Optimized automated survey design in wildlife population assessment

Increased pressure on the environment has placed numerous ecological populations under threat of extinction. Management schemes dedicated to the future conservation of wildlife populations rely on effective monitoring of the size of those populations. This requires that accurate and precise abundance estimates are obtained for the purposes of wildlife population assessment. The accuracy and precision of estimates are determined to a large extent by the survey design used to obtain population samples. Methods for optimizing the survey design process are detailed, with a particular- focus on automating the sui-vey designs using computer software. The technique of automated survey design is a simulation-based tool, which provides the means to assess the properties of any type of survey design, permits the evaluation of abundance estimates over sui-vey regions with assumed population densities, and from a practical standpoint facilitates the creation of a survey plan that can be implemented in the field. Survey design properties include the probability of a particular location being included in the sample, the spatial distribution of the sampling locations within the survey region, and the distances covered by observers to obtain the sample data. The design properties are directly linked to the accuracy and precision of estimates, as well as the efficiency, achieved by a type of design. A comparative study of a number of different survey designs that can be broadly classified as systematic or non-systematic is presented. The simulation results show their performance with regard to the above-mentioned properties and the abundance estimates obtained if the designs are applied to some known population densities. Due to the more even spatial distribution of the systematic designs the estimates they produce are potentially more precise and the distances covered by observers less variable as well. It is also shown how biased estimates can result if the probability of a particular location being included in the sample is assumed to be even over the entire survey region when it is not. The problems associated with surveying along the boundary of a survey region and within non-convex regions are addressed. The methods are illustrated with a number of survey design examples

New Grauer's Gorilla Population Estimate

First paragraph: A recent paper in the American Journal of Primatology by Andrew Plumptre and colleagues examined the largest survey dataset for Grauer's gorillas Gorilla beringei graueri to date, collected between 2011 and 2019. Grauer's gorilla range covers over 15,000 km² (just under 5,800 square miles, or an area equivalent to half the size of Belgium) in the eastern Democratic Republic of the Congo. The paper has updated our understanding of how many Grauer's gorillas exist in the wild, and the trend in that population size

New Grauer's Gorilla Population Estimate

First paragraph: A recent paper in the American Journal of Primatology by Andrew Plumptre and colleagues examined the largest survey dataset for Grauer's gorillas Gorilla beringei graueri to date, collected between 2011 and 2019. Grauer's gorilla range covers over 15,000 km² (just under 5,800 square miles, or an area equivalent to half the size of Belgium) in the eastern Democratic Republic of the Congo. The paper has updated our understanding of how many Grauer's gorillas exist in the wild, and the trend in that population size

Bird Use of Northern Alaska Oilfield Rehabilitation Sites

Breeding bird response to habitat rehabilitation after anthropogenic disturbance has received little attention in the Arctic. The North Slope of Alaska is an important breeding ground for many populations of migratory birds and has also supported major oilfields since the late 1960s. The most obvious impacts of industrial development to nesting birds are direct habitat loss and fragmentation resulting from the construction of infrastructure, along with increased mechanical noise, vehicle traffic, and other forms of anthropogenic disturbance. In response to state and federal requirements, efforts have been made to rehabilitate abandoned portions of the oilfields. We compared bird use at rehabilitation sites and at nearby paired reference sites. Densities of shorebirds and passerines varied between rehabilitation sites and reference sites, but waterfowl densities did not. Specifically, passerine and shorebird densities were higher at reference sites in the early or mid-season and lower at reference sites in the late season. Additionally, birds on rehabilitation sites were primarily observed foraging and resting, while behavior observed on paired reference sites was more diverse and included courtship displays, nesting, and aggression. Further, rehabilitation sites supported significantly fewer nests and fewer species than recorded at reference sites. Our findings suggest that sites 3 to 10 years post rehabilitation do not provide bird habitat comparable to nearby reference sites and, by extension, do not provide shorebird and passerine habitat comparable to that found prior to development. However, rehabilitation sites appear to provide adequate habitat for waterfowl and are important to shorebirds and passerines as foraging areas. Continued monitoring will be needed to establish the long-term suitability of rehabilitation sites, compared to reference sites, as breeding habitat for birds.Dans l’Arctique, la réponse des oiseaux nicheurs à la remise en valeur de l’habitat après des perturbations d’origine anthropique a été peu étudiée. Le North Slope de l’Alaska est un lieu de reproduction important pour de nombreuses populations d’oiseaux migrateurs. Des champs pétroliers d’envergure y ont également été aménagés depuis la fin des années 1960. Les incidences les plus évidentes du développement industriel sur les oiseaux nicheurs sont la fragmentation et la perte directe d’habitat découlant de la construction d’infrastructures ainsi que l’augmentation du bruit mécanique, de la circulation de véhicules et d’autres formes de perturbations anthropiques. En raison des exigences de l’État et de l’administration fédérale, des efforts ont été déployés pour remettre en valeur les zones abandonnées des champs pétroliers. Nous avons comparé l’utilisation par les oiseaux des lieux remis en valeur à des lieux de référence jumelés des environs. Les densités d’oiseaux de rivage et de passereaux variaient dans les lieux remis en valeur et les lieux de référence, mais ce n’était pas le cas des densités de la sauvagine. Plus précisément, les densités de passereaux et d’oiseaux de rivage étaient plus élevées aux lieux de référence en début ou en milieu de saison, et moins élevées aux lieux de référence en fin de saison. De plus, les oiseaux de lieux remis en valeur ont surtout été vus en train de se nourrir ou de se reposer, tandis qu’aux lieux de référence, leurs comportements étaient plus variés et comprenaient des comportements de parade nuptiale, de nidification et d’agression. Par ailleurs, les lieux remis en valeur abritaient un beaucoup moins grand nombre de nids et moins d’espèces que les lieux de référence. Selon nos constatations, de trois à dix ans après les travaux de remise en valeur, ces lieux ne présentent pas, pour les oiseaux, un habitat comparable aux lieux de référence des environs et, par conséquent, ils ne fournissent pas aux passereaux et aux oiseaux de rivage un habitat comparable à celui qui s’y trouvait avant le développement industriel. Toutefois, les lieux remis en valeur semblent présenter un habitat adéquat pour la sauvagine et revêtent de l’importance comme lieux de ravitaillement pour les oiseaux de rivage et les passereaux. Une surveillance continue s’avère nécessaire afin d’établir la convenance à long terme des lieux remis en valeur, comparativement aux lieux de référence, comme habitat de nidification pour les oiseaux

Pan troglodytes ssp. troglodytes (errata version published in 2016)

Assessment Information: Pan troglodytes troglodytes has a very large geographic range (over 700,000 km2) and a relatively large population size, currently estimated at about 140,000 individuals (Strindberget al. in prep). However, this subspecies has experienced a significant population reduction since the 1970s. Between 1983 and 2000, the country of Gabon lost half its great ape population to poaching and disease, at an annual rate of decline 4% (calculated from Walsh et al. 2003). A more recent study examined nest survey data collected between 2003 and 2013 across the entire range of the taxon and created a predictive model to map Central Chimpanzee density and distribution (Strindberget al. in prep). Although the results show no statistically significant decline during those 10 years,Central Chimpanzee populations remain highly vulnerable to poaching and disease. Due to their slow life history and a generation time estimated to be 25 years, Chimpanzee populations cannot sustain high mortality levels, whether disease-induced or caused by humans. Given the scale of the poaching problem across Central Africa, this taxon is likely to be experiencing declines significant in terms of the population status, which we do not have the statistical power to detect. It is suspected that this reduction will continue for the next 30 to 40 years due to illegal hunting and expansion of the commercial bushmeat trade, and to habitat loss and degradation occurring at an increasing rate as a result of expanding human activities. The causes of the reduction, although largely understood, have certainly not ceased and are not easily reversible. The predicted continuation of the population decline is a precautionary approach based on the rapidly-increasing human population density in the region, and the expansion of land clearing for industrial-scale agricultural plantations, which requires the clearcutting of forest and is likely to accelerate in the next two to three decades. The effects of climate change will also become increasingly evident. At the same time, the threat of emerging infectious diseases is ongoing; there is, for example, evidence that Ebolavirus will continue to spread (Walshet al. 2005), which would have devastating consequences for Central African great ape populations. At a conservative rate of loss of 1% each year, the population reduction over three generations (75 years) from 1975-2050 is likely to exceed 50%, hence qualifying Central Chimpanzees as Endangered under criterion A

Guns, germs, and trees determine density and distribution of gorillas and chimpanzees in Western Equatorial Africa

We present a range-wide assessment of sympatric western lowland gorillas Gorilla gorilla gorilla and central chimpanzees Pan troglodytes troglodytes using the largest survey data set ever assembled for these taxa: 59 sites in five countries surveyed between 2003 and 2013, totaling 61,000 person-days of fieldwork. We used spatial modeling to investigate major drivers of great ape distribution and population trends. We predicted density across each taxon’s geographic range, allowing us to estimate overall abundance: 361,900 gorillas and 128,700 chimpanzees in Western Equatorial Africa—substantially higher than previous estimates. These two subspecies represent close to 99% of all gorillas and one-third of all chimpanzees. Annual population decline of gorillas was estimated at 2.7%, maintaining them as Critically Endangered on the International Union for Conservation of Nature and Natural Resources (IUCN) Red List. We quantified the threats to each taxon, of which the three greatest were poaching, disease, and habitat degradation. Gorillas and chimpanzees are found at higher densities where forest is intact, wildlife laws are enforced, human influence is low, and disease impacts have been low. Strategic use of the results of these analyses could conserve the majority of gorillas and chimpanzees. With around 80% of both subspecies occurring outside protected areas, their conservation requires reinforcement of anti-poaching efforts both inside and outside protected areas (particularly where habitat quality is high and human impact is low), diligent disease control measures (including training, advocacy, and research into Ebola virus disease), and the preservation of high-quality habitat through integrated land-use planning and implementation of best practices by the extractive and agricultural industries.Additional co-authors: Nicolas Bout, Thomas Breuer, Genevieve Campbell, Pauwel De Wachter, Marc Ella Akou, Fidel Esono Mba, Anna T. C. Feistner, Bernard Fosso, Roger Fotso, David Greer, Clement Inkamba-Nkulu, Calixte F. Iyenguet, Max Kokangoye, Hjalmar S. Kühl, Stephanie Latour, Bola Madzoke, Calixte Makoumbou, Guy-Aimé F. Malanda, Richard Malonga, Victor Mbolo, David B. Morgan, Prosper Motsaba, Gabin Moukala, Brice S. Mowawa, Mizuki Murai, Christian Ndzai, Tomoaki Nishihara, Zacharie Nzooh, Lilian Pintea, Amy Pokempner, Hugo J. Rainey, Tim Rayden, Heidi Ruffler, Crickette M. Sanz, Angelique Todd, Hilde Vanleeuwe, Ashley Vosper, Ymke Warren, and David S. Wilki

Forest Elephant Crisis in the Congo Basin

Debate over repealing the ivory trade ban dominates conferences of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Resolving this controversy requires accurate estimates of elephant population trends and rates of illegal killing. Most African savannah elephant populations are well known; however, the status of forest elephants, perhaps a distinct species, in the vast Congo Basin is unclear. We assessed population status and incidence of poaching from line-transect and reconnaissance surveys conducted on foot in sites throughout the Congo Basin. Results indicate that the abundance and range of forest elephants are threatened from poaching that is most intense close to roads. The probability of elephant presence increased with distance to roads, whereas that of human signs declined. At all distances from roads, the probability of elephant occurrence was always higher inside, compared to outside, protected areas, whereas that of humans was always lower. Inside protected areas, forest elephant density was correlated with the size of remote forest core, but not with size of protected area. Forest elephants must be prioritised in elephant management planning at the continental scale

Are We Capturing Faunal Intactness? A Comparison of Intact Forest Landscapes and the “Last of the Wild in Each Ecoregion”

Efforts to designate priority areas for conservation have had a long history, with most modern initiatives focused on either designating areas important for biodiversity or those least impacted by direct human disturbance. Ecologically intact ecosystems are becoming increasingly limited on the planet, making their identification and conservation an important priority. Intact forest landscapes (IFL) are defined as forests that are mainly free of significant anthropogenic degradation and at least 500 km2 in size. Here we define a new metric, the Last of the Wild in each Ecoregion (LWE), as a preliminary scoping of the most intact parts of each ecoregion. IFL and LWE are approaches among a broad family of techniques to mapping ecological integrity at the global scale. Although both implicitly include species integrity as a dimension of intactness, this is inferred rather than directly measured. We assessed whether IFL or LWE areas were better at capturing species where they are most abundant using species distribution data for a set of forest species for which range-wide data were available and human activity limits the range. We found that IFL and LWE methods identified areas where species we assessed are either absent or at too low an abundance to be ecologically functional. As such many IFL/LWE polygons did not have intact fauna. We also show that 54.7% of the terrestrial realm (excluding Antarctica) has at least one species recorded as extinct and that two thirds of IFL/LWE areas overlap with areas where species have gone extinct in the past 500 years. The results show that even within the most remote areas, serious faunal loss has taken place at many localities so direct species survey work is also needed to confirm faunal intactness

Human footprint and protected areas shape elephant range across Africa

Over the last two millennia, and at an accelerating pace, the African elephant (Loxodonta spp. Lin.) has been threatened by human activities across its range. We investigate the correlates of elephant home range sizes across diverse biomes. Annual and 16-day elliptical time density home ranges were calculated by using GPS tracking data collected from 229 African savannah and forest elephants (L. africana and L. cyclotis, respectively) between 1998 and 2013 at 19 sites representing bushveld, savannah, Sahel, and forest biomes. Our analysis considered the relationship between home range area and sex, species, vegetation productivity, tree cover, surface temperature, rainfall, water, slope, aggregate human influence, and protected area use. Irrespective of these environmental conditions, long-term annual ranges were overwhelmingly affected by human influence and protected area use. Only over shorter, 16-day periods did environmental factors, particularly water availability and vegetation productivity, become important in explaining space use. Our work highlights the degree to which the human footprint and existing protected areas now constrain the distribution of the world’s largest terrestrial mammal. A habitat suitability model, created by evaluating every square kilometer of Africa, predicts that 18,169,219 km2 would be suitable as elephant habitat—62% of the continent. The current elephant distribution covers just 17% of this potential range of which 57.4% falls outside protected areas. To stem the continued extirpation and to secure the elephants’ future, effective and expanded protected areas and improved capacity for coexistence across unprotected range are essential