than in other forest zones, and fed from fewer tree families in riparian edge and forest interior compared to anthropogenic edge. Monkeys also fed from trees with smaller DBH in riparian edge compared to other forest zones, but trees of similar height to forest interior and taller than anthropogenic edge. Our results indicate that riparian zones are rich habitats for howler monkeys and conservation efforts should prioritize their preservation.
... We collected mantled howler monkey social behavior data from 11 groups that ranged across both forest interior and anthropogenic edge zones at LSBRS . These same groups have also been the subjects for other behavioral investigations at LSBRS (Bolt et al., 2020a(Bolt et al., , 2021a(Bolt et al., , 2023bSchreier et al., 2022a), and comprise an unusually dense population of at least 149 individual monkeys or 109.5 individuals/km 2 , which is one of the highest population densities recorded at any site worldwide for this species Schreier et al., 2023). While we could not consistently identify individual monkeys between sampling seasons due to changing group demography, we consistently observed 11 different groups across sampling seasons (Bolt et al., 2020a(Bolt et al., , 2023bSchreier et al., 2021). ...
... These same groups have also been the subjects for other behavioral investigations at LSBRS (Bolt et al., 2020a(Bolt et al., , 2021a(Bolt et al., , 2023bSchreier et al., 2022a), and comprise an unusually dense population of at least 149 individual monkeys or 109.5 individuals/km 2 , which is one of the highest population densities recorded at any site worldwide for this species Schreier et al., 2023). While we could not consistently identify individual monkeys between sampling seasons due to changing group demography, we consistently observed 11 different groups across sampling seasons (Bolt et al., 2020a(Bolt et al., , 2023bSchreier et al., 2021). Howler monkey groups were habituated and did not react to observer presence . ...
... To assess interobserver reliability, researchers simultaneously scored monkey behaviors during pilot data collection. We achieved a 94% reliability rate before the onset of data collection within each study season (Bolt et al., 2023b;Schreier et al., 2022b). ...
Social behavior is a key adaptation for group‐living primates. It is important to assess changes to social behavior in human‐impacted landscape zones to better understand the impact of anthropogenic disturbance on primate species. We investigated social behavior rate and type in three species of platyrrhines across 100 m anthropogenic edge and interior zones of a fragmented forest in Costa Rica, La Suerte Biological Research Station (LSBRS). Following results from other sites, we predicted that spider monkeys ( Ateles geoffroyi ), capuchin monkeys ( Cebus imitator ) and howler monkeys ( Alouatta palliata ) would show lower rates and fewer types of social behavior in forest edge compared to interior. We collected 1341 h of instantaneous focal data from 2017 to 2023 across the three monkey species. We found mixed support for our predictions, with spider and capuchin monkeys modifying some but not all aspects of social behavior across forest zones at LSBRS. Spider monkeys had lower rates of social behavior and capuchin monkeys performed different types of social behaviors in forest edge compared to interior at LSBRS. In contrast, howler monkeys did not modify social behavior. Two out of three platyrrhine species altered their social behavior when in anthropogenic edges, indicating behavioral adjustment when in human‐altered habitat areas at LSBRS.
... Differences in diet likely explain our findings. For example, howlers' more flexible frugivore-folivore diet enables them to persist in fragmented and anthropogenic landscapes [39,40], although they likely still require tall enough trees to meet this nutrient demand through high quality young leaves and fruit [41,42]. Capuchin monkeys can likely persist in relatively young and human-modified landscapes due to their diet characterized as highly omnivorous and opportunistic [43]. ...
Variation in tropical forest management directly affects biodiversity and provisioning of ecosystem services on a global scale, thus it is necessary to compare forests under different conservation approaches such as protected areas, payments for ecosystem services programs (PES), and ecotourism, as well as forests lacking any formal conservation plan. To examine the effectiveness of specific conservation approaches, we examined differences in forest structure and tree recruitment, including canopy cover; canopy height; seedling, sapling, and adult tree density; and average and total diameter at breast height (DBH) across 78 plots in 18 forests across Costa Rica representing protected areas, private forests utilizing PES and/or ecotourism, and private forests not utilizing these economic incentives. The effectiveness of conservation approaches in providing suitable primate habitat was assessed by conducting broad primate census surveys across a subset of eight forests to determine species richness and group encounter rate of three primate species: mantled howler monkey (Alouatta palliata), Central American spider monkey (Ateles geoffroyi), and the white-faced capuchin monkey (Cebus imitator). Only canopy height was significantly different across the three approaches, with protected areas conserving the tallest and likely oldest forests. Canopy height was also significantly associated with the group encounter rate for both mantled howler and spider monkeys, but not for capuchins. Total group encounter rate for all three monkey species combined was higher in incentivized forests than in protected areas, with capuchin and howler monkey group encounter rates driving the trend. Group encounter rate for spider monkeys was higher in protected areas than in incentivized forests. Incentivized conservation (PES and ecotourism) and protected areas are paragons of land management practices that can lead to variation in forest structure across a landscape, which not only protect primate communities, but support the dietary ecologies of sympatric primate species.
Habitat loss due to deforestation is a primary threat to global biodiversity. Clearing tropical rainforests for agriculture or development leads to forest fragmentation. Forest fragments contain fewer large trees and provide lower food availability for primates compared to continuous forests. Mantled howler monkeys (Alouatta palliata) inhabit fragmented rainforests and may need to alter their activity budgets and spatial cohesion to mitigate competition and conserve energy in fragments where food quality is lower. We compared howler monkey activity and spatial cohesion across a small forest fragment (La Suerte Biological Research Station, LSBRS) and a large, continuous forest (La Selva Research Station) in Costa Rica. We predicted that monkeys at LSBRS would rest more, feed more, travel less, and be less spatially cohesive compared to La Selva to contend with fewer resources in the small fragment. Using instantaneous scan sampling at 2-min intervals during 30-min focal samples, we recorded activity and the number of individuals within 5 m of the focal animal. We collected 1505 h of data from 2017–2024. Monkey activity and spatial cohesion differed significantly across sites. As predicted, monkeys at LSBRS spent more time feeding than at La Selva, but contrary to our predictions, they rested less and traveled more. The mean number of individuals within 5 m was significantly lower at LSBRS compared to La Selva. The ability to modify their activity and spatial cohesion in response to fragmentation provides insight into how primates can contend with fewer resources and higher competition in changing ecosystems worldwide.
Activity budget analyses are important for understanding how animals spend their time in daily activities like resting, foraging , moving and socializing. These behaviors are closely linked to energy management, so habitat quality and resource availability are known to influence the activity budgets of species. Therefore, many studies have examined the consequences of habitat loss and fragmentation on the energetic demands and activity budgets of species. However, we still have limited knowledge of how animals behave in large, continuous, and protected environments, as such habitats are currently rare. The present study analyzed how temporal variation, age, sex and reproductive status influenced the activity budget of wild red howler monkeys (Alouatta guariba clamitans), in one of the last Atlantic Forest remnants that remains large and protected. Between November 2017 and December 2018, we monitored two groups, G3 and G4, in Parque Estadual Carlos Botelho, São Paulo, Brazil. The groups were composed of one adult male, two adult females and their offspring and one (G3) or two (G4) subadult males, using scan sampling for behavioral for data collection every 20 min. The most common behavior was resting, followed by foraging, moving and social interactions, with inter-group differences. Temporal variation explained most of the fluctuations in the activity budget, so did age and sex, but to a lesser degree. The reproductive status of females did not alter their activity budget. These findings reveal that even neighboring groups display distinct and intricate relationships with their habitat. Future studies should be conducted in continuous forests to determine what is the expected range of variation in activity budget, particularly in those species considered as flexible and inhabiting endangered habitats, such as the Atlantic Forest.
Maderas Rainforest Conservancy (MRC) is a conservation non-profit organization that protects forests, offers primate field schools, and leads community outreach initiatives at sites in Central America, including La Suerte Biological Research Station (LSBRS) in Costa Rica. In 2018, MRC started Aula Verde, a conservation education initiative for elementary school students aged 5-12 at LSBRS. Groups of children from elementary schools and communities located within 50 km have visited LSBRS from 2018-2023 to participate in the 1.5-2 hour Aula Verde workshop, which consists of (1) an interactive lecture on conservation, (2) a guided forest walk, and (3) a snack, gift bag, and tree seedling for each participant. Workshops are funded by international donations to MRC and cost US $8-16 per student. Aula Verde has been successful, with multiple schools and communities making repeat visits, students’ families beginning to recycle their garbage and joining a WhatsApp group about conservation education that MRC staff initiated and lead, and teachers reporting improved learning outcomes for students who participate in the workshops. The success of Aula Verde is largely due to the ecological expertise and strong community ties of LSBRS staff. While the COVID-19 pandemic decreased Aula Verde offerings from 2020-2023, we expect workshops to resume at full capacity in 2024. In the future, MRC hopes to expand Aula Verde’s outreach to all children aged 5-12 living within 50 km of LSBRS.
Fragmented forests contain natural edges, including riparian zones, and anthropogenic edges. Edges generally have lower plant density and fewer large trees than forest interior. Riparian edges, however, contain gap-specialist trees yielding leaves with high protein content, providing primates with important resources. We examined mantled howler monkeys’ behavioral responses to riparian and anthropogenic edges at La Suerte Biological Research Station (LSBRS), Costa Rica. We predicted the monkeys would spend more time resting and feeding and less time traveling, and be less spatially cohesive, in both anthropogenic and riparian edges compared to forest interior due to lower resource abundance in edges, and in anthropogenic compared to riparian edge due to higher leaf quality in riparian zones. From 2017 to 2020, we collected data across forest zones on activity and spatial cohesion patterns via focal sampling, recording data every 2 min. Howler monkeys were significantly more likely to rest and significantly less likely to travel in both anthropogenic and riparian edges compared to forest interior; however, there were no differences between these edge types. There were significantly more monkeys within a 5-m radius of focal subjects in both anthropogenic and riparian edges compared to forest interior, but no differences between these edge types. While prior research found no differences across zones when only anthropogenic edge and forest interior were compared, results of this study demonstrate that howler monkeys at LSBRS modify their activity patterns in anthropogenic and riparian edge zones compared to forest interior, highlighting the importance of focusing on both natural and anthropogenic edge zones to fully understand primates’ behavioral responses in fragmented landscapes.
Maderas Rainforest Conservancy (MRC) is a conservation-focused non-profit organization that is devoted to protecting the tropical forests they manage in Costa Rica and Nicaragua and to providing conservation education for international university students through biological field schools. The MRC Primate Behavior and Ecology course is their most frequent course offering and is aimed at developing students to be independent field researchers. This course involves classroom lectures, training in primate identification and field methods, and the execution of independent research projects that students design, collect data for, and write up as scientific papers. Student development as conservationists is facilitated through the research experience provided by this field course as well as through co- and extracurricular research opportunities available to students at the sites that MRC manages: La Suerte Biological Research Station in Costa Rica, and Ometepe Biological Research Station in Nicaragua. In tandem with their participation in the MRC primate field course, we (Laura M. Bolt and Amy L. Schreier) consistently offer students research opportunities in our ongoing project examining the impact of forest fragmentation on primate behavioral ecology. MRC student course evaluations indicate that this co- and extracurricular research participation substantially contributes to student academic development and conservation awareness. Student research collaboration, therefore, greatly benefits students as well as furthers MRC's conservation goals as a non-profit organization. In future MRC primate field school sessions, we will continue to offer research collaboration opportunities to students and will also endeavor to improve conservation education at MRC by involving more local community members in MRC's academic programs.
Primate population size and demography are important to quantify as part of ongoing conservation efforts in tropical regions. The mantled howler monkey (Alouatta palliata) has a wide range from southern Mexico, through Central America to western Colombia, Ecuador and just into Tumbes, Peru. It is known to persist in anthropogenically-disturbed habitats, including forest fragments. As a Vulnerable species with a generally declining population, however, it is crucial to monitor their group size and population density at long-term study sites, particularly as habitats throughout their range are increasingly deforested. We present an updated group demography and population density estimate for the mantled howler monkey population at La Suerte Biological Research Station (LSBRS), Costa Rica, a long-term primate study site in a fragmented rainforest. From 2017-2022, we collected demographic data from 11 mantled howler monkey groups and several solitary individuals at LSBRS. Mean group size in 2022 was 13.1 individuals/group (±4.9 SD), adult male-to-female sex ratio was 1:2.2, and immature to adult female ratio (IFR) was 0.54. Estimated population density was 109.5 howlers/km 2 , to our knowledge, the highest ever recorded for this species at any site. Our results indicate that mantled howler monkeys can persist at a very high density in a fragmented forest over multiple years. Ongoing deforestation in the area surrounding LSBRS has likely led to the migration of howlers into LSBRS, which, along with the lack opportunities for dispersal from LSBRS, has probably contributed to the high population density in this surviving forest fragment. Our findings attest to the ability of mantled howler monkeys to survive in very high densities, which is important to consider for conservation efforts on their behalf. Resumen: Es importante cuantificar el tamaño y la demografía de la población de primates como parte de los esfuerzos de conservación en curso en las regiones tropicales. El mono aullador (Alouatta palliata) tiene una amplia distribución en todo el Neotrópico y es conocido por persistir en hábitats perturbados antropogénicamente, incluidos fragmentos de bosque. Sin embargo, como una especie vulnerable con una población generalmente en declive, es crucial monitorear el tamaño de su grupo y la densidad de población en los sitios de estudio a largo plazo, particularmente porque las áreas de hábitat a lo largo de su área de distribución están cada vez más deforestadas. Presentamos una demografía grupal actualizada y una estimación de densidad de población para la población de monos aulladores en la Estación de Investigación Biológica La Suerte (LSBRS), Costa Rica, un sitio de estudio de monos dentro de una selva tropical fragmentada. De 2017 a 2022, recopilamos datos demográficos de 11 grupos de monos aulladores y varios individuos solitarios en LSBRS. El tamaño medio del grupo en 2022 fue de 13.1 monos/ grupo (±4.9 DE), la proporción de sexos entre machos y hembras adultos fue de 1:2.2 y la proporción entre hembras inmaduras y adultas (IFR) fue de 0.54. La densidad de población estimada fue de 109.5 monos/km², la más alta jamás registrada para esta especie en cualquier sitio que sepamos. Nuestros resultados indican que el mono aullador puede persistir en una densidad muy alta en un bosque fragmentado durante varios años. La deforestación en el área que rodea LSBRS probablemente ha llevado a la migración de monos a LSBRS, así como a la falta de dispersión de monos de LSBRS, aumentando la densidad de población en este fragmento de bosque sobreviviente. Nuestros hallazgos dan fe de la capacidad de los monos aulladores para sobrevivir en condiciones de muy alta densidad y pueden usarse para informar los esfuerzos de conservación en su nombre.
With the majority of primates living close to forest edges, it is imperative to under-
stand how edges afect primate distribution and behaviour. Defnitions of edge,
however, vary across studies, with many defning edge a priori and few explicitly
measuring the depth of edge infuence (DEI). In this study, we aimed to functionally
defne edge for mantled howler monkey (Alouatta palliata) distribution and howling
behaviour in a fragmented rainforest. We surveyed howler monkey locations (walk-
ing 11 line transects a total of 253 times in May-August 2015 and 2016) and howl-
ing behaviour (584 observation hours across May-August 2017 and 2018) through-
out the forest fragment and ft our data to several candidate models to estimate DEI.
We found howler monkeys farther from anthropogenic edge and closer to river edge
than expected by a random distribution of locations. We estimated DEIs for howl
bout rate (bouts/hour), howl bout length, and howling rate per bout (howls/minute
per bout) that were diferent to those used in previous work at this site, suggesting
that a priori defnitions of edge used in prior work were likely too small to detect
edge efects and the methods used provide a more accurate picture of how edges
impact these monkeys. Our results provide an example of how using diferent edge
defnitions can alter research fndings, showing that mathematical methods of deter-
mining DEI are warranted. This mathematical approach to examining behavioural
edge efects can be applied more broadly across primates to help us better under-
stand how primates respond to edges.
Forest fragmentation increases forest edge relative to forest interior, with lower vegetation quality common for primates in edge zones. Because most primates live in human-modified tropical forests within 1 km of edge, it is critical to understand how primates cope with edge effects. Few studies have investigated how primates inhabiting a fragment alter their behaviour across forest edge and interior zones. Here we investigate how anthropogenic edges affect the activity and spatial cohesion of mantled howler monkeys (Alouatta palliata) at the La Suerte Biological Research Station (LSBRS), a Costa Rican forest fragment. We predicted the monkeys would spend greater proportions of their activity budget feeding and resting and a lower proportion travelling in edge compared to forest interior to compensate for lower resource availability in the edge. We also predicted that spatial cohesion would be lower in the edge to mitigate feeding competition. We collected data on activity and spatial cohesion (nearest neighbour distance; number of individuals within 5 m) in forest edge and interior zones via instantaneous sampling of focal animals. Contrary to predictions, monkeys spent equal proportions of time feeding, resting, and travelling in forest edge and interior. Similarly, there were no biologically meaningful differences in the number of individuals nor distance between nearest neighbours in the edge (1.0 individuals; 1.56 m) versus the interior (0.8 individuals; 1.73 m). Our results indicate that A. palliata at LSBRS do not adjust their activity or spatial cohesion patterns in response to anthropogenic edge effects, suggesting that the monkeys here exhibit less behavioural flexibility than A. palliata at some other sites. To develop effective primate conservation plans, it is therefore crucial to study primate species’ responses to fragmentation across their geographic range.
Objectives: Many group-living primate species have evolved the capacity for some individuals to live alone for part of their lives, but this solitary life stage has rarely been the subject of focused research. The mantled howler monkey (Alouatta palliata) is a social primate species with bisexual dispersal that lives in mixed-sex groups with low male-to-female sex ratios. Consequently, males often spend a long period of their lives as solitary individuals. This study compares the tree use, feeding, and long-distance vocalization behavior of solitary and group-living mantled howler monkey males living within a fragmented rainforest in Costa Rica, La Suerte Biological Research Station. Based on differences in competitive ability between solitary and group-living males, we predicted that lone males would be found in significantly smaller feeding and resting trees, consume more low-quality foods, and produce shorter howling bouts made at lower rates than group-living males.
Materials and methods: We collected data on tree use and feeding during 30-minute focal samples on male focal animals, recording data at 2-min intervals. We measured the trees in which the monkeys fed and rested for two or more intervals, and recorded the plant parts consumed. We recorded howling behavior using all-occurrences sampling.
Results: Lone males used significantly smaller feeding and resting trees, consumed more low-quality foods, and howled at lower rates but had longer howling bouts triggered by anthropogenic noise more than group-living males.
Discussion: Our results demonstrate that lone males differ in their behavioral ecology compared to group-living males, thus improving understanding of the solitary male life stage in primates.
Many species of terrestrial animals, including primates, live in varied association with the aquatic (e.g., riverine or coastal) environment. However, the benefits that each species receive from the aquatic environment are thought to vary depending on their social and ecological characteristics, and thus, elucidating those benefits to each species is important for understanding the principles of wild animal behaviour. In the present study, to gain a more complete picture of aquatic environment use, including social and ecological factors in primates, factors affecting riverine habitat utilization of two macaque species (Macaca nemestrina and M. fascicularis) were identified and qualitative comparisons were made with sympatric proboscis monkeys (Nasalis larvatus), which have different social and ecological characteristics. Temporal variation in sighting frequency of macaques at the riverbanks was positively related to the fruit availability of a dominant riparian plant species and negatively related to the river water level which affects the extent of predation pressure. Riverine utilization of macaques was greatly influenced by distribution and abundance of food (especially fruit) resources, possibly in association with predation pressure. Additionally, qualitative ecological comparisons with sympatric proboscis monkeys suggest that the drivers of riverine utilization depend on the feeding niches of the species, and different anti-predator strategies resulting from their differing social structures.
The ways that forest edges may affect animal vocalization behaviour are poorly understood. We investigated the effects of various types of edge habitat on the loud calls (howls) of a folivorous-frugivorous primate species, Alouatta palliata, with reference to the ecological resource defence hypothesis, which predicts that males howl to defend vegetation resources. We tested this hypothesis across four forest zones — interior, riparian, anthropogenic, and combined forest edges — in a riparian forest fragment in Costa Rica. We predicted vegetation and howling would differ between forest zones, with riparian and interior zones showing the highest values and anthropogenic edge the lowest. Our results indicated that vegetation was richer and howling longer in riparian and interior zones compared to combined and anthropogenic edges, supporting the resource defence hypothesis and providing some of the first evidence in animal communication scholarship for differences in behavioural edge effects between natural riparian and anthropogenic edges.
The function of long calling is a subject of interest across animal behaviour study, particularly within primatology. Many primate species have male‐specific long‐distance calls, including platyrrhines like the folivorous howler monkey (Alouatta spp.). Howler monkeys may howl to defend resources such as feeding trees or areas of rich vegetation from other monkey groups. This study tests the ecological resource defence hypothesis for howling behaviour in the mantled howler monkey (Alouatta palliata) and investigates how anthropogenic forest fragmentation may influence howling behaviour. More specifically, this study examines how howling bout rate, duration, precursors and tree species richness, DBH, and canopy cover vary in 100 m anthropogenic edge and interior forest zones at La Suerte Biological Research Station (LSBRS), a fragmented tropical rainforest in Costa Rica. Results show that tree species richness and canopy cover are higher in forest interior at this site, suggesting that monkeys should howl at greater rates in the interior to defend access to these higher‐quality vegetation resources. Overall, our results supported the ecological resource defence hypothesis. The main howl precursor was howling from neighbouring groups. Although howling rate did not differ between forest zones, howling bouts from forest interior were longer, had a greater number of howls per bout and were preceded by different precursors than howls from anthropogenic edge zones, including more howls from neighbouring groups. Our findings provide some of the first evidence for behavioural edge effects in primate vocal communication behaviour.
Widely recognized as the largest terrestrial mammal in the Neotropics, the globally endangered, IUCN Red-listed, Baird’s tapir Tapirus bairdii has been in a continual decline due to habitat loss, localized hunting, and their low reproductive rates. Because of its ecological role, the loss of this species is likely to have a cascading effect on a number of species that are important to the ecological functioning of the remaining fragments of tropical forests across Central America. As efforts continue to identify regions where this species still persists throughout its known range, we report here a new record of T. bairdii in the Caribbean lowlands of northeast Costa Rica. Although T. bairdii may have historical existed in the region surrounding the field station, they were believed to be extirpated with only anecdotal reports suggesting their continued existence.
Nonhuman primates, our closest biological relatives, play important roles in the livelihoods, cultures, and religions of many societies and offer unique insights into human evolution, biology, behavior, and the threat of emerging diseases. They are an essential component of tropical biodiversity, contributing to forest regeneration and ecosystem health. Current information shows the existence of 504 species in 79 genera distributed in the Neotropics, mainland Africa, Madagascar, and Asia. Alarmingly, ~60% of primate species are now threatened with extinction and ~75% have declining populations. This situation is the result of escalating anthropogenic pressures on primates and their habitats— mainly global and local market demands, leading to extensive habitat loss through the expansion of industrial agriculture , large-scale cattle ranching, logging, oil and gas drilling, mining, dam building, and the construction of new road networks in primate range regions. Other important drivers are increased bushmeat hunting and the illegal trade of primates as pets and primate body parts, along with emerging threats, such as climate change and anthroponotic diseases. Often, these pressures act in synergy, exacerbating primate population declines. Given that primate range regions overlap extensively with a large, and rapidly growing, human population characterized by high levels of poverty, global attention is needed immediately to reverse the looming risk of primate extinctions and to attend to local human needs in sustainable ways. Raising global scientific and public awareness of the plight of the world's primates and the costs of their loss to ecosystem health and human society is imperative.
Introduction to Forestry and Natural Resources presents a broad overview of the profession of forestry. The book details several key fields within forestry, including forest health, economics, policy, utilization, and forestry careers. Chapters deal specifically with forest products and harvesting, recreation, wildlife habitats, tree anatomy and physiology, and ethics. These topics are ideal for undergraduate introductory courses and include numerous examples (mainly graphical) and questions for students to ponder. Unlike other introductory forestry texts, which focus largely on forest ecology rather than practical forestry concepts, Introduction to Forestry and Natural Resources encompasses economic, ecological, and social aspects providing a uniquely balanced text. The wide range of experience of the contributing authors equips them especially well to identify missing content from other texts in the area and address topics currently covered in corresponding college courses.
We conducted an analysis of global forest cover to reveal that 70% of remaining forest is within 1 km of the forest’s edge, subject to the degrading effects of fragmentation. A synthesis of fragmentation experiments spanning multiple biomes and scales, five continents, and 35 years demonstrates that habitat fragmentation reduces biodiversity by 13 to 75% and impairs key ecosystem functions by decreasing biomass and altering nutrient cycles. Effects are greatest in the smallest and most isolated fragments, and they magnify with the passage of time. These findings indicate an urgent need for conservation and restoration measures to improve landscape connectivity, which will reduce extinction rates and help maintain ecosystem services.
While much is known about abiotic and vegetative edge effects in tropical forests, considerably less is known about the impact of forest edges on large mammals. In this study, we examine edge effects in a primate community to determine: 1) the distance from the edge over which edge effects in primate density are detectable, 2) whether individual species exhibit edge effects in their density, and 3) whether biological characteristics can be used to predict primate presence in edge habitats. Given their importance to many primate species, we also examine the influence of the number of large trees. We found edge penetration distances of 150 m for the five species that experienced edge effects, suggesting that primates respond to edge-related changes in the plant community that are known to be strongest over the first 150 m. Four species had higher edge densities: Alouatta macconnelli (folivore-frugivore), Chiropotes chiropotes (frugivorous seed predator), Saguinus midas (frugivore-faunivore), and Sapajus apella apella (frugivore-faunivore); one species' density was lower: Ateles paniscus (frugivore); and the final species, Pithecia chrysocephala (frugivorous seed predator), did not show an edge-related pattern. The lone significant relationship between the biological characteristics examined (body weight, diet, group size, and home range size) and primate presence in edge habitats was a negative relationship with the amount of fruit consumed. Though we did not examine primate responses to edges that border a denuded matrix, we have shown that edges influence primate distribution even following decades of secondary forest regeneration at habitat edges. Am J Phys Anthropol, 2014. © 2014 Wiley Periodicals, Inc.
Boundaries are ubiquitous across a wide range of ecological systems and spatial scales. However, most research on boundaries has been scale and system specific. To promote the synthesis of boundary studies across the range of environments and scales they represent, we present an inclusive scope for boundary studies. Three linked tools make the scope operative: (1) a causal framework covering all types of boundaries, (2) a model template, and (3) a strategy for constructing hypothetical models of boundary function in any ecological system. The framework focuses on flows of organisms, materials, energy, or information in heterogenous mosaics; it specifies patch contrast, identity of the flow, and nature of the boundary as the concepts to quantify in any model. The model template arranges these components in a functional form to elucidate specific boundary relationships. From the model template, working models that are system and scale specific can be developed. We exemplify the use of the linked tools of framework, model template, and working model with an experimental study of forest–field boundary function.
Research on fragmented ecosystems has focused mostly on the biogeograpbic consequences of the creation of habitat “islands” of different sizes and has provided little of practical value to managers. However, ecosystem fragmentation causes large changes in the physical environment as well as biogeograpbic changes. Fragmentation generally results in a landscape that consists of remnant areas of native vegetation surrounded by a matrix of agricultural or other developed land. As a result fluxes of radiation, momentum (La, wind), water, and nutrients across the landscape are altered significantly. These in turn can have important influences on biota within remnant areas, especially at or near the edge between the remnant and the surrounding matrix. The isolation of remnant areas by clearing also has important consequences for the biota. These consequences vary with the time since isolation distance from other remnants, and degree of connectivity with other remnants. The influences of physical and biogeographic changes are modified by the size, shape, and position in the landscape of individual remnant, with larger remnants being less adversely affected by the fragmentation process. The Dynamics of remnant areas are predominantly driven by factors arising in the surrounding landscape. Management of, and research on, fragmented ecosystems should be directed at understanding and controlling these external influences as much as at the biota of the remnants themselves. There is a strong need to develop an integrated approach to landscape management that places conservation reserves in the context of the overall landscape
Life generates discontinuites (boundaries) in the distribution of matter and energy. One class of these constitutes the edges between habitat-types; these are fundamental structures in landscape functioning, and hence are of central importance in conservation biology. The symposium on which this series of papers is based focused on the responses of mammals to habitat edges. A diversity of views are represented, and a variety of edge related behaviors illustrated. A survey of general ecology texts dating back to 1933 demonstrates a decline of interest in ecotones and edge effects extending into the 1980's but showing a resurgence of interest in the 1990's. Habitat edges are defined operationally with respect to particular focal species leading to a number of important corollary features. The variety of phenomena subsumed under edge effects is emphasized, and an initial attempt at classification is proposed based primarily on the presence or absence of emergent properties in edge response behaviors (matrix vs. ecotonal effects). This scheme provides for clear null hypotheses needed to distinguish the two types, enlightens mechanistic explanations of edge effects, and encourages predictions about the results of untested management schemes or other novel situations. The use and design of landscape corridors are tied to edge related behaviors. A functional and general definition of corridors is urged, so that their effectiveness can be judged with respect to specified attributes rather than to a general collection of things that might be termed corridors. Linear habitat patches are specifically excluded from the definition. Studies on small mammals have contributed to our understanding of the potential role of corridors in metapopulation dynamics. Fine versus coarse grained perceptions of environment by different species will generate ecotonal edge effects such as spillover predation. In general, the effects on landscape processes of various species operating on different spatial scales seems a fruitful direction for future research.
I conducted a 15- month ecological study of habitat preferences and activity and foraging patterns of two troops of mantled howling monkeys, Alouatta palliata,in a lowland rain forest at La Selva Biological Reserve in northeastern Costa Rica. The two troops specialized on different habitats in spite of the fact that both of them had all habitats available and were not constrained by neighboring troops since the population density of howlers is low (7- 15 howlers/km
2
).Troop 1 spent the majority of time in primary forest (80%) followed by secondary forest (10%), while troop 2 spent the majority of time in undisturbed riparian habitat (60%) followed by primary forest (30%). Habitat sampling indicates that neither the total number of stems, species, or families nor the diversity (Shannon index) or evenness is a good indicator for howler habitat selection. Instead the density of trees from the 12 species most commonly consumed by each troop is the most important factor. Activity and foraging patterns were not dependent upon the season as has been described for howling monkeys in forests with a more pronounced dry season at Barro Colorado Island, Panama, and La Pacifica in northwestern Costa Rica. This is likely a result of the more constant food supply at La Selva, combined with less intraspecific competition due to the low howler density. The intraspecific variability of foraging patterns and troop- specific habitat specialization observed in Alouatta palliatashould be considered in the conservation biology of primates. Primate relocation programs should include not only an ecological assessment of the release site but also a comparison of the release site with the habitat that the groups currently occupy.
Fragmentation reduces habitat area, increases the number of habitat patches, decreases their size, and increases patch isolation. For arboreal mammals such as howlers (Alouatta palliata), canopy modifications from fragmentation processes could also negatively affect habitat quality. We analyzed changes in the composition and plant structure of 15 fragments (1–76ha) and compared them with vegetation from a continuous tropical rain forest reserve (700ha) in Los Tuxtlas, Mexico. At each site, we sampled 1000m2 of all trees, shrubs, and lianas with a diameter at breast height (DBH) ≥10cm. We obtained estimates of species richness, density, and basal area for different ecological groups, DBH ranges, and top food resources for howlers. We used a stepwise multiple regression analysis to determine relationships between fragment characteristics (size, shape index, and isolation) and plant variables. Compared to continuous forest, fragments have altered composition and plant structure, with large trees absent from the canopy. The basal area of top food resources is higher in continuous forest. Fragment size is the best explanation for the differences in composition and plant structure. The largest fragments had greater basal area of top food resources and more large primary trees in the canopy. Overall, our results suggest that fragmentation altered the habitat quality for howlers.
The feeding preferences of howler monkeys at their northernmost distribution in the Neotropics are reported for an annual
cycle. A remarkable selectivity for 27 species representing 15 families was observed. The Moraceae and Lauraceae plant families
were the most important in the diet. The howlers spent an almost equal proportion of their feeding time eating leaves and
fruit, and displayed a marked preference for young leaves and mature fruit. The consumption of different plant parts was markedly
seasonal and the howlers’ ranging behavior was closely associated with the availability of young leaves and mature fruit.
Their home range was unusually large (ca. 60 ha) for howlers and the food species exploited occur at very low densities (93%,
≤ 4 ind/ha). They chose food items richer in protein and energy. Alkaloid compounds, present in some of the leaves, play a
secondary role in their dietary selectivity.
Pearson's chi-squared and related tests are not appropriate for all frequency-type data. Lack of independence between observations can invalidate traditional contingency table analysis because sampling distributions are no longer Poisson, multinomial or product multinominal. The usual consequence is that a true null hypothesis is rejected too often, making dubious a claim of significance. If possible, counts should be verified as coming from a Poisson or multinomial distribution before conducting tests. Assuming independence is not sufficient; chi-squared and related tests are shown not to be robust to the violation of this assumption. Frequency-type ethological data, such as the number of encounters between individuals or performances of a behaviour, are likely to violate the assumption of independence. A superior approach for the analysis of these data is demonstrated using parametric and non-parametric analysis of variance (ANOVA).
Evidence suggests that habitat heterogeneity, disturbance, disease, predation and food resources influence primate population abundance. However, few studies have focused on what habitat factors determine the probability that a primate species will occur in a habitat fragment. We analysed forest habitat and colobus population attributes to determine factors that influenced occurrence and abundance of the critically endangered Tana River red colobus. The probability of colobus inhabiting forests was positively related to the relative amount of habitat edge and canopy tree species composition. Most of the variance in the density of colobus monkeys was explained by basal area of food trees (per ha), basal area per food tree, density of food trees, and basal area per tree for all trees. We conclude that effective conservation of primates in fragmented habitats may require strategies that consider factors that influence both the occurrence of a species and its relative abundance.
Edges are presumed to have deleterious consequences for the organisms that remain in forest fragments. However, there is substantial discrepancy among recent studies about the existence and intensity of edge effects. Most studies have focused on seeking simplistic and static patterns. Very few have tested mechanistic hypotheses or explored the factors that modulate edge effects. Consequently,studies are very site-specifci and their results cannot be generalized to produce a universal theory of edges. Although estimates of the intensity and impact of edge effects in fragmented forests are urgently required, little can be done to ameliorate edge effects unless their mechanics are better understood.
The threat that forest fragmentation and habitat loss presents for several Alouatta taxa requires us to determine the key elements that may promote the persistence of howler monkeys in forest fragments and to evaluate how changes in the availability of these elements may affect their future conservation prospects. In this study we analyzed the relationship between the availability of both big trees of top food taxa (BTTFT) (diameter at breast height>60) and fruit of top food taxa (FrTFT) in the home ranges of two groups of Alouatta palliata mexicana occupying different forest fragments in Los Tuxtlas, Mexico, and their diet and activity pattern. Both study groups preferred big trees for feeding and the group with lower availability of BTTFT in their home range fed from more, smaller food sources. Furthermore, both study groups also increased the number of food sources when their consumption of fruit decreased, and the group with lower availability of FrTFT in their home range fed from more food sources. The increase in the number of food sources used under such conditions, in turn, set up a process of higher foraging effort and lower rest. In summary, our results support other studies that suggest that the availability of big trees and fruit may be two important elements influencing the persistence of howler monkeys in forest fragments.
Edge effects are caused by the penetration of abiotic and biotic conditions from the matrix into forest interiors. Although edge effects influence the biogeography of many tropical organisms, they have not been studied directly in primates. Edge effects are particularly relevant to lemurs due to the loss of 80-90% of forests in Madagascar. In this study, data are presented on how biotic edge effects influenced the distribution and density of lemurs in the Vohibola III Classified Forest in southeastern Madagascar. In total, 415 lemur surveys were conducted during June-October 2003 and May-September 2004 along six 1,250-m transects that ran perpendicular to the forest edge. Data were also collected on lemur food trees along the six transects (density, height, diameter at breast height, area, volume, and distance to forest edge). Four nocturnal species (Avahi laniger, Cheirogaleus major, Lepilemur microdon, and Microcebus rufus) and four diurnal species (Eulemur rubriventer, Eulemur fulvus rufus, Hapalemur grisesus griseus, and Propithecus diadema edwardsi) were sighted during surveys. Regression analyses of lemur densities as a function of distance to forest edge provided edge tolerances for A. laniger (edge-tolerant), M. rufus (edge-tolerant), E. rubriventer (edge-tolerant or omnipresent), and H. g. griseus (omnipresent). The density and distribution of M. rufus and their foods trees were correlated. Edge-related variations in food quality and predation pressures may also be influencing lemurs in Vohibola III. Tolerance for edge effects may explain, in part, how lemurs have survived extreme habitat loss and forest fragmentation in southeastern Madagascar.
Recent evidence indicates that primate populations may persist in neotropical fragmented landscapes by using arboreal agroecosystems, which may provide temporary habitats, increased areas of vegetation, and connectivity, among other benefits. However, limited data are available on how primates are able to sustain themselves in such manmade habitats. We report the results of a 9-month-long investigation of the feeding ecology of a troop of howler monkeys (n = 24) that have lived for the past 25 years in a 12-ha cacao plantation in the lowlands of Tabasco, Mexico. A vegetation census indicated the presence of 630 trees (> or =20 cm diameter at breast height (DBH)) of 32 shade species in the plantation. The howlers used 16 plant species (13 of which were trees) as sources of leaves, fruits, and flowers. Five shade tree species (Ficus cotinifolia, Pithecellobium saman, Gliricidia sepium, F. obtusifolia, and Ficus sp.) accounted for slightly over 80% of the total feeding time and 78% of the total number trees (n = 139) used by the howlers, and were consistently used by the howlers from month to month. The howlers spent an average of 51% of their monthly feeding time exploiting young leaves, 29% exploiting mature fruit, and 20% exploiting flowers and other plant items. Monthly consumption of young leaves varied from 23% to 67%, and monthly consumption of ripe fruit varied from 12% to 64%. Differences in the protein-to-fiber ratio of young vs. mature leaves influenced diet selection by the monkeys. The howlers used 8.3 ha of the plantation area, and on average traveled 388 m per day in each month. The howlers preferred tree species whose contribution to the total tree biomass and density was above average for the shade-tree population in the plantation. Given the right conditions of management and protection, shaded arboreal plantations in fragmented landscapes can sustain segments of howler monkey populations for many decades.
Forest corridors are often considered the main instrument with which to offset the effects of habitat loss and fragmentation. Brazilian forestry legislation requires that all riparian zones on private landholdings be maintained as permanent reserves and sets fixed minimum widths of riparian forest buffers to be retained alongside rivers and perennial streams. We investigated the effects of corridor width and degradation status of 37 riparian forest sites (including 24 corridors connected to large source-forest patches, 8 unconnected forest corridors, and 5 control riparian zones embedded within continuous forest patches) on bird and mammal species richness in a hyper-fragmented forest landscape surrounding Alta Floresta, Mato Grosso, Brazil. We used point-count and track-sampling methodology, coupled with an intensive forest-quality assessment that combined satellite imagery and ground truthed data. Vertebrate use of corridors was highly species-specific, but broad trends emerged depending on species life histories and their sensitivity to disturbance. Narrow and/or highly disturbed riparian corridors retained only a depauperate vertebrate assemblage that was typical of deforested habitats, whereas wide, well-preserved corridors retained a nearly complete species assemblage. Restriction of livestock movement along riparian buffers and their exclusion from key areas alongside deforested streams would permit corridor regeneration and facilitate restoration of connectivity.
Maderas Rainforest Conservancy (MRC) was incorporated as a conservation nonprofit organization in 2008, and manages two sites where biological field courses have been offered since the 1990s: La Suerte Biological Research Station in Costa Rica, and Ometepe Biological Research Station in Nicaragua. MRC employs a One Health approach to conservation education, and can serve as a model for other biological field sites. The Nicaraguan Molina family, who owns the sites, partnered with primatologist Paul Garber in 1994 to develop a primate field course aimed at introducing university students to field research. Through using their land to further conservation education and research, the Molina family has preserved the forest and engaged the local communities near their sites. Eight graduate theses and 46 refereed publications have been completed since 2010 based on research undertaken at MRC sites. While primate field courses have been offered at least once annually since 1994 and remain popular, a range of other ecological courses are now additionally offered. MRC operates from a One Health perspective, engaging in forest restoration and ecological monitoring projects, and has gradually expanded community outreach initiatives. MRC now conducts regular medical and veterinary missions in the communities surrounding the research stations which provide health care to local people and limit the population growth of domestic animals, thereby increasing the survival of wild animals. MRC is also active in ESL-teaching and conservation education, and funds Proyecto Jade, which empowers local women to make and sell organic jewelry. Through these programs, MRC works to help the local communities live more sustainably with the environment around them. MRC's support of research, commitment to education, medical and veterinary missions, and outreach initiatives to the local community all work together for the well-being of both the people and the environment, thus exemplifying the One Health perspective.
Research Highlights
• Maderas Rainforest Conservancy (MRC) exemplifies the One Health concept.
• MRC was incorporated as a conservation nonprofit organization in 2008.
• MRC initiatives include biological field schools, veterinary and medical missions, and local empowerment initiatives.
Anthropogenic forest fragmentation impacts many aspects of animal behaviour, including feeding ecology. With forests increasingly fragmented in tropical regions due to human development, the proportion of forest edge (≤ 100 m from clear-cut regions) is higher relative to forest interior. Forest edges differ in vegetation from interior, making it important to better understand how anthropogenic edges impact the feeding behaviour of primates such as mantled howler monkeys (Alouatta palliata). We predicted that howler monkeys would feed on higher-quality plant resources, from a larger number of tree families, and from larger trees in forest interior compared to anthropogenic forest edge. We surveyed howler monkey feeding behaviour across forest zones in a fragmented rainforest in Costa Rica, La Suerte Biological Research Station. We observed individual monkeys for 30-minute periods, collecting data on their feeding behaviour and tree use at 2-minute intervals. We measured feeding trees and recorded the plant parts and taxonomy of resources consumed. Monkeys consumed more leaves and fewer stems and fed from a smaller number of tree families in the forest interior, while they consumed fewer leaves and more stems and fed from a larger number of tree families in the forest edge. Monkeys also fed from larger, taller trees in the forest interior than the edge. The differences in howler monkey feeding behaviour between forest zones attest to the impact of human disturbance on howler monkey feeding ecology.
Rivers represent natural edges in forests, serving as transition zones between landscapes. Natural edge effects are important to study to understand how intrinsic habitat variations affect wildlife as well as the impact of human‐induced forest fragmentation. We examined the influence of riparian and anthropogenic edge on mantled howler, white‐faced capuchin, Central American spider monkeys, and vegetation structure at La Suerte Biological Research Station (abbreviated as LSBRS), Costa Rica. We predicted lower monkey encounter rate, tree species richness, and median dbh at both edge types compared to interior and that monkeys would show species‐specific responses to edge based on size and diet. We expected large, folivorous–frugivorous howler monkeys and small, generalist capuchins would be found at increased density in forest edge, while large, frugivorous spider monkeys would be found at decreased density in forest edge. We conducted population and vegetation surveys along interior, riparian, and anthropogenic edge transects at LSBRS and used GLMM to compare vegetation and monkey encounter rate. Tree species richness and median dbh were higher in forest interior than anthropogenic edge zones. Although spider monkey encounter rate did not vary between forest edges and interior, howler monkeys were encountered at highest density in riparian edge, while capuchins were encountered at highest density in anthropogenic edge. Our results indicate that diverse forest edges have varying effects on biota. Vegetation was negatively affected by forest edges, while monkey species showed species‐specific edge preferences. Our findings suggest that riparian zones should be prioritized for conservation in Neotropical forests.
Abstract in Spanish is available with online material.
When a forest is fragmented, this increases the amount of forest edge relative to the interior. Edge effects can lead to loss of animal and plant species and decreased plant biomass near forest edges. We examined the influence of an anthropogenic forest edge comprising cattle pasture, coconut plantations, and human settlement on the mantled howler (Alouatta palliata), white-faced capuchin (Cebus capucinus), Central American spider monkey (Ateles geoffroyi), and plant populations at La Suerte Biological Research Station (LSBRS), Costa Rica. We predicted that there would be lower monkey encounter rate, mean tree species richness, and diameter at breast height (DBH) in forest edge versus interior, and that monkeys would show species-specific responses to edge based on diet, body size, and canopy height preferences. Specifically, we predicted that howler monkeys would show positive or neutral edge effects due to their flexible folivorous diet, large body size, and preference for high canopy, capuchins would show positive edge effects due to their diverse diet, small body size, and preference for low to middle canopy, and spider monkeys would show negative edge effects due their reliance on ripe fruit, large body size, and preference for high upper canopy. We conducted population and vegetation surveys along edge and interior transects at LSBRS. Contrary to predictions, total monkey encounter rate did not vary between the forest edge and forest interior. Furthermore, all three species showed neutral edge effects with no significant differences in encounter rate between forest edge and interior. Interior transects had significantly higher mean tree species richness than edge transects, and interior trees had greater DBH than edge trees, although this difference was not significant. These results suggest that forest edges negatively impact plant populations at La Suerte but that the monkeys are able to withstand these differences in vegetation.
http://rdcu.be/GqFs
The Maderas Rainforest Conservancy (MRC) was founded in 2008 and manages two forested properties: (i) the La Suerte Biological Field Station, which is located in an Atlantic lowland rain forest in northeastern Costa Rica (4000 mm of annual rainfall) and (ii) the Ometepe Biological Research Station, which is part of a tropical dry forest found on the southeastern coast of Ometepe Island in Nicaragua (1400 mm of annual rainfall). Ometepe Island consists of two forested volcanoes, Volcán Concepción and Volcán Maderas, from which MRC gets its name. Ometepe Island itself is very important ecologically, and on June 5, 2010, it was declared a biosphere status by the United Nations Educational, Scientific, and Cultural Organization (UNESCO).
Research was conducted at the EI Zota biological field station to determine the amount and type of food processing exhibited by mantled howling monkeys (Alouatta palliata) prior to consumption. Mantled howling monkeys have been labeled as behavioral folivores with limited morphological adaptations for foliage digestion. The purpose of this study was to determine if A. palliata displayed any food manipulations and how food was selected by the species. Breakdown of the data was done to evaluate differences based on sex for these feeding and foraging behaviors. Results showed no behaviors that could be classified as manipulating food items and limited inspection or sampling. Low reported manual dexterity for the species and foraging through learned behaviors is reasoned for the lack of these behaviors. A .. palliata was shown to select food items smaller than the size of their hand which were most likely immature leaves. Female selectivity may be greater with regards to food inspection; however further studies would be necessary to test this finding. A focal sampling methodology was used to show these findings and 434 full feeding bouts were observed over 32.5 observation hours.
This study quantifies the effects of low-intensity logging (affecting <10% of the forest surface) on leaf chemistry, leaf and fruit production, and their effects on lemurs in a dry deciduous forest in western Madagascar. Logging exposed the remaining trees to more sunlight. Within a single tree and among trees, this resulted in higher protein concentrations in sun-exposed leaves, while fiber content remained constant. Concentrations of condensed tannins were also higher at higher sun exposure, but they leveled off at lower light intensities before protein and sugar concentrations. Within the 2-yr study period, crown extension due to higher availability of sunlight could compensate only for parts of the crown area lost due to logging. Thus, the biomass of leaves available was reduced, while average leaf quality (measured as the ratio of protein to fiber) increased. Fruit production was also positively correlated with sun exposure of the tree crown. Since fruits of the main timber trees (Commiphora spp.) are rarely consumed by frugivorous lemurs, removal of these trees increases sun exposure of other potential food trees for frugivores. At the described level of logging intensity, sightings of all lemur species increased (significantly in three out of seven species at P less than or equal to 0.05) compared to the pre-logging state and two control plots. This increase was attributed to increased fruit production and higher protein concentration in sun-exposed leaves. In natural forests, treefall gaps may have effects similar to those of logging in the present study. Low level disturbances, in general, may be important for the carrying capacity for folivorous and frugivorous lemurs and possibly for most primates.
Many types of biological studies require the estimation of food abundance in tropical forests, and a variety of methods have been used to estimate this parameter. Here we compare the accuracy and precision of three methods for estimating the fruit abundance (biomass and number) of tropical tree species: tree diameter, crown volume, and visual estimation. Diameter at breast height (DBH) was the most consistently accurate method and exhibited low levels of interobserver variability. Generally, crown volume was neither precise nor accurate. The visual estimation method was accurate for trees with very large fruit, but exhibited high interobserver variability.
Seven major types of sampling for observational studies of social behavior have been found in the literature. These methods differ considerably in their suitability for providing unbiased data of various kinds. Below is a summary of the major recommended uses of each technique: In this paper, I have tried to point out the major strengths and weaknesses of each sampling method. Some methods are intrinsically biased with respect to many variables, others to fewer. In choosing a sampling method the main question is whether the procedure results in a biased sample of the variables under study. A method can produce a biased sample directly, as a result of intrinsic bias with respect to a study variable, or secondarily due to some degree of dependence (correlation) between the study variable and a directly-biased variable. In order to choose a sampling technique, the observer needs to consider carefully the characteristics of behavior and social interactions that are relevant to the study population and the research questions at hand. In most studies one will not have adequate empirical knowledge of the dependencies between relevant variables. Under the circumstances, the observer should avoid intrinsic biases to whatever extent possible, in particular those that direcly affect the variables under study. Finally, it will often be possible to use more than one sampling method in a study. Such samples can be taken successively or, under favorable conditions, even concurrently. For example, we have found it possible to take Instantaneous Samples of the identities and distances of nearest neighbors of a focal individual at five or ten minute intervals during Focal-Animal (behavior) Samples on that individual. Often during Focal-Animal Sampling one can also record All Occurrences of Some Behaviors, for the whole social group, for categories of conspicuous behavior, such as predation, intergroup contact, drinking, and so on. The extent to which concurrent multiple sampling is feasible will depend very much on the behavior categories and rate of occurrence, the observational conditions, etc. Where feasible, such multiple sampling can greatly aid in the efficient use of research time.
In 1993 and 1999, with the assistance of a Nicaraguan family, we founded La Suerte Biological Research Station in northeastern Costa Rica and Ometepe Biological Research Station in southern Nicaragua as a privately owned conservation-oriented business. Our goal was to develop a program of sustainable community ecology focused on education, research, and the conservation of primates and tropical forests. In order to accomplish this we developed field courses in which undergraduate and graduate students conduct scientific research, experience local cultures, and learn about conservation. Over 120 of these students have received doctoral degrees or are currently in graduate programs. Four doctoral dissertations, several MA theses, and some 20 scientific articles have been published based on research conducted at our field stations. In order to achieve our long-term goals of preserving the environment, we also needed to engage directly with local communities to address their needs and concerns. To this end, we developed a series of community-based initiatives related to health care, bilingual education, and conservation education using traditional and on-line teaching tools. In this article, we describe our efforts in Costa Rica and Nicaragua teaching conservation-oriented field courses and working with the local human communities. Building upon these experiences, we outline a set of ethical considerations and responsibilities for private reserves, conservation-oriented businesses, NGOs, and conservancies that help integrate members of the local community as stakeholders in conservation.
Physical anthropologists use the term "fallback foods" to denote resources of relatively poor nutritional quality that become particularly important dietary components during periods when preferred foods are scarce. Fallback foods are becoming increasingly invoked as key selective forces that determine masticatory and digestive anatomy, influence grouping and ranging behavior, and underlie fundamental evolutionary processes such as speciation, extinction, and adaptation. In this article, we provide an overview of the concept of fallback foods by discussing definitions of the term and categorizations of types of fallback foods, and by examining the importance of fallback foods for primate ecology and evolution. We begin by comparing two recently published conceptual frameworks for considering the evolutionary significance of fallback foods and propose a way in which these approaches might be integrated. We then consider a series of questions about the importance of fallback foods for primates, including the extent to which fallback foods should be considered a distinct class of food resources, separate from preferred or commonly eaten foods; the link between life history strategy and fallback foods; if fallback foods always limit primate carrying capacity; and whether particular plant growth forms might play especially important roles as fallback resources for primates. We conclude with a brief consideration of links between fallback foods and primate conservation.
In Neotropical rain forests, fresh mammal dung, especially that of howler monkeys, constitutes an important resource used by dung beetles as food and for oviposition and further feeding by their larvae. Tropical rain forest destruction, fragmentation, and subsequent isolation causing reductions in numbers of and the disappearance of howler monkeys may result in decreasing numbers of dung beetles, but this has not been documented. In this study, we present information on the presence of howlers and dung beetles in 38 isolated forest fragments and 15 agricultural habitats. Howler monkeys were censused by visual means, while dung beetles were sampled with traps baited with a mixture of howler, cow, horse, and dog dung. Results indicated that loss of area and isolation of forest fragments result in significant decrements in howlers and dung beetles. However, dung beetle abundance was found to be closely related to the presence of howler monkeys at the sites and habitats investigated. Scenarios of land management designed to reduce isolation among forest fragments may help sustain populations of howler monkeys and dung beetles, which may have positive consequences for rain forest regeneration.
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