Hungarian stock of game is not only part of our national treasure but also one of our domestic products and economic income. Not indifferent therefore the number and the state of health of our wildlife. Population decline of the Brown hare (Lepus europaeus, Pallas 1758) (one of our most important small game in Hungary) takes a long time. Demographic parameters of Brown hare was examined, particularly the factors affecting the decline of the species in Hungary. We took samples from typical habitats where the Brown hare could be found in relatively high density in our country. The article reports data of reproductive characteristics, diseases, parasites of Brown hare and other factors such as climatic and anthropogenic which could influence of the population dynamics. We mention sample collection and processing methods eg: population size estimates, examination of reproductive organs, the sex ratio and the age structure as well as the individual condition based on data of domestic and foreign authors and our partial results.

The objective of the research partly is to compare the reproduction performance of the populations living in different regions with regard to some special characteristics (age, condition).When estimating the age through tooth wear and cementum-layer-counting there was a difference of 0.87 years in favour of the first one (r=0,840; p<0,001). I found cementum layers at 42% of the does in the study after examining the MI teeth.There was lose connection between the weight (eviscerated, with head and legs) and the KFI (r=0,296; p<0,01), and for further analysis, I used only the KFI as the index for condition.The regional average KFI varied from 0.24-0.37 in fawns, 0.82-1.73 in does, with individual extremes of 0-4.05. Within the examined regions the highest index belonged to the prime-aged does, while the 1-year-olds had a lower rate, and it was the lowest in the does older than 8 years.The rate of fertility was between 83,3(ns)-100% as we can see from the presence of the CL. All the examined does were fertile, except in one region, while among the female fawns in two regions I only found three with active ovaries. The average number of CL was 1.5-2.13, and this varied by regions; all in all it was the highest in the 2-7-year-old group (1.96) and in the ones over 8 years (2.00!), while it was lower in the does younger than 1 year (1.90). The high fertility of the does over 8 years is remarkable.I could examine the number of embryos in two regions during the post-implantation period, and beside 100% fertility I found significant differences among the does, which can be associated with the condition. The ratio of CL carriers and the pregnant does was 100% and 73% in the two regions, the average number of CL were 1.92 and 1.72, while the average embryo number were 1.83 and 1.36 per doe. The difference between the CL and the embryo numbers on the two regions were 5% and 21%. The difference (prenatal loss) is in connection with the age (age class) of the doe. It is possible, however, that in some cases oestrus was not followed by gestation. But in roe deer, owing to the commonly known lack of luteolysis-mechanism (Flint et al., 1994), the regression of the CL of the does that did not get pregnant takes place in December and January, so the CL found in January cannot prove a previous pregnancy, which might have been followed by an abortion.Although it has to be proven, it seems that the number of the CL (potential progeny) can be associated with the age (r=0,418; p<0,01) and the weight (r=0,312; p<0,01) of the doe, while the embryo number (realised progeny) is influenced by the age of the doe and probably by external factors.It is essential to continue and extend the research to increase the reliability of the results and their correlation.

It is widespread that roe deer are very choosy. It needs this sorting because the micro organisms, which help the digestion of high fibre plants, are missing in its stomach that is why they are mostly called „concentrate selectors” (Hoffmann, 1985, 1988, 1989).These animals should mostly eat easily digestible plants with high nutrition level (pulses, buds, sprouts and flowers), and they are able to do this sorting because of their small mouth size. In winter there is a lack of these plants, so the high selectivity occurs only when the feed is in abundance.Examining the amount and quality of vegetation available on the habitat of roe deer we can identify the species which can satisfy their feed demand. It is known, that roe deer as other large ruminants, from the plant abundance prefer certain plants and plant parts while there are others which are avoided. The identification of the eaten species and the rate of their occurrence in the feed is the first step to become acquainted with theinteraction between animal and the surroundings.

It is widespread that roe deer are very choosy. He needs this sorting because the micro organizms, which help the digestion of high fibre plants, are missing in his stomack, that is why they are mostly called „concentrate selectors” Hoffmann, 1985, 1988, 1989).These animals should mostly eat easily digestable plants with high nutrition level (pulses, buds, sprouts and flowers), and they are able to do this sorting because of their small mouth size. In winter there is a lack of these plants, so the high selectivity occurs only when the feed is in abundance.Examining the amount and quality of vegetation available on the habitat of roe deer we can identify the species which can satisfy their feed demand. It is known, that roe deer as other large ruminants, from the plant abundance prefer certain plants and plant parts while there are others which are avoided. The identification of the eaten species and the rate of their occurance in the feed is the first step to become acquainted with the interaction between animal and the surroundings.

I studied the variations of kidney fat indexes (KFI) in two game management units of the Great Hungarian Plain between 2002 and 2004 in the autumn and winter months. I was looking for correlation between the autumn and winter KFI as well as between the autumn KFI and reproductive parameters (number of corpora lutea, recruitment rate). There was a significant positive correlation between the average winter and the average next autumn KFI (r=0.991, p<0.1). The average winter KFI showed strong positive correlation with the average number of corpora lutea (CL) in the next rutting season (r=0.978, p<0.05). The average autumn KFI and the average grown up offspring showed positive but not significant correlation (r=0.725, p=0.275).