Buicu, Florin - Cristea, Doina (szerk.): Satu Mare. Studii şi comunicări. Seria ştiinţele naturii 9. (2008)
Ştiinţele naturii
Satu Mare - Studii şi Comunicări Seria Ştiinţele Naturii\io\. IX (2008) juveniles frequently eat terrestrial Coleopteras, Hymenopteras Formicides, Afidine and Diptera. Varying on the period there are also differences concerning the weight of these taxas. Thus, in May the Coleopteras have a high value, in June appear, beside these, the Hymenoptera Formicida. In July first place ■ is occupied by the Diplopoda and Araneida, in August the Hymenopteras and in September the Araneida. In the stomachal contents we also identified vegetal fragments and shed-skin, beside animal prey. The vegetales are more frequendy consumed by the adults. With concern to the consumption of shed-skin we can also notice a higher consumption in the case of the adult males. With regards to the seasonal variation of plant consumption, these were consumed monthly by more than 50% of the individuals. In July we can observe a 76% consumption. With concern to the shed-skin consumption we can remark a negative correlation of this towards the vegetal frequency. Thus in June, when the vegetal consumption registered the lowest value, the frequency of shed-skin consumption recorded the highest value (34%). Discussions Different studies suggest that food is. an important factor in the relation between Amphibians and the environment (Duellman 1994). The reduced number of empty stomachs suggests the fact that they had good feeding conditions. The fact that the few individuals which do not present a stomachal content appear only in the warmest months of the year (July and August), can be explained through the fact that, in that period, the puddle was smaller, thus the living contidions were relatively more severe. The number of consumed preys can be influenced by their size, the smaller ones being eaten in a larger number, having a lower energetic value than those that are larger in size. This fact can be observed in our case as well, when in the first months the maximum number of prey/individual is very high because of the large consumption of Brahicera, Culicida and Afidina larvae. Together with the appearance of larger preys (terrestrial Coleoptera, Diplopoda and terrestrial Gastropoda) this value decreases. Situations such as these have also been observed in the case of the vicariant Bombina bombina species (Széplaki et al. 2006). The high weight of consumed terrestrial prey is due to the fact that the frogs hunt in the terrestrial environment. The appearance of aquatic prey in September is due to the autumn rain, when the puddle is quite large, thus having better feeding conditions. The results highlight that with concern to the sexes, the females spend more time in the water, whereas the males and juveniles are more terrestrial. On the one hand, this fact can be explained through the differences that occur in the hunting strategies (Huey and Piankal981; Perry and Pianka 1997). On the other hand juveniles need to go out on dry land, being forced to find more food in order to grow, whereas the adults have a tendancy to retreat in hibernation. Even scientific literature considered that the terrestrial prey holds a majority in the case of the Bombina bombina (Széplaki et al. 2006; Sas et al.2004a), Bombina variegata (Ghiurcă şi Zaharia 2005; Peter et al 2005; Sas et al.2005a; Groza et al. 2006) or Bombina hybrids (Sas et al.2005b; Ferenti et al. 2007). With regards to the weight of prey taxa, we can notice the presence of the larger preys as well as that of the smaller ones. This fact suggests that their feeding is not selective, so they capture the richest food in their vicinity, essentially feeding with mobile preys that have the proper size to be captured (Török and Csörgő, 1992). In the case of the females, we can remark the presence of larvae, especially in the first periods of the year. According to Brooks et al. (1996), larvae are more nutritious because of their higher lipide contents. Due to this fact, they are prefered by the females, which need energy in mantaining their reproductive activity, particularly in the first periods of the year. The large consumption of Coleoptera is a very common phenomenon for the case of Bombina. They represent a vejy important element in the feeding spectrum of other Bombina populations as well (Peter et al. 2006). Considering the vegetal consumption, the adults consumed them more. We can observe a positive correlation between the consumption of terrestrial prey and the vegetal one. Perhaps the plant fragments reached into the frogs’ stomach along with the capture of the terrestrial preys’ from the plants’ surface. There were some other occurrences in the case of the adult frog ,when the vegetals were actively consumed (daSilva et. al 1989). From the species in our country, the consumption of plants and acicular leaves has been noticed at the red mountain frog, Rana temporaria (Itämies & Koskela, 1970). Some authors consider that vegetals are consumed in order to help crush the exoskeleton of the eaten insects’ , or to contribute to the elimination of some intestinal parasites. (Evans and Lampo 1996). In the case of the yellow bellied toad, the consumption of plants can not be considered as active, because they are regarded as carnivores 19
