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Author Vervaecke, H.; Stevens, J.; Vandemoortele, H.; Sigurjönsdöttir, H.; De Vries, H. doi  openurl
  Title (up) Aggression and dominance in matched groups of subadult Icelandic horses (Equus caballus) Type Journal Article
  Year 2007 Publication Journal of Ethology Abbreviated Journal J. Ethol.  
  Volume 25 Issue 3 Pages 239-248  
  Keywords Equus – Dominance – Aggression – Hierarchy – Steepness  
  Abstract Abstract  We studied sex differences in the nature of aggression and dominance behaviour in two newly formed groups of 1-year-old Icelandic horses. One herd contained nine geldings, the other nine mares. The groups were matched with regard to dominance-determining traits such as age, weaning age, composition of native herd, social experience, genetic origin, body condition and maternal dominance status. High-ranking individuals of both sexes were more aggressive, high-ranking males were older, and high-ranking females had a better body condition. Frequencies of aggressions were similar in both groups. The mares reacted significantly more by showing submission upon an aggression rather than by not responding or by escalating the aggression. For the geldings, this difference was not observed due to a lower tendency to submit. A linear dominance hierarchy was found in both groups. David`s scores provided additional information regarding cardinal rank distances and were used to calculate steepness of hierarchies. The female hierarchy was somewhat steeper compared to the male hierarchy, suggesting somewhat lower despotism among males. This was mainly a consequence of the lower unidirectionality in male submission. Male contests occurred predominantly between dyads at top and mid positions, suggesting a low degree of acceptance of the hierarchy.  
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  Call Number Equine Behaviour @ team @ Serial 2192  
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Author VanDierendonck, M.C., de Vries, H., Schilder, M.B.H. url  doi
openurl 
  Title (up) An Analysis of Dominance, Its Behavioural Parameters and Possible Determinants in a Herd of Icelandic horses in captivity Type Journal Article
  Year 1995 Publication Netherlands Journal of Zoology Abbreviated Journal Netherl. J. Zool.  
  Volume 45 Issue 3-4 Pages 362-385  
  Keywords Dominance; rank order; horses; Icelandic horses.  
  Abstract Feral horses are social animals, which have to rely on survival strategies centered on the formation of cohesive social bonds within their bands. Many problems in the husbandry of social animals such as horses, are due to the fact that the limits of their adaptive abilities are exceeded. Evidence suggests that the fundamental social characteristics of domestic horses have remained relatively unchanged. The social structure, social strategies and social interactions were investigated (3 non-consecutive years, 24 hr per day for several weeks) in long term established groups of domestic horses (mares and geldings of all ages) and a few small introduced groups, kept in (semi)natural environments. The general aim was to investigate the social needs of domestic horses. The social life of domestic horses was characterised by long lasting bonds with preferred partners which were established and maintained by allogrooming, play, proximity and dominance behaviours. Bonding partners were mainly found within the same sex-age group, but adult geldings also bonded with sub-adult mares and geldings. Adult mares were clustered in a group, while the other animals formed a second group. Among the adult mares, subgroups according to reproductive state were formed. Individuals regulated their social network by interfering with interactions between other members of the herd, which in itself is complex. An intervention is a behavioural action of one animal that actively interferes with an ongoing interaction between a dyad with the apparent aim of altering that interaction. This was verified by post-hoc analyses of disturbed and undisturbed interactions. Interventions in allogrooming or play were performed significantly more often when at least one member of the initial dyad was a preferred partner of, or familiar to (within the small introduced bands) the intervener. The stronger the preferred association in allogrooming between the intervener and member(s) of the initial dyad, the higher the probability the intervener would displace one initial member and continue allogrooming with the other. Just five behaviours were extracted which reliably reflected the dominance relations among horses. Aggression with the hind quarters was used both offensively and defensively and therefore not suitable as a reliable parameter. Individual dominance relationships were related to social experience. The implications of these findings for horse husbandry were assessed. It is argued that the execution of affiliative behaviours may be rewarding in itself, and therefore always will be a highly motivated behaviour. It is shown that social positive physical interactions (allogrooming, play) with other horses is an ethological need and therefore indispensable in modern husbandry systems. Ethological needs are so important for the animal that husbandry systems that lack the possibilities to execute such behaviours will cause chronic stress. It is concluded that all horses need physical social contact, and that horses, which lack appropriate social learning experiences during ontogeny, may be hampered in their social functioning later in life. Solutions for problems, including dominance problems, in individual social housing and group housing are presented.  
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  Call Number Equine Behaviour @ team @ Serial 2368  
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Author VanDierendonck, M.C.; de Vries, H.; Schilder, M.B.H. url  openurl
  Title (up) An Analysis of Dominance, Its Behavioural Parameters and Possible Determinants in a Herd of Icelandic orses in Captivity Type Journal Article
  Year 1995 Publication Netherlands Journal of Zoology Abbreviated Journal Netherl. J. Zool.  
  Volume 45 Issue 3-4 Pages 362-385  
  Keywords Dominance; rank order; horses; Icelandic horses.  
  Abstract Th e applicability of the concept of dominance was investigated in a captive herd of  Icelandic

horses and  ponies of diff erent breeds. Eight out of  behaviours possibly related

to dominance occurred frequently enough to be investigated in detail. For these eight agonistic

behaviours the coverage, the unidirectionality in the exchange, and the degree of

transitivity (Landau`s linearity index) were calculated. Four off ensive behaviours, together

with avoidance, were suitable for further analysis with regard to dominance. Th e patterns

of asymmetries with which these behaviours were exchanged were suffi ciently similar as to

justify the application of the dominance concept and to construct a (nearly) linear dominance

hierarchy. Th e rank order of the castrated stallions was completely linear, the hierarchy

of the mares was almost completely linear. Th e results suggest that off ensive and defensive

aggressive behaviours should be treated separately and that the concept of dominance

is applicable. However, ritualized formal dominance signals between adult horses appear to

be (almost) absent. Th e rank positions of the individuals were correlated with age and residency

in the herd but not with height. Middle ranking horses tended to be more frequently

in the close vicinity of another horse than high ranking or low ranking horses. Over and

above this correlation at the individual level, it was found that pairs of horses close in rank

to each other were more often also spatially close to each other. Being in oestrus did not infl

uence the dominance relationships between mares. For castrated stallions the rank positions

were correlated with the age at which they were castrated. Th is suggests that in male

horses experience prior to neutering infl uences the behaviour afterwards.
 
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  Notes Approved no  
  Call Number refbase @ user @ Serial 440  
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Author de Vries, H. url  doi
openurl 
  Title (up) An improved test of linearity in dominance hierarchies containing unknown or tied relationships Type Journal Article
  Year 1995 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.  
  Volume 50 Issue 5 Pages 1375-1389  
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  Abstract Appleby (1983, Anim. Behav., 31, 600-608) described a statistical test, based on the work of Kendall (1962, Rank Correlation Methods), for the significance of linearity in dominance hierarchies. He suggested that unknown relationships should be assigned the value 1/2 and that subsequently the same test procedure can be used. In this paper it is shown that incorrect results are obtained by this method whenever there are unknown relationships. Values of the linearity index are systematically too low. P-values can be too high (underestimating the significance) or too low (overestimating), and seem to differ by not much more than a factor two (respectively a half) from the correct P-value. An improved method is developed for testing linearity in a set of dominance relationships containing unknown relationships. Furthermore, it is argued that, if one admits the possibility of tied dominance relationships, which should indeed be assigned the value 1/2, Landau's linearity index is to be preferred to Kendall's index. A randomization test is developed for assessing the significance of linearity or non-linearity in a set of dominance relationships containing unknown or tied relationships. The test statistic employed in this testing procedure is based on Landau's linearity index, but takes the unknown and tied relationships into account.  
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  Call Number Equine Behaviour @ team @ Serial 4284  
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Author Gammell, M.P.; de Vries, H.; Jennings, D.J.; Carlin, C.M.; Hayden, T.J. url  doi
openurl 
  Title (up) David's score: a more appropriate dominance ranking method than Clutton-Brock et al.'s index Type Journal Article
  Year 2003 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.  
  Volume 66 Issue 3 Pages 601-605  
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  Call Number refbase @ user @ Serial 453  
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Author Vervaecke, H.; de Vries, H.; van Elsacker, L. doi  openurl
  Title (up) Dominance and its Behavioral Measures in a Captive Group of Bonobos (Pan paniscus) Type Journal Article
  Year 2000 Publication International Journal of Primatology Abbreviated Journal Int. J. Primatol.  
  Volume 21 Issue 1 Pages 47-68  
  Keywords  
  Abstract We investigated the existence of a social dominance hierarchy in the captive group of six adult bonobos at the Planckendael Zoo. We quantified the pattern of dyadic exchange of a number of behaviors to examine to what extent each behavior fits a linear rank order model. Following de Waal (1989), we distinguish three types of dominance: agonistic dominance, competitive ability and formal dominance. Fleeing upon aggression is a good measure of agonistic dominance. The agonistic dominance hierarchy in the study group shows significant and strong linearity. The rank order was: 1. female (22 yr), 2. female (15 yr)., 3. male (23 yr.), 4. female (15 yr.), 5. male (9 yr.), 6. male (10 yr.). As in the wild, the females occupy high ranks. There is prominent but nonexclusive female agonistic dominance. Teeth-baring does not fulfil the criteria of a formal submission signal. Peering is a request for tolerance of proximity. Since its direction within dyads is consistent with that of fleeing interactions, it is a useful additional measure to determine agonistic ranks in bonobos. In competitive situations, the females acquire more food than other group members do. The rank obtained from access to food resources differs from the agonistic rank due to female intrasexual social tolerance, expressed in food sharing. We typify the dominance styles in the group as female intrasexual tolerance and male challenging of rank differences. The agonistic rank order correlates significantly with age and has a strong predictive value for other social behaviors.  
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  Call Number Equine Behaviour @ team @ Serial 2197  
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Author Albers, P.C.H.; de Vries, H. url  doi
openurl 
  Title (up) Elo-rating as a tool in the sequential estimation of dominance strengths Type Journal Article
  Year 2001 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.  
  Volume 61 Issue 2 Pages 489-495  
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  Call Number refbase @ user @ Serial 858  
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Author de VRIES, H.A.N. url  doi
openurl 
  Title (up) Finding a dominance order most consistent with a linear hierarchy: a new procedure and review Type Journal Article
  Year 1998 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.  
  Volume 55 Issue 4 Pages 827-843  
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  Abstract A procedure for ordering a set of individuals into a linear or near-linear dominance hierarchy is presented. Two criteria are used in a prioritized way in reorganizing the dominance matrix to find an order that is most consistent with a linear hierarchy: first, minimization of the numbers of inconsistencies and, second, minimization of the total strength of the inconsistencies. The linear ordering procedure, which involves an iterative algorithm based on a generalized swapping rule, is feasible for matrices of up to 80 individuals. The procedure can be applied to any dominance matrix, since it does not make any assumptions about the form of the probabilities of winning and losing. The only assumption is the existence of a linear or near-linear hierarchy which can be verified by means of a linearity test. A review of existing ranking methods is presented and these are compared with the proposed method.  
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  Notes Approved no  
  Call Number refbase @ user @ Serial 457  
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Author De Vries, H.; Appleby, M.C. url  doi
openurl 
  Title (up) Finding an appropriate order for a hierarchy: a comparison of the I&SI and the BBS methods Type Journal Article
  Year 2000 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.  
  Volume 59 Issue 1 Pages 239-245  
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  Call Number refbase @ user @ Serial 869  
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Author VanDierendonck, M.C.; de Vries, H.; Schilder, M.B.H.; Colenbrander, B.; Þorhallsdóttir, A.G. and Sigurjónsdóttir, H. url  doi
openurl 
  Title (up) Interventions in social behaviour in a herd of mares and geldings Type Journal Article
  Year 2009 Publication Applied Animal Behaviour Science Abbreviated Journal Appl. Anim. Behav. Sci.  
  Volume 116 Issue 1 Pages 67-73  
  Keywords Horses; Social relationships; Interventions; Mares; Geldings; Play; Allogrooming; Social network  
  Abstract Social dynamics and maintenance of social cohesion were studied by analysing social interventions in two groups of horses consisting of adult mares, their offspring, adult geldings and sub-adults. The animals were observed for a total of 1316 h. All relevant dyadic and triadic social interactions, including initial behaviour, possible intervention and outcome, were recorded. The main question was: do horses use interventions in affiliative interactions to safeguard their social network? Horses were significantly more likely to intervene in allogrooming or play interactions that involved a preferred partner. The stronger the preferred association in allogrooming, the higher the likelihood the intervener took over allogrooming with an initial dyad member. Interveners originating from two newly introduced groups (n = 3 and 5), intervened significantly more often when a member of their own group allogroomed with an unfamiliar horse. In play, no correlation with unfamiliarity was found. Overall, the intervening horses stopped more than half of the initial allogrooming interactions, and a third of all interactions. Therefore, social facilitation cannot sufficiently explain interference behaviour. This study shows that maintaining relationships with preferred partners is important to horses and has implications for equine husbandry and management.  
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  ISSN 0168-1591 ISBN Medium  
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  Notes Approved no  
  Call Number Equine Behaviour @ team @ Serial 4766  
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