Habitat loss and fragmentation have profound effects on species abundance and persistence. That is why understanding how fragmentation influences relative abundance patterns is crucial for conservation planning. Our goal was to examine the influence of fragmentation on the Malay tapir’s relative abundance in Thailand’s protected areas. We conducted a quantitative analysis of spatial fragmentation patterns across the protected areas within tapir’s range in Thailand. We found that the Malay tapir populations exist in just a few, fragmented habitat patches in nine protected areas. Surprisingly, we found high relative abundance in small protected areas in the southern forest complex. Additionally, the Malay tapir’s relative abundance was highly associated with patch density and clumpiness index. Our work highlights an urgent need to protect high quality of habitat patches and improve habitat connectivity to facilitate subpopulations of the Malay tapir in fragmented protected areas.
We found strong evidence that the Malay tapir is distributed in small and fragmented populations throughout its range in Thailand 37. Interestingly, we found that the Malay tapir’s relative abundance was negatively associated with clumpiness index and protected area size. That does not mean that smaller protected areas are better for tapir, but rather that more conservation efforts are necessary in the south to support higher relative abundances of this endangered mammal. Our finding adds further supporting evidence of the effects of habitat fragmentation on the Malay tapir in other regions. The Malay tapir studies in Malaysia and Sumatra demonstrate that roadkill and large-scale deforestation cause tapir populations to become small and isolated 41. In addition, while tapir populations were found in fragmented landscapes, yet they avoid the edge areas and human disturbance 35,39,40
Importantly, across Thailand the relative abundance of the Malay tapir was highest in small, fragmented protected areas in the southern forest complex. Our results demonstrated that the protected areas in the south were significantly smaller with more fragmented habitats. However, within the western forest complex, relative abundance was higher in larger protected areas with less fragmented habitats. There are many reasons explaining the discrepancies in relative abundance patterns in both western and southern protected areas. First, the Malay tapir prefers moist evergreen forest with the lower elevation (300–1000 m) and away from human disturbance 34,37,38. The protected areas in southern Thailand are dominated by lowland moist evergreen forests, which are more suitable than the dry evergreen forest in the western forest complex 42. Second, the average precipitation is higher in Thailand’s south providing more available water sources for tapir populations as they prefer to stay near water bodies and their life activities are strongly associated with water 43. Third, even while habitat patches have become more fragmented and are smaller in size, the patches are still aggregated. Such a fragmentation pattern may still be able to sustain the movement among the current populations within the protected areas.
Indeed, empirical evidence shows that Malay tapir can persist in a variety of habitat types including logged forests 26,40. However, the effects of habitat fragmentation can also have time-delayed response effects on species persistence, and the high relative abundance in fragmented protected areas may be temporary if it reflects time-delayed responses to past fragmentation 44. We had predicted that large protected areas in Thailand were less fragmented, especially its protected areas in the western forest complex. The western forest complex is the most important wildlife refuge for Thailand because it is connected to the large forest in Myanmar called the transboundary forests. Many conservation organizations allocate research funding and manpower to protect wildlife and forest ecosystems there 42. Those conservation resources may have reduced human disturbances and limited fragmentation. In contrast, the protected areas in the south are smaller and more fragmented, yet harbored high relative abundance of the Malay tapir. We found that patch density, clumpiness index, proportion of habitat, and landscape shape index were important variables in explaining the Malay tapir’s relative abundance. This supports prior studies on the Malay tapir habitat use, which found that the proportion of evergreen forest cover, distance from forest edge, and connectedness of the habitat patches associated with tapir occurrences 27,39.
Our results highlight the importance of habitat fragmentation for the Malay tapir’s relative abundance, and we identified priority areas for tapir conservation in the Thailand. Yet, our study had some limitations. First, our abundance data derived from the relative abundance in each protected area, even though it is a systematically transect survey, lacks detail on abundances of subpopulations in each protected area, and without that we could not analyze the habitat suitability of individual patches. Second, it is a challenge of selecting fragmentation metrics that were ecologically meaningful for the Malay tapir due to limitations of studies in the region. In our study, we selected fragmentation metrics that may affect the tapir relative abundance based on the Malay tapir habitat requirements and threats to their populations, as well as which fragmentation metrics predicted relative abundance of other mammal species. Third, Fragstats offers many fragmentation metrics, however many metrics need to be interpreted with caution. For example, a comparison between different protected areas needs to be based on standardized metrics 45. Accordingly, we selected patch density, edge density, and landscape shape index, which are standardized metrics that can be used to compare different landscapes. Last, we suggested further study to examine potential time lags in the effect of habitat fragmentation on relative abundance when the next re-survey of tapir relative abundance becomes available. Our results indicated that the tapir populations in Thailand currently exist in small, fragmented protected areas which raises concerns for population persistence, especially if fragmentation continues.
Our findings have important ramifications for conservation. First, our results highlight that endangered species, such as tapir can persist in fragmented habitats within the protected areas, but may require urgent improvements in habitat quality and increased connectivity among fragmented patches to facilitate the movement and gene flow in order to prevent extirpations. Second, our results highlight the importance of connectedness of habitat patches for subpopulations. To mitigate the impact of habitat fragmentation, habitat connectivity is a key for species survival. Lastly, we found that larger protected areas were less fragmented, suggesting that more conservation allocations are needed for small, underrepresented protected areas.
In summary, our study provides insights on the importance of habitat fragmentation for endangered mammals in tropical ecosystems where habitat loss and fragmentation remain the most important threat for biodiversity. This is especially a concern where species exist as sub-populations are more vulnerable to the effects of habitat fragmentation. Additionally, we highlight the importance of protected area management in preserving continuous habitat and improving connectivity between fragmented habitats to mitigate the threats from rapid changes in land use and climate.