The Proximate Mechanisms of Natal Dispersal in Female Horses
The Proximate Mechanisms of Natal Dispersal in Female Horses
复制标题
母马出生扩散的近因机制
DOI：
10.1163/156853996x00611
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发表时间：
1996
期刊：
影响因子：
1.3
通讯作者：
V. Boy
中科院分区：
文献类型：
--
作者：
A. Monard;P. Duncan;V. Boy
本研究的目的是调查近机制的纳塔尔扩散的雌马，马caballus（即近的原因和影响因素的时间），并测试预测从两个功能假说：内的性竞争假说，避免近亲繁殖。这些数据涉及1974-1985年出生的40只个体，这些个体在密切监测的牛群中形成了自然的社会结构。所有的女性分散从他们的纳塔尔群体，没有成为孤独的，80%转移到现有的后宫，其他人形成了新的群体与单身汉种马。被种马绑架只影响了四分之一的女性，其转让被观察到。这项研究的结果不支持这一假设，即纳塔尔扩散的功能是减少性内竞争。年轻的女性没有被驱逐的居民女性的纳塔尔组，并没有，作为一项规则，经验增加侵略这些女性移民前。在离开之前，他们与纳塔尔群体成员的社会联系没有逐渐减弱，与他们转移到的群体中的个人的联系也没有逐渐加强。没有证据表明年轻女性和其纳塔尔群体的居民之间的生殖竞争，因为年轻女性总是拒绝这些群体的男性的性接近。最后，年龄分散并没有减少居民的女性在他们离开的群体的数量。与此相反，预测的近亲繁殖避免假说，分散的主要原因似乎是性吸引不熟悉的男性。在发情期和分散之前，年轻的女性只接受交配与其他群体的男性，尽管频繁的性行为的男性纳塔尔组（通常是近亲）。此外，在第一次发情之前没有分散，大多数在发情期间，在第一个马驹的概念或之前。大多数年轻女性的母亲介入时，近亲男性的纳塔尔组接近他们的女儿性，这可能有助于避免近亲繁殖。在其他因素的研究，有些没有影响分散的年轻女性：他们经历了低水平的侵略成年种马的纳塔尔组，特别是在出发时，他们的体重和身体状况没有显着影响离开年龄也没有他们的母亲的排名，兄弟姐妹的数量，或出生的另一个。相反，随着群体数量和繁殖性别比的增加，扩散年龄下降，在后期的中位年龄为23个月（范围12-42个月），当时牛群已经发展出一个自然的社会系统。
The aim of this study was to investigate proximate mechanisms of natal dispersal by female horses, Equus caballus (i.e. proximate causes and the factors influencing the timing), and to test predictions from two functional hypotheses: the intrasexual competition hypothesis, and inbreeding avoidance. The data concerned 40 individuals born between 1974-1985 in a closely monitored herd which developed a natural social structure during this period. All the females dispersed from their natal groups; none became solitary; 80% transferred to existing harems, the others formed new groups with bachelor stallions. Abduction by stallions affected only a quarter of the females whose transfers were observed. The results of this study do not support the hypothesis that a function of natal dispersal is to reduce intrasexual competition. The young females were not expelled by resident females of their natal groups, and did not, as a rule, experience increased aggression from these females before emigration. Their social bonds with members of their natal groups showed no progressive weakening prior to departure, and there was no gradual strengthening of bonds with individuals in the groups to which they transferred. There was no evidence for reproductive competition between the young females and resident mares of their natal groups, since the young females always refused the sexual approaches by males of these groups. Finally, age at dispersal did not decrease with the number of resident females in the groups they left. In contrast, as predicted by the inbreeding avoidance hypothesis, the primary cause of dispersal appeared to be sexual attraction to unfamiliar males. When in oestrus and before dispersing, the young females accepted matings only with males of other groups in spite of frequent sexual approaches by males of their natal groups (normally close relatives). In addition, none dispersed before first oestrus, and most did so during an oestrous period, at or before the conception of their first foal. The mothers of most young females interposed themselves when close kin males of the natal group approached their daughters sexually; this could contribute to the avoidance of close inbreeding. Among the other factors examined, some did not influence dispersal of the young females : they experienced low levels of aggression by adult stallions of their natal groups, particularly at the time of departure; their weight and body condition had no significant effects on leaving age nor did their mother's rank, the number of siblings, or the birth of another. In contrast, as the number of groups and the breeding sex ratio increased, dispersal age declined, occurring at a median age of 23 months (range 12-42 months) in the later years, when the herd had developed a natural social system.