Bears are often considered ecological equivalents of large primates, but the latter often respond with fear, avoidance, and alarm calls to snakes, both venomous and non-venomous, there is sparse information on how bears respond to snakes. We videotaped or directly observed natural encounters between black bears (Ursus americanus) and snakes. Inside the range of venomous snakes in Arkansas and West Virginia, adolescent and adult black bears reacted fearfully in seven of seven encounters upon becoming aware of venomous and non-venomous snakes; but in northern Michigan and Minnesota where venomous snakes have been absent for millennia, black bears showed little or no fear in four encounters with non-venomous snakes of three species. The possible roles of experience and evolution in bear reactions to snakes and vice versa are discussed. In all areas studied, black bears had difficulty to recognize non-moving snakes by smell or sight. Bears did not react until snakes moved in 11 of 12 encounters with non-moving timber rattlesnakes (Crotalus horridus) and four species of harmless snakes. However, in additional tests in this study, bears were repulsed by garter snakes that had excreted pungent anal exudates, which may help explain the absence of snakes, both venomous and harmless, in bear diets reported to date.

中文翻译：

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北美东部黑熊对毒蛇和无毒蛇的反应

熊通常被认为是大型灵长类动物的生态等价物，但后者通常对毒蛇和无毒蛇的反应是恐惧、回避和警报，关于熊如何应对蛇的信息很少。我们录制了或直接观察了黑熊 (Ursus americanus) 和蛇之间的自然相遇。在阿肯色州和西弗吉尼亚州的毒蛇范围内，青少年和成年黑熊在七次遭遇中的七次遇到毒蛇和无毒蛇时会做出可怕的反应；但在密歇根州北部和明尼苏达州几千年来一直没有毒蛇，黑熊在与三种无毒蛇的四次遭遇中几乎没有表现出恐惧。讨论了经验和进化在熊对蛇的反应中的可能作用，反之亦然。在所有研究领域，黑熊都难以通过气味或视觉识别静止的蛇。在 12 次遇到不动的木材响尾蛇 (Crotalus horridus) 和四种无害蛇的 12 次中，有 11 次遇到了蛇，熊才做出反应。然而，在本研究的其他测试中，熊被排泄出刺激性肛门分泌物的吊带蛇排斥，这可能有助于解释迄今为止报道的熊饮食中没有毒蛇和无害蛇的原因。