Environmental drivers of the distribution and density of the European badger (Meles meles): a review Carme Piza Roca1,2, Maurice J.J. La Haye1,2 & Eelke Jongejans1 1Radboud University Nijmegen, Institute for Water and Wetland Research, Animal Ecology and Ecophysiology group, P.O. Box 9100 (mail box 31), NL-6500 GL Nijmegen, the Netherlands, email: [email protected] 2Dutch Mammal Society, P.O. Box 6531, NL-6503 GA Nijmegen, the Netherlands Abstract: Knowing the environmental factors affecting species’ distribution is an important basic step in ecologi- cal research. Here, we present a literature review on the environmental factors influencing European badger (Meles meles) distribution and density. According to the published literature, the badger is a highly adaptive species, capa- ble of using different environmental services and adapting to different conditions. However, when studying badger populations across their distribution, a general pattern of preferred environmental characteristics and influencing factors arises. These environmental characteristics may indicate the badger’s realised niche and may potentially give an approximation of its fundamental niche. A combination of environmental factors favouring both sett (bur- row) location and food availability appears to drive local badger success: terrain characteristics (both suitable soil type for sett excavation and terrain heterogeneity for visual hiding), wood coverage and earthworm-rich grassland. The presence and density of badgers vary depending on the geographic study area and the relative importance of these specific environmental drivers. We discuss how these insights can assist spatial modelling studies, conserva- tion and management, and future research on habitat suitability and badger density. We stress that more research is needed to understand how each component of the life cycle of badgers is affected by environmental drivers, and what the cumulative effect is on their spatial population dynamics. Key words: environmental factors, European badger, fundamental niche, Meles meles, occurrence, review, sett. Introduction the European badger is now described as a distinct species from the Asian badger (Meles The European badger Meles( meles) is present leucurus) and the Japanese badger (Meles in almost all European countries, from the anakuma) (Abramov 2001, 2003, Wozen- British Islands eastwards to the west bank of craft 2005, Abramov & Puzachenko 2005, the River Volga (figure 1). The species belongs 2006). The Asian badger occurs from the to the family of Mustelidae, in the order of east of the Volga River to China and Korea, Carnivora. Recent studies showed that the till the border of the distribution of the Euro- genus Meles includes several distinct species, pean badger throughout the Lower and Mid- while this was considered only one species in dle Volga and the interfluves of the Volga the past, the Eurasian badger. Accordingly, and Kama (Abramov & Puzachenko 2006). A clear geographic border in the northern © 2014 Zoogdiervereniging. Lutra articles also on the Caucasus between Meles leucurus and Meles internet: http://www.zoogdiervereniging.nl meles has not yet been clearly defined, as they Piza Roca et al. / Lutra 2014 57 (2): 87-109 87 Lutra_57_2_Text_v3.indd 87 06/02/2015 21:27 Figure 1. Distribution range of the European badger (Meles meles), based on the distribution maps of Del Cerro et al. (2010) and Abramov & Puzachenko (2013). can occur sympatrically and may even repro- breeding at an age of two years, that annual duce, giving hybrids with mixed characters juvenile survival (63%-77%) is lower than (Abramov & Puzachenko 2007). The Japanese adult survival (76%-88%), giving a genera- badger occurs on the Japanese Islands (Bary- tion time of 5.8 years, and that by an age of 7.3 shnikov et al. 2003). Finally, Del Cerro et al. years an average female has contributed half (2010) provide evidence for a fourth species of of what she is going to contribute (through badger named Meles canescens, distributed in reproduction) to population growth in her South-West Asia, from south of the Caspian life (Macdonald et al. 2009, van de Kerk et al. see and the Northern Caucasus to Tajikistan. 2013). See figure 2 for a graphic representation The taxonomic status of the badger nowadays of the badger’s life cycle based on the study of admits therefore four distinct species (Abra- Macdonald et al. (2009). mov & Puzachenko 2013). The European badger is relatively abundant The European badger is a generalist, highly in Europe, being only uncommon or present adaptive, species which is capable of exploit- in lower densities in the Netherlands, Bel- ing a wide variety of habitats (Feore & Mont- gium, Estonia, Slovakia and Poland (Kranz et gomery 1999, Kauhala & Auttila 2010). It is al. 2008). Nevertheless, there is a general con- only absent from arctic zones, high altitude cern about this species because it has showed regions and some islands (Griffiths & Thomas strong fluctuations in numbers in many coun- 1993). Analyses of the dynamics of an Eng- tries in the last century (Griffiths & Thomas lish population have shown that badgers start 1993). In the 1970s and 1980s badgers obtained 88 Piza Roca et al. / Lutra 2014 57 (2): 87-109 Lutra_57_2_Text_v3.indd 88 06/02/2015 21:27 Figure 2. Matrix projection model for a European badger population near Oxford (Macdonald et al. 2009), based on post-breeding census data. The first stage therefore represents newborn cubs (zero-year olds). The population model consists of five parameters: age of first reproduction (2), age of last reproduction (15), juvenile survival (0.717), adult survival (0.837), and fertility (0.267). Figure 3. Countries where the studies containing data relevant to the search topic were performed, i.e. the factors influencing distribution and density of the European badger as presented in this review. a protected status in Britain, Ireland, Spain, tions. Therefore, knowledge is required about Portugal, Italy, Belgium, the Netherlands, the environmental factors driving the distribu- Albania, Greece, Estonia, Luxemburg and tion and density of badger, which makes it pos- Hungary (Griffiths 1991b). In 2008 the species sible to quantify habitat requirements, weigh- was ranked as Lower Risk/Least Concern on ing management options, and assessing the the European Red List (Baillie & Groombridge impact of habitat change. In broader ecological 1996, Kranz et al. 2008), which means that pro- studies, it is also of great importance to know tection had positive results. With its history as the interaction of the species of interest with its a threatened species it is an interesting object environment in order to situate the species in to formulate and study policy recommenda- the ecosystem, its used niche and so on. Piza Roca et al. / Lutra 2014 57 (2): 87-109 89 Lutra_57_2_Text_v3.indd 89 06/02/2015 21:27 Lutra_57_2_Text_v3.indd 90 90 Table 1. Main environmental drivers of badger spatial population dynamics. Environmental Components Contribution Potential effect on Effect Literature driver Climate Rainfall range Higher seasonality Badger presence, spatial organisation, pop- Negative 1–3 Temperature range Higher seasonality ulation size and density and group size. Negative Rain, temperature between 5– 15ºC Favours earthworm availability. Positive 4–8 and high air humidity Cold winters, dry summers and wind Decreases earthworm availability. Negative 9 Spring rainfall and high temperature Increase cub parasitic susceptibility. Negative Terrain character- Suitable geology Facilitates digging and drainage. Badger presence, Limiting fac- 10–21 istics and sett site Slope Favours earth removal. size and shape of occupied territory and tor availability Aspect Selection of sites on south to west-facing spatial organisation. slopes. Terrain heterogeneity Visual hiding Vegetation cover or small landscape Visual hiding elements Groundwater level Sett building Abandoned old setts Possibility for recolonisation Positive 22 Presence of habited setts Induces construction of new setts. Piza Roca et al. et Piza Roca Habitat type Woodland Offers cover, shelter, structural support Population density, group size and terri- Positive 1, 4–5, for sett building and additional source of tory size. 10–15, food items. 23–32 Hedgerows and scrub Cover and shelter Grassland and pasture Foraging, source of earthworms. Short grass is more suitable. / Lutra 201457(2):87-109 /Lutra Arable fields: e.g. maize, wheat, barley Food source: cultivated food and earth- worm content. Food availability Large variety of items: e.g. earth- Food source. Population size and density, territory size Limiting fac- 1, 11, 24, worms, other invertebrates, birds’ eggs and shape and spatial organisation. tor 29, 33, 43 and chicks, rodents, carrion, fruits, cereals 06/02/2015 21:27 Lutra_57_2_Text_v3.indd 91 Piza Roca et al. al. et Piza Roca Built-up areas Urban infrastructure Decreases sett site availability. Badger presence, density and spatial Negative 26–27, Habitat destruction. organisation. 44–48 Fragmentation. Human population density. Disturbance on habitat. Population size and density. Negative Agricultural land Habitat destruction. Badger presence and spatial organisation. Negative / Lutra 201457(2):87-109 / Lutra Fragmentation. Population size and density. Urban and industrial areas Provide anthropogenic food sources. Population size and density. Positive 10, 14 Roads Increase mortality. Badger presence and spatial organisation. Negative 14, 26, Habitat destruction.