853 ISSN 1062-3590, Biology Bulletin, 2018, Vol. 45, No. 8, pp. 853–864. © Pleiades Publishing, Inc., 2018. Original Russian Text © I.V. Seryodkin, D.G. Miquelle, J.M. Goodrich, A.V. Kostyria, Y.K. Petrunenko, 2017, published in Zoologicheskii Zhurnal, 2017, Vol. 96, No. 12, pp. 1446–1458. Interspecific Relationships between the Amur Tiger (Panthera tigris altaica) and Brown (Ursus arctos) and Asiatic Black (Ursus thibetanus) Bears I. V. Seryodkin a, b, *, D. G. Miquelle b, c , J. M. Goodrich d , A. V. Kostyria e, f , and Y. K. Petrunenko a a Pacific Geographical Institute, Far East Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia b Far Eastern Federal University, Vladivostok, 690091 Russia c Wildlife Conservation Society, New York, 10460 USA d Panthera Foundation, New York, 10018 USA e Institute of Biology and Soil Sciences, Far East Branch, Russian Academy of Sciences, Vladivostok, 690022 Russia f World Wide Fund for Nature, Amur Branch, Vladivostok, 690003 Russia *e-mail: seryodkinivan@inbox.ru Received October 16, 2016 Abstract—During the years 1992–2013, we studied the relationship between Amur tigers and brown and Asi- atic black bears in the Sikhote-Alin Nature Reserve and surrounding areas in the southern part of the Russian Far East. To determine the importance of bears in the diet of tigers, 763 kills were located and identified, and 430 tiger scat samples were collected and analyzed. To detect kills and scat samples, we used radio telemetry and satellite tracking, as well as snow-tracking. Relying on evidence revealed by tracks, as well as radio telem- etry, we determined whether bears exploited tiger kills as a food resource and how the two may have interacted at kill sites. Thirty-two Asiatic black bear and 12 brown bear den sites were measured to define properties that might assist in protection from the threat of a tiger attack. We identified 641 instances of marking on trees by both tigers and bears, an indication of the complexity of their relationship. Bears are an important part of the tigers’ diet, representing 2.2% of all kills found. Bear remains were found in 8.4% of examined tiger scat. Bears exploited tiger kills after a tiger had left, by usurping a kill, or by “sharing” a kill at alternate times. The occur- rence of den properties that provided some protection from tigers was dependent on the den type and loca- tion. Evidence of both tiger and bear marking was detected at 50.1% of marked trees. A review of the literature on the relationship of tigers and bears is provided. Keywords: Amur tiger, brown bear, Asiatic black bear, diet, scavenger, predation DOI: 10.1134/S1062359018080149 INTRODUCTION The range of the Amur tiger in the southern part of the Far East of Russia is inhabited by brown and Asi- atic black bears. All three species prefer coniferous- broadleaf and deciduous forests. The significant dimensions and mutual overlap of the habitats of the tiger (Yudakov and Nikolaev, 1987; Goodrich et al., 2010) and two species of bears (Seryodkin et al., 2006), as well as the broad seasonal movements of bears (Seryodkin et al., 2014, 2014a), suggest the simultaneous presence of differently aged individuals of these species on the same territory. Having com- mon habitats, tigers and bears come into contact with each other, as a result of which a complex of relation- ships is established between these species. The relationship of the Amur tiger with the brown and Asiatic black bears has not specifically been stud- ied by researchers. In the numerous publications on these species, there are mainly episodic and interrog- atory data on this issue collected by different authors in some areas of the Primorskii and Khabarovsk krais, which do not give a complete picture of the nature of the relationship and the mutual inf luence of the pred- ators on each other (Bromley, 1965; Gorokhov, 1973; Kostoglod, 1977; Khramtsov, 1993; Tkachenko, 2012; etc.). The possibility to complete the picture of the relationships appeared owing to the application of methods of radiotelemetry and satellite tracking along with the traditional methods of studying predators. Such a comprehensive research program, including the tracking of tigers and brown and Asiatic black bears collared with radio and satellite collars, was car- ried out in the Sikhote-Alin’ Biosphere Reserve and its environs (Miquelle et al., 1993; Seryodkin et al., 2011). Analysis of the results obtained and their dis- cussion using previously published information allowed us to explore this topic in more detail.