Differences in Habitat Use of the Native Raccoon Dog (Nyctereutes
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Differences in habitat use of the native raccoon dog (Nyctereutes procyonoides albus) and the invasive alien raccoon (Procyon lotor) in the Nopporo Natural Forest Park, Hokkaido, Japan Go Abe, Tohru Ikeda and Shirow Tatsuzawa Department of Regional Sciences, Faculty of Letters, Hokkaido University, N10-W7 Kita-ku Sapporo 060-0810, Japan Abstract We investigated differences in home range sizes and in the pattern of habitat use between the raccoon (Procyon lotor), an invasive alien species, and the native raccoon dog (Nyctereutes procyonoides albus), which lived sympatrically in Nopporo Natural Forest Park, Hokkaido, Japan. The mean home range size of raccoons (±2SD) was 116.2ha (±203.8ha), and that of raccoon dogs was 125.2ha (±71.1ha). The mean size of core areas was 12.1ha (±18.4ha) for raccoons, and 10.6ha (±12.8ha) for raccoon dogs. There were no significant differences between these two species in home range size (U-test, p=0.571) or in core areas (U-test, p=0.571). The pattern of habitat use, however, differed between these two species. Diurnal resting sites were located in woodland margins for raccoons, but in woodland for raccoon dogs. A comparison of the utilisation rates of farm fields in the home range showed that raccoons used farm fields significantly (U-test, p<0.05) more than raccoon dogs. This result supports that in Japan raccoons use farmer’s properties for feeding and breeding. Keywords: raccoon; raccoon dog; pattern of habitat use; invasive alien species; home range; radio-tracking INTRODUCTION The irresponsible breeding and release of pet raccoons Hokkaido, Japan. (Procyon lotor Linnaeus, 1758) in Japan, coupled with their rapid naturalisation, has caused this species to pose problems to native habitats and biodiversity METHODS (Ikeda 2000). Raccoons naturalised 28 years ago in Hokkaido and dispersed to more than half of its Study area municipalities. Now, their number is estimated to be over three thousand in the central part of the island The study was conducted in the Nopporo Natural (Hokkaido Prefecture 2003). Severe damage to crops Forest Park, located 11 - 15km east of the City of and predation on endangered species such as the Sapporo (43'25"N, 141'32"E), central Hokkaido, Japan. Japanese crayfish (Cambaroides japonicus) have been This is a 2,040ha sub-isolated forest (ca. 6×4km), with reported (Hori and Matoba 2001, Ikeda et al. 2004). altitudes between 20 to 100m above sea level. The The raccoon dog (Nyctereutes procyonoides albus annual precipitation and the mean temperature are Beard, 1904) is a native carnivore of Family Canidae in 899mm and 6.6ºC (-25.8ºC in February and up to Japan, whose body size (Kinoshita and Yamamoto 29.8ºC in August), respectively (Data from Japan 1996, Kishimoto et al. 1998, Zeveloff 2002, Asano Meteorological Agency). This forest is a mixed 2003b), breeding season (Ikeda 1983, Asano 2003a), conifer-hardwood forest, dominated by Abies seasonal activity patterns (Yamamoto 1993, Kurashima sachalinensis, Acer mono, Quercus mongolica var. grosserrata, et al. 1998) and diet (Hori and Matoba 2001, Furukawa and Fraxinus mandshurica var. japonica (Ishikawa 1989). 2001, Kasuya 2001) are similar to those of the feral The presence of raccoons was first verified in this raccoon Small animals and fruits are major food forest in 1992 (Kadosaki 1996). Subsequently, they sources for both species. The impact of raccoons on have been suspected of serious agricultural damage the native raccoon dogs is important and it is a and attacks on a colony of herons (Ardea cinerea) inside frequently debated issue in nature conservation in the forest (Ikeda 1999, Hokkaido Prefecture 2003). Japan. They are very attracted to crops like sweet corn, Raccoons are known to live sympatrically with melons and strawberries. During the study period, only raccoon dogs in Hokkaido, but information about the strawberries were ripening in and around the research relationship between these two species is still fields. incomplete. In the present study we report on the differences in the pattern of habitat use between these Trapping and radio-collaring two sympatric nocturnal carnivores, during daytime and night-time, in Nopporo Natural Forest Park, Traps were set for 48 days in total, from 26 March to Pages 116-121. In Koike, F., Clout, M.N., Kawamichi, M., De Poorter, M. and Iwatsuki, K. (eds), Assessment and Control of Biological Invasion Risks. Shoukadoh Book Sellers, Kyoto, Japan and IUCN, Gland, Switzerland, 2006. G. Abe et al. year (Maesaki et al. 2002). Live cage traps (model #1089: 82Lx27Wx30H cm; ca 4.0kg; Havahart, Litiz, Pennsylvania, USA) were used, baited with dog food, corn snacks and doughnuts. We set traps at intervals of about 500m, which was smaller than the raccoon's home range length reported by Kurashima and Niwase (1998). We estimated that this distance is the potential trapping radius for each trap (Fig. 1). On their first capture, trapped raccoons and raccoon dogs weighing 3.5kg or more were immobilised with an intramuscular injection of ketamine hydorochloride (Ketaral, 1mg/kg), medetomidine hydrochloride (Domitor, 40µg/kg) and midazolam (Dormicam, 0.15mg/kg). Body mass, head-body length and tail length were measured and radio-collars were fitted (ca 120g, ATS, Inc., USA). After finishing these procedures, the reversal agent potential trapping radius atipamezole hydrochloride (Antisedan, 40µg/kg) was trap point (500m) administered, assisting recovery. Animals were released drive way farm field at the site of capture after approximately two hours, by heavy traffic road woodland which time they had fully recovered from the river residential area anaesthesia. Figure 1 Nopporo Natural Forest Park and the adjacent Juvenile individuals of less than 3.5kg and areas. This park is wedged between the north-western individuals suspected to be suffering from sarcoptic residential area and the south-eastern farm fields. We set mange (Sarcoptes scabie Linnaeus, 1758) were not a maximum of 34 traps in the southern part of the park collared, for animal welfare reasons. and estimated the potential trapping radius of each trap as 500m. The dashed line shows the research target area, where the home ranges of some raccoons and raccoon dogs were thought to overlap. Radio-tracking From June to July in 2003, we recorded telemetry 24 May 2003 (except for 23 - 29 April and 6, 7, and 14 locations for all radio-collared individuals once a day in - 16 May), using a maximum of 34 traps (25 days for the daytime, between 0700 - 1800. As both raccoons each trap; 851 Trap-nights; Fig.1) in the southern part and raccoon dogs are nocturnal (Mech et al. 1966, of Nopporo Natural Forest Park, where both species Yamamoto 1993), we assumed that these location had been trapped most frequently during the previous points represented their resting sites. We radio-tracked Table 1 Radio-collared raccoons and raccoon dogs, both of which were captured in Nopporo Natural Forest Park, Hokkaido in May, 2003. All individuals in the table were radio-tracked during the daytime, and those with asterisks were also radio-tracked at night. The “head body” was larger estimation since we measured the length along the curve of neck. Body length Head Body + tail Body mass Radio-tracking Species ID Sex length (kg) at night (cm) r-f1 female 64.0 + 28.0 6.0 * r-f2 female 61.0 + 31.0 8.0 * r-f3 female 63.0 + 25.0 4.4 * r-f4 female 62.5 + 31.0 5.7 Raccoons r-f5 female 64.0 + 23.5 6.4 (Procyon lotor) r-f6 female 62.0 + 28.0 5.6 r-f7 female 54.0 + 24.0 4.3 r-f8 female 62.0 + 28.0 5.4 r-m1 male 60.0 + 26.0 4.2 * rd-f1 female 56.7 + 17.0 5.6 * Raccoon dogs rd-f2 female 51.0 + 16.0 4.3 * (Nyctereutes rd-f3 female 54.0 + 16.0 3.5 procyonoides albus) rd-f4 female 58.0 + 21.0 3.8 rd-m1 male 57.0 + 18.0 3.8 * 117 Habitat use of native raccoon dogs and alien raccoons particular individuals whose nocturnal home ranges RESULTS were assumed to overlap with each other (based on the fact that their resting sites overlapped). This Trapping and radio-tracking radio-tracking at night was done every hour between 1800 - 0700, once per week. Nine raccoons (one male and eight females) and nine Radio signals were detected with a hand-held raccoon dogs (one male, five females, and three of four-element Yagi antenna and receiver (FT290, unknown sex) were trapped and all nine raccoons and YAESU, Japan). Azimuths were triangulated from at five raccoon dogs (one male and four females) were least three positions to fix a location. radio-collared. One female raccoon dog weighing less than 3.5kg and three other raccoon dogs suspected to be suffering from sarcoptic mange were not collared. Data analysis Based on the telemetry location data for resting sites, we selected four raccoons (one male and three To examine only the nocturnal activities of raccoons females) and three raccoon dogs (one male and two and raccoon dogs, which live sympatrically, we females), because they were assumed to have home compared location data of individuals monitored for ranges overlapping with the other species. The home more than three nights. Home ranges as well as core ranges of other radio-collared individuals (five areas that each animal used frequently were calculated raccoons and one raccoon dog) did not have such based on the whole nocturnal activity pattern for each overlapping at all (see details on Tab. 1 and Figs. 2 and individual. Their home ranges were estimated with the 3). 100% Minimum convex polygon method and the core We obtained 355 locations for the four raccoons areas were estimated with the 50% Fixed Kernel and 247 locations for the three raccoon dogs for method (Worton 1989), which calculated the utilisation nocturnal activities.