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In response to Timothy Darvill's article, ‘Mythical rings?’ (this issue), which argues for an alternative interpretation of Waun Mawn circle and its relationship with Stonehenge, Parker Pearson and colleagues report new evidence from the Welsh site and elaborate on aspects of their original argument. The discovery of a hearth at the centre of the circle, as well as further features around its circumference, reinforces the authors’ original interpretation. The authors explore the evidence for the construction sequence, which was abandoned before the completion of the monument. Contesting Darvill's argument that the Aubrey Holes at Stonehenge originally held posts, the authors reassert their interpretation of this circle of cut features as Bluestone settings.
The discovery of a dismantled stone circle—close to Stonehenge's bluestone quarries in west Wales—raises the possibility that a 900-year-old legend about Stonehenge being built from an earlier stone circle contains a grain of truth. Radiocarbon and OSL dating of Waun Mawn indicate construction c. 3000 BC, shortly before the initial construction of Stonehenge. The identical diameters of Waun Mawn and the enclosing ditch of Stonehenge, and their orientations on the midsummer solstice sunrise, suggest that at least part of the Waun Mawn circle was brought from west Wales to Salisbury Plain. This interpretation complements recent isotope work that supports a hypothesis of migration of both people and animals from Wales to Stonehenge.
Wildlife is an essential component of all ecosystems. Most places in the globe do not have local, timely information on which species are present or how their populations are changing. With the arrival of new technologies, camera traps have become a popular way to collect wildlife data. However, data collection has increased at a much faster rate than the development of tools to manage, process and analyse these data. Without these tools, wildlife managers and other stakeholders have little information to effectively manage, understand and monitor wildlife populations. We identify four barriers that are hindering the widespread use of camera trap data for conservation. We propose specific solutions to remove these barriers integrated in a modern technology platform called Wildlife Insights. We present an architecture for this platform and describe its main components. We recognize and discuss the potential risks of publishing shared biodiversity data and a framework to mitigate those risks. Finally, we discuss a strategy to ensure platforms like Wildlife Insights are sustainable and have an enduring impact on the conservation of wildlife.
Methods that accurately estimate animal abundance or density are crucial for wildlife management. Although numerous techniques are available, there have been few comparisons of the precision and cost-effectiveness of different approaches. We assess the precision and cost of three methods for estimating densities of the Endangered Grevy's zebra Equus grevyi. We compare distance sampling and photographic capture–recapture, and a new technique, the random encounter model (REM) that uses camera-trap encounter rates to estimate density. All three methods provide comparable density estimates for Grevy's zebra and are preferable to the common practice of raw counts. Photographic capture–recapture is the most precise and line-transect distance sampling the least precise. Line transects and photographic capture–recapture surveys are cost-effective in the first year and REM is most cost-effective in the long-term. The methods used here for Grevy's zebra may be applied to other rangeland ungulates. We suggest that for single species monitoring programmes in which individuals can be identified, photographic capture–recapture surveys may be the preferred method for estimating wildlife abundances. When encounter rates are low, distance sampling lacks the precision of the other methods but its cost advantage may make it appropriate for long-term or multi-species monitoring programmes. The REM is an efficient and precise method of estimating densities but has high initial equipment costs. We believe REM has the potential to work well for many species but it requires independent estimates of animal movements and group size.
We distributed questionnaires and conducted interviews between July and November 1996 to develop a better understanding of the status and distribution of Bornean Peacock-pheasant Polyplectron schleiermacheri in Central Kalimantan, Indonesia. We found that many people were familiar with the species, that it is apparently widely distributed but rare in lowland forest, and that populations may be declining. We received reports of recent sightings of the pheasant at 23 locations in 9 survey areas. The primary threats to Bornean Peacock-pheasants are habitat loss within logging concessions and hunting. Recommendations for future conservation action include increasing the representation of lowland rainforest in Kalimantan's protected area system, specifically the proposed extension of Bukit Raya National Park, and control of hunting within logging concessions.
This study reviews the use of remotely triggered still cameras, known as camera traps, in bird research and suggests new methods useful for analyzing camera trap data. Camera trapping may be most appropriate for large, ground-dwelling birds, such as cracids and pheasants. Recent applications include documentation of occurrence of rare species and new species records, nest predation studies and behavioural studies including nest defence, frugivory, seed dispersal, and activity budgets. If bird postures are analyzed, it may be possible to develop behavioural time budgets. If birds are marked or individually identifiable, abundance may be estimated through capture-recapture methods typically used for mammals. We discourage use of relative abundance indices based on trapping effort because of the difficulty of standardizing surveys over time and space. Using the Great Argus Pheasant Argus argusianus, a cryptic, terrestrial, forest bird as an example, we illustrate applications of occupancy analysis to estimate proportion of occupied habitat and finite mixture models to estimate abundance when individual identification is not possible. These analyses are useful because they incorporate detection probabilities < 1 and covariates that affect the sample site or the observation process. Results are from camera trap surveys in the 3,568 km2 Bukit Barisan Selatan National Park, Indonesia. We confirmed that Great Argus Pheasants prefer primary forest below 500 m. We also find a decline in occupancy (6–8% yr−1). Point estimates of abundance peak in 2000, followed by a sharp decline. We discuss the effects of rarity, detection probability and sampling effort on accuracy and precision of estimates.
We examined the influence of forest fragmentation and resource availability on the abundance and distribution of Sumba Hornbill Aceros everetti, a large, canopy-dwelling bird endemic to Sumba Island, Indonesia. Hornbill numbers were estimated monthly from August 1998 to September 1999. Estimates were made in three large (≥1,000 ha) and three small (<1,000 ha) forest fragments, using a standard line transect method. Phenological patterns of canopy trees were assessed in 10 × 50 m plots. Our data indicated that forest patch size may be a better predictor of Sumba Hornbill abundance and distribution than overall resource availability. Hornbills occurred at higher densities in large forests (6/km2) than small forests (2.4/km2). Small forests produced more fruit/ha per month but lacked a number of important hornbill food species. Monthly fruit availability in large and small forest fragments had no significant effect on fluctuations in hornbill density. However, hornbill densities were significantly higher in forests with high densities of strangling figs, after controlling for patch size, and in larger forests hornbill densities correlated with the abundance of ripe figs. We hypothesize that small patches still have conservation value if they are within hornbill ranging distance, and speculate that Sumba's forests are in a dynamic phase before the full impact of fragmentation has been expressed.
We show a direct impact of El Niño/Southern Oscillation (ENSO) related fires on the demography and persistence of the siamang (Symphalangus syndactylus), a frugivorous, Southeast Asian rainforest primate. Siamang groups affected by ENSO-related wildfires in a Sumatran rainforest were significantly smaller and experienced significantly lower infant and juvenile survival. Likelihood of infants surviving to subadults was higher by a factor of 2.8 for groups in undisturbed habitat. Burn groups had access to 48% fewer reproductive-size strangling fig trees in their territories, compared to non-burn groups. Dietary and foraging behaviour changes associated with habitat disturbance may result in lower productivity and higher mortality of young animals. Reproductive potential of burn groups is insufficient to offset low survival and groups are unlikely to persist for more than two generations. Increasing frequency of ENSO events increases the likelihood that siamang and other long-lived species that rely on fruiting trees will experience multiple fires within one generation; the resulting reduction in seed dispersal services will slow recovery of burned forest.
We examine the abundance and distribution of Sumatran tigers (Panthera tigris sumatrae) and nine prey species in Bukit Barisan Selatan National Park on Sumatra, Indonesia. Our study is the first to demonstrate that the relative abundance of tigers and their prey, as measured by camera traps, is directly related to independently derived estimates of densities for these species. The tiger population in the park is estimated at 40-43 individuals. Results indicate that illegal hunting of prey and tigers, measured as a function of human density within 10 km of the park, is primarily responsible for observed patterns of abundance, and that habitat loss is an increasingly serious problem. Abundance of tigers, two mouse deer (Tragulus spp.), pigs (Sus scrofa) and Sambar deer (Cervus unicolor) was more than four times higher in areas with low human population density, while densities of red muntjac (Muntiacus muntjac) and pigtail macaques (Macaca nemestrina) were twice as high. Malay tapir (Tapirus indicus) and argus pheasant (Argusianus argus), species infrequently hunted, had higher indices of relative abundance in areas with high human density. Edge effects associated with park boundaries were not a significant factor in abundance of tigers or prey once human density was considered. Tigers in Bukit Barisan Selatan National Park, and probably other protected areas throughout Sumatra, are in imminent danger of extinction unless trends in hunting and deforestation are reversed.
We examined the influence of fruit availability and habitat disturbance, including past and recent forest fires, on an assemblage of hornbills over a four-month period in the Bukit Barisan Selatan National Park, Sumatra. The assemblage is dominated by Wreathed Hornbills Aceros undulatus (7.5 birds/km2), followed by Bushy-crested Hornbills Anorrhinus galeritus (3.05 birds/km2), Rhinoceros Hornbills Buceros rhinoceros (2.6 birds/km2), and Helmeted Hornbills Buceros vigil (1.9 birds/km2). Overall densities for each species were consistent with estimates from other South-East Asian sites but densities varied temporally and spatially, even for territorial species. We speculate that Rhinoceros and Helmeted Hornbills may exhibit facultative territoriality or they may not be territorial at this site. We found a positive relationship between temporal variability in hornbill numbers and the availability of ripe fruits. All hornbills, especially Rhinoceros and Bushy-crested Hornbills, tended to avoid highly disturbed areas; these areas had a lower than expected number of fruiting trees in five important hornbill diet families. Densities of Bushy-Crested, Rhinoceros, and Helmeted Hornbills declined from 28 to 63% in the post-burn surveys. Wreathed Hornbills, however, increased slightly in the post-burn surveys, possibly because they were nesting there at the time. Movement of hornbills between disturbed and primary forest habitat may enhance regeneration of disturbed areas if hornbills are transporting viable seeds.
Bukit Barisan Selatan National Park in south-west Sumatra is one of the largest protected areas in Sumatra and thus of considerable importance to the conservation of biodiversity in Indonesia. Until recently, little was known of the wildlife in the park. The authors' surveys document the presence of an intact community of the birds and mammals known to occur in lowland Sumatran rain forests. While hunting and collection of forest products threaten a number of plant and animal species in the park, the primary threat to the park's integrity is from agricultural encroachment and expansion of enclaves beyond their boundaries. The future survival of Bukit Barisan National Park and its wildlife requires that active measures be taken to curb non-sustainable exploitation of plants and wildlife. It will also be necessary to resolve land-use conflicts with communities in, and adjacent to, the park.
The issues of habitat loss and hunting are of paramount importance to wildlife conservation in Asia. In Sulawesi, Indonesia, these problems are having a serious impact on the vertebrate fauna. Using line-transect methods, the densities of 11 species of large birds and mammals were compared between 1979 and 1994 in the Tangkoko-DuaSudara Nature Reserve in North Sulawesi. During those 15 years, populations ofanoa Bubalus depressicornis, bear cuscus Phalanger ursinus, crested black macaque Macaca nigra, maleo Macrocephalon maleo and red junglefowl Gallus gallus declined by 50–95 per cent while populations of Sulawesi pig Sus celebensis, Tabon scrubfowl Megapodius cumingii, Sulawesi tarictic hornbill Penelopides exarhatus and red-knobbed hornbill Aceros cassidix increased by 5–100 per cent. We considered hypotheses for these changes: habitat loss outside the reserve, habitat degradation inside the reserve, and hunting. Only hunting adequately explained the pattern of changing densities observed. Unless protection from hunting is enforced for these species, we may soon witness the demise of these unique animals in North Sulawesi and possibly throughout the island.
Indonesia, like many other developing countries, is turning to ecotourism in an attempt to integrate the goals of development and nature conservation. Although ecotourism may be a valuable tool for preservation of biodiversity, it can have long-term negative effects on reserves, wildlife and local communities if improperly managed. In this study the authors evaluated ecotourism in the Tangkoko DuaSudara Nature Reserve, North Sulawesi, by examining trends in visitor numbers, the tourist experience, the distribution of tourist revenues, and tourist impact on the Sulawesi black macaque Macaca nigra and spectral tarsier Tarsier spectrum. The data collected showed that, although tourism is expanding rapidly, local benefits are not being fully realized, the reserve does not generate enough money to implement management, and primate behaviour is being affected. There is urgent need for a change in legal status of the reserve if ecotourism is to be managed. National park status would accommodate ecotourism planning and development, provide for greater participation by the local community, and allow for increased revenues for management.
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