Assessing and predicting the spread of non-native raccoons in Germany using hunting bag data and dispersal weighted models

Abstract

34As the second largest cause of biodiversity loss worldwide, there is an urgent need to study the dynamics of 35 biological invasions and identify factors limiting the distribution of invasive alien species. In the present study 36 we analyze national-scale hunting bag data from Germany to predict the dispersal of raccoons in the largest non-37 native population of the species. Our focus is (1) to document changes in the distribution and abundance of 38 raccoons, (2) to identify the species-environment relationship and predict which areas will be suitable for future 39 colonization and (3) to apply a dispersal model to predict how fast the raccoon will spread to these areas. The 49 Introduction 50Worldwide, Invasive Alien Species (IAS) are associated with significant damage to the economy and public 51 health, and are considered to be one of the major threats to native biodiversity (Mack et al. 2000; Pimentel et al. 54monitoring programs help to determine the distribution of non-native species, which is necessary in order to 55 assess the impact of non-native species in terms of disease risks, economic damage and negative effects on 56 native species and the environment, and plan management actions to reduce these impacts (Engeman et al. 2006; 57 Sterner and Smith 2006; Yokomizo et al. 2009). Monitoring programs for terrestrial mammals are usually based 58 on the collation of ad-hoc records (Roy et al. 2014a), systematic surveys of abundance (such as road-kill surveys, 59tracking plots, spotlighting, pellet counts along fixed routes), or more cost intensive and logistically complicated 60 methods such as radio-tracking, mark-recapture, camera trapping, aerial surveys and DNA genotyping 61 (Woodroffe et al. 1990; Bartel et al. 2012; Engeman et al. 2013). Hunting bag data are routinely collected for 62 3 game species, and these offer an additional monitoring strategy as they can be used as a general index of long 63 term trends, population and distribution change and a proxy of abundance across time (Cattadori et al. 2003; 64 Kitson 2004; Carlsson et al. 2010). 65These abundance or presence/absence data are used in species distribution models (SDMs) to identify 66 suitable or unsuitable areas for a species based on a set of environmental covariates, and these SDMs can be used 67 to predict where a non-native species will spread to. Generally SDMs assume that the species being modelled is 68 at equilibrium with the environment (Guisan and Thuiller 2005), which means unoccupied areas are considered 69 as unsuitable for the species. However non-native species are often spreading from a few release sites and are 70therefore not at equilibrium with their environment, so absences may be due to dispersal limitation as well as 71 unsuitable environmental conditions (Václavík and Meentemeyer 2012). One approach to address this is to 72 model the dispersal process, and then weight the species distribution model by the predicted probability of 73 different areas being dispersed to (Sullivan et al. 2012 ...

Cryptosporidium spp. and Enterocytozoon bieneusi in introduced raccoons (Procyon lotor)—first evidence from Poland and Germany

“…Müritz National Park (MNP) (53° 27′ N, 12° 49′ E) located in Mecklenburg-Vorpommern contains a large amount of wetland habitats, especially bog and swamp districts. This area demonstrates a very opportune habitat for raccoon—its population density in the area is twice as much as that in the middle part of Germany (6–8 individuals per 1 km 2 ) (Fischer et al 2016; Hohmann 1998; Köhnemann and Michler 2008; Muschik et al 2011).

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Environmental drivers of raccoon (Procyon lotor L.) occurrences in Austria - established versus newly invaded regions

“…Consequently, studies involving native or established occurrences of raccoon are not comparable to those from newly invaded areas. Previous invasive species distribution models (iSDMs) in the core area of the European raccoon population [41] and at the southern border of its current distribution range [42] revealed that either land-cover data or climate data explained raccoon distribution. Furthermore, the habitat preferences of alien species can spatially vary across landscapes and depend on the stage of colonization, with less favorable habitats only being occupied when comparably high population densities are reached [41,43].…”

“…Previous invasive species distribution models (iSDMs) in the core area of the European raccoon population [41] and at the southern border of its current distribution range [42] revealed that either land-cover data or climate data explained raccoon distribution. Furthermore, the habitat preferences of alien species can spatially vary across landscapes and depend on the stage of colonization, with less favorable habitats only being occupied when comparably high population densities are reached [41,43]. Studies of other invasive species have provided indications that including distribution data both from native and invasive ranges might yield better iSDMs than models relying solely on data from native ranges [44].…”

“…Basic data have been gained from telemetry studies [16,24], DNA genotyping [45], systematic records using scent stations, spotlight and latrine surveys, track surveys or camera traps [27] and nonsystematic records (e.g. hunting bags, sightings, trappings, camera trappings, road-kills [41,43,46]). Using these variables, relative abundance calculations (e.g.…”

Elevational range shifts in four mountain ungulate species from the Swiss Alps

“…Such harvesting inventories may extend continuously over several decades, and thus describe an abundant source of information for many game species. Although they may have a multitude of limitations, systematically aggregated and wellreplicated hunting/harvesting records can provide a particularly useful supplement for the estimation of large vertebrate spatial distribution dynamics (Fischer et al 2016).…”