Monitoring conservation threats, interventions and impacts on wildlife in a Cambodian tropical forest

While there are many scientifically rigorous methods for monitoring wildlife populations and the threats that they face, they are often difficult to implement in tropical forest environments. In some cases traditional gold standard methodologies can be employed despite the inherent practical and theoretical challenges, but in other situations more novel approaches must be developed. In this thesis we investigate these issues within the context of a large protected area in Eastern Cambodia. The aims of this study were to; 1. Evaluate the status and trends of wild ungulate populations using distance sampling derived density estimates. 2. Develop and implement an approach to reliably estimate the detectability and abundance of wire snares, which currently represent the greatest threat to mammal populations within the area. 3. Quantify the association between snare abundance and a number of natural and anthropogenic factors hypothesised to influence snare placement. 4. Assess the utility of law enforcement records, and specifically catch-per-unit-effort (CPUE) indices derived from patrol data, as a tool for monitoring threats. I present rigorous density estimates for several key ungulate species, representing the first such data from the entire lower Mekong region. Whilst smaller ungulate populations appear to be stable, larger species are likely undergoing a decline. A sampling protocol was developed for surveying snares which balanced the requirements of statistical rigour against feasibility and efficiency of implementation in the field. The results of this survey were analysed using N-mixture models to produce detectability-corrected spatially explicit estimates of snare abundance. As predicted, forest type, proximity to settlements, and distance to the Vietnamese border were shown to be important determinants of snare abundance whereas the relationship between snaring levels and both patrol effort and wildlife densities was less clear. This study also demonstrated that while CPUE indices derived from patrol data can adequately reflect true levels of threat, their utility depends greatly on the quality of the patrol data, and on identifying the appropriate spatio-temporal scale at which to undertake the analysis.Open Acces

Long-term monitoring of wildlife populations for protected area management in Southeast Asia

Long-term monitoring of biodiversity in protected areas (PAs) is critical to assess threats, link conservation action to species outcomes, and facilitate improved management. Yet, rigorous longitudinal monitoring within PAs is rare. In Southeast Asia (SEA), there is a paucity of long-term wildlife monitoring within PAs, and many threatened species lack population estimates from anywhere in their range, making global assessments difficult. Here, we present new abundance estimates and population trends for 11 species between 2010 and 2020, and spatial distributions for 7 species, based on long-term line transect distance sampling surveys in Keo Seima Wildlife Sanctuary in Cambodia. These represent the first robust population estimates for four threatened species from anywhere in their range and are among the first long-term wildlife population trend analyses from the entire SEA region. Our study revealed that arboreal primates and green peafowl (Pavo muticus) generally had either stable or increasing population trends, whereas ungulates and semiarboreal primates generally had declining trends. These results suggest that ground-based threats, such as snares and domestic dogs, are having serious negative effects on terrestrial species. These findings have important conservation implications for PAs across SEA that face similar threats yet lack reliable monitoring data

Experimentally assessing the effect of search effort on snare detectability

Reducing threats to biodiversity is the key objective of ranger patrols in protected areas. However, efforts can be hampered by rangers' inability to detect threats, and poor understanding of threat abundance and distribution in a landscape. Snares are particularly problematic due to their cryptic nature and limited selectivity with respect to captured animals' species, sex, or age. Using an experimental approach, we investigated the effect of search effort, habitat, season, and team on rangers' detection of snares in a tropical forest landscape. We provide an effort-detection curve, and use our findings to make preliminary predictions about snare detection under different scenarios of patrol effort. Results suggest that the overall probability of a searcher detecting any given snare in a 0.25/km2 area, assuming 60 min (or approximately 2 km) of search effort is 20% (95% CI ± 15–25%), with no significant effect of season, habitat or team. Our models suggested this would increase by approximately 10% with an additional 30mins/1 km of search effort. Our preliminary predictions of the effectiveness of different patrolling scenarios show that detection opportunities are maximised at low effort levels by deploying multiple teams to a single area, but at high effort levels deploying single teams becomes more efficient. Our results suggest that snare detectability in tropical forest landscapes is likely to be low, and may not improve dramatically with increased search effort. Given this, managers need to consider whether intensive snare-removal efforts are the best use of limited resources; the answer will depend on their underlying objectives

Searching for snares - How much effort is enough?

The use of wire snares to hunt wildlife is prolific, particularly in the forests of Southeast Asia (1). Tackling this threat is a primary objective of law enforcement operations throughout protected areas, yet often efforts to remove snares are thwarted by a lack of information about hunter behaviour and an inability to detect snares. Even in areas of high snare abundance, rangers can spend many hours searching for snares with few results, eroding ranger morale, motivation and resources. Understanding how best to allocate ranger search effort is of critical importance for protected area managers, especially in sites with exponential levels of snare hunting. Few studies systematically assess the factors that affect snare distribution (2), or explore efficiency in snare removal. Often studies rely on ranger-collected data through systems such as SMART. Whilst this data is undoubtedly useful for monitoring, data analyses typically fail to account for underlying biases, resulting in misleading conclusions being drawn. Here we present a conceptual framework for evaluating the factors that influence snare detection by rangers. An experiment to calculate snare detectability in eastern Cambodia, carried out by Dr Hannah O'Kelly in 2011, achieved an average snare detection rate of about 30%, with variation between habitat and snare types. We introduce an experimental design which builds on that study (3), and aims to quantify how snare detectability varies with ranger search effort, whilst controlling for factors such as season, habitat, and ranger morale. We present our results, and detail the wider impact of the research for protected area management. References (1) GRAY, T.N.E., HUGHES, A.C., LAURANCE, W.F., LONG, B., LYNAM, A.J., KELLY, H.O., ET AL. (2017) The wildlife snaring crisis: an insidious and pervasive threat to biodiversity in Southeast Asia. Biodiversity and Conservation, 1–7. (2) O’KELLY, H.J., ROWCLIFFE, J.M., DURANT, S.M. & MILNER-GULLAND, E. (2018) Robust estimation of snare prevalence within a tropical forest context using N-mixture models. Biological Conservation, 217, 75–82 (3) O’KELLY, H.J., ROWCLIFFE, J.M., DURANT, S. & MILNER-GULLAND, E. (2018) Experimental estimation of snare detectability for robust threat monitoring. Ecology and Evolution, DOI: 10.10, 1–8.peerReviewe

Impacts of hunting on tropical forests in Southeast Asia

Although deforestation and forest degradation have long been considered the most significant threats to tropical biodiversity, across Southeast Asia (Northeast India, Indochina, Sundaland, Philippines) substantial areas of natural habitat have few wild animals (>1 kg), bar a few hunting-tolerant species. To document hunting impacts on vertebrate populations regionally, we conducted an extensive literature review, including papers in local journals and reports of governmental and nongovernmental agencies. Evidence from multiple sites indicated animal populations declined precipitously across the region since approximately 1980, and many species are now extirpated from substantial portions of their former ranges. Hunting is by far the greatest immediate threat to the survival of most of the region's endangered vertebrates. Causes of recent overhunting include improved access to forests and markets, improved hunting technology, and escalating demand for wild meat, wildlife-derived medicinal products, and wild animals as pets. Although hunters often take common species, such as pigs or rats, for their own consumption, they take rarer species opportunistically and sell surplus meat and commercially valuable products. There is also widespread targeted hunting of high-value species. Consequently, as currently practiced, hunting cannot be considered sustainable anywhere in the region, and in most places enforcement of protected-area and protected-species legislation is weak. The international community's focus on cross-border trade fails to address overexploitation of wildlife because hunting and the sale of wild meat is largely a local issue and most of the harvest is consumed in villages, rural towns, and nearby cities. In addition to improved enforcement, efforts to engage hunters and manage wildlife populations through sustainable hunting practices are urgently needed. Unless there is a step change in efforts to reduce wildlife exploitation to sustainable levels, the region will likely lose most of its iconic species, and many others besides, within the next few years

The wildlife snaring crisis: an insidious and pervasive threat to biodiversity in Southeast Asia

Southeast Asia, a region supporting more threatened species than any other comparable continental area, is in the midst of a conservation crisis. Hunting constitutes the greatest current threat to the region's threatened vertebrates and has resulted in many areas of largely intact forest losing much of their former vertebrate diversity and abundance. Though numerous hunting methods are used, capture with home-made snares is a major driver of this defaunation. Snares are cheaply constructed and easy to set but can be difficult to detect and are highly damaging to vertebrate populations due to their indiscriminate and wasteful nature. The primary response to snaring is the removal of snares by patrol teams: more than 200,000 snares were removed from just five of the region's protected areas between 2010 and 2015. However due to the low opportunity costs of replacing snares, removal alone is largely ineffective. Without the proactive search, arrest and prosecution of snare-setters, along with incentives not to hunt, snares will continue to be replaced. Legislative reform that criminalises the possession of snares, and the materials used for their construction, inside and immediately adjacent to protected areas is also required. Consistent enforcement of such legislation is essential. This must be combined with longer-term demand reduction activities aimed at changing cultural attitudes and behaviors related to the consumption of wildlife products in Southeast Asia

Identifying conservation successes, failures and future opportunities; assessing recovery potential of wild ungulates and tigers in Eastern Cambodia.

Conservation investment, particularly for charismatic and wide-ranging large mammal species, needs to be evidence-based. Despite the prevalence of this theme within the literature, examples of robust data being generated to guide conservation policy and funding decisions are rare. We present the first published case-study of tiger conservation in Indochina, from a site where an evidence-based approach has been implemented for this iconic predator and its prey. Despite the persistence of extensive areas of habitat, Indochina's tiger and ungulate prey populations are widely supposed to have precipitously declined in recent decades. The Seima Protection Forest (SPF), and broader Eastern Plains Landscape, was identified in 2000 as representing Cambodia's best hope for tiger recovery; reflected in its designation as a Global Priority Tiger Conservation Landscape. Since 2005 distance sampling, camera-trapping and detection-dog surveys have been employed to assess the recovery potential of ungulate and tiger populations in SPF. Our results show that while conservation efforts have ensured that small but regionally significant populations of larger ungulates persist, and density trends in smaller ungulates are stable, overall ungulate populations remain well below theoretical carrying capacity. Extensive field surveys failed to yield any evidence of tiger, and we contend that there is no longer a resident population within the SPF. This local extirpation is believed to be primarily attributable to two decades of intensive hunting; but importantly, prey densities are also currently below the level necessary to support a viable tiger population. Based on these results and similar findings from neighbouring sites, Eastern Cambodia does not currently constitute a Tiger Source Site nor meet the criteria of a Global Priority Tiger Landscape. However, SPF retains global importance for many other elements of biodiversity. It retains high regional importance for ungulate populations and potentially in the future for Indochinese tigers, given adequate prey and protection