犬群位階的線性程度與其對人類依賴程度的關連

Abstract

有些群居物種會透過競爭互動建立位階關係，位階影響了牠們使用資源的順 序並降低衝突的產生。然而資源的豐富程度會影響位階的線性程度。在資源充足 的情況下，個體間無需競爭食物資源，因此位階的重要性下降。許多研究顯示犬 科動物的位階關係有明確的線性程度，優勢個體可優先使用資源，減少競爭的再 發生率。然而，有些犬群完全依賴人類供食與照顧，並與人類互動頻繁，有些則 僅部分依賴人類供食，且與人類互動少，而人類是否影響犬群位階的線性程度， 卻尚未被探討。因此，本研究目的是了解犬群對人類不同依賴程度是否影響其位 階線性程度。本研究之假說為:相較於部分依賴人類供食且與人類互動少的犬群， 完全依賴人類的犬群位階線性程度較低。本研究將犬群分類成第一類完全依賴人 類 (n = 4 群) 以及第二類部分依賴人類 (n = 2 群)。在第一類犬群中，犬隻完全依 賴人類提供充足的食物量，並與人類互動頻繁。而在第二類犬群中，犬隻僅部分 依賴人類供食，人類提供的食物量無法支撐整個犬群食用，且犬隻不常與人類接 觸，互動較少。我利用攝影機分別記錄此兩類犬群的行為，包含 (1) 服從性行為、 (2) 攻擊性行為。我使用此兩種行為計算出各犬群位階的線性指數 (Landau’s index)，並比較兩類犬群群內成員間以及犬群對人的攻擊性行為表現比例是否有 差異。結果顯示，第一類中的四個犬群以兩種行為計算的位階線性指數皆無顯著 線性程度。第二類中的兩個犬群以攻擊性行為計算的位階線性指數皆無顯著線性 程度，而以服從性行為計算時，一群的位階無顯著線性程度，另一群的位階則有 顯著線性程度且優勢犬隻會優先使用食物資源。此外，相較於第二類犬群，第一 類犬群對人表現出較少的攻擊性行爲比例。本研究之結果顯示，人類會影響犬群 位階關係與犬隻行為。人類除了提供充足食物資源而影響犬群位階的線性程度外， 人類與犬隻的密切互動，也影響了犬隻對人類的行為表現。犬隻可能因爲人類掌 握食物資源，而將人類視為群體中的優勢個體。犬隻減少了對人類的攻擊性行為，並傾向與人互動，展現出更多服從性行為，此行為傾向可以增加犬隻獲得食物資 源的機會。Social species often establish dominance hierarchies through agonistic interactions. Dominance hierarchy influences the order in which they use resources, thereby reducing the occurrence of conflicts. However, abundant resources may affect the linearity of dominance hierarchy. When resources are sufficient, group members don’t need to compete for them, diminishing the significance of dominance hierarchy. Many studies on Canidae have shown significant linearity of dominance hierarchy. However, some groups of domestic dogs (Canis familiaris) are completely dependent on humans for sufficient food and interact with humans frequently, while others are partially dependent on humans for food and have little interaction with humans. Whether humans affect the linearity of dominance hierarchy in these groups has not been studied. Therefore, the aim of this study is to understand whether the different degrees of dependence of dogs on humans affect the linearity of their dominance hierarchy. I hypothesize that dog groups that are completely dependent on humans for adequate food and frequent interactions with humans will not have a clear linearity of dominance hierarchy compared to a group of dogs that are partially dependent on humans. This study classified dog groups into Full dependency (FD; n = 4) and Semi-dependency (SD; n = 2) categories. The FD category is completely dependent on humans to provide abundance food and interact frequently with humans, while the SD category is partially dependent on humans for food. The amount of food provided by humans cannot support all dogs in the SD category. Moreover, dogs don’t often come into contact with humans and have less interaction. I used camera to record the behaviors of these two dog groups, including (1) submissive behavior and (2) aggressive behavior. Each of these two behaviors were used to calculate the linearity index (Landau's index, h) of dominance hierarchy in the dog groups. I compared the differences in (1) submissive behavior and (2) aggressive behavior between the two categories. The results showed that all groups in the FD category had no significant linearity of dominance hierarchy as calculated by the two behaviors. All groups in the SD category (n = 2) had no significant linearity of dominance hierarchy based on aggressive behavior. When calculated based on submissive behavior, there was no significant linearity of dominance hierarchy in one group of the SD category, but there was significant linearity of dominance hierarchy in the other one group of the SD category, with dominant individuals having priority access to food resources. The FD category displayed less aggressive behavior towards humans than the SD category. This study demonstrates that humans are an important factor influencing the linearity of dominance hierarchy in dog groups and dog behavior. In addition to providing sufficient food resources, the close interaction between humans and dogs also affects the dogs' behavior. Dogs may consider humans as the dominant individuals in the group because humans control food resources. Dogs reduce aggressive behavior towards humans, and they tend to interact with humans and display more submissive behavior, which can increase the dog's access to food resources.