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Habitat and Prey Resource Overlap Between the Iriomote Cat

Habitat and Prey Resource Overlap Between the Iriomote Cat

Mammal Study 28: 47–56 (2003) © the Mammalogical Society of

Habitat and prey resource overlap between the Iriomote iriomotensis and introduced cat catus based on assessment of scat content and distribution

Shinichi Watanabe*, Nozomi Nakanishi and Masako Izawa Faculty of Science, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan

Abstract. The Prionailurus iriomotensis occurs only on in the Ryukyu Archipelago of southern Japan. The population is estimated at 100 individuals and is on the decline. We examined resource overlap for prey and between this species and introduced Felis catus by scat census and analysis of scat contents. The distribution of scats was completely different between the two species. The distribution of scats from Iriomote cats was associated with environmental factors such as vegetation types and terrain conditions, while the distribution of scats from feral cats mainly depended on locations of garbage dumps. Although the feral cat heavily utilized human rubbish, it also preyed upon thirteen species of native , ten of which were also used by Iriomote cats. From 1997 to 2001, the number of observed scats from Iriomote cats declined significantly, while feral cat scat became more common. Feral cats on Iriomote Island still depend on humans, but the expansion of their distribution into of Iriomote cats may increase the competition for prey and habitat resources in the future.

Key words: Felis catus, habitat use, interspecific competition, introduced species, Prionailurus iriomotensis.

Introduced species often greatly affect local and status or even extinction (Kitching and Jones 1981; King flora through predation, resource competition and 1984). In Okinawa and the Amami Islands of southern hybridization with native species (Elton 1958; Diamond Japan, introduced to control a venomous and Case 1986; Ecological Society of Japan 2002). Iso- snake (Habu Trimeresurus flavoviridis) and rats have lated fauna and flora with a small number of species are become established in vacant niches. As a result, many particularly vulnerable to invasive introduced species rare or endemic species of , , terres- (Elton 1958; Diamond and Case 1986; Frankel and Soulé trial , and have been preyed upon and 1981). In recent history, 75% of extinctions of birds and threatened (Abe et al. 1991, 1998; Ogura et al. 2002; mammals have occurred on isolated islands, and 43% of Kawauchi and Sasaki 2002; Ministry of the Environment these were caused by introduced predators (Frankel and 2002a, b, c). Soulé 1981). Species are more susceptible in islands Introduced species often compete for prey and habitat because of restricted habitats and lack of experience with resources against native species, but the impacts of com- new predators, and are often at a competitive disadvan- petition are notably stronger on closely related species tage against aggressive invasive species (Frankel and (Diamond and Case 1986; Ecological Society of Japan Soulé 1981). Well-documented examples occurred in 2002). The Iriomote cat Prionailurus iriomotensis is a Australia and New Zealand, where unique fauna in iso- small felid and inhabits only Iriomote Island of the lated habitats were affected by introduced like Ryukyu Archipelago. This species is listed as endan- dingos lupus dingo, feral cats Felis catus, and red gered because of its restricted habitat and small popula- vulpes. Predation on native marsupials and tion size, (IUCN 2000) estimated at approximately 100 terrestrial birds pushed many populations to threatened individuals (JWRC 1994). The population has declined

*To whom correspondence should be addressed. E-mail: [email protected] 48 Study 28 (2003)

Fig. 1. Location of the census route to collect scats on Iriomote Island in the Ryukyu Archipelago of southern Japan. A census route along a paved road six kilometers long and five meters wide was divided into 24 sections (a–x) at 250 m intervals. during the last decade due to habitat loss from develop- Study area ment and mortality from traffic accidents (Izawa and Doi 1991). While P. iriomotensis is the only native member The study was conducted on Iriomote Island (284 km2, of the order on Iriomote Island, the introduced 24°20’N, 123°49’E) located in the southern Ryukyu feral cat F. catus distribution has been expanding away Archipelago, Japan. The climate is warm-temperate to from human settlements, often following new road subtropical with average monthly temperatures ranging construction. from 17°C in January to 29°C in July, and average Among carnivores, scat provides information about annual precipitation of approximately 2,300 mm at the individuals at specific sites (Macdonald 1980). The Iriomote Meteorological Station. Most of the island is Iriomote cat leaves scat on exposed surfaces such as dominated by highly folded mountains (the highest point on bare lands, rocks, and roads (Sakaguchi et al. 1986). = 469 m, Mt. Komi) and covered with subtropical ever- Sakaguchi et al. (1986) frequently observed scats from green broad-leaved forests dominated by Castanopsis Iriomote cats along streams, along the edges of forests sieboldii and Quercus miyagii. Flatlands occur only and grasslands. Scats were not present in the interior along the coast, where human activities, cultivated fields of cultivated fields, grasslands, or barren ground. Similar and villages are concentrated. About 2,000 people live patterns of habitat use were observed in radio-tracking on the island, mostly inhabiting twelve villages along the surveys (Watanabe 2001; Watanabe et al. 2001). Saka- coast. guchi et al. (1986) also suggested that the distribution The study site is in the eastern part of the island near of scat from Iriomote cats reflects both habitat use and two small villages (Fig. 1) with populations of 70 people specific preferences for latrine sites. In the current in Komi and 24 people in Mihara in January 2002. A study, we used scat locations to evaluate habitat use by paved road, 5 m wide and 50 km long was constructed in both Iriomote cats and feral cats. We also assessed prey 1976. We established a 6 km census route on the road preferences through fecal analysis of both species. divided into 24 sections (a–x) at 250 m intervals (Fig. 1). The route crosses three streams, and traverses subtropi- Watanabe et al., Resource overlap of native and feral cats 49 cal evergreen forests, rice fields, cultivated fields, man- containing a prey type/total number of analyzed scats) groves, and swampy forests. The two villages are along was calculated for each prey type and for each taxon sections h–j (Komi) and adjacent to sections w–x (mammals, birds, reptiles, amphibians, , , (Mihara). Two garbage dumps are located 250 m away , and others). from section i in a cane field and 50 m away from section u in a forest. Analysis of scat distribution According to the statistical reports of Taketomi Town Habitat utilization of P. iriomotensis is reported to be Office, while the population on Iriomote Island grew affected by environmental factors including terrain and from 1,892 people in 1995 to at least 1,976 people in vegetation (Watanabe 2001; Watanabe et al. 2001). In 2000, visitor numbers increased from 201,967 people in this study, we analyzed the relationships between scat 1995 to 285,080 people in 2000. locations for the two cat species and the surrounding environment by using a geographic information system Methods (GIS). Deflection of scat distribution was tested for each Scat census species by one-sample Kolmogorov-Smirnov tests. Scat Scats were collected by one or two observers walking distribution was compared between species by two- along both sides of the route at the end of each month sample Kolmogorov-Smirnov tests. from November 1997 to October 2001. Locations, cir- Multiple regression models were developed according cumstances, and conditions of scat were recorded during to quantification theory type I (Hayashi 1952) for the dis- these censuses. tribution of scat of the two species. The total number of scats collected in each section was the dependent Scat identification variable and six environmental factors were independent It was necessary to distinguish between the scats of variables. Three variables related to terrain: (1) mean the two cat species at the point of collection. Scat of P. elevation, (2) mean slope in each section, and (3) dis- iriomotensis can be easily distinguished by the specific tance from streams to the center of each section, were odors secreted from anal glands (Imaizumi et al. 1977; derived from digital elevation models (Digital Map 50 m Sakaguchi et al. 1986). Fecal odors withstand weather- mesh, Elevation published by Geographical Survey ing and degradation for longer periods than the interval Institute, Japan). Vegetation type (4) in each section between our censuses. Therefore, scats having the was categorized as forest, rice field and swamp, and specific odor of P. iriomotensis could be positively cultivated and bare land according to digital vegetation identified based on the odor. However, scat with no data, from the Natural Environment Information GIS characteristic odors could not be designated as F. catus (Environment Agency 1999). Variables related to human scat without further evidence. Since mammals ingest activities such as (5) distance from garbage dumps, and their own hair during grooming and pass it in their scat (6) distance from residential areas to the center of (Imaizumi et al. 1977), we characterized cat hairs in scat each section were calculated using GIS software, IDRISI at the time of collection and during lab analysis. version 32.2 (Clark Labs, The Idrisi Project). Multiple Although some feral cats have similar collar patterned regression analysis was performed using a macro in fur to that of Iriomote cats, hairs in scat were clearly Microsoft Excel. identified by hair-length, solidity, and color pattern when All independent variables were categorized, and each viewed under a stereomicroscope. variable was evaluated with a category score (CS). Posi- tive effects are given a positive score and negative Analysis of scat content effects are given a negative score with the absolute value Collected scats were washed on 1 mm mesh sieve. indicating the strength of the effect. The magnitude of Remnants were dried and identified as hair, bone frag- the effect of environmental variables is indicated by ments, teeth, feathers, scales, and arthropod chitin using partial correlation coefficients (PCC) (Hayashi 1952). reference samples of potential prey species collected in the study area. We tried to identify prey to the level of species depending on the type and the quality of the sample. Frequency of occurrence (the number of scats 50 Mammal Study 28 (2003)

Table 1. Frequency of occurrences of prey items found in 156 scats of P. iriomotensis and 31 scats of F. catus collected along a paved road in the eastern part of Iriomote Island from 1997 to 2001.

P. iriomotensis F. catus Prey item Frequency of occurrence (%) MAMMALIA *Rattus rattus 23.1 9.7 Sus scrofa riukiuanus 0.6 Pteropus dasymallus yaeyamae 3.2 AV ES Egretta garzetta 3.2 Accipiter gularis 0.6 Rallina eurizonoides 1.3 *Amaurornis phoenicurus 6.4 3.2 Streptopelia orientalis 1.3 *Chalcophaps indica yamashinai 0.6 3.2 Sphenurus formosae 0.6 *Halcyon coromanda bangsi 0.6 3.2 Turdus pallidus 3.2 Turdus spp. 1.3 Corvus macrorhynchos osai 5.8 Unknown spp. of Ardeidae sized birds 3.2 Unknown spp. of Rallidae sized birds 11.5 Unknown spp. of Turdidae sized birds 5.1 16.1 Unknown spp. of Zosteropidae sized birds 6.4 Unknown spp. of Aves 0.6 3.2 REPTILIA Japalura polygonata ishigakiensis 5.1 Eumeces kishinouyei 11.5 Eumeces spp. 4.5 Dinodon rufozonatus 0.6 Elaphe taeniura 1.9 Trimeresurus elegans 0.6 Unknown spp. of Colubridae 2.6 AMPHIBIA *Rana (Limnonectes) sp. 19.2 3.2 Rana supranarina 0.6 Rana supranarina or utsunomiyaorum 1.9 Rana spp. 10.3 Rhacophorus owstoni 4.5 ornata 2.6 Unknown spp. of Anura 10.9 *: Ten prey items identified are overlapped between two cat species.

Results odors different from those of P. iriomotensis. Based on hair content analysis, 83.9% of scats in Scat identification the group without the specific odor associated with P. From November 1997 to October 2001, 272 scats iriomotensis contained hairs of feral cats, and none con- were collected in 48 censuses. Scat odors allowed sepa- tained hairs of P. iriomotensis. Hairs of P. iriomotensis ration of the samples into two categories. Odors from are longer (3–5 cm), harder and substantial with a 236 scats were identified as those of P. iriomotensis, and banded pattern of dark brown and white. Hairs in scats 36 scats emitted odors distinctly associated with F. catus. with odors different from P. iriomotensis were shorter We excluded weathered and eroded scat from the analy- (2–3 cm), thinner and slight with the white un-patterned sis of scat content, and examined contents of 156 scat colors hairs of F. catus. Hair content analysis supported samples from P. iriomotensis and 31 scats with distinct the results of odor analysis. After assigning a species for Watanabe et al., Resource overlap of native and feral cats 51

Table 1 (continued)

P. iriomotensis F. catus Prey item Frequency of occurrence (%) OSTEICHTHYES Unknown spp. of Perciformes 2.6 INSECTA Pycnoscelis surinomensis 0.6 Periplaneta suzukii 0.6 Rhabdoblatta guttigera 0.6 R. yayeyamana 1.3 Diestrammena apicalis 0.6 Diestrammena sp. 2.6 Euconocephalus thunbergi 6.5 Unknown spp. of Tettigoniidae 1.3 6.5 *Teleogryllus occipitalis 1.9 9.7 *Duolandrevus coulonianus 1.9 6.5 *Cardiodactylus novaeguineae 9.0 9.7 Unknown spp. of Blattidae 2.6 Gryllotalpa orientalis 1.9 Aiolopus tamulus 0.6 *Hieroglyphus annulicornis 3.2 Unknown spp. of Catantopidae 1.9 3.2 Unknown spp. of Orthoptera 1.3 3.2 Platypleura yayeyamana 0.6 Meimuna iwasakii 3.2 Unknown spp. of Carabidae 0.6 Unknown spp. of Scarabaeidae 0.6 3.2 Unknown spp. of Hymenoptera 0.6 Unknown spp. of Insecta 3.2 CRUSTACEA Macrobrachium spp. 3.8 Unknown spp. of 0.6 Unknown spp. of Decapoda 0.6 ARACHNIDA Macrotheis gigas 1.3 Heteropoda sp. 0.6 *Unknown sp. of Araneae 0.6 3.2 GASTROPODA Acusta despecta despecta 0.6 Gramineae 38.5 16.1 ARTIFACTS Garbage 87.1 *: Ten prey items identified are overlapped between two cat species. each scat, we examined the distribution of 236 scat tensis. Artifacts from garbage were not found in scats of locations for P. iriomotensis and 36 scat locations for P. iriomotensis, but occurred in 87.1% of scats from F. F. catus. catus, and 35.5% of these scats contained only artifacts such as pieces of paper, plastic bags, and silver foil. Comparison of food habits However, 61.3% of F. catus scats contained thirteen Identity and frequency of occurrence of prey species species of native animals: a mammal, three birds, an in scats from the two cat species are shown in Table 1. , seven insects, and a spider. Although ten of From a total of 46 prey species, three species of these prey species overlapped with prey found in scats of mammals, ten birds, five reptiles, four amphibians, a , P. iriomotensis, three species of insects were not eighteen insects, at least two crustaceans, two spiders, recorded on the prey list of P. iriomotensis. and a gastropod were identified in the scats of P. iriomo- The frequency of occurrence for each prey taxon of 52 Mammal Study 28 (2003)

Fig. 2. Monthly fluctuations in the number of P. iriomotensis and F. catus scats collected in censuses conducted from November 1997 to October 2001.

P. iriomotensis was calculated as follows: birds (52%), 20, with a mean and standard deviation of 4.92 ± 4.45 (n amphibians (37%), insects (28%), mammals (26%), = 48) (Fig. 2). Scats from F. catus had a range of 0–11, and reptiles (23%). Among the food items of F. catus, 0.75 ± 1.92 (n = 48) for each census (Fig. 2). The num- human-derived artifacts occurred more frequently than ber of P. iriomotensis scats collected per period was 8.92 any prey type, but the frequency of birds (26%) was rela- ± 5.65 in the first year (November 1997 to October tively high and insects (35%) occurred more frequently 1998), 5.08 ± 3.29 in the second year, 3.58 ± 2.71 in the than in P. iriomotensis (28%). third year, and 2.08 ± 2.50 in the fourth year. Multiple Scats from feral cats containing native prey were more comparison analysis of the four years of grouped data distant from garbage dumps (465 ± 335 m with native shows that the number of scats collected in the third and prey, n = 19; 280 ± 211 m without native prey, n = 12) the fourth years were significantly lower than in the first and residential areas (404 ± 359 with native prey and year (Tukey’s HSD multiple comparison test, P < 0.05). 335 ± 218 m without native prey). However, these When annual samples were used to calculate an average differences were not significant (Mann-Whitney U test, number of F. catus scats collected per census period, the P > 0.05). average was 0.08 ± 0.29 in the first year, 0.08 ± 0.29 in the second year, 2.33 ± 3.23 in the third year, and 0.50 ± Number of scats 1.17 in the fourth year. The number of F. catus scats in While P. iriomotensis scats were found in most cen- the third year was significantly higher than in the first suses, F. catus scats were found in only twelve censuses and the second years (Tukey’s HSD multiple comparison (25%) during the study period. Felis catus scats were test, P < 0.05). rarely found before 2000, then were consistently found from May to December 2000, and were rarely found Distribution of scats after January 2001. The number of scats collected in The distributions of scats from both cat species are each census period for P. iriomotensis had a range of 0– shown in Fig. 3. The number of scats collected differed Watanabe et al., Resource overlap of native and feral cats 53

Fig. 3. Number of scats observed and predicted values derived from a predictive model for P. iriomotensis and F. catus, along the census route. Two villages are located in sections h–j and at w–x, and garbage dumps are adjacent to sections i and u. significantly among census sections for both species affect habitat preferences. Therefore, mean elevation (one-sample Kolmogorov-Smirnov test; P. iriomotensis: was excluded from the multivariate analysis of scat D = 0.254, F. catus: D = 0.611, d.f. = 23, P < 0.001). distribution to avoid distortion caused by significant The distribution pattern between the two species also correlation among independent variables (Hayashi 1952). differed significantly (two-sample Kolmogorov-Smirnov Significant correlation was not found among any other test: D = 0.417, d.f. =23, P < 0.05). Scats of P. iriomo- combinations (P > 0.05). tensis were not found in sections g–j adjacent to the vil- Multivariate analysis (Table 2) gives coefficients of lage, but were abundant in sections a–f and l–r. At least determination (R 2) indicating particularly high accuracy one F. catus scat was found in each of sections f and j in the predicted models of scat distributions of both spe- adjacent to the village and within sections q–x. Felis catus cies. However, the accuracy of the model of F. catus (R 2 scats were most abundant in section u adjacent to a = 0.906, F = 12.5, d.f. = 10, 13, P = 0.00004) was higher garbage dump. There was a slightly negative correlation than that for P. iriomotensis’s (R 2 = 0.804, F = 53.4, d.f. between numbers of scats of the two species, however it = 10, 13, P = 0.0031). Predicted and observed values was not significant (r = –0.36, P = 0.087). were compared to verify the goodness of fit (Fig. 3). In the model of F. catus, there were small residual errors Predictive model of scat distribution between predicted and observed values in all sections; Of the six independent variables identified in this however, there were large errors in some sections in the study, only mean elevation and distance from garbage model of P. iriomotensis. Absolute values of these dumps were found to be significantly correlated (r = residuals (predicted values minus observed values) –0.71, P < 0.01) in a correlation matrix. Locations of were smaller in F. catus (0.63 ± 0.51, mean ± SD, n = garbage dumps were an important factor for feral cats 24) than in P. iriomotensis (3.1 ± 2.2, n = 24). but elevation in the census route varied only from 2 to Scat distribution of P. iriomotensis was most affected 55 m; presumably the small difference does not directly by distance from garbage dumps. The CS predicted that 54 Mammal Study 28 (2003)

Table 2. Predictive models of scat distributions of P. iriomotensis and F. catus created by multivariate analysis, quantification theory type I by Hayashi (1952) with five environmental variables. CS = Category score, R = Range of category scores, PCC = Partial correla- tion coefficient.

P. iriomotensis F. catus Variables Category n CS R PCC CS R PCC <2.5 7 –2.71 6.12 0.43 –1.03 3.83 0.86 Slope (°) 2.5? <5 10 –0.14 –0.87 O5 7 3.41 2.80 <100 8 0.33 7.48 0.61 –0.42 0.66 0.30 Distance from streamside (m) 100? <200 8 –3.90 0.24 O200 8 3.58 0.17 Forest 7 1.88 6.42 0.53 –0.75 1.14 0.36 Vegetation type Rice field & Swamp 8 2.62 0.38 Cultivated & Bare land 9 –3.80 0.24 <400 3 –10.38 14.47 0.70 4.68 5.83 0.88 Distance from garbage (m) 400? <800 9 –1.99 –1.16 O800 12 4.09 –0.30 <400 11 –4.30 8.56 0.64 0.42 0.95 0.40 Distance from residence (m) 400? <800 6 2.91 –0.54 O800 7 4.26 –0.19 Coefficient of determination (R 2) 0.804 0.906 F 5.34 12.5 p 0.0031 0.00004

P. iriomotensis would be less common in the vicinity of Discussion garbage dumps and residential areas than in areas far away from these sites, more abundant in forests, rice The accuracy of the predicted model of F. catus scat fields and swamps than in cultivated and bare land, and distribution was higher than for P. iriomotensis because less abundant on flat land than steep land. However, for of the strong association between F. catus and garbage distance from streams, there is no clear trend for the dumps. Scats of F. catus were less abundant in forests category within 100 m. P. iriomotensis was expected compared to cultivated and bare lands. Nakamura (2000) to be less abundant within 100–200 m of streams and reported that a radio-tagged F. catus in section g–j more abundant in distances of over 200 m. depended on residents and utilized only residential areas The scat distribution of F. catus was most affected by and cultivated land. The model for P. iriomotensis distance from garbage dumps, followed by slope, dis- included other environmental factors. Scat distributions tance from residential areas, and vegetation type, and of P. iriomotensis were affected by human activities least affected by distance from streams. The only areas (avoided garbage dumps and residential areas), vegeta- of distribution overlap with P. iriomotensis were rela- tion types (preferred forests, rice fields and swamps, and tively abundant areas of rice fields, swamps and steep avoided cultivated land and bare land) and terrain condi- lands, while their scats were abundant in vicinities of tions (avoided flat open spaces). Radio-tracking surveys garbage dumps and residential areas. Although scats (Watanabe 2001; Watanabe et al. 2001) confirm that from F. catus were also relatively abundant on steep frequently used areas coincide with areas of high scat slopes (slope over 5°), this might reflect the location of abundance. In future studies, additional habitat varia- garbage dump in section u located on steep slope. bles assessed with higher resolution would create more Within vegetation types, scats were relatively abundant accurate predictive models of scat distributions for P. in cultivated and bare lands compared to forests. While iriomotensis. the distribution of P. iriomotensis was affected by many Scats from F. catus contained many human-derived environmental factors, F. catus was most strongly artifacts, presumably from garbage, indicating a high affected by distance from garbage dumps. dependence on garbage for food resources. On the other, P. iriomotensis ate various prey and artifacts were never Watanabe et al., Resource overlap of native and feral cats 55 observed in scat, so the degree of dietary overlap was not been expanded, and traffic due to construction vehicles high. However, F. catus also fed on various prey that and tourists increased during the 4-years period. The were also the main prey of P. iriomotensis including the more plausible explanation for the decline is that the white-breasted water hen Amaurornis phoenicurus, the habitat of P. iriomotensis was drastically reduced. In Sakishima rice frog Rana (Limnonectes) sp., and the contrast the preferred habitat of F. catus increased, and spotted cricket Cardiodactylus novaeguineae, making this might be reflected in increasing appearance of F. interspecific competition for prey resources possible. catus scat. A growing volume of garbage derived from Additionally, F. catus preyed on the emerald dove the growing number of tourists likely supplied plenty of Chalcophaps indica yamashinai, an endangered species food for population growth of F. catus. on the 2002 Red Data List of Ministry of the Environ- Another native felid in Japan, the Tsushima leopard ment. cat Prionailurus bengalensis euptilura and F. catus both In a study of food habits of feral cats on Okinawa, inhabit Tsushima Islands of northern Kyushu, Japan. an island in the middle of Ryukyu archipelago, the cats Nishimura et al. (1999) reported that a native individual did not depend only on human-derived foods, but had of Tsushima was infected by FIV (Feline a diet very similar to P. iriomotensis, preying upon immunodeficiency virus: a causative agent of AIDS-like various native animals ranging from mammals to insects disease and immunological abnormalities in F. catus) (Kawauchi and Sasaki 2002). In Australia, feral cats are and cautioned that the spread of epidemics seriously also reported to prey and impact various native animals. affects non-resistant native species. Therefore it is While perhaps initially depending on human on resi- expected that the increasing feral cat population on Irio- dents, they adapted to inhabit a wide range of habitats in mote Island has the potential to impact P. iriomotensis Australia (Dickman 1996). In our study area, F. catus is pathologically as well as ecologically through resource not completely feral as in the above studies, yet even at competition. this stage, feral cats fed upon many types of prey, some- Although the preferred habitats for each species are times more frequently for insects than P. iriomotensis. different, there is some possibility of contact between Scats found far away from garbage dumps and resi- feral and native cats on Iriomote Island. Some scats of dential areas tended to contain more native prey. Feral F. catus in our study area were found 700 m away from cats in our study area frequently hunt abundant and vul- garbage dumps and residential areas, and we sometimes nerable prey such as insects at the present stage. If the observed the same individual feral cats traveling in wide population of F. catus grows and expands beyond the ranges between section u–x during the study period. garbage dumps and residential areas, it is possible that Their ranges might have expanded widely from the feral cats with feeding habits similar to P. iriomotensis garbage dumps using the paved road as a path. Radio- may compete for the same habitat resources. tagged Iriomote cats did not utilize the residential areas, The number of P. iriomotensis scats collected declined but scats of F. catus were found in the home ranges of significantly over our study period. The Kumamoto Iriomote cats, especially in areas adjacent to the garbage Regional Forest Office of the Forestry Agency had irreg- dump in section u (Watanabe 2001). It suggests that ularly conducted scat censuses along the route in January contact between the two species is unlikely to occur in 1995 and October 1997; more P. iriomotensis scat (18.0 residential areas, but is likely near garbage dumps in ± 11.3, n = 11) were collected than in our study period forested areas. Therefore, we propose that immediate and no F. catus scat were collected (Forestry Agency action be taken to control the F. catus population and to 1995; Environment Agency and Forestry Agency 1996, reduce access to garbage dumps before the cats become 1998). Although interspecific competition for spatial well-adapted to native habitats. habitat resources is a possible explanation, it is con- sidered unlikely. Habitat preferences differed between Acknowledgments: We are grateful to Kumamoto Re- species, and there was a slight negative correlation in gional Forestry Office of Forestry Agency and Iriomote the abundance of scat of P. iriomotensis and F. catus, Conservation Center (IWCC) of the Ministry of indicating distinct habitat utilization. Watanabe et al. the Environment for supporting this research. We also (2002) reported that the population of P. iriomotensis appreciate the help we received from Dr. T. Doi, Kyushu was declining due to habitat loss due to recent human University, and Dr. M. Okamura, IWCC, and people in developments. In the study area, road and bridges had the laboratory of the Faculty of Science, Uni- 56 Mammal Study 28 (2003) versity of the Ryukyus for precious comments, and the of two cat species of in Japan. Honyurui Kagaku [Mam- kindness of many local people, particularly Mr. M. malian Science] 31: 15–22 (in Japanese with English abstract). 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