Structural Characteristics of Red Fox (Vulpes vulpes) Dens in the Wild in Northeast China and in a Captive Facility in South Korea

The red fox (Vulpes vulpes) has a worldwide distribution (Lariviere and Pasitschniak-Arts 1996), which includes most of North America, Europe, Asia, and northern Africa (Yu et al. 2012). In the past, red foxes were distributed extensively in Korea, and were considered friendly animals in history and culture (National Park Research Institute 2010). However, since the 1980s, it has been speculated that red foxes may have been driven to extinction due to activities such as the protection of livestock, illegal hunting, rodenticide use, and habitat loss (Won and Smith 1999; Yu et al. 2012).Consequently, the species has been placed on the list of endangered species I (Ministry of the Environment of Korea 2005). After 24 years of believing the red fox was endangered, a red fox carcass was found in Yang-gu Gangwondo, Korea, in 2004. Thus, it was suggested that the red fox might still exist in the wild. Although no other wild red foxes have been seen since, a red fox restoration project was initiated in 2009 through basic investigative research. Many carnivores are currently extinct in Korea, and large carnivores in particular have not been found in the wild for many years (National Institute of Biological Resources 2012). Therefore, the red fox restoration program is very important for the healthy recovery of the forest ecological food chain and the restoration of other carnivorous mammals facing extinction. The Ministry of the Environment has performed genetic analyses on a stuffed domestic museum specimen and samples from northeast Asia in an effort to introduce the same variant of red fox as that identified in Korea. The results of these genetic analyses showed that the Korean red fox was part of the same group of red foxes inhabiting North Korea, northeast China, Russia, and Mongolia (Yu et al. 2012). Therefore, 10 red foxes raised under the red fox restoration project were introduced to Korea from northeast China in 2012. The first step of the red fox restoration project in Korea was to continually monitor the foxes after release in the wild. The red fox uses its den year-round (Lindstrom 1994; Carter and Finn 1999; Tryjanowski et al. 2002; Dell’Arte and Leonardi 2007) for shelter, protection from predators, and to raise its cubs (Macdonald and Reynolds 2004). Thus, an understanding of fox den characteristics is needed for managing and monitoring the released foxes. Fox den characteristics are different depending on the habitat type and environment, as well as the species (Tannerfeldt et al. 2003). Although there are many studies on fox dens (Russell and Scotter 1984; Cotterill 1997; Jackson and Choate 2000; McGee et al. 2006), few studies have focused on the characteristics of red fox dens (Nakazono and Ono 1987; Meia and Weber 1992). Research on red fox dens in northeast Asia is particularly rare, except for the studies by Nakazono and Ono (1987) and Uraguchi and Takahashi (1998), while in Korea, no study has examined red fox dens in natural or captive conditions. Although the red fox is endangered in Korea, making it difficult to study wild red fox den characteristics in this region, we have collected various ecological and structural data on the characteristics of fox dens in large captive facilities in Korea. However, fox den characteristics can vary depending on food availability and the environment (Tannerfeldt et al. 2003). In the artificial facilities in Korea, environmental factors such as soil quality, river system accessibility, and vegetation may be different from the features in a future release area. Therefore, we assume that the structural characteristics of dens used in captivity are different from those used in the wild after release. Thus, the purpose of this study was to understand the structural characteristics of fox dens and to use this information for post-release monitoring. Therefore, to study not only the characteristics and structure of red fox dens in captivity, but also in the wild, we visited northeast China and searched for the dens of wild red foxes, which were identified as belonging to the same genetic group as the foxes managed in Korea.