Use of space, activity patterns, and foraging behavior of red howler monkeys (Alouatta seniculus) in an Andean forest fragment in Colombia

Howler monkeys are among the most studied primates in the Neotropics, however, behavioral studies including estimation of food availability in Andean forests are scarce. During 12 months we studied habitat use, behavior, and feeding ecology of two groups of red howler monkeys (Alouatta seniculus) in an isolated fragment in the Colombian Andes. We used a combination of focal animal and instantaneous sampling. We estimated fruit production (FP) using phenology transects, and calculated young leaf abundance by observing marked trees. The home range area used by each group was 10.5 and 16.7 ha and daily distances traveled were 431 ± 228 and 458 ± 259 m, respectively. We found that both groups spent most of their time resting (62–64%). Resting time did not increase with leaf consumption as expected using a strategy of energy minimization. We did not find a relationship between daily distances traveled and leaf consumption. However, howlers consumed fruits according to their availability, and the production of young leaves did not predict feeding time on this resource. Overall, our results are similar to those found on other forest types. We found that despite limited FP in Andean forests, this did not lead to a higher intake of leaves, longer resting periods, or shorter traveling distances for red howlers. Am. J. Primatol. 73:1062–1071, 2011. © 2011 Wiley‐Liss, Inc.     

Habitat-specific ranging patterns of Dian's tarsiers (Tarsius dianae) as revealed by radiotracking

Dian's tarsier Tarsius dianae, one of the smallest primates on earth, is endemic to the central regions of Sulawesi, Indonesia. To evaluate the effects of increasing land use by humans on the ranging patterns of this nocturnal insect hunter, four study plots along a gradient of anthropogenic disturbance were selected for this study. In these plots, 71 tarsiers were captured with mist nets, and 30 of these were fitted with 3.9 g radiotransmitters and subsequently tracked over the course of 2 weeks per animal. The average home ranges were 1.1-1.8 ha in size, with the smallest ranges in slightly disturbed habitat and the largest ranges in a heavily disturbed plantation. These findings coincide with different estimates of insect abundance in the study plots. Nightly travel distances were smallest in undisturbed old-growth forest and slightly increased along a gradient of human disturbance. The tarsiers were most active shortly after dusk and just before dawn. The results of this comprehensive radiotracking study on tarsiers show that T. dianae adapts its ranging behavior to the degree and type of human land use. Integrated data on home range size and travel distance indicate that slightly disturbed forest is as favorable to these animals as undisturbed habitat. However, with increasing anthropogenic effects, the living conditions of the tarsiers appear to deteriorate, resulting in the necessity for larger home and night ranges. The results of this study provide an important tool for directing conservation efforts targeted at the survival of this primate in central Sulawesi.     

Ranging patterns and habitat use of Sulawesi Tonkean macaques (Macaca tonkeana) in a human-modified habitat

The goal of this study was to investigate the ecological flexibility of Tonkean macaques (Macaca tonkeana) by examining how they respond to human-induced habitat alteration. To do so, I observed movement patterns, forest strata use, microhabitat use, and home range use in two groups that occupied habitats with different levels of human alteration and habitat quality in Lore Lindu National Park, Sulawesi, Indonesia. The group occupying the heavily altered habitat (Anca) spent a significantly greater proportion of time traveling on the ground than the group in minimally altered habitat (CH), and significantly more time than expected in microhabitats within their range that were characterized by greater alteration (e.g., agroforestry areas). There was no significant difference between the two groups in daily path length, despite differences in group size. The Anca group exhibited a greater home range area per individual than the CH group, and utilized a more limited area within their home range with greater intensity, relative to the CH group. Tonkean macaques therefore show considerable flexibility in response to anthropogenic disturbance by adjusting their use of forest strata to facilitate travel and increase foraging opportunities and by intensively using particular areas within their home range where known resources are present and predictably available.     

Selective logging intensity in an East African rain forest predicts reductions in ant diversity

As natural forest ecosystems increasingly face pressure from deforestation, it is ever more important to understand the impacts of habitat fragmentation and degradation on biodiversity. Most studies of anthropogenic change in the tropics come from Southeast Asia and South America, and impacts of habitat modification are often taxon‐specific. Here we empirically assessed the impact of habitat fragmentation and recent (within 25 yr) and historic (>25 yr ago) selective logging on the diversity of ants in the Kakamega rain forest in western Kenya, and asked whether these forms of degradation interact as multiple stressors. We found that the severity of recent selective logging was negatively related to overall species richness and abundance as well as the richness and abundance of forest specialists, but found no detrimental effect of past selective logging or habitat fragmentation on ant diversity, although habitat fragment size was correlated with estimated species richness. There was also no effect of any form of habitat degradation on the richness or abundance of open habitat specialists, even though these species often exploit niches created in disturbed environments. Ultimately, this study reveals the detrimental impact of even moderate forms of habitat degradation on insect biodiversity in the understudied African rain forests.     

Bird richness and composition along an agricultural gradient in New Guinea: The influence of land use,habitat heterogeneity and proximity to intact forest

Abstract We examined variation in bird species richness, abundance and guild composition along an agricultural gradient in New Guinea, and looked for any additive influence of habitat heterogeneity on these variables. The study was based on a grid of survey plots, six plots wide and 24 plots long with the long axis running from a settlement 2.4 km through active and abandoned agricultural plots towards a large area of forest. Each circular survey plot (25 m radius) was assigned to a broad habitat type, ten habitat measures taken, and birds counted for 1 h in each plot. Principal component analysis (PCA) habitat axis 1 described an axis of decreasing forest alteration (larger trees, greater tree densities, fuller canopy) that was positively correlated with distance from the settlement. Bird richness and abundance were highest at intermediate disturbance levels (plots with mid‐range axis 1 scores). Proportions of insectivores and frugivores increased with decreasing forest alteration, while proportions of nectarivores decreased. We calculated three measures of habitat heterogeneity by comparing each plot's PCA score to those of eight neighbouring plots (50–110 m away). These measures reflected how different the plot was to its neighbours, how variable the habitat was around the plot, and the degree to which the plot bordered less disturbed forest. We related these measures to plot bird variable scores independently, and to residuals following regressions of bird scores against PCA scores. Heterogeneity measures had no significant influence on abundance or richness measures, but there were greater proportions of frugivores in plots showing a given degree of habitat alteration if they bordered more pristine habitat. While we readily identified differences in bird communities along the agricultural gradient, the influences of habitat heterogeneity were not striking for birds at this fine scale.     

Vegetative predictors of primate abundance: utility and limitations of a fine-scale analysis

Determining ecological predictors of primate abundance is important for both theoretical and applied conservation management. For forest primates, research has focused on comparisons of primate abundance and vegetation in different forest blocks or forest compartments with different management histories. However, great variation in primate abundance often occurs within single forests, especially in mountainous areas or in areas with habitat mosaics due to past disturbance. Here we assess, for the first time, the usefulness and limitations of small-scale, within-transect analysis of vegetative parameters as predictors of primate abundance in a very heterogeneous forest habitat in the Udzungwa Mountains of Tanzania. Relative abundance of four species of diurnal primates was recorded over a period of 2.5 years by walking three census transects 48 times each. Tree size, density, species composition, and food plants were measured along the same census lines. The fine-scale relationship between primate abundance and vegetative variables was analyzed through generalized linear modeling applied to 58 segments of these three census lines. Each segment was 200 m in length. For all four primate species, we found significant associations between their abundance and selected vegetative variables. The abundance of the endemic and endangered Udzungwa red colobus Procolobus gordonorum was positively related to mean basal area of large trees (diameter at breast height greater than 20 cm) and to the species richness of their food plants. Considering the very great variation in primate abundance that was recorded among segments of the census lines, our approach proved useful in predicting the relationship between primate abundance and small-scale habitat differences. The main limitation of this study, however, was the relatively low-predictive power of the models for some species, especially the Angolan colobus Colobus angolensis. We discuss the potential reasons for this problem and suggest possible improvements for future studies.     

Effects of habitat fragmentation and disturbance on howler monkeys: a review

We examined the literature on the effects of habitat fragmentation and disturbance on howler monkeys (genus Alouatta) to (1) identify different threats that may affect howlers in fragmented landscapes; (2) review specific predictions developed in fragmentation theory and (3) identify the empirical evidence supporting these predictions. Although howlers are known for their ability to persist in both conserved and disturbed conditions, we found evidence that they are negatively affected by high levels of habitat loss, fragmentation and degradation. Patch size appears to be the main factor constraining populations in fragmented habitats, probably because patch size is positively related to food availability, and negatively related to anthropogenic pressures, physiological stress and parasite loads. Patch isolation is not a strong predictor of either patch occupancy or population size in howlers, a result that may be related to the ability of howlers to move among forest patches. Thus, we propose that it is probable that habitat loss has larger consistent negative effects on howler populations than habitat fragmentation per se. In general, food availability decreases with patch size, not only due to habitat loss, but also because the density of big trees, plant species richness and howlers' home range size are lower in smaller patches, where howlers' population densities are commonly higher. However, it is unclear which vegetation attributes have the biggest influence on howler populations. Similarly, our knowledge is still limited concerning the effects of postfragmentation threats (e.g. hunting and logging) on howlers living in forest patches, and how several endogenous threats (e.g. genetic diversity, physiological stress, and parasitism) affect the distribution, population structure and persistence of howlers. More long‐term studies with comparable methods are necessary to quantify some of the patterns discussed in this review, and determine through meta‐analyses whether there are significant inter‐specific differences in species' responses to habitat loss and fragmentation. Am. J. Primatol. 72:1–16, 2010. © 2009 Wiley‐Liss, Inc.     

Abundance responses of frugivorous bats (Stenodermatinae) to coffee cultivation and selective logging practices in mountainous central Veracruz,Mexico

Shifting and permanent cultivation, selective logging, cattle production and coffee plantations are among the most important factors in montane cloud forest conversion and disturbance. Although shaded-coffee plantations can contribute to the preservation of local species richness, abundance of organisms could be determined by habitat resource availability in agricultural landscapes. We compared abundance of Sturnira and Artibeus bats (Phyllostomidae, Stenodermatinae), in shade coffee plantations and disturbed cloud forest fragments, which represent habitats with different chiropterochorous plant density. We also investigated the relationship between bat species abundance and food plant richness, abundance and diversity. We captured 956 bats, 76% in cloud forest fragments and 24% in shaded coffee plantations. Abundance of Sturnira spp. (small bats) was greater in cloud forest than in coffee plantations, but Artibeus spp. (large bats) abundance was similar in both habitats. Chiropterochorous plant abundance was positively related with bat abundance for Sturnira spp., while chiropterochorous plant richness and diversity were negatively related for Artibeus spp. This suggests that frugivorous bats with different morphological and ecological characteristics respond differentially to anthropogenic activities. For landscape management purposes, the maintenance and augmentation of diverse food resources, for frugivorous bats with different foraging requirements in coffee plantations, will benefit the resilience of bats to modification of their natural habitat.     

Female Spider Monkeys (<Emphasis Type="Italic">Ateles geoffroyi</Emphasis>) Cope with Anthropogenic Disturbance Through Fission–Fusion Dynamics

Most primates live in habitats with some level of anthropogenic disturbance, and such disturbances have a larger impact on frugivorous primates that are more sensitive to ecological disruptions than folivores. Fecal glucocorticoid metabolites provide insight into how the external environment affects internal physiological state, and thus provide information on how anthropogenic pressures become embodied. Here, I examine how subgroup size and glucocorticoids vary with high and low fruit abundance, and how fruit abundance, subgroup size, and activity budget affect fecal glucocorticoid metabolites in female spider monkeys (Ateles geoffroyi) living in an anthropogenically disturbed habitat. I measured these variables via behavioral, ecological, and fecal sampling for 15 months in 17 female spider monkeys at El Zota Biological Field Station. Subgroup size was significantly larger during periods of high fruit abundance, but glucocorticoids did not differ between periods of low and high fruit abundance. Monthly fruit abundance predicted subgroup sizes significantly, but did not predict fecal glucocorticoid concentrations. Increased resting time and reproductive state predicted fecal glucocorticoid concentrations significantly, but travel and foraging time had no significant effect on glucocorticoid concentrations. Individual resting time over the study period correlated negatively with glucocorticoid concentrations. These results suggest that spider monkeys cope with variation in fruit abundance by adjusting subgroup size, and that these adjustments may mitigate environmental stress in this mildly seasonal environment. The large, relatively productive forest size at this site, and the availability of anthropogenic food sources, enable this population of spider monkeys to cope with human-induced habitat disturbance.     

西双版纳片段化石灰岩森林附生兰科植物多样性研究

西双版纳石灰岩地区拥有丰富的兰科植物资源,但近年来随着橡胶树的大面积种植,使得该地区很多石灰岩森林呈片段化。为了解片段化石灰岩森林中附生兰科植物多样性状况以及片段化对附生兰科植物的影响,该研究选取了生境片段化的青岩寨和曼纳览,以及连续生境的绿石林和巴卡新寨等4个样地的29个样方进行多样性调查和对比研究。结果表明:4个石灰岩森林样共记录到附生兰科植物34属76种1 528株(丛)。通过对坡向、坡度、海拔、地形、郁闭度和森林类型等6个环境因子与附生兰科植物丰富度进行CCA分析,发现石灰岩地区附生兰科植物的分布主要受海拔和森林类型2个因素的影响,在海拔较高的青岩寨和巴卡新寨附生兰科植物物种丰富度高于低海拔的绿石林和曼纳览,而片段化对附生兰科植物的物种多样性和多度均无显著影响,这可能与片段化的历史较短有关。虽然目前来看生境片段化对石灰岩地区的附生兰科植物多样性无显著影响,但生境脆弱的石灰岩森林植被的保护对于兰科植物多样性保护则更具重要性。     

Acridids as indicators of disturbance in dry deciduous forest of West Bengal in India

Acridid communities are sensitive to anthropogenic disturbance and the community structure of acridids plays vital role in functioning the forest ecosystem. They are potentially useful bioindicators for conservation planning and habitat disturbances. Acridid assemblages of three different habitat types based on degree of disturbance as follows five natural sites, five moderately disturbed sites and five highly disturbed sites in Chaupahari forest, West Bengal, India were studied. Diversity, abundance, equitability and species richness of acridid were observed in respect to undisturbed and disturbed habitats. The species richness and diversity of the sites tracked the intensity of disturbance, the greatest value being associated with the natural site followed by the moderately disturbed site and highly disturbed site. The highest species richness and diversity index indicate the suitable habitat for acridid population. Statistical analysis infers that different species show different behavior and the sites are also different in relation to different habitat types.     

A Meta-Analysis of the Impact of Anthropogenic Forest Disturbance on Southeast Asia's Biotas

The impacts of tropical deforestation and forest degradation on SE Asia's biotas have been documented, but a quantitative synthesis is currently lacking. We examined the responses of biodiversity to anthropogenic forest disturbance by comparing key ecological attributes between undisturbed and neighboring disturbed forests. Based on data from four taxonomic groups (vascular plants, invertebrates, birds, and mammals), six broad measures of 'ecological health' ( e.g. , richness, abundance, and demographics), and a range of different impact types from 120 articles published, we calculated the proportion of pairwise comparisons in which the measure of ecological health was lower in impacted than in pristine sites, as would be expected if forest disturbance was detrimental. The explanatory power of correlates of disturbance sensitivity was assessed using an information-theoretic evaluation of a candidate set of generalized linear models (GLMs). Overall, 73.6 percent (95% CI = 70.8–76.2%) of 1074 pairwise comparisons supported the expectation that forest disturbance was detrimental to ecological health, with mammals being the most sensitive group. The median effect size was for pristine areas to have 22.2 percent higher ecological health than equivalent disturbed areas. The most responsive measure of ecological health was species richness (median = 28.6% higher in pristine), and agricultural areas were the most ecologically degraded (median = 35.6% higher in pristine). However, the GLMs revealed no marked differences overall between taxonomic groups, habitat impact types, or ecological health measures. Our finding implies that the sensitivity of biodiversity to forest disturbance is moderately high, but essentially universal, suggesting urgent forest conservation actions.     

Ranging patterns of Japanese macaques in the coniferous forest of Yakushima: Home range shift and travel rate

Ranging is one of the most important behavioral adaptations for coping with seasonally fluctuating food and thermal conditions. We studied the ranging patterns, in particular home range shift and travel rate of Japanese macaques (Macaca fuscata) in the coniferous forest of Yakushima by tracking a group for 17 months. We also supplemented our data with records collected every August over a 5-year annual census. The macaque group used the eastern part of their home range from May to September and the western part during the rest of the year. The eastern part of the home range was largely primary forest in the national park, and the altitude was higher than in the western part. When they used the western part, the macaques ate more herbs and fruits from small-sized trees, the availability of which was higher in the logged forest. This east–west home range shift occurred repeatedly over multiple years. A neighboring group occupied the western part of the focal group's home range in summer, which the focal group did not use in that season. Both temperature and diet affected seasonal changes in the monthly average travel rate. Animals need more energy for thermoregulation when the temperature is low, so the macaques decreased their ranging efforts to save energy at times of low temperature. They increased their ranging distance to eat fungi, since their encounters with this food would increase with the total distance walked. They also increased their travel rate when eating flowers, which had lower food patch (tree) density than other foods such as fruits. The data supported the hypothesis that the macaques capitalize on habitat heterogeneity in a seasonally fluctuating habitat by shifting their home range and modifying their travel rate.     

Effects of Forest Fragmentation on the Abundance of <Emphasis Type="Italic">Colobus angolensis palliatus</Emphasis> in Kenya’s Coastal Forests

We documented the occurrence and abundance patterns of Angola black-and-white colobus (Colobus angolensis palliatus) in 46 coastal forest fragments ranging from 1 ha to >1400 ha in the Kwale District, Kenya. In field surveys conducted in 2001, we also recorded forest spatial, structural, resource, and disturbance characteristics to determine the effects of habitat quality and fragmentation and the factors most critical to the continued survival of the little-known species. We tested 13 hypotheses to explain variation in patch occupancy and abundance patterns of Colobus angolensis palliatus in relation to habitat attributes. Minimal adequate models indicated that the occurrence of colobus in forest fragments is positively associated with fragment area and canopy cover, whereas the density of colobus in occupied fragments is attributable to forest area, the proportion of forest change over the previous 12 yr, and the basal area of 14 major food trees. Large-scale illegal extraction of major colobus food trees in the District for human resource use, in both protected and unprotected forests, together with ongoing forest clearance and modification, are the major threats to Colobus angolensis palliatus in Kenya.     

Ecological correlates of abundance in the Tana mangabey (Cercocebus galeritus)

I investigated the ecological correlates of abundance in the Tana mangabey (Cercocebus galeritus), one of the world's most endangered primates, with the goal of recommending management strategies. I systematically selected 31 forest fragments throughout the mangabey's 60-km distribution along the lower Tana River in southeastern Kenya. Within the 31 fragments, I measured vegetation structure, food abundance, and human forest product use in 107 belt transects, and conducted 370 mangabey surveys. I used a weighted multiple regression analysis to determine whether there was a dependence between the selected forest attributes and the mean number of mangabey groups per fragment. Fragment area and density of trees > or =10 cm diameter at breast height (DBH) were the only variables that significantly correlated with the variation in mangabey abundance. No additional variables were significant when the analysis was limited to forest fragments inside the Tana River Primate National Reserve (TRPNR) or to fragments outside the TRPNR. When I estimated the resources available before recent human forest product use by adding nonharvested and harvested variables, the total basal area of the top 15 food species became significant. This was only within the TRPNR, however. Management, therefore, should focus on increasing forest area, density of trees > or =10 cm DBH, and coverage of food trees throughout the mangabey's distribution. Solutions must be found for the problem of forest clearing, and forest product use must be better managed to protect the habitat of this critically endangered primate. The significance of food abundance only within the TRPNR suggests a need to collect dietary data from mangabey groups in fragments toward the southern limit of the mangabey's distribution, where plant species composition differs from that in fragments in which dietary data have been previously collected.     

Habitat alteration,hunting and the conservation of folivorous primates in African forests

Abstract The colobus monkeys and gorillas of African forests share a strong tendency to depend on foliage during lean seasons. In many areas, both kinds of primate are threatened by habitat destruction. But while the total removal of natural habitat is clearly a major threat to the survival of many African forest primates, an analysis of survey data suggests that human predation tends to have a greater negative impact on primate populations than does selective logging or low-intensity bush-fallow agriculture. In the absence of hunting, the population density of colobus monkeys correlates with the protein: fibre ratio of mature tree foliage in their habitat, and the density of gorillas appears to be correlated with the abundance of terrestrial herbaceous vegetation. Because moderately disturbed forest can be relatively rich in high-quality lean-season folivore foods, such forest sometimes supports a higher density of folivorous primates than forest that has not been recently disturbed but that has been subject to hunting. Conservation plans for African forests should place more emphasis on the control of hunting and less on rural development, and long-range plans should also allow for the strong possibility of political instability.     

Effects of Habitat Quality and Seasonality on Ranging Patterns of Collared Brown Lemur (Eulemur collaris) in Littoral Forest Fragments

Degraded forest habitats typically show low fruit availability and scattered fruit tree distribution. This has been shown to force frugivorous primates either to move further in search of food, resulting in large home ranges, or to use energy saving strategies. Malagasy lemurs are known to face pronounced seasonality and resource unpredictability, which is amplified by the overall reduction in food availability due to the human-driven habitat disturbance on the island. To explore lemur flexibility to habitat disturbance, we examined the ranging behavior of collared brown lemurs (Eulemur collaris) in two differently degraded fragments of littoral forest of southeastern Madagascar. We collected data from February 2011 to January 2012 on two groups living in a degraded area and two groups living in a less disturbed forest. We calculated annual ranges, monthly ranges, and daily distance traveled. We then ran repeated measures ANOVAs using seasonality as dichotomous, intrasubject factor and site/group as intersubject nested factors. In the degraded forest, the lemurs had larger monthly ranges, and their annual ranges were either fragmented or characterized by multiple core areas. They were able to use a habitat mosaic that also included nonforested areas and swamps. In addition, they shortened their daily path length, possibly to preserve energy, and used different areas of their annual home ranges seasonally. Although a number of possible confounding factors may have been responsible for the observed differences between sites, our findings highlight the ranging flexibility of collared brown lemurs in littoral forest fragments.     

Response of ants to human‐altered habitats with reference to seed dispersal of the myrmecochore Corydalis giraldii Fedde (Papaveraceae)

Anthropogenic habitat disturbance has potential consequences for ant communities. However, there is limited information on the effects of ant responses on associated ecological processes such as seed dispersal. We investigated the effect of disturbance on the abundance, richness, and composition of ant communities and the resulting seed‐dispersal services for a herbaceous myrmecochore, Corydalis giraldii (Papaveraceae), in an undisturbed habitat (forest understory), moderately disturbed habitat (abandoned arable field), and highly disturbed habitat (road verge) on Qinling Mountains, China. In total, we recorded 13 ant species, and five out of these were observed to transport seeds. The community composition of dispersers was significantly different amongst habitats. The richness of the dispersers did not differ among the habitats, but their total abundance varied significantly across habitats and was 21% lower in the road verge than in the abandoned arable fields. The major seed‐dispersing ant species in both the forest understory and the abandoned arable field were large‐bodied (Myrmica sp. and Formica fusca, respectively), whereas the major seed‐dispersing ants found in the road verge were the small‐bodied Lasius alienus. This difference resulted in lower seed removal rates and dispersal distances in the road verge than in the other two habitats. The different dispersal patterns were attributed primarily to differences in dispersing ant abundance and identity, most likely in response to habitats with different degree of anthropogenic disturbance. The possible influence of disturbance on the ecological specialization of ant‐seed dispersal interaction is also discussed.     

人类休闲活动对森林鸟类群落无有害影响

我们对西班牙马德里森林深处(未受到人类干扰)、森林小路沿线(间或有徒步旅行者经过)以及森林野餐区(有较持久干扰)的鸟类进行了调查,以查明人类休闲活动对该地区鸟类群落的分布和多度的影响.结合样方法对以上3类区域鸟类群落的总体特征(如:鸟类的多度、物种的丰富度和多样性)、不同鸟类群体的特征(如:鸦科鸟类的多度,营巢或者取食集团的特征)、各鸟种的多度等参数进行了比较.结果表明:小路沿线和野餐区样方内鸟类的多度和物种丰富度比森林深处更高,已查明14种鸟类的多度在人为干扰区域比森林深处高,只有5种鸟类的多度在森林深处更高一些;在树冠层筑巢的鸟类、在树干和地面觅食的鸟类及鸦科鸟类在休闲活动区有更高的多度;地巢性鸟类在休闲区的多度较低,这种差别尤以阔叶落叶林中加明显.而森林小路的鸟类群落结构与森林内部非常相似,说明人类休闲活动对这些林区鸟类群落的影响更多缘自野餐.原因是野餐区常常具有以下特点:具有高大的乔木、中层植被稀疏、有较多的洞和缝隙以及野餐后会遗留下一些垃圾.以上结论与研究的预期目标正好相反,人类的这些休闲活动可能会降低地巢性鸟类的适宜度,但是对大多数鸟的类栖息地没有不利影响.     

Diademed Sifaka (Propithecus diadema) Ranging and Habitat Use in Continuous and Fragmented Forest: Higher Density but Lower Viability in Fragments?

The mechanisms through which forest fragmentation threatens the survival of mammal populations remain poorly known, yet knowledge of this process would greatly aid conservation efforts. I investigated ranging behaviors of diademed sifakas ( Propithecus diadema ) in continuous and fragmented forest at Tsinjoarivo, eastern Madagascar, using focal animal observations to examine home range size, daily path length (DPL), and habitat use relative to forest edges over 12 mo. Sifaka groups in forest fragments had home ranges that were 25–50 percent as large as continuous forest groups, and moderately reduced DPLs. Continuous forest groups foraged more than expected near forest edges while fragment groups avoided edges. Fragments have higher population density than continuous forest; however, several lines of evidence suggest that fragment groups' food resources may be denser, but lower quality. Continuous forest groups appear to be energy-maximizers, maintaining large ranges and preferentially feeding in rare fruiting trees found only in continuous forest interiors, while fragment groups appear to be time-minimizers, using small home ranges and primarily feeding on mistletoe (a fallback food in continuous forest). Therefore, the consequences of fragmentation on long-term viability remain unknown; it is possible that the advantage of increased density is outweighed by longer-term demographic challenges, or other threats ( e.g. , nutrition, health, social behavior, disease). When animals stranded in forest fragments exhibit complex and potentially unpredictable responses, simple ecological proxies ( e.g. , incidence patterns and density) are probably inadequate in assessing population health and viability. Ecological study and monitoring is essential in judging the viability of fragmented populations.