Dispersal patterns in a growing population of Przewalski’s horse (Equus ferus przewalskii) in the semi-reserve Pentezug (Hortobágy National Park/Hungary).

Diplomarbeit

155 Seiten

Zoolog. Institut, Universität Köln
Betreuung: Arndt/Kolter
Kölner Zoo

Abstract:

In this thesis, patterns of natal and maternal dispersal in a growing population of Przewalski’s horses in the semi-reserve Pentezug / Hungary were investigated. Based on ethological observations of 19 focal horses (10 subadult males and 9 subadult females), paternity data of all of these horses and data about the population dynamics (1998-2006), proximate causes of male and female dispersal were identified. Dispersal patterns concerning dispersal ages and seasonality of dispersal were determined. On the basis of the results two hypotheses for the function of dispersal in phylogenesis were discussed: the inbreeding avoidance hypothesis and the resource competition hypothesis. It was shown that subadult horses of both sexes generally dispersed before first breeding in the first three years of their lives. The only exceptions were noted for the early years of the project, when the sex distribution in the population and the social structure were far from natural. At that time, only few adult stallions were present and all adult mares were organized in one big band, so that young females had no bands or suitable bachelor stallions they could disperse to. Under these circumstances three mares failed to disperse and remained in their natal bands for breeding.

Male and female dispersal occurred most frequently in summer and autumn. Females dispersed about half a year earlier than males at an age of about 20 months, although males were confronted with higher frequencies of agonistic behaviour by band members in their natal bands. Females left their bands without being forced to do so, whereas several males were expelled from their natal bands by the band stallion.

All dispersed females joined other bands; dispersed males joined the bachelor group.

The proximate causes of dispersal differed for males and females. Females left after the time of first oestrus, as their band stallions refused to mate with them. Matings with stallions from outside the band were prevented by the band stallion, so that females had to leave the natal band to reproduce. Only in three cases females mated before dispersal. In all three cases they did so with a stallion from outside the band.

Male dispersal occurred due to a high level of aggression by both, adult mares and the band stallion of the natal band. It was noted that males dispersed later when peers were present. The assumption of different authors, that this delay of dispersal might be due to the availability of playmates in the natal band, could not be confirmed for the males in this population. Although most of the focal males had peers in their bands, none of them was observed playing. As soon as these males dispersed to the bachelor group, they started to play with their peers and other stallions. It is assumed, that males in the natal bands are hindered from playing by the aggression of band members. The presence of peers effected that the aggression of band members was distributed to several individuals. If one of the males dispersed, the remaining one suffered more aggression than before. Additionally, criteria for the choice of a new band by dispersing females were analysed. Females tended to disperse to bands that were smaller than their original bands and contained fewer resident females. Dispersed females received little or no agonistic behaviour from their new band members; the only exception was Gréta, who joined the biggest band of the population together with her grandmother Sima.

The choice of a small band was more important than the choice of a band stallion, which was successful in fights. Whereas adult mares chose successful stallions when they changed bands in breeding dispersal, young females rather dispersed to less successful stallions with smaller bands.

Highly significant was the choice of an unfamiliar stallion as new band stallion: all dispersed females chose a stallion with which they had not been associated in the same band previously. In most cases the choice of an unfamiliar stallion involved the avoidance of inbreeding. Only in two cases females joined unfamiliar stallions, which were closely related to them (father and paternal half-brother). All dispersed females showed affiliative interactions with members of their new bands exclusively. The preffered partners were in one case the grandmother (Gréta) and in the other case the only foal of the band (Helka). The third female (Hóvirág) dispersed to a bachelor stallion and had no other partners for affiliative interactions than him.

The dispersal patterns found for this population of Przewalski’s horses indicate that both the inbreeding avoidance hypothesis and the resource competition hyothesis can explain the function of dispersal. Dispersal assured inbreeding avoidance as both females and males dispersed before first reproduction and females joined bands with unfamiliar stallions only. But for both females and males, resource competition appeared to be another crucial factor. Males avoided aggressive behaviour of band members by dispersing to the bachelor groups, and females dispersed before first foaling

brabender-biblio

Keeping and breeding of the coral catshark (Atelomycterus marmoratus) at the Aquarium of the Cologne Zoo.

Zool. Garten N.F. 79: 243-253.

Abstract:

Coral catsharks (Atelomycterus marmoratus) are kept at the Aquarium of Cologne Zoo in a public exhibit tank measuring 300 x 160 x 110 cm (length x width x water height) with a water volume of ca. 5000 l. The 1.3 adults have been producing fertilized eggs since early 2010. Deposited eggs are longish-oval in shape, with a length of about 10 cm. Juveniles hatched in our rearing tanks (measuring 100-210 x 45-80 x 30-50 cm, with 280-430 l water volume) after periods of 4-6 months. The freshly hatched coral catsharks measured from 10-13 cm in total length. After 3 months, each juvenile had grown about 4-5 cm in length and the distinct, bright color pattern of the juveniles had faded towards the more subtle adult colour pattern. The keeping and breeding of coral catsharks can be classified as uncomplicated, given that sufficient swimming space and hiding places are provided. So far, 14 juvenile coral catsharks have been successfully reared at the Cologne Zoo Aquarium and are now available for breeding projects.

Wie die Philippinenkrokodile an den Rhein kamen.

Zeitschrift des Kölner Zoos 54, Heft 3: 119-141. ISSN 0375-5290.

Zusammenfassung:

Die Haltung und Vermehrung von Krokodilen hat im Aquarium des Kölner Zoos langjährige Tradition, wovon vielfache in den letzten vier Jahrzehnten dort erfolgte erfolgreiche Nachzuchten von Nilkrokodilen (Crocodylus niloticus) und Brauen-Glattstirnkaimanen (Paleosuschus palpebrosus) zeugen. Angesichts des ersten Transfers von Philippinenkrokodilen (Crocodylus mindorensis) in EAZA-Zoos beschloss der Kölner Zoo, sich am Aufbau einer Haltung dieser von der Ausrottung bedrohten Art im Rahmen eines Erhaltungszuchtprogramms zu beteiligen. Durch nachfolgende Verträge der jeweiligen europäischen Partnerzoos mit der philippinischen Regierung und dem für den Transfer verantwortlichen Krokodille Zoo in Eskilstrup, Dänemark, kam es schließlich zur ersten EAZA-Einfuhr von Philippinenkrokodilen in die EU. Alle europäischen Partnerzoos verpflichteten sich in diesem Rahmen, für die bei ihnen gehaltenen, aber immer noch im Besitz der philippinischen Regierung befindlichen Philippinenkrokodile die Mabuwaya-Stiftung in San Mariano auf der philippinischen Insel Luzon zu unterstützen, so dass eine Verbindung von ex situ mit in situ Krokodilschutzaktivitäten gegeben ist. Da die Krokodilschauanlage im Aquarium des Kölner Zoos zum Zeitpunkt der Einfuhr der Philippinenkrokodile noch mit Nilkrokodilen besetzt war, wurde zunächst eine insgesamt 315 x 762 cm messende, dreifach unterteilbare Anlage mit unterschwimmbaren Landteilen für das noch junge Philippinenkrokodilpärchen hinter den Kulissen des Aquariums geschaffen. Als im Mai 2010 die Nilkrokodile in das neue Tropenhaus Hippodom umgezogen sind, wurde von Juli bis Oktober 2010 im Aquarium des Kölner Zoos gemessen, geplant und ausgeschrieben und anschließend mit der Renovierung der alten Krokodilschauanlage begonnen.

In diesem Rahmen wurde die alte Krokodilanlage um ein nebenstehendes Terrarium erweitert und Teile der ehemals für Besucher zur Verfügung stehenden Flächen wurden als zwei zusätzliche Landteile zur neuen Krokodilanlage hinzugefügt. Aufgrund einer aktuellen Konfiszierung von bedrohten Gelbgebänderten Philippinenbindenwaranen (Varanus cumingi), die dringend auf Zoos verteilt werden mussten, wurde kurzfristig die Haltung dieser Art mit in die neu zu schaffende Philippinenanlage integriert. Statt der alten Besucherabsperrung sind die neuen Waran- und Krokodilanlagen nun direkt durch eine 22 m lange, aus 10 Doppelscheiben bestehende, 2 m hohe Glasbrüstung einsehbar.

Um die in menschlicher Haltung als aggressiv geltenden Philippinenkrokodile artgerecht und sicher halten zu können, wurden zwei unauffällige Schieber in die Schauanlage eingebaut, um einerseits Männchen- von Weibchengehege abtrennen zu können, andererseits das Weibchengehege noch einmal in sich abtrennen zu können, damit den Tierpflegern bei Reinigungsarbeiten immer ein freier Anlagenbereich zugänglich ist und die Anlage gefahrlos betreten werden kann.

Am 2. Mai 2011 bezogen die derzeit einzigen beiden Philippinenkrokodile in Deutschland – das zu diesem Zeitpunkt 161 cm lange und 16,0 kg schwere Männchen Pinoy und das etwas kleinere, 153 cm lange und 11,3 kg schwere Weibchen Mindo – ihre neue, ca. 62 m² umfassende Schauanlage im Aquarium des Kölner Zoos, die wenige Tage später eröffnet wurde. Neben Informationen zum ersten EAZA Transfer von Philippinenkrokodilen nach Europa sowie Details zu Planung und Bau der Anlagen hinter den Kulissen und im Schaubereich des Kölner Aquariums werden im vorliegenden Artikel Informationen zur Biologie des Philippinenkrokodils und erste Erfahrungen im Umgang mit dieser Art bereitgestellt. Die nun in Köln und den anderen europäischen EAZA-Zoos gehaltenen Philippinenkrokodile sollen künftig zum Aufbau einer europäischen Erhaltungszucht dieser von der Ausrottung bedrohten Art beitragen.

First F2 Breeding of the Quince Monitor Lizard Varanus melinus Böhme & Ziegler, 1997 at the Cologne Zoo Aquarium.

Biawak, 4(3), pp. 82-92 © 2010 by International Varanid Interest Group

Abstract:

We report the first breeding of the quince monitor lizard Varanus melinus in a European
Zoo, which at the same time represents to our knowledge the first F2 breeding of the species in
general. In June 2009, a clutch containing nine eggs was produced at the Aquarium of the Cologne
Zoo by a V. melinus pair received seven years earlier as offspring from a private breeder. Two of these
eggs showed no development and one egg contained dead conjoined twins. Six offspring with weights
of 33-35 g (mean 34 g) and total lengths of 266-281 mm (mean 274 mm) finally hatched in December
2009 from eggs measuring 47.1-58.6 mm (mean 54.0 mm) x 32.0-36.0 mm (mean 34.2 mm) in size,
after 164–166 (mean 164.8) days of incubation at 29° C. A second clutch comprised of five eggs was
laid in September 2009, about three months after the deposition of the first clutch. Two of these eggs
showed no development and one egg contained a dead, slightly malformed embryo. Two V. melinus
subsequently hatched from this second clutch in February 2010 after 164–165 days of incubation
at 29° C. We compare our data with previously published information on the successful breeding
of the species. All eight V. melinus hatched at the Cologne Zoo are developing well, and some will
be subsequently provided for conservation breeding projects. Because this attractive species seems
to play an important role in the international animal trade, and due to only very few husbandry
and breeding reports available, we herewith intend to encourage the conservation breeding of this
monitor lizard and to add to the scarce knowledge of the natural history of this beautiful species
through both ex situ zoo breeding efforts and in situ population research, to finally contribute to
improved conservation measures.

ziegler-biblio

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