Terrestrial mammal and bird communities in heavily hunted landscapes of the Greater Annamites in Vietnam

Tropical forests are critical reservoirs of biodiversity, and their wildlife plays an essential role in maintaining ecosystem structure and services. Globally, deforestation has reduced the extent of tropical forests, and in many remaining areas, defaunation has transformed them into “empty forests”, where wildlife is severely depleted by unsustainable hunting. As an ecological consequence, ecosystem processes and the resilience of these tropical forests are degrading. To strengthen protection efforts for terrestrial mammals and birds in tropical forests a better understanding of the extent of defaunation, species occurrences, and the factors driving species distributions is crucial. In this thesis, I focused on the Greater Annamites ecoregion in Vietnam, a global biodiversity hotspot and the epicenter of the ongoing “Southeast Asian snaring crisis”, where unsustainable hunting with wire snares is the primary driver of wildlife declines. The main goal of this dissertation was to provide insights into species distribution and richness, and to identify factors shaping species occurrences. To achieve this, I used fine-scale data from an extensive camera-trap dataset, comprising more than 1,800 stations and 250,000 trap-nights, and analyzed these within a hierarchical modelling framework. In Chapter 2, I analyzed camera-trap data across 19 Protected and 12 non-Protected Areas in Vietnam. Results showed that fine-scale species richness was not significantly higher in Protected than in non-Protected Areas. Rather than protection status, size of study sites and remoteness better explained species distributions and community structures. Decades of intensive snaring likely have undermined the effectiveness of the Protected Area network, highlighting a broader challenge in which habitat protection alone cannot counter unsustainable hunting, especially snaring. In Chapter 3, I explored habitat associations and anthropogenic impacts on terrestrial mammals and birds in the Southern Annamites. Results showed that many species had their highest occupancy probabilities in remote broadleaf evergreen forests. Consequently, species diversity was higher in broadleaf evergreen compared to the coniferous forests. Spatially explicit species occurrence and richness predictions highlighted areas of special conservation interest, helping local authorities to target their patrols and snare-removal efforts to these hotspot areas. In Chapter 4, I investigated ground-dwelling mammal and bird community patterns across three habitat types (dry, semi-dry, and broadleaf evergreen forests) in Nui Chua National Park, in the coastal dry forest landscape of southeastern Vietnam. The results showed the highest species diversity and the greatest number of threatened and endemic species, such as the silver-backed chevrotain Tragulus versicolor, in the semi-dry forests, while the broadleaf evergreen forests harbored the lowest diversity. These findings underscore the importance of ecotones and demonstrate that local environmental conditions can override general biodiversity patterns, such as the commonly observed trend towards higher diversity in broadleaf evergreen forests (see Chapter 3). Across all three chapters, the results indicate that defaunation has been widespread and severe throughout the Greater Annamites. Large herbivores and apex predators were lost or are now severely depleted, likely leading to cascading effects with inevitable consequences for forest structure and ecosystem functioning. To date, Protected Areas have been unable to halt indiscriminate hunting or prevent the continued decline of terrestrial wildlife. The site-specific results of this dissertation are therefore crucial for directing on-the-ground conservation efforts toward areas of greatest concern. Only such targeted approaches can effectively reduce local snare pressures and prevent the threatened species from local or even global extinction.