Facing Truths About Population Management

Zoo Biology

Abstract

Even without considering genetic diversity, managing zoo populations sustainably without applying controlled mortality faces a predictable dilemma: Holding space is limited, and zoos worth their salt will inevitably become better at reducing accidental (uncontrolled) mortality. For most species, longevity attainable under good husbandry conditions is considerably longer than generation time, and even though most animals can reproduce until death, there is reproductive senescence, where the probability of successful reproduction decreases with age. Thus, over time, available holding space will inevitably be filled by older animals of lower fecundity. Breeding recommendations that aim at exact numerical replacement to avoid surplus at all cost rather than accounting for average success rates (so that the number of offspring will overshoot the target by up to 50% of the time) will stochastically lead to declines in population size. For small populations, extinction in zoos thus predictably becomes a matter of time. Only large populations will be able to exist at high proportions of old animals, with waves of replacement cycles. Therefore, gaining public acceptance for respectful and humane controlled mortality is essential for the long-term sustainability of small zoo populations. Concepts of continuously increasing holding capacities, using frozen gametes to generate offspring when needed, or nonspecific hopes that compassionate conservation will align individual longevity and conservation goals, detract from the necessity to act. Details of welfare and education can support the call for controlled mortality, but it is the inevitability of the outlined process that obliges us to choose honestly between being empathetic observers of extinction or taking responsibility to conserve animal species.

Authors 46

1. Marcus Clauß corresponding

   University of Zurich

   Affiliation as printed

   Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty University of Zurich Zurich Switzerland

2. Andrew J. Abraham

   Hunter College

   Affiliation as printed

   Department of Anthropology, Hunter College City University of New York (CUNY) New York City New York USA

3. Jörg Beckmann

   Nuremberg Zoo · Zoo am Meer Bremerhaven

   Affiliation as printed

   Nuremberg Zoo Nürnberg Germany

   current address: Bremerhaven Zoo Bremerhaven Germany

4. Laurie Bingaman Lackey

   World Association of Zoos and Aquariums

   Affiliation as printed

   World Association of Zoos and Aquariums Hendersonville North Carolina USA

5. Anita Burkevica
   Affiliation as printed

   Parken Zoo Eskilstuna Sweden

6. Severin Dressen

   Zürich Zoological Garden

   Affiliation as printed

   Zoo Zurich Zürich Switzerland

7. Adam Eyres
   Affiliation as printed

   Fossil Rim Wildlife Center Glen Rose Texas USA

8. Karin Federer
   Affiliation as printed

   Walter Zoo Gossau Switzerland

9. Sven Hammer
   Affiliation as printed

   Naturschutz‐Tierpark Görlitz Görlitz Germany

10. Therese Hård

    Swedish University of Agricultural Sciences

    Affiliation as printed

    Department of Clinical Science Swedish Agricultural and Veterinary University Uppsala Sweden

    Foundation Nordens Ark Hunnebostrand Sweden

11. Stefan Hoby
    Affiliation as printed

    Bern Animal Park Bern Switzerland

12. Felix V. Husemann
    Affiliation as printed

    NaturZoo Rheine Rheine Germany

13. Jacques Kaandorp

    Cheetah Conservation Fund

    Affiliation as printed

    Cheetah Conservation Fund Tilburg The Netherlands

14. Christine Kaandorp-Huber
    Affiliation as printed

    GaiaZOO Kerkrade the Netherlands

    Rotterdam Zoo Rotterdam The Netherlands

15. Bjarne Klausen
    Affiliation as printed

    Odense Zoo Odense Denmark

16. Tobias Knauf‐Witzens
    Affiliation as printed

    Wilhelma Zoologisch‐Botanischer Garten Stuttgart Stuttgart Germany

17. José Kok Aachen Ouwehand Zoo Rhenen Rhenen The Netherlands

    Rijk Zwaan (Netherlands) · GGZ Rivierduinen · Zorg in Ontwikkeling

    Affiliation as printed

    Ouwehand Zoo Rhenen Rhenen The Netherlands

18. Maya Kummrow

    University of Zurich

    Affiliation as printed

    Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty University of Zurich Zurich Switzerland

19. Sébastien Laurent
    Affiliation as printed

    Parc Zoologique de La Boissière du Doré La Boissière‐du‐Doré France

20. Arne Lawrenz
    Affiliation as printed

    Zoo Wuppertal Wuppertal Germany

21. Sabrina Linn

    Frankfurt Zoological Society

    Affiliation as printed

    Zoo Frankfurt Frankfurt Germany

22. Imke Lüeders
    Affiliation as printed

    Allwetterzoo Münster Münster Germany

23. Pascal R. Marty

    Landesamt für Umwelt, Naturschutz und Geologie

    Affiliation as printed

    Natur‐ und Tierpark Goldau Goldau Switzerland

24. Dennis W. H. Müller

    Halle Zoo

    Affiliation as printed

    Zoological Garden Halle Halle Germany

25. Baptiste Mulot
    Affiliation as printed

    ZAHRC Brittany France

26. Rolf‐Arne Ølberg
    Affiliation as printed

    Kristiansand Zoo and Amusement Park Kristiansand Norway

27. T. Pagel
    Affiliation as printed

    Zoological Garden Cologne Köln Germany

28. Zjef J. J. M. Pereboom

    Royal Zoological Society of Antwerp

    Affiliation as printed

    Antwerp Zoo Centre for Research and Conservation Royal Zoological Society of Antwerp Antwerpen Belgium

29. Jan Pluháček

    University of Ostrava

    Affiliation as printed

    Department of Biology and Ecology, Faculty of Science University of Ostrava Ostrava Czechia

    Zoo Olomouc Olomouc Czechia

30. Emile F. Prins
    Affiliation as printed

    GaiaZOO Kerkrade the Netherlands

31. Sandra Reichler-Danielowski
    Affiliation as printed

    Tiergarten Heidelberg gGmbH Heidelberg Germany

32. Douglas M. Richardson
    Affiliation as printed

    Zoological Consultancy Ltd. Scotland UK

33. Marco Roller

    Halle Zoo · Frankfurt Zoological Society

    Affiliation as printed

    Zoological Garden Karlsruhe Karlsruhe Germany

34. Lara Scherer

    University of Zurich

    Affiliation as printed

    Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty University of Zurich Zurich Switzerland

35. Tim Frederic Schikora
    Affiliation as printed

    Schwerin Zoo Schwerin Germany

36. Chrispijn M. Schilp
    Affiliation as printed

    DierenPark Amersfoort Amersfoort The Netherlands

37. Mark Snowball
    Affiliation as printed

    Independent Researcher Adelaide Australia

38. Julia Stagegaard

    Museum of Southwest Jutland

    Affiliation as printed

    Ree Park Safari Djursland Ebeltoft Denmark

39. Hanspeter W. Steinmetz
    Affiliation as printed

    Munich Zoo Hellabrunn Munich Germany

40. Job B. G. Stumpel
    Affiliation as printed

    Wildlands Adventure Zoo Emmen Emmen The Netherlands

41. Cyriel Ververs
    Affiliation as printed

    Royal Burgers' Zoo Arnhem The Netherlands

42. Chris Walzer

    Wildlife Conservation Society · University of Veterinary Medicine Vienna

    Affiliation as printed

    Research, Institute of Wildlife Ecology University of Veterinary Medicine Vienna Austria

    Wildlife Conservation Society, Health Program Bronx New York USA

43. Christian Wenker
    Affiliation as printed

    Basel Zoo Basel Switzerland

44. Guido Westhoff
    Affiliation as printed

    Tierpark Hagenbeck gGmbH Hamburg Germany

45. Brian Zimmerman

    Bristol Zoological Society

    Affiliation as printed

    Bristol Zoological Society, Bristol Zoological Society Hollywood Mansion House, Hollywood Estate Bristol UK

46. João Pedro Meireles

    University of Zurich

    Affiliation as printed

    Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty University of Zurich Zurich Switzerland