Transect Censuses Research Articles

Population decline in the Rustic Bunting Emberiza rustica in Norway

Since the expansion of the Rustic Bunting (Emberiza rustica) westwards in northern Europe during the 19th and 20th centuries, declines have been reported in Fennoscandia. The Norwegian population was 100-500 breeding pairs in 1994. We carried out censuses to detect Rustic Buntings in Norway during 2008-12, and compared these results with previous records to evaluate recent population changes. Transect censuses made along 15 km of optimal habitat (swamp forest along rivers) yielded 18 territories during 1972-78, but in 2008 we found only 5 territories, and none since 2011. We also detected Rustic Buntings in 21 of 74 previously-occupied sites (one or more records during 1963-2007). During the study period 2008-12, we recorded Rustic Buntings in 41 sites, with a maximum of 47 territories in 2008. However, from 2008 to 2012 we detected a decline of 82% (yearly decline of 34% ± 9%; 95% CI). Local extinctions occurred in at least 31 sites. The current known population size is 13 territories in 9 sites, and the true population size may be only slightly larger. About half of all territories were associated with beaver dams, but the rate of decline during 2008-12 did not depend on dams. Extinctions could be attributed to habitat loss or change in 9/53 sites (1 logging, 1 cultivation, and 7 loss of a beaver dam). We suggest that the population decline of Norwegian Rustic Buntings is due to factors operating during migration or in wintering areas.

Leaf chemistry as a predictor of primate biomass and the mediating role of food selection: A case study in a folivorous lemur (Propithecus verreauxi)

Folivorous primate biomass has been shown to positively correlate with the average protein-to-fiber ratio in mature leaves of tropical forests. However, studies have failed to explain the mismatch between dietary selection and the role of the protein-to-fiber ratio on primate biomass; why do not folivores always favor mature leaves or leaves with the highest protein-to-fiber ratio? We examined the effect of leaf chemical characteristics and plant abundance (using transect censuses; 0.37 ha, 233 trees) on food choices and nutrient/toxin consumption in a folivorous lemur (Propithecus verreauxi) in a gallery forest in southern Madagascar. To assess the nutritional quality of the habitat, we calculated an abundance-weighted chemical index for each chemical variable. Food intake was quantified using a continuous count of mouthfuls during individual full-day follows across three seasons. We found a significant positive correlation between food ranking in the diet and plant abundance. The protein-to-fiber ratio and most other chemical variables tested had no statistical effect on dietary selection. Numerous chemical characteristics of the sifaka's diet were essentially by-products of generalist feeding and "low energy input/low energy crop" strategy. The examination of feeding behavior and plant chemistry in Old World colobines and folivorous prosimians in Madagascar suggests that relative lack of feeding selectivity and high primate biomass occur when the average protein-to-fiber ratio of mature leaves in the habitat exceeds a threshold at 0.4.

Status and distribution of Rhesus Macaque, Macaca mulatta in metropolitan Dhaka City

A field study was conducted on the status and distribution of the population of rhesus macaque, Macaca mulatta (monkeys) between June 2005 to September 2005. The population survey was made in 10 study sites of old Dhaka city employing transect census technique. I found a total of 178 rhesus macaques ranging in 10 individual troops in old part of Dhaka city. A good number of rhesus population was noted in three places, among them the highest population was seen in Shadhana Awshadhalaya Factory area (59 individuals) and the lowest was (4 individuals) in Radhika Mohan Bosak lane. Population study of rhesus macaques and investigation of their distribution is extremely important as they become part of the ecosystem of those areas. Hence, appropriate conservation measures should be taken to protect the monkeys. DOI: http://dx.doi.org/10.3329/jasbs.v38i2.15606 J. Asiat. Soc. Bangladesh, Sci. 38(2): 175-181, December 2012

Distribution and Abundance of White-Fronted Spider Monkeys, Ateles belzebuth (Atelidae), and Threats to Their Survival in Peruvian Amazonia

The white-fronted spider monkey, Ateles belzebuth, is listed as ‘Endangered’ according to the IUCN classification. In Peru it is found in the departments of Loreto, San Martín, Amazonas and Cajamarca, but detailed data on its geographic distribution, population densities and conservation status are scarce. In order to obtain such information, we conducted transect censuses on the Río Aushiri and Río San Antonio (right bank of Río Napo), and between the Río Curaray and the Río Arabela and Río Nashiño, respectively, and made additional explorations on the northern and southern banks of the Río Marañón. We obtained 48 sightings along 761 km of census transect. Group size and population densities were lower in an area with high hunting pressure compared to areas with medium or low hunting pressure. Besides hunting, increasing deforestation is a major threat to the survival of A. belzebuth in Peruvian Amazonia.

Large and medium-sized mammals of the Humaitá Forest Reserve, southwestern Amazonia, state of Acre, Brazil

Large and medium-sized mammals are essential to forest ecosystems as they are responsible for prey population control, seed dispersal and predation. A mammal survey was conducted in the Humaitá Forest Reserve (HFR), a 20 km² forest fragment located in the southeastern part of the state. The survey was carried out using census transects, camera traps, and occasional records such as bones and footprints. In all, 27 species of large to medium-sized mammals were recorded for the RFH, representing 48% of those expected for the region. Dasyprocta fuliginosa, Pecari tajacu and Didelphis marsupialis were the species with the highest number of records with camera traps. The occurrence of two species of cats (Leopardus pardalis and Puma concolor) and three endangered species (Callimico goeldii, Myrmecophaga tridactyla and Priodontes maximus) are important records for the RFH. The results may aid future research on the ecology, biogeography and conservation of mammals in the region.

A Survey of mid and large bodied mammals in Núcleo Caraguatatuba, Serra do Mar State Park, Brazil

We applied complementary survey techniques to obtain a baseline species list of mid and large bodied mammals in Núcleo Caraguatatuba, Serra do Mar State park, Brazil. Between May and September 2011 we surveyed the community of mid and large bodied mammals using diurnal line transect census (212.4 km), camera-traps (223.2 camera-trap days) and track-stations (478 track-station days). A total of 18 species were recorded from 14 families in eight orders. We recorded the presence of seven species considered threatened in the State of São Paulo, including Primates (Brachyteles arachnoides), Artiodactyla (Mazama cf. americana and Tayassu pecari), Carnivora (Leopardus pardalis, Leopardus tigrinus and Puma concolor) and Perissodactyla (Tapirus terrestris). Based on extrapolated (First order jackknife) species richness estimates we predict that there are between 19 and 32 species of mid and large bodied mammals in the Núcleo. Our revised Mammal Priority Index ranked Núcleo Caraguatatuba as being of medium overall importance for the conservation of mid and large bodied mammals in the Atlantic Forest. Combined with the number and diversity of species recorded, our results demonstrate that this Núcleo is an important area for mammal conservation.

Leaf nutritional quality as a predictor of primate biomass: further evidence of an ecological anomaly within prosimian communities in Madagascar

Abstract:The correlation between the biomass of forest primates and a chemical index of the average nutritional quality of leaves in tropical forests has been repeatedly documented since 1990. We tested the role played by protein : fibre on lemur biomass in a gallery forest in southern Madagascar. Plant species abundance was determined based on transect censuses. We calculated an average ratio of protein-to-fibre in leaves and an abundance-weighted ratio, i.e. the mean weighted by the basal area of tree species, to be compared with the figures available for other forest ecosystems in Madagascar and a number of anthropoid habitats. Lemur densities were evaluated through compilation of previous studies made from prior to 1975 and up until 2011 based on strip censuses and/or identification of all groups supplemented with new censuses. A high mean ratio of protein to fibre (> 0.4) supports high folivore biomass at 390 kg km−2 (reaching 630 kg km−2 in the closed-canopy forest area) compared with primate communities in other Malagasy forests (protein : fibre: < 0.5; folivore biomass: < 440 kg km−2), as predicted. However, the data corroborate the finding that the total biomass of lemur communities as well as the biomass of folivorous lemur species are low compared with those of African and Asian primate communities for a given protein : fibre ratio. Tree diversity and leaf production do not consistently explain this pattern. In contrast, the extinction of large folivorous lemurs during the past two millennia presumably allowed too little time for smaller-sized species to evolve equally effective morphological and physiological specializations for processing a large range of fibrous foods.

Aspectos ecológicos y sostenibilidad de la caza del majás (Cuniculus paca) en la cuenca del río Itaya, Amazonía peruana

This report contains information about sleeping dens, population structure and the impact of hunting of the paca (Cuniculus paca Linnaeus, 1766). It is based in sleeping den observations, transect censuses and hunt- ing records. We found that each sleeping den has one to three orifices for regular access and way out, one to four orifices for circumstantial escape, and an internal cavity for the diurnal sleep. Of the total sleeping dens inspected, 67% where located between 0 and 60 m from water bodies, but some were also found as far as 100 m away. Of the population extracted by hunters, 74% were adults and only 4% were infants. The annual hunting pressure was estimated at 0,4 individuals/ km2 and the population density for the overall area at 6,2 individuals/ km2. Finally, the harvest model suggests that hunting of the paca is sustainable in Alto Itaya river basin.

How to not inflate population estimates? Spatial density distribution of white-lipped peccaries in a continuous Atlantic forest

In a world with poor biological inventorying and rapid land-use change, predicting the spatial distribution of species is fundamental for the effective management and conservation of threatened taxa. However, on a regional scale, predicting the distribution of rare terrestrial mammals is often unreliable and/or impractical, especially in tropical forests. We apply a recently developed analytic process that integrates density estimation (kernel smoothing), niche-analysis and geostatistics (regression-kriging) to model the occupancy and density distribution of a threatened population of white-lipped peccaries Tayassu pecari in a Brazilian Atlantic forest. Locations (n=45) within a protected area of the Serra-do-Mar state park were obtained from diurnal line transect census (233 km), camera-trapping (751 camera-trap days) and surveys (>626 km) conducted by park rangers. Niche modelling (environmental niche-factor analysis and MAXENT) revealed a restricted niche compared with the available habitat as defined by seven environmental variables. From the occupancy model obtained from regression-kriging, we found that 72% of a 170 km2 protected area is likely to be used by peccaries. We demonstrate that the distribution of large mammals can be restricted within continuous areas of Atlantic forest and therefore population estimates based on the size of protected areas can be overestimated. Our findings suggest that the generation of realized density distributions should become the norm rather than the exception to enable conservation managers and researchers to extrapolate abundance and density estimates across continuous habitats and protected areas.

Population estimation of the Japanese giant flying squirrel Petaurista leucogenys by the line transect census and the use ratio count of tree hollow nests

Population estimation of the Japanese giant flying squirrel Petaurista leucogenys by the line transect census and the use ratio count of tree hollow nests

Relationship between Census Efforts and the Number of Species Encountered in Line Transect Censuses of Breeding Bird Populations in Woodland and Grassland Habitats of Eastern Hokkaido

Two 2-km line transects were deployed in Kushiro district, Hokkaido, Japan, one in woodland and one in grassland. Censuses were conducted 22 times along each route during the same breeding season. The relationship between census efforts and the number of species encountered was examined, and suitable census combinations for two-fold census and five-fold census were investigated. Furthermore, seasonal changes in individual bird numbers for major species were examined. Thirty-eight species were recorded along both routes. In woodland, 14 species considered to have established breeding territories along the route and were categorized as major species; 24 other species were categorized as minor species. Nine species were major and 29 were minor species in grassland. For both routes, occurrence rates for major species were more than 40%, while rates for most minor species were less than 20%. To analyze the relationship between census efforts and the number of species encountered, I constructed all possible combinations of census efforts by using the data compiled from 22 visits. The total number of species increased with increasing census efforts in both woodland and grassland. Approximately 90% of major bird species could be recorded in two-fold censuses and 99% in five-fold censuses. Censuses conducted twice in June or once each in May and June can provide census data for most bird species including the majority of major species along the routes, but do not allow discrimination of major and minor species. Five-fold repeat censuses allow discrimination of these two categories by using occurrence rates. Furthermore, the number of individual songbirds appeared to differ among breeding stages. To investigate these seasonal changes, the breeding season should be divided into more than five periods, and a census should be performed in each period. This protocol will also confirm the presence of 99% of major species.

Camera trapping photographic rate as an index of density in forest ungulates

Summary1.Calibrating indices of animal abundance to true densities is critical in wildlife studies especially when direct density estimations are precluded by high costs, lack of required data or model parameters, elusiveness and rarity of target species. For studies deploying camera traps, the use of photographic rate (photographs per sampling time) as an index of abundance potentially applies to the majority of terrestrial mammals where individual recognition, and hence capture–recapture analysis, are unfeasible. The very few studies addressing this method have either been limited by lack of independence between trapping rates and density estimations, or because they combined different species, thus introducing potential bias in camera trap detection rates. This study uses a single model species from several sites to analyse calibration of trapping rates to independently derived estimations of density. The study also makes the first field test of the method byRowcliffeet al.(2008)for density derivation from camera trapping rates based on modelling animal‐camera contacts.2.We deployed camera traps along line transects at six sites in the Udzungwa Mountains of Tanzania and correlated trapping rates of Harvey’s duikerCephalophus harveyiwith densities estimated from counts made along the same transects.3.We found a strong, linear relationship (R2 = 0·90) between trapping rate and density. Sampling precision analysis indicates that camera trapping rates reach satisfactory precision when trapping effort amounts to 250–300 camera days. Density estimates usingRowcliffeet al.’s (2008)gas model conversion are higher than from transect censuses; we discuss the possible reasons and stress the need for more field tests.4.Synthesis and applications. Subject to rigorous and periodic calibration, and standardization of sampling procedures in time and over different sites, camera trapping rate is shown to be, in this study, a valid index of density in the target species. Comparative data indicate that this may also apply to forest ungulates in general. The method has great potential for standardizing monitoring programmes and reducing the costs of wildlife surveys, especially in remote areas.

Are pheasants attracted or repelled by roads? A test of a crucial assumption for transect censuses

Censuses are widely used to monitor populations. One of the most interesting modern techniques is distance sampling, which depends on some crucial assumptions, including the random distribution of animals with respect to transect lines, which are often asphalt and gravel roads. We tested the assumption of a random distribution of animals with respect to roads for females of ring-necked pheasants (Phasianus colchicus). Roads can be used to census pheasants using distance sampling, without significant bias because pheasants are randomly distributed with respect to roads. Our method is easy to apply to other field conditions where radio tracking data are available and can be used to test the assumption in other studies and/or with different species.

Geographic distribution and demography ofPithecia aequatorialis(pitheciidae) in Peruvian Amazonia

To study the geographic distribution and demographic characteristics of Pithecia aequatorialis in Peruvian Amazonia, we undertook surveys and transect census in three river basins (Río Itaya, Río Tigre and Río Curaray) between 2004 and 2008. A total of 123 groups of P. aequatorialis was encountered during 1623 km of transect walks. Group size was uniform among the three areas (3.4-3.6 individuals), but surprisingly, population densities were higher in the area with strong hunting pressure (Río Itaya: 7.8 ind./km(2), vs. 5.6 and 5.9 km(2) in the Río Tigre and Río Curaray basins, respectively). The most common group composition included an adult pair with one offspring. Groups with more than one adult male and/or female accounted for 35% of sightings. Our observations extend P. aequatorialis range in Peru further south to the area between the Río Tigre and Río Corrientes, but exclude the area to the north between the Río Curaray and Río Napo. These findings are in contrast to previous distribution maps. P. aequatorialis was rarely seen in interspecific association during our censuses.

Distribution of potential suitable hammers and transport of hammer tools and nuts by wild capuchin monkeys

Selection and transport of objects to use as tools at a distant site are considered to reflect planning. Ancestral humans transported tools and tool-making materials as well as food items. Wild chimpanzees also transport selected hammer tools and nuts to anvil sites. To date, we had no other examples of selection and transport of stone tools among wild nonhuman primates. Wild bearded capuchins (Cebus libidinosus) in Boa Vista (Piauí, Brazil) routinely crack open palm nuts and other physically well-protected foods on level surfaces (anvils) using stones (hammers) as percussive tools. Here we present indirect evidence, obtained by a transect census, that stones suitable for use as hammers are rare (study 1) and behavioral evidence of hammer transport by twelve capuchins (study 2). To crack palm nuts, adults transported heavier and harder stones than to crack other less resistant food items. These findings show that wild capuchin monkeys selectively transport stones of appropriate size and hardness to use as hammers, thus exhibiting, like chimpanzees and humans, planning in tool-use activities.

Impact of outdoor winter sports on the abundance of a key indicator species of alpine ecosystems

Summary Tourism and leisure activities have increased continuously all over the world during the past decades, exerting a growing pressure upon naturally fragile ecosystems, such as mountainous habitats. Recent studies have established that disturbance by outdoor winter sports (e.g. skiing, snowboarding and snowshoeing) is a source of stress for wildlife. This may in turn affect its abundance, but we still lack quantitative evidence. We tested the effect of outdoor winter sports (ski lifts and related recreational activities) on the abundance of the alpine black grouse Tetrao tetrix, a vulnerable indicator species of the timberline ecosystem, the favoured habitat for outdoor winter sports in the European Alps. Generalized linear models and a model selection approach were used to rank environmental factors influencing black grouse abundance and to make predictions about population status in the theoretical absence of ski resorts. We modelled the number of displaying cocks along census transects in spring, as a function of habitat characteristics (vegetation structure and typology), ski lift density and hunting pressure at 15 natural sites (none or a very low level of anthropogenic disturbance) and 15 ski resorts in the south‐western Swiss Alps. Ski lift density and habitat typology were the principal determinants of black grouse abundance, whereas hunting pressure had no discernable effect. Ski lifts and related winter sport activities had a strong negative effect on the number of displaying cocks, which may have led to a mean 36% reduction of local abundance in ski lift areas, as determined after controlling for the confounding effect of habitat type. Synthesis and applications. Conservation action plans for black grouse should aim at reducing the multiple negative effects generated by outdoor winter sports (ski facilities and related winter sport activities). First, vegetation patchiness (i.e. a mosaic of grassy shrubland with scattered trees) should be maintained along ski runs. Secondly, wintering preserves where human access is banned or strictly limited should be promoted within ski resorts. Spatially explicit human–wildlife conflict maps can be constructed from the present model to allow delineation of those areas likely to become effective protection areas.

Geographic distribution and possible taxonomic distinction ofCallicebus torquatuspopulations (Pitheciidae: Primates) in Peruvian Amazonia

Population densities of yellow-handed titi monkey (Callicebus torquatus) were estimated using transect census methods. Densities were 2.8 individuals/km(2 )in the upper Rio Itaya basin and 2.5 individuals/km(2) in the lower Rio Algodón basin. Group size varied from two to five individuals, with an average of 2.9 individuals per group at the Rio Itaya. Groups were generally composed of two adults, probably the reproductive pair, with progeny from one to three previous birth seasons. Although the Rio Itaya population is phenotypically identical to populations from the rivers Nanay and Tigre, it differs from population on the rivers Napo and Putumayo. This suggests the existence of two disjunct populations of C. torquatus in Peruvian Amazonia whose taxonomic status warrants further examination.

Role of Honey Bees (Hymenoptera: Apidae) in the Pollination Biology of a California Native Plant, <I>Triteleia laxa</I> (Asparagales: Themidaceae)

A central focus of pollination biology is to document the relative effectiveness of different flower visitors as pollinators. Ongoing research seeks to determine the role that introduced honey bees (Apis mellifera L.) play in the pollination of both invasive and native plants. Here we report on the importance of A. mellifera as pollinators of a California native plant, Triteleia laxa Bentham. In observation plots and transect censuses, A. mellifera overwhelmingly dominated the T. laxa flower visitor assemblage. We believe the proximity to agriculture, where A. mellifera density is higher relative to areas far from agriculture, contributes to the discrepancy between A. mellifera abundance at the two sites. Although A. mellifera were inferior flower visitors qualitatively (visited less flowers per minute), they were the most frequent interactors with flowers. Furthermore, the proportion of visits to flowers on the same plant among flower visitor species did not differ, suggesting a general mechanism by which insects forage at T. laxa flowers and that A. mellifera do not cause more deleterious geitonogamy than do native pollinators. Flower visitation rates as a function of floral display size did not differ between A. mellifera and other flower visitors. The difference in the magnitude of flower visitation (largely by A. mellifera) between sites is consistent with a difference in seed set between sites. These results suggest that non-native A. mellifera bees can play an important role in the pollination of native plant species.

Density of pack-ice seals and penguins in the western Weddell Sea in relation to ice thickness and ocean depth

Aerial band transect censuses were carried out parallel with ice thickness profiling surveys in the pack ice of the western Weddell Sea during the ISPOL (Ice Station POLarstern) expedition of R.V. Polarstern from November 2004 to January 2005. Three regions were surveyed: the deep sea of the Weddell Sea, a western continental shelf/slope region where R.V. Polarstern passively drifted with an ice floe (ISPOL), and a northern region (N). Animal densities were compared among regions and in relation to bathymetry and ice thickness distribution. Crabeater seals Lobodon carcinophaga were the most abundant species in all three regions. Their density was significantly lower in the deep sea (0.50 km � 2 ) than in the ISPOL (1.00 km � 2 ) and northern regions (1.21 km � 2 ). Weddell seals Leptonychotes weddellii were not sighted in the deep-sea region, their density elsewhere ranging from 0.03 (N) to 0.08 km � 2 (ISPOL). Leopard seals Hydrurga leptonyx were observed in all three areas, but could only be quantified in the deep-sea (0.05 km � 2 ) and northern regions (0.06 km � 2 ). The abundance of emperor penguins Aptenodytes forsteri was markedly higher in the northern (0.75 km � 2 ) than in the ISPOL (0.13 km � 2 )

Effects of forest fragmentation on two sister genera of Amazonian rodents (Myoprocta acouchy and Dasyprocta leporina)

Because agoutis (Dasyprocta sp.) and acouchies (Myoprocta sp.) are the most important dispersers of several large-seeded Amazonian trees, knowing their responses to forest fragmentation is essential and urgent. But until now, there was no study showing their population trends in Amazonian land forest fragments. The present study was conducted at the Biological Dynamics of Forest Fragments Project, Central Amazon, Brazil. Eleven sites (three fragments of 1ha, three of 10ha, two of 100ha and three sites of continuous forest) were surveyed between 2003 and 2005. Agoutis and acouchies were systematically counted at each site through standard transect censuses and their densities were estimated with DISTANCE 4.1. Overall, I walked 100km, and encountered 136 acouchies and 35 agoutis. Fragmentation had a significant negative effect on acouchies and a significant positive effect on agouti densities. Acouchy density was 0.64±0.09 inds./ha (X¯±SE,N=3) in continuous forests and 0.07±0.07 inds./ha in 1-ha fragments. On the other hand, agouti density was 0.16±0.05 inds./ha in continuous forests and 0.71±0.24 inds./ha in 1-ha fragments. This study is consistent with the idea that in fragments, larger species of mammals are initially less affected by forest fragmentation than smaller ones. More critical to conservation is the fact that acouchies, which were negatively affected by fragmentation, are restricted to the core region of the Amazonian rainforests. Continued fragmentation of Amazonian forests should have vast negative consequences for the genus.