Journal für Ornithologie

, Volume 142, Issue 2, pp 204–211 | Cite as

The response of the Eagle Owl (Bubo bubo) to an outbreak of the rabbit haemorrhagic disease

Article

Summary

The Eagle Owl (Bubo bubo) is a generalist predator that in Mediterranean areas feeds mainly on Rabbits (Oryctolagus cuniculus) At the end of 1997, a local outbreak of the rabbit haemorrhagic disease (RHD) decimated Rabbit populations in the area of Alicante (eastern Spain) so that Rabbit numbers in 1998 crashed to almost nil. Prior to the outbreak we had found 19 occupied Eagle Owl territories, and the owls had been feeding mainly on Rabbits. After the RHD epidemic, we found only six occupied territories and the owls were still feeding mainly on Rabbits. Diet composition was very similar between the periods, indicating that the owls did not diversify their diet in response to main prey scarcity. No significant differences in the proportion of Rabbit in the diet were found between the periods, suggesting that the impact of predation on Rabbits may be independent of the density of Rabbit populations (type I functional response). This response is not typically associated with generalist predators. In the territories that were still occupied after the outbreaks, the owls took substantial numbers of Hedgehogs (Erinaceus europaeus) and Red-legged Partridges (Alectoris rufa). Rats (Rattus spp), a common alternative prey, were not taken in the study area. Six breeding attempts were recorded before the RHD, and none after the RHD. This leads a to believe that only the combination of Hedgehog and Red-legged Partridge availability with the readier availability of sick Rabbits allowed a small population of owls to survive in the area, but did not allowed breeding. The predator-prey system formed by Eagle Owls and Rabbits in Mediterranean regions is more fragile than previously thought.

Keywords

diet predation breeding foraging conservation 

Die Reaktion des Uhus (Bubo bubo) auf einen Ausbruch der hämorraghischen Krankheit bei Kaninchen (Oryctolagus cuniculus)

Zusammenfassung

Der Uhu (Bubo bubo) ist ein wenig spezialisierter Greifvogel, der sich im Mittelmeerraum hauptsächlich von Kaninchen ernährt. Ende 1997 wurde die Kaninchenpopulation im Gebiet von Alicante (Ostspanien) durch einen Ausbruch der hämorrhagischen Krankheit (RHD) so stark dezimiert, dass der Kaninchenbestand 1998 nahezu zusammengebrochen war. Vor dem Ausbruch der Krankheit waren 19 Uhu-Reviere besetzt, und die Uhus lebten hauptsächlich von Kaninchen. Nach dem RHD-Ausbruch zählten wir nur noch sechs besetzte Reviere; die Uhus ernährten sich aber immer noch hauptsächlich von Kaninchen. Die Zusammensetzung der Nahrung war in beiden Perioden sehr ähnlich, was darauf hinweist, dass Uhus ihr Beutespektrum nicht erweitern, wenn ihr hauptsächliches Beutetier knapp wird. Dies legt nahe, dass die Anzahl geschlagener Kaninchen unabhängig von deren Populationsdichte ist (Typ I funktionelle Reaktion). Diese Reaktion ist untypisch für nicht spezialisierte Greifvögel. In den Revieren, die nach dem Ausbruch der Seuche noch bewohnt waren, fraßen die Uhus eine beträchtliche Anzahl Igel (Erinaceus europaeus) und Rebhühner (Alectoris rufa). Auf gewöhnliche alternative Beutetiere wie Ratten (Rattus spp) wurde im untersuchten Gebiet nicht zurückgegriffen. Sechs Brutversuche waren vor dem RHD-Ausbruch verzeichnet worden, danach kein einziger. Demzufolge lässt sich vermuten, dass nur der vereinte Effekt eines Igel- und Rebhuhnvorrats und darüber hinaus ein größeres Vorhandenseins kranker Kaninchen einer kleinen Anzahl der Uhus das Überleben in dem Gebiet ermöglichte, das Brüten jedoch nicht zuließ. Das im Mittelmeergebiet aus Uhu und Kaninchen bestehende Raubtier-Opfer-System ist anfälliger als bisher angenommen wurde.

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Copyright information

© Deutsche Ornithologen-Gesellschaft/Blackwell Wissenschaftsverlag 2001

Authors and Affiliations

  1. 1.Departamento de Ecología, Edificio Los ArcosUniversidad de AlicanteSpain
  2. 2.Lab. Zoología, Dpto. de Zoología y Dinámica Animal. Fac. CienciasUniversidad del Pais VascoBilbaoSpain

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