Changes in forest fragment sizes and primate population trends along the River Tana floodplain, Kenya

The Tana River forest patches significantly decreased in total area by 1875 ha (34.5%), from 5439 to 3564 ha between 1979 and 2000. The area covered by forests outside the Tana River Primate National Reserve declined by 1246 ha (38%) from 3283 to 2037 ha. This loss was higher than that inside the reserve, where total forest area reduced by 629 ha (29%) from 2156 to 1527 ha. The numbers of Tana River red colobus (Procolobus rufomitratus) and Tana crested mangabey (Cercocebus galeritus galeritus) groups were significantly correlated with forest sizes suggesting that both red colobus and crested mangabeys are likely to be affected by forest loss and fragmentation. However, comparison of the 1974/75 and 2001 census data did not reveal any significant change in the number of groups of either the red colobus or crested mangabey. The two endangered primates may have developed strategies to cope with a shrinking habitat.     

Comprehensive Conservation Profile of Tana Mangabeys

Forests along 60 kilometers of the lower Tana River, Kenya, provide habitat for one of the world’s top 25 most endangered primates, the Tana mangabey (Cercocebus galeritus). There is no current accurate estimate of the mangabey population, but a 1994 census estimated the population at 1,000–1,200. Their habitat has been severely degraded since then: visual estimates indicated that 30% of the forest area has been cleared and product use has increased in > 80% of forests surveyed. As the mean number of mangabey groups per forest is positively correlated with forest area and density of trees, this loss is damaging to the mangabey population. There has also been an increase in mangabey-human conflict, e.g., crop raiding, set traps, mangabeys chased by dogs. Mangabeys exhibit ecological flexibility, but behavioral data come from only a few mangabey groups. A new conservation approach is needed because past approaches, particularly the Tana River Primate National Reserve and a World Bank/Global Environment Facility Project, failed to protect the forests. The failure was mainly due to a disregard of the land-tenure issue within the Reserve, exclusion of local people from decision-making, and neglect of forests outside the reserve. Future actions must include community conservation programs and forest and corridor restoration. Research should focus on traditional management, status of primate groups in severely degraded forests, ecology of additional groups, and a population estimate to inform management as they implement more specific conservation strategies for the species.     

Population Sizes and Distribution of Primates in the Lower Tana River Forests,Kenya

We studied the population size and distribution of diurnal primates in the lower Tana River forests, Kenya. They are the only remaining habitats for 2 threatened primates: the Tana River red colobus (Procolobus rufomitratus) and the Tana River crested mangabey (Cercocebus galeritus galeritus). We conducted censuses in 73 forest patches from January through March 2001. We estimate population size of the red colobus to be 788 individuals in 82 groups and that of the crested mangabeys to be 2,070 individuals in 59 groups. The data suggest that over a 7-year period (1994-2001), there was an 18% increase in the crested mangabey population and a 5% decline in red colobus numbers. Further, the red colobus range has expanded both north and south, whereas that of crested mangabeys has only expanded south. Fifty-six percent of crested mangabeys and 46% of red colobus groups were inside the Tana River Primate National Reserve (TRPNR). Other primates encountered included 170 groups of Sykes' monkeys (Cercopithecus mitis), 70 groups of yellow baboons (Papio cynocephalus) and 4 groups of grivets [Chlorocebus (Cercopithecus) aethiops]. Mean group densities of the 2 endangered primates and of baboons were higher inside than outside the TRPNR, reinforcing the importance of TRPNR for their conservation. An intervention program is required to stem further decline in the red colobus population and to protect small isolated groups in forest patches outside TRPNR.     

Trends in forest condition,threats and conservation action as derived from participatory monitoring in coastal Kenya

The coastal forests of Kenya are conservation priorities hosting high levels of biodiversity. Monitoring of biodiversity in these forests is therefore necessary to understand and reverse negative trends in good time. Using the Important Bird Area (IBA) monitoring framework, a participatory approach, state (habitat condition), pressure (threats) and response (conservation action) indicators of twelve coastal Kenya forest IBAs were assessed from 2004 to 2011. Trends for these indicators were assessed at six sites for which sufficient data existed: Arabuko‐Sokoke, Dakatcha Woodlands, Gede Ruins, Lower Tana River, Shimba Hills and Taita Hills, and baselines were described for remaining six. Changes were always small, but state deteriorated in Gede, Lower Tana and Shimba Hills, remained the same (unfavourable) in Arabuko‐Sokoke and Dakatcha, and improved in Taita Hills. Pressure reduced in Arabuko‐Sokoke, Dakatcha and Taita Hills, deteriorated in Lower Tana and Shimba Hills and remained the same (medium) in Gede. Response improved in Dakatcha, remained the same (medium) in Shimba Hills, and deteriorated in the rest. As there was an apparent overall deterioration in the forests assessed, improved management of the protected sites and increased conservation action through community engagement around protected areas and within the nonprotected IBAs are recommended.     

Primate census and habitat evaluation in the Tana delta region, Kenya

Nineteen indigenous forest patches in the Tana River delta region, Kenya were surveyed between October and November 2000 for primates and habitat disturbance. Special emphasis was placed on the endangered Tana River red colobus (Procolobus rufomitratus Peters) and crested mangabeys (Cercocebus galeritus galeritus Peters), both of which are endemic to the region. Habitat disturbances evident in the forests included cutting of trees, harvesting of thatching material, firewood collection, dyke construction, cultivation, palm wine tapping and charcoal burning. A total of 85 groups of five primate species were counted. These comprised eighteen, ten, 22, 31 and four groups of red colobus, crested mangabey, baboons (Papio cynocephalus L.), sykes monkeys (Cercopithecus mitis Wolf) and vervet monkeys (Cercopithecus aethiops L.), respectively. A wider distribution of red colobus and crested mangabeys than was documented previously was noted, implying that they are probably more abundant than hitherto reported. It is hypothesized that extensive studies on some fauna considered endangered world‐wide would probably redefine their conservation status. Future studies in the lower Tana River region should cover the previously unsurveyed forests and focus on ways of curbing forest destruction.     

Tana river red colobus and crested mangabey: Results of recent censuses

Censuses of the Tana River red colobus (Colobus badius rufomitratus) and crested mangabey (Cercocebus galeritus galeritus), primate species endemic to riverine forests of the lower Tana River in eastern Kenya, showed significant population declines for both species between the mid-1970s and 1980s. Red colobus declined in terms of group size and number of groups per forest; the mangabey population declined only in numbers of groups per forest. There was no significant change in mean group age/sex composition between the two time periods for either species. Differences in the feeding and ranging ecology of the two species may explain why the mangabey population suffered a less severe decline than the red colobus. Similarities in census results over 3 years in the late 1980s suggest that the primate populations are no longer decreasing.     

Tana River Mangabey Use of Nonforest Areas: Functional Connectivity in a Fragmented Landscape in Kenya

Habitat loss and fragmentation is a serious threat to biodiversity. Fragment isolation can be reduced if fragments are connected, either structurally through habitat corridors or functionally if the species can move through the surrounding matrix. One-way to evaluate landscape connectivity is to observe natural movements of animals within fragmented landscapes. The Tana River mangabey (Cercocebus galeritus) is an endangered monkey endemic to fragmented forests along the lower Tana River in Kenya, and who has been observed to move through matrix between fragments. One mangabey group moved through 1 km of matrix, while another group moved through two areas of matrix. I collected behavioral and ranging data on the latter group to describe its behavior and time spent in the matrix. Utilizing data from belt transects in the matrix and forest fragments, I characterized the vegetation structure of the matrix and compared it to the forests included in each group's home range. The group spent the majority of their time eating while in the matrix, and spent an average 36.4 min in one matrix area and 100 min in the other. The matrix is generally characterized by the highest measures for a nonforest attribute and the lowest measures for forest attributes. These results suggest that forest fragments are functionally, but not structurally, connected for the mangabey; a landscape approach to conservation, therefore, should be taken for the lower Tana River. Research investigating the limitations of the mangabey's ability to use the matrix is needed.     

Coastal forests of eastern Africa: status, endemism patterns and their potential causes

Eastern African coastal forests are located within the Swahili regional centre of endemism and Swahili-Maputaland regional transition zone in eastern Africa, between 1d? North and 25d? South, and 34—41d? East. Approximately 3167 km² coastal forest remains: 2 km² in Somalia, 660 km² in Kenya, 697 km² in Tanzania, 16 km² in Malawi, 3 km² in Zimbabwe and perhaps 1790 km² in Mozambique. Most forests are small (≤ 20 km²), and all but 19 are under 30 km² in area. Over 80% of coastal forest is located on government land, principally Forest Reserves; only 8.3 km² is found in National Parks (6.2 km² in Kenya (Arabuko-Sokoke), 2 km² in Tanzania (Mafia Island) and tiny patches in Zimbabwe). Coastal forests are an important and highly threatened centre of endemism for plants (c 550 endemic species), mammals (6 species), birds (9 species), reptiles (26 species), frogs (2 species), butterflies (79 species), snails (>86 species) and millipedes (>20 species). Endemic species are concentrated in the forests of the Tana River, between Malindi in Kenya to Tanga in northern Tanzania, and in southern Tanzania. Forests with highest numbers of endemics are: lower Tana River, Arabuko-Sokoke, Shimba Hills (Kenya); lowland East Usambara, Pugu Hills, Matumbi Hills, Rondo and Litipo and other plateaux near Lindi (Tanzania); the Tanzanian offshore island of Pemba; Bazaruto archipelago (Mozambique), and tiny forest remnants of southern Malawi, eastern Zimbabwe and Mozambique. Most coastal forest endemics have a narrow distributional range, often exhibiting single-site endemism or with scattered or disjunct distributional patterns. They are best interpreted as relicts and not the result of recent evolution. Relictualization probably started with the separation of the ancient Pan African rainforest into two parts during the Miocene. The coastal forests are interpreted as a ‘vanishing refuge’ with the endemic species gradually becoming more and more relict (and presumably extinct) due historically to climatic desiccation and more recently to human destruction.     

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.     

云南西双版纳自然保护区建设的展望

<正> 西双版纳是我国仅有的几个热带区域之一,天然热带森林覆盖面积较大,野生生物种类丰富。这是西双版纳的一个资源优势,如何在加强保护的基础上合理开发利用这些资源,不仅是本地经济建设的一个重要部分,而且是全国甚至全世界人们所关心的事情。因为,全球热带森林由于过分的开发,正以惊人的速度消失,对于热带陆地区域面积不大的中国来说,西双版纳热带森林的重要意义是可想而知的。1979年以前各个自然保护区遭到严重的破坏已成过去,不必再提,关键在于对1979年以后总结了过去的经验教训重新划     

Diet and habitat overlap in two sympatric primate species, the Tana crested mangabey Cercocebus galeritus and yellow baboon Papio cynocephalus

Diet and habitat overlap was studied in two sympatric primate species sharing two neighbouring patches of fragmented gallery forest in Tana River, Kenya. Systematic data on feeding and ranging behaviour was collected on one group each of the Tana crested mangabey Cercocebus galeritus and yellow baboon Papio cynocephalus between August 1992 and February 1993. When rainfall was low and fruit resources scarce, yellow baboons spent most of their foraging time in the open woodlands while mangabeys foraged within the forest. At this period, diet and habitat overlaps between the two species were low. As rainfall increased, followed by a gradual rise in fruit availability, yellow baboons shifted their foraging range and both species became confined to the forest habitat. Consequently, both diet and habitat overlaps increased, peaking at the end of the rainy season. Mangabeys showed a reduced within-group dispersal and also spent significantly less time foraging in a given forest patch when yellow baboons were also present within the same forest patch.
Increased habitat and diet overlaps during the wet season need not have resulted in increased interspecific competition for food because at this period, fruits were readily available in the forest.     

The role of phytochemistry in dietary choices of Tana River red colobus monkeys(Procolobus badius rufomitratus)

We conducted a phytochemical survey of tree species growing within the riverine forests of the Tana River National Primate Reserve in Kenya to understand better the feeding ecology of an endangered resident primate, the Tana River red colobus monkey (Procolobus badius rufomitratus).Young leaves, which make up a large percentage of this monkey's diet, are significantly higher in nitrogen and lower in acid detergent fiber than more abundant mature leaves are. Phenolic chemistry had little inhibitory effect on feeding by P. b. rufomitratus.Choice among tree species by P. b. rufomitratusappears to be influenced largely by leaf availability,once an acceptable threshold of nitrogen and fiber is reached When mature leaves are eaten, they selected species that are high in nitrogen and low in fiber. A significantly higher nitrogen content was found for the mature leaves of all leguminous versus nonleguminous tree species. Consequently, the availability of certain types of mature leaf species during periods of preferred food scarcity may prove critical to groups of Tana River red colobus monkeys.     

Tree mortality due to an El Niño flood along the lower Tana River, Kenya

This study investigated forest tree mortality as a result of the extremely strong 1997–1998 El Niño flood in Tana River, Kenya, directly tested how mortality varied in relation to tree species and diameter at breast height (DBH), and indirectly tested how mortality varied in relation to floodwater depth. The study forest was under 2 m of water for approximately 71 days, from December 1997 until February 1998. Twenty-five liana, subcanopy tree, and canopy tree species were selected based on their importance in the diet of the Tana River mangabey ( Cercocebus galeritus Peters), a critically endangered primate endemic to the Tana River. Reproductive-sized individuals of these species were enumerated in 16.25 ha. I also enumerated trees killed by the El Niño flood, recorded their location in the forest, and measured their DBH. Ninety-two trees in fifteen species were killed by the flood. There were significant differences in mortality by species and by 0.25 ha quadrat. There were negative correlations between number of dead and DBH, number of dead and distance from the river, and per cent of quadrat killed and distance from the river. There appear to have been few long-term consequences of the El Niño flood in the forest or for the mangabeys.     

Spatial and temporal deforestation dynamics in protected and unprotected dry forests: a case study from Myanmar (Burma)

Tropical dry forests are more threatened, less protected and especially susceptible to deforestation. However, most deforestation research focuses on tropical rain forests. We analyzed spatial and temporal changes in land cover from 1972 through 2005 at Chatthin Wildlife Sanctuary (CWS), a tropical dry forest in Myanmar (Burma). CWS is one of the largest protected patches of tropical dry forest in Southeast Asia and supports over half the remaining wild population of the endangered Eld’s deer. Between 1973 and 2005, 62% of forest was lost at an annual rate of 1.86% in the area, while forest loss inside CWS was only 16% (0.45% annually). Based on trends found during our study period, dry forests outside CWS would not persist beyond 2019, while forests inside CWS would persist for at least another 100 years. Analysis of temporal deforestation patterns indicates the highest rate of loss occurred between 1992 and 2001. Conversion to agriculture, shifting agriculture, and flooding from a hydro-electric development were the main deforestation drivers. Fragmentation was also severe, halving the area of suitable Eld’s deer habitat between 1973 and 2001, and increasing its isolation. CWS protection efforts were effective in reducing deforestation rates, although deforestation effects extended up to 2 km into the sanctuary. Establishing new protected areas for dry forests and finding ways to mitigate human impacts on existing forests are both needed to protect remaining dry forests and the species they support.     

Feeding strategy of the Tana mangabey (Cercocebus galeritus galeritus) (Mammalia: Primates)

Systematic data on the feeding behaviour and ecology of the Tana mangabey ( Cercocebus g. galeritus ) were collected over a period of 13 months in a riverine forest study site on the Tana River in Kenya. A total of 1151 hours of observation was conducted on two study groups, containing 36 and 17 animals respectively. Both spatial and temporal aspects of vegetation were studied. Particular emphasis was placed on quantification of foraging behaviour , which has not been treated as a distinct category in previous primate studies. (Feeding behaviour = foraging + eating.)
Dietary composition varied according to season, but there was also evidence that the diversity of the diet increased as food availability decreased. In addition, foraging increased when food was scarce, as did total distance moved and area searched for food. Results of analysis of major food items indicated that the mangabeys were possibly selecting such items in association with their metabolisable energy values. The conspicuous foraging behaviour and locomotor versatility of the mangabeys, combined with these quantitative observations, support the interpretation that this primate is a "generalist" in terms of feeding strategy, compared with "specialist" folivores exhibiting minimal searching and manipulation of food items. It is suggested that as "generalists" the mangabeys are particularly suited to forests lining meandering river systems, with their fluctuating mosaic of vegetation and food availability.     

The small mammal community of Mukogodo Forest, Kenya

Species richness and diversity of rodents and insectivores were investigated at relict forest patches of Mukogodo, Laikipia, Kenya using Sherman's live traps and pitfall traps. Two hundred and nineteen individuals were captured in 3021 trap‐nights. There were eleven species in two taxonomic groups, Rodentia and Insectivora. Two other rodent species were sighted but not captured. Thirteen bats belonging to four species (Epomophorous wahlbergi, Pipistrellus kuhlii, Scotophilus dingani and Nycteris thebaica) were opportunistically trapped using mist nets. Two of the four species accumulation curves for forest patches did not reach an asymptote. Species richness and diversity were highest at Kurikuri compared with other patches because of habitat variability. The results support the prediction that forest disturbance and degradation lead to an increase in generalist species as compared with specialists and highlight the importance of relict afromontane forests in the conservation of small mammals in Kenya.     

Spatial and Temporal Patterns of Deforestation in Rio Cajarí Extrative Reserve,Amapá, Brazil

The Rio Cajarí Extractive Reserve (RCER) is a sustainable use protected area located in Southern Amapá state, Brazil. This protected area is home to traditional agro-extractive families, but has been increasingly invaded by commercial agriculture producers. In this work, we test the hypothesis that the RCER implementation has distinctly affected spatial patterns of deforestation and rates of bare soil and secondary forest formation by the social groups occupying the protected area and its surrounding area. Detailed maps of vegetation cover and deforestation were elaborated, based on Landsat TM images from 1991, 1998, 2007 and 2008 and Linear Spectral Mixture Models. Based on an extensive fieldwork, patches were classified according to the agents causing deforestation and characterized with ten explanatory variables. A discriminant function analysis was used to identify homogeneous groups based on the data. Results show increased rates and distinct spatial patterns of deforestation by three groups: extractivists, non traditional commercial agriculture producers, and a less representative group constituted of miners, cattle and timber producers. In all analyzed dates, clearings by the extrativist community presented the highest total area and smaller average sizes and were located in close proximity to villages. Deforestation patches by the non-traditional group were exclusively associated with ombrophilous forests; these presented higher average sizes and proximity indexes, and showed increased aggregation and large cluster formation. No significant differences were observed in deforestation patterns by the three groups inside or outside the reserve.     

Buffer zones for forest reserves: opinions of land owners and conservation value of their forest around nature reserves in southern Sweden

Buffer zones around reserves are often suggested, but have rarely been evaluated. We examined their design for small forest reserves (5–225 ha), where buffer zones (200 m wide) would protect the reserves and reduce negative edge effects. The potential buffer zones could be partly protected, but remain as private land. Alternatively, the state may buy land outside reserves (to be included in reserves). To consider opinions of forest owners, we interviewed 33 private forest owners in potential buffer zones of reserves. The respondents were weakly positive to conservation, but disliked a state reserve on their land, or a buffer zone where 50% of the forest would be protected without compensation; however, with compensation the majority of them were neutral or positive to such a buffer zone. In a choice between buffer zone or reserve bought by the state, the great majority of the respondents chose the buffer zone (compensation paid, land still private). We found no relationships between opinions of respondents and conservation values of their forests (densities of old and dead trees), but older owners had forests of higher value. The forest in the potential buffer zones had higher conservation value than other non-protected forests in southern Sweden. Thus, buffer zones may be valuable, and we suggest they are created in cooperation with local residents where this is possible.     

Impact of landscape and corridor design on primates in a large-scale industrial tropical plantation landscape

Tropical plantations are rapidly expanding as a source of industrial wood. In Indonesia, such large-scale industrial plantations are generally made of large mono-specific blocks interspersed with natural forest remnants. The extent and biodiversity value of these remnants vary as laws and regulations on their design and management are either unclear, without solid scientific basis or left to the interpretation of private companies responsible for the plantations. Our study area comprises of three Acacia mangium plantations, which have on average 18% of their total area set aside from production and conserved as natural forests. These remnant natural forests may, if appropriately designed and managed, be used to mitigate the negative impact of plantations on biodiversity by providing some degree of connectivity with and between remaining natural forest patches (such as the Tesso Nilo conservation area). We sampled natural vegetation in one and primate diversity in all three plantation sector and examined patterns of primate species richness and abundance with relation to spatial arrangement and dimensions of conservation area, which has been set aside from plantation production. We demonstrate unambiguously the critical importance of a well-connected network of natural forest corridors in the plantation landscape to maintain primates and discuss the potential biodiversity value of natural forest remnants in broad-scale industrial landscapes.     

Identifying Conservation Priority Zones for Effective Management of Tropical Forests in Eastern Ghats of India

There are thousands of protected forest areas existing on earth, yet the deforestation rate continues unabated both inside and outside the protected areas especially in the tropical forests. It identifies the less effectiveness of the current conservation strategies, which is normally oriented around the forest area cover rather than the quality of the protected areas. This calls for realistic and effective management strategies for forests. Based on the drawbacks the present study aims at identifying conservation priority sites within the protected areas (Reserved Forests) of Shervarayan hills, Eastern Ghats of Tamil Nadu, India. The remnant forest patches having less effective management/protection is identified and analysed for its qualitative contribution to the ecosystem. Quadrats of 20 × 20 m were laid in different vegetation based on the percentage of forest cover and assess the species diversity pertaining the richness, Endemism and Red list categories. Thematic layers (maps) such as vegetation type, floristic species richness, floristic endemism, and red list flora are created and categorized according to their weightage classes and overlaid in GIS domain to demarcate the Conservation Priority Zones (CPZ). The CPZ are classified according to the priority status i.e., high, moderate and low based on the contributing species richness, levels of endemism and concentration of Red listed plants.