Charles McDougal

Science deficiency in conservation practice: the monitoring of tiger populations in India

Conservation practices are supposed to get refined by advancing scientific knowledge. We study this phenomenon in the context of monitoring tiger populations in India, by evaluating the ‘pugmark census method’ employed by wildlife managers for three decades. We use an analytical framework of modern animal population sampling to test the efficacy of the pugmark censuses using scientific data on tigers and our field observations. We identify three critical goals for monitoring tiger populations, in order of increasing sophistication: (1) distribution mapping, (2) tracking relative abundance, (3) estimation of absolute abundance. We demonstrate that the present census-based paradigm does not work because it ignores the first two simpler goals, and targets, but fails to achieve, the most difficult third goal. We point out the utility and ready availability of alternative monitoring paradigms that deal with the central problems of spatial sampling and observability. We propose an alternative sampling-based approach that can be tailored to meet practical needs of tiger monitoring at different levels of refinement.

The use of photographic rates to estimate densities of cryptic mammals: response to Jennelle et al.

Most species-specific conservation efforts require estimates of population size to establish priorities and to monitor management activities. Yet obtaining reliable estimates of animal populations is often difficult, especially given time and funding limitations experienced by many research programmes. Consequently, there is a great need for practical methods to provide indices of animal density. Ideally, accurate estimates of populations would be obtained through mark-recapture data collected from recognizable individuals over multiple censuses that cover the entire population range. Such data are rarely available, so conservation biologists have no alternative but to resort to analyses of less perfect data, ranging from permanent-point censuses from cameras through to transect data on sightings and spoor encounters. The importance of census and monitoring data makes the development, and validation, of new techniques a priority. Because we do not live in a perfect world, there is a need to develop methods that can give an estimate of population sizes. It would be naive to assume that these will give hugely accurate estimates of population size, but these techniques can prove useful in identifying areas that are likely to benefit from conservation action.

How much gene flow is needed to avoid inbreeding depression in wild tiger populations

The number and size of tiger populations continue to decline owing to habitat loss, habitat fragmentation and poaching of tigers and their prey. As a result, tiger populations have become small and highly structured. Current populations have been isolated since the early 1970s or for approximately seven generations. The objective of this study is to explore how inbreeding may be affecting the persistence of remaining tiger populations and how dispersal, either natural or artificial, may reduce the potentially detrimental effect of inbreeding depression. We developed a tiger simulation model and used published levels of genetic load in mammals to simulate inbreeding depression. Following a 50 year period of population isolation, we introduced one to four dispersing male tigers per generation to explore how gene flow from nearby populations may reduce the negative impact of inbreeding depression. For the smallest populations, even four dispersing male tigers per generation did not increase population viability, and the likelihood of extinction is more than 90% within 30 years. Unless habitat connectivity is restored or animals are artificially introduced in the next 70 years, medium size wild populations are also likely to go extinct, with only four to five of the largest wild tiger populations likely to remain extant in this same period without intervention. To reduce the risk of local extinction, habitat connectivity must be pursued concurrently with efforts to increase population size (e.g. enhance habitat quality, increase habitat availability). It is critical that infrastructure development, dam construction and other similar projects are planned appropriately so that they do not erode the extent or quality of habitat for these populations so that they can truly serve as future source populations.

Temporal Variation in Tiger (Panthera tigris) Populations and Its Implications for Monitoring

Abstract Tigers (Panthera tigris) are endangered wild felids whose elusive nature and naturally low densities make them notoriously difficult to count. We present 7 years of camera trapping, tracking, and observational data on a local tiger population in Chitwan National Park, Nepal, to quantify changes in abundance of demographic groups and to identify underlying causes. Mean abundance in the 100-km2 study area was 18 tigers, but there was high variance among years. Transients were generally recorded at low levels, but there were large oscillations in numbers of tiger offspring, driven by infanticide perpetrated by male tigers taking over territories. The number of breeding animals in the study area remained relatively stable, with about 6 breeding females and 1 or 2 breeding males. The high density of breeding adults in Chitwan National Park highlights the region as a potential stronghold for tigers. Concentrating on counting breeding animals increases the power of monitoring programs to detect change over time. An alternative approach is to carry out surveys on a scale large enough to encompass sufficient territories to compensate for the local impacts of periodic turnover of adult males on total abundance.

Securing the Future for Nepal’s Tigers: Lessons from the Past and Present

Publisher Summary The story of tiger conservation in Nepal is a narrative with many twists and turns. Insights from this account are more important to understanding the persistence of tigers than the details of rigorous scientific analysis of a single aspect of tiger population dynamics or ecology. Key components of tiger conservation clearly include knowledge of their ecology and behavior and rigorous, scientific techniques for monitoring changes in the vital rates of tigers. However, the primary agents of change in numbers of tigers and tiger habitat quality are humans, so it is equally important to focus our conservation efforts to understand human behaviors that impact tigers and their habitat. For tiger habitats, Nepals rapidly developing co-management provide insights that may be helpful in stemming the range-wide decline in tiger numbers and increasing pace of local population extinctions. There is an emerging, alternative view that suggests that when conservation focuses at landscape and ecosystem levels the result is a healthier, intact ecosystem, which in turn better sustains tigers, biodiversity, and human economies at various levels. This chapter reviews the history of tigers in Nepal beginning with the early years of tiger hunting by Nepals rulers through the malaria eradication program that permanently altered the tigers habitat.

Chapter 25 – Securing the Future for Nepal’s Tigers: Lessons from the Past and Present

Publisher Summary The story of tiger conservation in Nepal is a narrative with many twists and turns. Insights from this account are more important to understanding the persistence of tigers than the details of rigorous scientific analysis of a single aspect of tiger population dynamics or ecology. Key components of tiger conservation clearly include knowledge of their ecology and behavior and rigorous, scientific techniques for monitoring changes in the vital rates of tigers. However, the primary agents of change in numbers of tigers and tiger habitat quality are humans, so it is equally important to focus our conservation efforts to understand human behaviors that impact tigers and their habitat. For tiger habitats, Nepals rapidly developing co-management provide insights that may be helpful in stemming the range-wide decline in tiger numbers and increasing pace of local population extinctions. There is an emerging, alternative view that suggests that when conservation focuses at landscape and ecosystem levels the result is a healthier, intact ecosystem, which in turn better sustains tigers, biodiversity, and human economies at various levels. This chapter reviews the history of tigers in Nepal beginning with the early years of tiger hunting by Nepals rulers through the malaria eradication program that permanently altered the tigers habitat.

Securing the Future for Nepal’s Tigers

Publisher Summary The story of tiger conservation in Nepal is a narrative with many twists and turns. Insights from this account are more important to understanding the persistence of tigers than the details of rigorous scientific analysis of a single aspect of tiger population dynamics or ecology. Key components of tiger conservation clearly include knowledge of their ecology and behavior and rigorous, scientific techniques for monitoring changes in the vital rates of tigers. However, the primary agents of change in numbers of tigers and tiger habitat quality are humans, so it is equally important to focus our conservation efforts to understand human behaviors that impact tigers and their habitat. For tiger habitats, Nepals rapidly developing co-management provide insights that may be helpful in stemming the range-wide decline in tiger numbers and increasing pace of local population extinctions. There is an emerging, alternative view that suggests that when conservation focuses at landscape and ecosystem levels the result is a healthier, intact ecosystem, which in turn better sustains tigers, biodiversity, and human economies at various levels. This chapter reviews the history of tigers in Nepal beginning with the early years of tiger hunting by Nepals rulers through the malaria eradication program that permanently altered the tigers habitat.