Failure to account for behavioral variability overestimates bonobo populations and compromises accuracy in population monitoring

Wildlife population monitoring depends on accurate counts of individual animals or artefacts of behavior (e.g., nests or dung), but also must account for potential biases in the likelihood to encounter these animals or artefacts. In indirect surveying, which depends largely upon artefacts of behavior, likelihood to encounter indirect signs of a species is derived from both artefact production and decay. Although environmental context as well as behavior contribute to artefact abundance, variability in behaviors relevant to artefact abundance is rarely considered in population estimation. Here we demonstrate how ignoring behavioral variability contributes to overestimation of population size of a highly endangered great ape endemic only to the Democratic Republic of the Congo, the bonobo (Pan paniscus). Variability in decay of signs of bonobo presence (i.e., nests) is well documented and linked to environmental determinants. Conversely, a single metric of sign production (i.e., nest construction) is commonly used to estimate bonobo density, assumed to be representative of bonobo nest behavior across all contexts. We estimated nest construction rates from three bonobo groups within the Kokolopori Bonobo Reserve and found that nest construction rates in bonobos to be highly variable across populations as well as seasonal within populations. Failure to account for behavioral variability in nest construction leads to potentially severe degradation in accuracy of bonobo population estimates of abundance, accounting for a likely overestimation of bonobo numbers by 34%, and in the worst cases as high as 80% overestimation. Using bonobo nesting as an example, we demonstrate that failure to account for inter- and intra-population behavioral variation compromises our ability to monitor population change or reliably compare contributors to population decline or persistence. We argue that variation in sign production is but one of several potential ways that behavioral variability can affect conservation monitoring, should be measured across contexts whenever possible, and must be considered in population estimation confidence intervals. With increasing attention to behavioral variability as a potential tool for conservation, conservationists must also account for the impact that behavioral variability across time, space, individuals, and populations can play upon precision and accuracy of wildlife population estimation.

Socioeconomics drive population change in the world's largest carnivores

Land-use and climate change have been linked to wildlife population declines, but the role of socioeconomic factors in driving declines, and promoting population recoveries, remains relatively unexplored despite its likely importance. Here, we evaluate a comprehensive array of potential drivers of population changes observed in some of the world's most charismatic species - large mammalian carnivores. Our results reveal a strong role of human socioeconomic development, which we find has a greater impact on population change than habitat loss and climate change. Increases in socioeconomic development are linked to sharp population declines but, importantly, once development is high, carnivore populations have the potential to recover. These links between human development and wildlife population health highlight the challenges ahead to achieve the different UN Sustainable development goals.

Wildlife Population Estimates by Census and Distance Measuring Techniques

Methodologies based on counting the number of sightings to estimate are described. These techniques are particularly useful for large or easily seen animals such as birds, large grassland mammals, whales, crocodilians, and large, active insects such as butterflies. Point and line survey methods are described. Distance sampling methods, including Fourier series estimators, are presented, and R code listings to undertake the computations presented. Plotless density estimators are described based on nearest-neighbour, and closest-individual measurements are described.

Is There a Wild Animal Welfare Emergency Facilitated by Negative Linguistic Framing in Wildlife Population Control Studies?

As the world’s human population continues grow in number and mobility, and the impacts of climate change take effect, the opportunities for problematic relationships with non-human animals multiply. There are escalating threats to health from wild vectors of zoonotic disease, and so-called “invasive” species have been identified as a significant direct driver of an unprecedented period of global biodiversity loss. This brings a sense of genuine urgency to control problematic wild populations; in the UK alone, it is estimated that 38 million wild mammals and birds are killed as pests. However, the impact of these animals is not always objectively appraised. Control interventions are often ineffective, may be counterproductive and can cause severe suffering. Decisions about when, where and how to control animal populations can be affected by attitudes and philosophical perspectives, influenced by how language is used. A systematic review of wildlife population control studies was carried out to determine whether negative linguistic framing of animals was associated with poor welfare outcomes. Framework analysis of titles, abstracts and keywords was used, and assessments made of the welfare impacts of control methods. This analysis revealed language that framed target populations in terms of War, Threat, Place, Victim, Value, Sentience and Naturalness with a range of associated themes. There was a relationship between negative framing and methods with the most adverse welfare outcomes, but the effect was not consistent. It was clear that there are cultural conventions within the science that were reinforced or challenged depending on many factors including the status of the species and the context of the intervention. More work to explore and challenge cultural conventions in describing targeted animals, and robust reporting of the welfare impacts of control methods are needed to tackle this, often disregarded, animal welfare emergency.

A global indicator of utilised wildlife populations: regional trends and the impact of management

The sustainable use of wildlife is a core aspiration of multi-lateral conservation policy but is the subject to intense debate in the scientific literature. We use a global data set of over 11,000 population time-series to derive indices of ‘used’ and ‘unused’ species and assess global and regional changes in wildlife populations – principally for mammals, birds and fishes. We also assess whether ‘management’ makes a measurable difference to wildlife population trends, especially for the used species populations. Our results show that wildlife population trends globally are negative, but with used populations tending to decline more rapidly, especially in Africa and the Americas. Crucially, where used populations are managed, using a variety of mechanisms, there is a positive impact on the trend. It is therefore true that use of species can both be a driver of negative population trends, or a driver of species recovery, with numerous species and population specific case examples making up these broader trends. This work is relevant to the evidence base for the IPBES Sustainable Use Assessment, and to the development of indicators of sustainable use of species under the post-2020 Global Biodiversity Framework being developed under the Convention on Biological Diversity.