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About a closed hybrid population between Bombina bombina and Bombina variegata from Oradea (Bihor county, Romania)

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Author(s): I. Sas | S.D. Covaciu-Marcov | M. Pop | R.D. Ile | N. Szeibel | Cr. Duma

Journal: North-Western Journal of Zoology
ISSN 1584-9074

Volume: 1;
Start page: 41;
Date: 2005;
Original page

Keywords: Bombina | hybrids | population size | feeding ecology

ABSTRACT
In 1997 there was recorded a perfect hybrid population nearby the Oradea Railway Station, which was mentioned in a population ranking study in 2001 (but only 21 samples were studied - Covaciu-Marcov et al. 2001). Our study had the following objectives: to analyse the affiliation of the population, analysing a larger number of individuals then in 2001; to estimate the population size; to analyse the food resource utilization of this population. The study period was April-July 2002. The affiliation study was relaying on the morphological and chromatic characteristics of the two parental species, using two gratings. The studied population is a typical hybrid population, despite the low altitude they were found at (140 m). The individuals are pretty much similar according to both gratings, respective according to their average. The Jolly-Seber estimate gives a population size of 515 toads. The small number of recaptured animals is surprising, because that this is a limited and closed population where no individuals leaved out or came in. Almost all studied individuals had stomach content. In the stomach contents we found vegetal remains, shed-skins and animal preys as well. The most important category of stomach contents was the animal prey's. The consumed animals were 32 categories. The essential food was Nematocera larvas, Coleoperas, Dipteras, Hymenopteras, Brahiceras, Homoptera Afidas and Crustacea Izopadas. There is an important variation for these groups of prey animals depending on the time of the year. In summer months the food diversity decreases compared to spring months. As the study succeeds the food similarity increases. In spring there are predominant terrestrial preys whilst in summer time the toads we’ve analysed eat in aquatic environment. We noticed that, the minimum number of samples necessary for feeding spectrum study varies depending on the time of the year. The taxonomical composition of preys, being a tight connection between the food availability and it’s presence in the stomach contents. The type of feeding strategy (active foraging / sit-and-wait) used by the analysed toads, varies with the period of the study, abundance and accessibility of certain preys in the habitat. The high adaptability of their feeding strategies and the consuming of the most abundant prey shows a high ecological plasticity and an opportunist feeding behavior.
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