Stable Fighting Strategies to Maintain Social Ranks in Captive Male Alpine
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bs_bs_banner Animal Science Journal (2012) 83, 617–622 doi: 10.1111/j.1740-0929.2011.01007.x ORIGINAL ARTICLE Stable fighting strategies to maintain social ranks in captive male Alpine musk deer (Moschus sifanicus)asj_1007 617..622 Xiuxiang MENG, Nicholas CODY, Baocao GONG and Leilei XIANG College of Life and Environmental Sciences, Minzu University of China, Beijing, China ABSTRACT This study was conducted at the Xinglongshan Musk Deer Farm of China from July to September 2008. Results showed that captive male musk deer exhibit aggressive dominance behavior, by which a stable social ranking is established. Generally, there were three types of aggression in agonistic interactions among males: attacking, displacing and threatening. Threatening was more frequently observed than displacing and attacking. When in conflict with other deer, high-rank males exhibited significantly more attacking than displacing and threatening. Moreover, no attacking occurred in low-rank and middle-rank males, but these individuals initiated significantly more threatening displays than high-rank individuals. Among musk deer groups with different social ranks, there were no significant differences between threats received by middle-rank and low-rank groups, but attacks directed to high-rank males was significantly lower than displacing and threatening behaviors. On the basis of these results, it is suggested that when a captive male musk deer population is assembled, individuals should be diversified in fighting ability and level of aggression. In particular, deer with higher aggression should not be enclosed with deer with similar tendencies, but should be enclosed with individuals with lower fighting levels. This should maintain stable social structures within captive musk deer groups and improve the overall welfare of captive musk deer. Key words: Alpine musk deer (Moschus sifanicus), dominance hierarchy, fight strategy, in captivity. INTRODUCTION Wildlife farming is generally conducted through the In social animal populations, competition may occur establishment of captive populations, and compared to among individuals for limited resources, with conse- the availability of resources in nature, the temporal quent conflicts leading to the establishment of social and spatial pattern of resource distribution in captive rank patterns within such populations (Alados & Escos populations is more even and controlled (Craig 1981). 1992). A stable dominance hierarchy can lead to more Because they mate in an enclosed space, have fixed- constant social structures and individuals with higher time feeding at a consistent location and lack the dominance rank in the hierarchy will have priority ability to escape from their relatively space-limited access to resources such as food and shelter (Clutton- enclosures, captive animals tend to more strongly Brock 1982). In both wild and captive animal popula- express fighting and dominance behavior (Fraser & tions, the creation and maintenance of social rank Broom 1990). Barroso et al. (2000) reported that the will always lead to some form of conflict. The most aggression level in a population of domestic goats common forms of conflict include aggressive interac- (Capra hircus) was far stronger when the individuals tions, antagonistic interactions and assessment of were fed at the same trough in a relatively narrow an individual’s fighting ability shown by individual space. recognition, ritual display and physical contact The five species of musk deer (Moschus spp.) are (Kaufmann 1983; Barroso et al. 2000). In conflict primitive, small, solitary forest ruminants well-known interactions, the behavior displayed is related to the dominance rank of the individual that initiates the attack and the one that receives it. For example, male Correspondence: Xiuxiang Meng, College of Life and Environmental Sciences, Minzu University of China, 27 fallow deer (Dama dama) expressed more non-contact Zhongguancun Nandajie, Beijing 100081, China. (Email: attacks toward opponent deer with a lower social [email protected]) rank, but more physical attacks between individuals of Received 31 March 2011; accepted for publication 25 similar rank (Mattiangeli et al. 1999). October 2011. © 2012 The Authors Animal Science Journal © 2012 Japanese Society of Animal Science 618 X. MENG et al. for the musk secreted by adult males, which has been dominance and fighting patterns (Rushen 1985), this used broadly in traditional Asian medicine and the research could ultimately have implications for musk perfume industry. Because of habitat degradation and deer farming, sustainable musk production and animal loss and long-term illegal hunting, musk deer have welfare. become endangered. To protect musk deer, in situ conservation measures, such as the establishment of MATERIALS AND METHODS nature reserves, have been undertaken. In addition, Experimental animals to provide ex situ protection of musk deer while maintaining sustainable musk production, musk deer This study was conducted at Xinglongshan Musk Deer Farm (XMDF) in Gansu Province, northwest China. Groups of 10 farming has been encouraged in China since the 1950s captive male alpine musk deer (Moschus sifanicus) were kept (Homes 1999; Parry-Jones & Wu 2001). As many as in two separate enclosures with five males in each enclosure. 5000 musk deer are held in more than 10 musk deer Individuals were housed in outdoor yards (100 m2), with farms and breeding centers in China (Meng et al. 2006; unrestricted access to adjoining indoor brick cells (4 m2). Sheng & Liu 2007). Neighboring enclosures were separated by wire mesh, Although behavioral studies are essential for suc- enabling olfactory and auditory communication between cessful conservation of the species, it has proven diffi- individuals, but preventing physical contact. The enclosure facilities and daily management system were the same as in cult to study the social structure and dominance Meng et al. (2003). hierarchy of wild musk deer. Due to their solitary, The musk deer were all adults but had different origins, territorial nature, along with the difficulty in accessing that is, bred in captivity, captured as fawns or adults in the their closed forested habitat (Green 1986, 1987a,b) wild, or introduced from another farm. However, the origin there are few reports on musk deer social structure in of each individual could not be determined. The detailed the wild except for some anecdotal reports and direct animal management has been reported in Meng et al. (2003). All animals were healthy and individually identified by num- descriptions of threatening and fighting behavior bered plastic ear-tags. (Zheng & Pi 1979, 1984; Ohtaishi & Sheng 1993). Through the creation of musk farming, it became pos- Behavior sampling and definition sible to study social rank and fighting patterns once Focal sampling and particular behavior recording (Altmann deer were enclosed in social groups. Some researchers 1974) were used to collect all occurrences of aggression on have observed a small number of captive musk deer a focal group during a 10-min period, with binoculars and described their general fighting patterns and (10 ¥ 42°) being used to both observe behavior and verify dominance structure (Zhang 1979, 1983), but, so far, animal identification. Recorded aggression behaviors were no quantitative research has been conducted to inves- defined as follows (i) Attacking: an obvious physical contact agonistic interaction, initiated by one individual against tigate the real characteristics of the social structure another. This category included attacks by mouth or foreleg of captive musk deer. Musk deer farming in China as well as chase attacking. (ii) Threatening: an individual encloses the normally solitary musk deer into larger standing with head up and ears erect, displaying canines to social groups to save enclosure space and reduce costs rivals with lips vibrating, and the rear part of its body wag- (Parry-Jones & Wu 2001; Meng et al. 2006). However gling. This category included threatening approaches, circling intense fighting has been witnessed in these artificial and aggressive retreats. (iii) Displacing: one individual populations, which can result in physical injury or approaches another and the latter retreats. Because conflicts among individuals typically occur during death to deer, ultimately affecting the success of musk the peak activity period of captive musk deer, behavioral production (Hu et al. 1990; Lai & Sheng 1990; Sheng & sampling was conducted from 05.00 to 08.00 hours and from Liu 2007). It was therefore hypothesized that aggres- 17.00 to 20.00 hours (Meng et al. 2002). All observations and sion levels in captive musk deer would be related to data recording were conducted by the same researcher and the fighting ability of a population’s individuals and took place 3 days a week from July to September 2008 (total that optimal social structure would lessen the aggres- of 220 observation hours). sion level, improving the success and sustainability of Statistical analysis musk deer farming (Zhang 1979). Thus far, there has been no research related to this issue, so any conclu- Musk deer dominance index (DI) was calculated as: (1/N) ¥S (W /T ) where: N = total number of opponents; sions on the topic cannot be justified. i i Wi = number of wins in agonistic interactions with opponent Therefore, it is necessary to study displays of aggres- i; Ti = total number of agonistic interactions with opponent sion and social rank patterns of musk deer in captivity. i (Bro-Jørgensen