Parthenogenesis in Komodo dragons.

Nature 444, 1021-1022 (21 December 2006) | doi:10.1038/4441021a; Received 4 October 2006; Accepted 16 November 2006; Published online 21 December 2006.

Abstract:

Should males and females be kept together to avoid triggering virgin birth in these endangered reptiles?

Parthenogenesis, the production of offspring without fertilization by a male, is rare in vertebrate species, which usually reproduce after fusion of male and female gametes. Here we use genetic fingerprinting to identify parthenogenetic offspring produced by two female Komodo dragons (Varanus komodoensis) that had been kept at separate institutions and isolated from males; one of these females subsequently produced additional offspring sexually. This reproductive plasticity indicates that female Komodo dragons may switch between asexual and sexual reproduction, depending on the availability of a mate — a finding that has implications for the breeding of this threatened species in captivity. Most zoos keep only females, with males being moved between zoos for mating, but perhaps they should be kept together to avoid triggering parthenogenesis and thereby decreasing genetic diversity.

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Montag, 10 Juli 2017 08:56

HORN, H.-G. (1977)

Notizen zu Systematik, Fundortangaben und Haltung von Varanus (Varanus) karlschmidti (Reptilia, Sauria, Varanidae).

Salamandra 13 (2): 78-88.

Zusammenfassung:

Es werden die systematischen Merkmale von vier weiteren Exemplaren von Varanus karlschmidti beschrieben sowie über die Haltungsbedingungen und das Verhalten der lebenden Tiere im Terrarium berichtet. Die Fundorte werden tabelliert und Klimadaten nahe gelegener Orte in Beziehung zur möglichen Lebensweise der Tiere gesetzt.

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Samstag, 08 Juli 2017 15:31

MENDYK, R. W. (2017)

An Annotated Bibliography of Captive Reproduction in Monitor Lizards (Varanidae: Varanus). Part II. Empagusia and Philippinosaurus.

Biawak, 11(1), pp. 40–49.
© 2017 by International Varanid Interest Group. ISSN: 1936-296X.

Abstract:

Popular in zoos and private collections, monitor lizards have been maintained in captivity for nearly two centuries. During this time, but especially over the past three decades, a voluminous body of publications has brought to light important details and perspectives that have helped advance their captive husbandry  and  reproductive  management. This bibliography  presents an annotated compilation of publications pertaining strictly to the captive reproduction of  monitor lizards belonging to the Varanus subgenera Empagusia and Philippinosaurus. It is intended  to serve as a guide for zoos and private herpetoculturists looking to expand their knowledge and familiarity with this group and introduce readers to different perspectives on their management and reproduction in captivity.

Volltext (PDF)

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Warane und Krustenechsen: Varanoid Lizards.

148 Seiten, 444 Farbfotos, Verbreitungskarten. Zweisprachig Deutsch-Englisch
Terralog 6 - Chimaira Vuchhandelsgesellschft mbH. ISBN 978-3-89973-356-3

Verlagstext:

Warane, Krustenechsen und die monotypische Familie der Taubwarane werden im sechsten Band der TERRALOG-Reihe vorgestellt. Die hier versammelten Echsen sind so vielgestaltig wie die Lebensräume, in denen sie heimisch sind: Von Nord- und Mittelamerika über Afrika bis zur indo-australischen Region besiedeln sie Wüsten, Steppen, Regenwälder und Mangrovensümpfe. Neben Portraits aller rezenten Arten und Unterarten werden im vorliegenden Band auch Biotope, Jungtiere und Verhaltensbeobachtungen dokumentiert.

Symbolbasisierte Beschreibungen der individuellen Bedürfnisse bei der Terrarienhaltung finden sich zu jeder Art.

Die Fülle der rund 440 Farbfotos und Verbreitungskarten macht diesen TERRALOG-Band zu einer fotografischen Synopsis für Wissenschaftler wie für Terrarianer, die die erstaunliche Vielfalt der Varanoidea in einzigartiger Weise veranschaulicht.

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Samstag, 01 Juli 2017 13:51

TRUTNAU, L. (1994)

Krokodile: Alligatoren, Kaimane, echte Krokodile und Gaviale.

Die Neue Brehm Bücherei Bd. 593.
Westarp Wissenschaften Magdeburg. isbn 3-89432-420-1

Verlagstext:

Nur wenige Menschen wissen, daß die heute noch lebenden Krokodile enger mit den ausgestorbenen Dinosauriern oder den Vögeln verwandt sind als mit anderen Reptiliengruppen. Ihre isolierte Stellung ist durch viele Besonderheiten in der Biologie gekennzeichnet. Von den 22 noch lebenden Krokodilarten sind 21 in ihrer Existenz bedroht*. Die Verwendung ihrer Häute als überflüssige Lederwaren, die Zerstörung der Lebensräume und die Jagd auf sie als vermeintlich gefährliche Konkurrenten um Nahrung und Raum haben zu dieser dramatischen Situation geführt. Auf der anderen Seite werden Farmen errichtet, um die kommerziellen Interessen zu steuern und die Wildbestände zu schonen. Der Verfasser greift diese Themenvielfalt auf. Er beschreibt in einem allgemeinen Teil auf der Grundlage der Biologie der Tiere diese Gegensätze und behandelt auch Fragen zu Haltung und Nachzucht. In einem speziellen Teil werden alle Arten mit Abbildungen und Verbreitungskarten vorgestellt. Angaben zu Färbung und Aussehen, Verbreitung und Lebensraum sowie zur Ökologie runden diese Besprechungen ab.

* NB: Das trifft heute nicht mehr zu!

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Freitag, 30 Juni 2017 08:44

DA SILVA, A. & LENIN, J. (2010)

Mugger Crocodile - Crocodylus palustris.

In: Crocodiles.Status Survey and Conservation Action Plan: 94-98.
Third Edition, ed. by S.C. Manolis and C. Stevenson. Crocodile Specialist Group: Darwin.

Aus dem Inhalt:

The  mugger is a hole-nesting species, with egg-laying taking place during the annual dry season. Females become sexually mature at approximately 1.8-2 m, and lay 25-30 eggs. Nests are located in a wide variety of habitats, and females have even been known to nest at the opening of, or inside, their burrow. In captivity, some Muggers are known to lay two clutches in a single year, but this has not been observed in the wild. Incubation is relatively short, typically lasting 55-75 days. Like a number of other crocodilians, C. palustris is known to dig burrows. Whitaker and Whitaker (1984) referred to mugger burrows in Sri Lanka and India (Gujarat and South India) and noted that yearling, sub-adult and adult mugger all dig burrows. In Iran they are sometimes known to dig two burrows close to each other, which may be used by one or  more  crocodiles  (Mobaraki  2002).  These  burrows  are presumably utilized as an effective refuge from hot daytime ambient temperatures. These burrows play a critical role in the survival of crocodiles living in harsh environments, allowing them to avoid exposure to excessively low and high temperatures (<5ºC and >38ºC respectively) for long periods of time, which may be lethal. Mugger are known to undertake long-distance overland treks.

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Donnerstag, 29 Juni 2017 16:39

DAUDIN, F. M. (1802-05)

Histoire naturelle, générale et particulière, des reptiles.

Ouvrage faisant suite à l'Histoire naturelle générale et particulière, composée par Leclerc de Buffon, et rédigée par C.S. Sonnini.

Tome 1 - 8 . Imprimerie de F. Dufart, Paris

DAUDIN's Naturgeschichte der Reptilien, die im Rahmen der Sonnini-Ausgabe von Buffon´s Naturgeschichte herausgegeben wurde, galt als Standardwerk und zu seiner Zeit vollständigstes Werk über Reptilien. Er beschrieb darin nach eigenen Angaben 517 Arten basierend auf 1100 Exemplaren, darunter einige Erstbeschreibungen. Das waren dreimal mehr Arten als in dem zuvor erschienenen Werk von Bernard Germain Lacépède.

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Donnerstag, 29 Juni 2017 15:59

FERGUSSON, R. A. (2010)

Nile Crocodile - Crocodylus niloticus.

In: Crocodiles.Status Survey and Conservation Action Plan: 84-89.
Third Edition, ed. by S.C. Manolis and C. Stevenson. Crocodile Specialist Group: Darwin.

Aus dem Inhalt:

More than 750 surveys using a variety of methods have been carried out for C. niloticus since the 1950s. Despite covering 315 different locations only  8  of  these  have  been  surveyed  enough  to  allow estimation of population trends. All of these are located in southern and East Africa where there have been significant recent improvements in monitoring. In central and West Africa the availability of survey data is very poor. Overall, survey data are insufficient or non-existent in 25 of 42 Range States. The need for wild population recovery and/or conservation is moderate throughout much of east and southern Africa with recent  detailed  studies suggesting an urgent need for conservation action in specific areas, but is high in central and West Africa. Many populations are believed  to  have  recovered by the 1990s but are now constrained or in decline due to anthropogenic factors.

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Mittwoch, 28 Juni 2017 14:00

THORBJARNARSON, J.B. (2010)

American Crocodile - Crocodylus acutus.

In: Crocodiles.Status Survey and Conservation Action Plan: 46-52.
Third Edition, ed. by S.C. Manolis and C. Stevenson. Crocodile Specialist Group: Darwin

Aus dem Inhalt:

The American crocodile is the most widely distributed of the New World crocodiles, ranging from the southern tip of Florida, along both the Atlantic and Pacifi c coasts of southern Mexico, Central America, and northern South America, as well
as the Caribbean islands of Cuba, Jamaica, and Hispaniola. The habitat of C.  acutus consists largely of brackish water coastal habitats such as the saltwater sections of rivers, coastal lagoons, and mangrove swamps. However, populations are
known from freshwater areas located well inland, including a number of reservoirs. A signifi cant population is known from Lago Enriquillo, a landlocked hypersaline lake situated 40 m below sea level in the arid southwestern Dominican Republic.

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Mittwoch, 28 Juni 2017 08:43

COX, J. H. (2010)

New Guinea Freshwater Crocodile - Crocodylus novaeguineae.

In: Crocodiles.Status Survey and Conservation Action Plan: 71-78.
Third Edition, ed. by S.C. Manolis and C. Stevenson. Crocodile Specialist Group: Darwin.

Aus dem Inhalt:

In Papua New Guinea, recognition of unregulated hunting taking  place  led  the  Department  of  Environment  and Conservation (DEC) to: introduce legislative controls in the late 1960s; and, and establish a regulated program in the 1970s based on cropping and ranching. Crocodiles are managed at sustainable levels for the benefi t of customary landowners who own most of the land in Papua New Guinea. Crocodiles can  be  legally  harvested  by  landowners  for  personal use (food and ritual), but commercial sale and export of hides is restricted to the size range of 18-51 cm belly width, which corresponds to approximately 0.9-2.1 m total length.

Wild harvests declined from over 20,000/year in 1977-1980 to 12,000-20,000/year in 1981-1989, then fl uctuated between 10,000-20,000/year  (1997-2005)  (Solmu  and  Sine  2009). Until  the  mid-1990s  hatchlings  and  eggs  were  collected and raised in centralized ranches. Harvests for this purpose ranged  from  2500  to  10,000.  Early  attempts  to  establish village level ranches fl oundered due to technical limitations, particularly feed (locally caught fi sh), water and management defi ciencies. Trade in live juveniles and eggs to centralized raising facilities continued until 1995 when the largest farm halted purchases of the species due to market prospects and its Saltwater crocodile-oriented management strategy.

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