Alien terrestrial vertebrates of Hong Kong : species richness, taxonomic composition and introduction pathways

Invasive alien vertebrates have multiple negative impacts on biodiversity and impact human well-being and the economy. Hong Kong has been a major international shipping and trading hub for centuries. With less than a quarter of Hong Kong’s land developed, its subtropical landscapes host rich native biodiversity. However, Hong Kong is also at high risk of biotic invasions that can threaten its native species and ecosystems. Limited systematic, published data on alien species in Hong Kong impedes our ability to understand introduction sources, pathways and patterns, which is needed to prevent future introductions and tackle the potential impacts of invasive species. We aimed to address this gap by creating and analyzing the first database of alien terrestrial vertebrates in Hong Kong. Overall, we recorded 213 alien terrestrial vertebrate species, including 155 bird, 37 reptile, 15 mammal and six amphibian species, of which 49 are established and seven are invasive. Most of these alien vertebrate species (92%) were affiliated with the pet trade derived from captivity and were released or escaped to the wild. Cultural and religious practices had a major role in shaping the alien species composition in Hong Kong. Other introduction sources include biocontrol, agriculture or horticulture, hitchhiking on traded plants and on freight. This study provides a baseline for further monitoring, management and control of introduced alien species in Hong Kong.