202008/18
Over the past six years, the Forestry Bureau has gradually completed a population monitoring network for medium and large mammals in Taiwan, including protected species such as otter, leopard cat, Formosan black bear, Taiwan serow, and civet, as well as other wildlife that have been moved from the protected species category to the general wildlife category, such as the Reeves's muntjac and Formosan rock macaque. Long-term monitoring will provide a clearer picture of population trends for each species. This is also the first time the government has systematically established a long-term monitoring system in a standardized manner for medium to large mammals in the country, which will serve as an important reference in wildlife management.
Establishing a Systematic and Standardized Species Population Trend Monitoring Network
Lin Hwa-Ching, Director General of the Forestry Bureau, said that the trends of changes in wildlife populations is an important reference in the formulation of conservation policies. In the past, assessments of wildlife conservation status were mostly based on regional surveys and personal research experiences of experts and scholars, which lacked the long-term and systematic collection and analysis of large data. Starting from the installation of a total of 285 automatic cameras to monitor carnivorous wildlife in mountainous areas below 1,500 meters in elevation in response to the rabies epidemic since 2013, the Forestry Bureau has gradually expanded the number of monitoring sampling sites in mid- and high-altitude mountain areas, outlying islands, and protected areas, and began setting up more than 500 automatic infrared cameras across Taiwan from 2017 to monitor wildlife 24 hours a day, 365 days a year.
In addition to monitoring by automatic infrared camera systems, the Forestry Bureau has since last year also mobilized forest rangers from the eight forest district offices to conduct regular, systematic sample plot surveys of Taiwan macaques, which are often found in tree canopies, in order to obtain a more accurate picture of their population trends. The forest rangers are also participating in a Breeding Bird Survey (BBS), which, together with the long-running fish species monitoring surveys of forest streams, will provide more complete and comprehensive information to Taiwan's wildlife base.
Understanding the Long-Term Changes in Wildlife Distribution and Abundance
According to the Forestry Bureau, by the end of 2019, more than 5 million work hours and 3.55 million photos have been accumulated through automatic camera monitoring. With the huge amount of monitoring data accumulated over such a long period of time, it is possible to gain better understanding on the distribution of wildlife, changes in population abundance, observations on animal behavior, activity patterns, life history, and population estimates, as well as analyze and evaluate the various risks that wild animals face, such as disease, hunting, and stray dogs and cats. In addition, the data can also assist in the trend analysis of species and population changes required for wildlife conservation status assessment; or understanding the impact on wildlife populations from traditional hunting by indigenous peoples.
At present, a total of 29 mammal species have been photographed in the monitoring network, and up to 11 species of mammals have been photographed in the same camera location. Further analysis shows that the most widely distributed mammal is the Reeves's muntjac, which have appeared in 91% of camera locations; followed by the small-toothed ferret-badger, appearing in 90% of the camera locations. With regards to population abundance, wild boars, civets, and leopard cats have shown a decline in recent years, while the relative numbers for sambar deer, Taiwan serow, weasels, yellow-throated martens, as well as the Reeves's muntjac and Formosan rock macaques, which have been reclassified as general wildlife since last year, have continued to increase. The number of camera sites capturing sightings of the popular Formosan black bear continues to increase. Overall, most of the wildlife populations are stable or increasing.
From the monitoring footage, it can be seen that the yellow-throated martens and the weasels are probably the most important solely carnivorous predators among the wild mammals in Taiwan. This is especially true of the yellow-throated marten, which plays an important role in diurnal hunting even-toed ungulates such as the sambar deer and Reeves's muntjac. The weasel, which is also a member of the Mustelidae family, feeds mainly on rodents and is active mainly at night.
In the case of small-toothed ferret-badgers, which are threatened by the rabies epidemic, the population abundance in infection areas was clearly showing a year-on-year decline until mid-2017, but from mid-2017 onwards to the present, population abundance has stabilized. The abundance of populations in both infection and non-infection areas is consistent, indicating that the threat of the epidemic is stabilizing.
Obvious Impact of Dogs and Cats on Wildlife
Recently the threats posed to wildlife by stray dogs and cats have gradually become a matter of concern, and the Forestry Bureau has indicated that surveillance cameras have recorded images of stray cats catching birds or snatching fish caught by otters, and dogs attacking water birds. The number of automatic camera locations that have captured dogs and cats is also increasing. It is worth noting that automatic camera monitoring data also shows that the relative abundance of pangolins and stray dogs is negatively correlated, meaning that when the number of stray dogs increases, the number of pangolin decreases. This indirectly explains why the number of dog attacks on pangolin has been on the rise in recent years. This is an issue that needs to be addressed.
Establishment of Individual Animal Identification Technology Helps to Set Up Life History Information
The Forestry Bureau said that in the past, to estimate the density of wildlife populations, wild animals had to be captured, tagged, and then released, and then repeatedly captured, causing serious disturbance and even harm to wildlife. If the animals' unique patterns, spots, and horn marks can be used as features to identify individual animals, then capturing can be avoided. Take the leopard cat, for example. The Forestry Bureau, Endemic Species Research Institute (ESRI), and National Chiayi University conducted research in the Zhongliao area of Nantou County in 2019-2020 and successfully established a methodology for identifying individual leopard cats using images captured by the automatic cameras. In addition to understanding the number of individuals and population density of the local leopard cat population, information on the birth, range, and population size fluctuations can also be collected.
Increase Monitoring Capacity and Expand Database Information
According to the Forestry Bureau, in response to the increasing amount of data collected by the monitoring network and the need to invest a large amount of manpower to identify species, the Forestry Bureau will develop an AI species automatic identification technology to save labor costs. In order to enhance the data digital storage and system analysis capacity, the Forestry Bureau is also working with the ESRI and Academia Sinica to build an automatic camera image integration database, which can efficiently process the large amount of wildlife photo data accumulated over a long period of time and estimate the relative abundance of species. In addition to providing data for academic research and analysis, it will serve as an important reference for the development of conservation policies.