Abstract
Long–term variation of demographic parameters in four small game species in Europe: opportunities and limits to test for a global pattern. For decades, decreases in several populations of some small sedentary game species have been reported in Europe. From the literature, we extracted mortality and reproductive rates that were available for European populations in four iconic species, the grey partridge (Perdix perdix), the black grouse(Tetrao tetrix), the capercaillie (T. urogallus) and the brown hare (Lepus europaeus), to examine how demographic parameters vary with time. Our study revealed the need to consider many confounding factors (age, sex, origi of studied individuals, season, country and methods) and the scarcity of recent demographic studies. Statistical analyses showed contrasted patterns of demographic traits with time within and between species. Our results highlighted that there may be consistency with a population decrease in grey partridge and black grouse that has been reported in the literature. However, analyses in capercaillie and brown hare showed less support for a population decrease at the European scale. The significant effects of interactions between time and age (in grey partridge, capercaillie and brown hare), method or origin of individuals on demographic traits and the emergence of contrasted patterns between short, intermediate and long monitoring periods (in grey partridge and black grouse) suggested that further studies should pay particular attention to potential confounding factors. Finally, the lack of recent data and doubts about the relative importance of reported causal factors indicate the need for further studies on the links between demographic traits, densities and environmental changes in the long term, and particularly on the role of predation and habitat change
Highlights
Decreases in several populations of farmland and woodland species have been highlighted in different areas of geographical Europe by various stakeholders (Comolet–Tirman et al, 2015), including hunting associations (Tapper, 2001; Vallance et al, 2008) and academic researchers (Sumption and Flowerdew, 1985; Smith et al, 2005; Storch, 2007; Inger et al, 2014)
From the data available in the scientific literature, our aim was to explore whether estimates of mortality and reproductive rates might be used as empirical support of the demographic declines in four small game species in Europe: the grey partridge, the black grouse, the capercaillie (Tetrao urogallus), and the brown hare (Lepus europaeus)
Mortality rates Analysis showed a significant association between time and mortality rate estimates in grey partridge, but this link differed between the temporal scales at which it was assessed
Summary
Decreases in several populations of farmland and woodland species have been highlighted in different areas of geographical Europe by various stakeholders (Comolet–Tirman et al, 2015), including hunting associations (Tapper, 2001; Vallance et al, 2008) and academic researchers (Sumption and Flowerdew, 1985; Smith et al, 2005; Storch, 2007; Inger et al, 2014). Wide–scale analyses controlling for the effects of, for instance, heterogeneity in studied areas and methods and individuals used as biological models would be useful to investigate whether demographic parameters might be used as proxy for variation in the abundance of small game species in Europe. Direct testing of populations decreases from abundance estimates might appear to be an intuitive approach to examine the temporal variations of small game species in Europe (European Environment Agency, 2014). A decrease in only one trait, reproduction (Panek, 1992b; Lindström et al, 1997), might require complementary information as potential demographic trade–offs or density–dependent processes might be involved in population dynamics (Panek, 1992b; Lindström et al, 1997; Grimm and Storch, 2000; Sachot et al, 2006)
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