Behaviour of Bachelor Males of the Przewalski Horse (Equus ferus przewalskii) at the Reserve Askania Nova

doi:10.1016/j.zoolgart.2009.10.005

Der Zoologische Garten

Volume 78, Issues 5–6, 2009, Pages 282-299

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Zusammenfassung

Das Ziel dieser Studie war, das Verhalten von Przewalskipferden bei hoher Besatzdichte in einer Junggesellengruppe auf einer Fläche von 3,5 ha zu untersuchen. Die Gruppe bestand aus 16 männlichen Tieren im Alter von 5 bis 16 Jahren. Verhaltensdaten wurden über 18 Tage gesammelt, insgesamt 216 h. Fünfzehnminütige fokussierte Tierbeobachtung wurde angewendet; jedes Pferd wurde drei Mal am Tag beobachtet, insgesamt 45 Minuten. Das Auftreten von 25 Verhaltensweisen wurde aufgezeichnet und das Raumverhalten wurde untersucht indem “nächste Nachbar” aufgezeichnet wurde. Die Gruppe teilte sich in vier Untergruppen; was frühere Ergebnisse von der Teilung von Junggesellengruppen (n≥10) in zwei oder mehr Untergruppen unterstreicht; vorausgesetzt die Gruppen enthielten männliche Tiere über 5 Jahre. Die gesamte Frequenz der sozialen Interaktionen war 14,6±1,1 Pferd/ Std. Obwohl die Besatzdichte der Gruppe in dieser Studie höher war als in anderen Zoos, verhielten sich die Tiere nur 3,6 Pferd/ Std agonistisch. Am häufigsten wurde freundliches Sozialverhalten beobachtet. Diese Studie zeigt Möglichkeiten einige investigative Verhaltensweisen (markieren, flehmen, olfaktorische Erkundung, etc.) als Indikator für die soziale Stellung des Tieres in einer Gruppe zu verwenden.

Abstract

The aim of this study was to investigate social relationships between Przewalski horses at a high density in a bachelor group housed in a 3.5-ha enclosure. The group consisted of 16 males aged 5 to 16. Behavioural data were collected during 18 days, total 216 h. Fifteen minute focal animal sampling was used; each horse was observed three times a day for a total of 45 min. The occurrence of 25 behaviours was recorded, and group spacing behaviour was studied using nearest neighbour recordings. The group divided into four subgroups; this supports earlier findings of bachelor groups (n≥10) dividing into two or more subgroups if they included several males aged >5 years. The total frequency of social interactions was 14.6±1.1 h⁻¹. Although the density of the group in this study was higher than in other zoos, the males interacted agonistically only 3.6 h⁻¹. The most frequently observed social behaviour categories were friendly interactions. This study shows possibilities to use some investigative behaviours (marking, flehmen, olfactory investigation, etc.) as indicators of social status of animals in a group.

Introduction

The Przewalski horse (Equus ferus przewalskii) became extinct in the wild in the mid-1960s. However, the species has been successfully maintained in captivity for more than 100 years. Despite the fact the horses had never been studied in their natural habitat, it is known that Przewalski horses use the harem system of social organization (Keiper, 1986). The horses live in small, permanent harem groups composed of females, their offspring, and a harem stallion. Adult males that do not belong to harem bands either live in bachelor groups or temporarily live alone.

At the present time, a multitude of studies concerning behaviour in harem groups of Przewalski horses in zoos have been published (Boyd, 1988; Hogan et al., 1988; Keiper, 1988; Kolter & Zimmermann, 1988; Mackler & Dolan, 1980). There is much less information about bachelor groups (Tilson et al., 1988; Wakefield, 1996). Kolter & Zimmermann (2001) gave a detailed analysis of management of bachelor groups of Przewalski horses and their behaviour in zoos and semi-reserves except the Reserve “Askania Nova”. Since regional programmes for the Przewalski horse (EEP, SSP, SMP) were established in the mid 1980s, almost all zoos discarded the practice of keeping adult Przewalski stallions in isolation. In this connection a question about their behaviour in mix-aged groups is rather topical as often increasing aggression becomes a problem for wild Equids in captivity. Some comparative behavioural studies have revealed that of Przewalski horses and domestic horses, the former are more aggressive (Feh, 1988; Christensen et al., 2002). Kolter & Zimmermann (2001) reported that about 10% of the Przewalski bachelor population in captivity died between 1986 and 2000 as a result of injuries caused by fights. In Askania Nova, about 8% of bachelors died by the same reason between 1992 and 2003.

As no zoo but Askania Nova Reserve has an experience of keeping large groups of bachelors (n>10) in rather small enclosures, the aim of the present investigation is studying relationships between Przewalski horse males at a high density in a bachelor group.

Section snippets

Animals

Przewalski horses have been kept at Askania Nova Reserve since 1899. For more than 25 years, one or several bachelor groups have been kept at the Reserve; each group consists of 2 to 43 males of different ages. Colts under the age of 2 years live in their natal groups on pasture. At the age of 2 they are removed to a group of young bachelors in a 90-ha separate steppe enclosure where they remain until 4–5 years of age. Males above the age of 5 are removed to another mixed-age bachelor group, up

Data collection

The study was conducted between July 30 and August 16, 2003 (18 days). All observations for the study were made by the authors. Before the study a preliminary observation was made for 5 days in order to get the horses accustomed to the presence of the observers. Although no formal interobserver accuracy tests were conducted, the observers had trained with one another during the preliminary observation.

During the actual observation period the mean daily temperature was 22.2°C (max. 32°C),

Data analysis

Data on group spacing behaviour were analyzed by the calculation of the frequency of recordings at a specified distance (<2 m, or 2–5 m, or >5 m) from other horses (frequency of neighbours) for each horse in the following way: the number of recordings at a specified distance from other horses was summed and then divided by doubled number of all recordings (288) in order to get the final result within the range from 0 to 1. The zero value means that the horse was never observed within a specified

Results

Most of the Przewalski males (n=15) spent their time in the close vicinity of other males, and the frequency of any neighbour within one horselength (<2 m) averaged 0.69±0.02 (mean±Se). Correspondingly, they spent much less time keeping the distance more than 5 m from others (0.22±0.02), or within 2–5 m (0.09±0.01). The male with freeze brand #173 was an exception, because he kept apart from other males all the time, and the frequency of neighbours at the distance more than 5 m averaged 0.98.

Discussion

The present study supports that bachelor herds can be kept in close quarters without problematic aggression (which may be contrary to what was previously believed). Even if the density of the group is high the aggressive potential of the animals may be expressed within acceptable levels so that no serious injuries occur.

Some factors determined the reduction of aggressions within the group.

First the Przewalski males divided into several subgroups. Members of the same subgroup not only tended to

Conclusion

When keeping a bachelor group of Przewalski horses at a high density, a few factors may conduce to the reduction of aggression. Among the factors, there is a division of the complete group into several subgroups, which spend the most time within a certain area in their enclosure.

Bachelor males may unite into subgroups of two different types. Although a dominance hierarchy was established in subgroups of both types, the dominant members in subgroups of type 2 showed some behaviours, which were

Acknowledgements

Many thanks to Janne Winther Christensen (The Danish Institute of Agricultural Sciences, Denmark), for comments on an earlier version of the manuscript, and again to Janne Winther Christensen, to Inna Draganova (Hartpury College, UK), Waltraut Zimmermann, Franziska Roth (Cologne Zoo, Germany) for literature granted.

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One mechanism to resolve conflict among group members is third party intervention, for which several functions, such as kin protection, alliance formation, and the promotion of group cohesion have been proposed. Still, empirical research on the function of intervention behaviour is rare. We studied 40 cases of intervention behaviour in a field study on 13 semi-wild bachelor horses (Equus ferus przewalskii) in (a) standard social situations, and (b) when new horses joined the group (i.e. introductions). Only interventions in agonistic encounters were analysed. Eight of 13 animals directed intervention behaviour toward threatening animal in agonistic encounters of group members. One stallion was particularly active. The stallions did not intervene to support former group mates or kin and interventions were not reciprocated. In introduction situations and in standard social situations, the interveners supported animals which were lower in rank, but targeted, threatening animals of comparable social rank. After introductions, stallions received more affiliative behaviour from animals they supported and thus appeared to intervene for alliance formation. In standard social situations, interveners did not receive more affiliative behaviour from animals they supported and may primarily have intervened to promote group cohesion and to reduce social disruption within the group.
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Behaviour of Bachelor Males of the Przewalski Horse (Equus ferus przewalskii) at the Reserve Askania NovaVerhalten einer Hengstgruppe von Przewalskipferden (Equus ferus przewalskii) im Reservat Askania Nowa

Zusammenfassung

Abstract

Introduction

Section snippets

Animals

Data collection

Data analysis

Results

Discussion

Conclusion

Acknowledgements

Appl. Anim. Beh. Sci.

Appl. Anim. Beh. Sci.

Appl. Anim. Beh. Sci.

Appl. Anim. Beh. Sci.

Appl. Anim. Ethol.

Vet Clinics of North America

Appl. Anim. Beh. Sci.

Appl. Anim. Beh. Sci.

Appl. Anim. Beh. Sci.

Vet Clinics of North America: Equine Practice

Appl. Anim. Beh. Sci.

Ibid.

Ibid.

Observational study of behavior: sampling methods

Behavior

An analysis of dominance, its behavioural parameters and possible determinants in a herd of Icelandic horses in captivity

Netherlands Journal of Zoology