Camera trap records of leucistic Eurasian badgers (Meles meles) in central Norway

Abstract Coat coloration plays an important role in communication, camouflage, and sexual selection in animals. Genetic mutations can lead to anomalous colorations such as melanism and leucism, where animals appear, respectively, darker or lighter than normal. Reporting abnormal coloration in wild animals is an important first step to understand the distribution, prevalence, and potential fitness consequences of these rare events. Here, we report several records of suspected leucism in the Eurasian badger (Meles meles) in a population in central Norway. Several camera traps recorded at least two leucistic individuals between 2017 and 2020. It took considerable effort, almost 400,000 camera trap nights over a period of 10 years all over Norway, to obtain a total of eleven records of leucistic badgers, indicating the rarity of this phenotype. It is unclear what has caused the presence of multiple leucistic badgers in a single population, but recent colonization and lack of predators might have played a role. Due to our observations, future studies can now be developed to study the underlying mechanisms and potential consequences of leucism in this badger population. The increasing use of networks of camera traps in wildlife research will provide new opportunities to record rare coloration in wild animals.

that suggests a natural selection against these coat colorations (Caro, 2005). However, in order to better study coat color anomalies, we first need better information on how often and where these color anomalies occur in wild populations.
The Eurasian badger normally has a distinct coat coloration with a gray-brown body, dark legs, and black and white marks on the head (Figure 1; Kruuk, 1989;Roper, 2010). Albino, leucistic, melanistic, and erythristic Eurasian badgers have been described before (Roper, 2010) and seem to occasionally be sighted in the UK (Badger Trust, 2021). However, to date these observations have not been recorded in an accessible format, such as in the scientific literature, making it difficult to assess the frequency of occurrence and study the causes and consequences of coat color anomalies in Eurasian badgers. Here, we report the observation of several leucistic Eurasian badgers in Norway.
The study area is situated on the coast of the Atlantic Ocean and is characterized by relatively mild winters and a rugged coastline of many fjords, islands, and peninsulas. It is relatively isolated with the Atlantic coast and two large fjords on the north, northeast, and southwest sides. On the south, it is bordered by a mountain range.
The topography consists of many forested hills and mountains with rocky outcrops and bare rock at higher elevations. Human activity is Eurasian badgers are native to Norway and occur as far north as the Arctic Circle, but are absent from large parts of western Norway (Artsdatabanken, 2021). The study area was colonized from the east only relatively recently, likely somewhere between the 1970s and the 1990s (Bevanger & Lindström, 1995).

| RE SULTS
We first recorded a light-colored badger interacting with a regularly in Figure 2), 4 km from the HA1 location. We have seven more observations at the HA2 location over the period between 21 March 2019 and 18 August 2020, potentially of the same badger or several related individuals. We have never observed more than one leucistic badger at the same time and were unable to find any other distinguishing features that could help identify individuals. All observed leucistic individuals were fully grown, at least one-year-old badgers.
However, because the two records on 18 and 19 August 2020 at OD F I G U R E 1 Camera trap image of a regularly colored badger from the study area, showing the distinct gray-brown body, dark legs, and black and white facial marks and HA2 were 70 km apart, we conclude that we have observed at least two individuals.
We believe these to be leucistic Eurasian badgers as several images show a dark nose (inset Figure 3c). Such dark nose coloration has also previously been found in a leucistic fisher (Olson & Allen, 2019).
Taking into account the total effort in the Scandcam project, 386,589 camera trap nights (approximately 1,060 camera trap years) over 10 years at 1,399 locations spread throughout Norway, we conclude that leucism is rare in Norwegian badgers. In the total dataset, we only recorded 11 observations of leucistic badgers in a total of 19,820 independent badger observations, with 2,442 observations of badgers at the 90 camera locations in the study area. We consider each sequence of images taken with a maximum time interval of 5 min between previous and subsequent images containing one or more badgers as an independent observation. If we assume an equal detectability of leucistic badgers compared with normal coloration, we derive a frequency of 0.5% leucistic badgers in the study area, and 0.06% in the whole of Norway.

| D ISCUSS I ON
Distinct coloration in the anterior parts of the body in mesocarnivores is likely related to aposematic communication toward larger predators (Buesching & Stankowich, 2017;Caro et al., 2017;Newman et al., 2005), and it has been suggested that the facial F I G U R E 2 Study area where we detected the leucistic badgers. Blue points represent camera trap locations, the three locations where we detected leucistic badgers are presented as triangles: ODthe location in Orkdal; HA1 and HA2the two locations close to Halsa. Inset: location of the study area in Norway  (Kitchener et al., 2017). Therefore, leucism might affect intra-and interspecific communication in badgers. Furthermore, leucism will increase the visibility of the badger, as it is lighter than its surroundings, which might increase predation risk, except for situations when there is snow on the ground. Only two out of 11 observations of leucistic badgers were under snowy conditions (Figure 3b).

This is likely because badgers reduce body temperature and activity
in winter as they have difficulty hunting when the ground is covered in snow or ice (Bevanger & Brøseth, 1998;Bevanger & Lindström, 1995;Kruuk, 1989), reducing the potential adaptive advantage of being light-colored. Alternatively, increased visibility might potentially also decrease the risk of crossing roads, an important cause of mortality in many badger populations (Griffiths & Thomas, 1993).
However, studies on the importance of different causes of mortality for badgers in Norway are lacking. Consequently, it is hard to say whether the light coloration causes an adaptive disadvantage for badgers in Norway, especially as all observed individuals at least survived to be fully grown.

Although it is unknown what has caused multiple leucistic bad-
gers to occur in the study region, there are several factors that might have played a role. As badgers only recently colonized the study area, there might be a founder effect that caused low genetic diversity and a larger probability of rare phenotypes being expressed (Hubbard et al., 2010). Due to the topographically fragmented land-

scape of fjords and mountains, it is likely that only a few individuals
founded the badger population in the study area, which would increase the chance of a point mutation, such as leucism, spreading through the population. A population genetic study of the badger population in the study area is, however, lacking. Furthermore, the lack of predators of adult badgers, such as wolves and wolverines (Olsson et al., 1997), in the study area likely results in a low increased mortality risk due to leucism, although it is allowed for people to hunt badgers in the study area. Lastly, it cannot be ruled out that local environmental contamination might have caused an increased presence of leucism (Møller & Mousseau, 2001). It would thus be very interesting to study the genetics of this badger population to unravel the genetic history of the leucistic badgers and determine whether the leucistic individuals are genetically related to each other. That would also allow for a better estimation of the number of leucistic individuals and the proportion of leucistic badgers in the population. Furthermore, it would enable the study of other deleterious mutation that might be associated with the presence of leucism in badgers, similar to albinism-related diseases in humans (Witkop et al., 1990).
Leucism has been found in several other carnivore species, especially in the Neotropics, and seems to be relatively common in mustelids (Abreu et al., 2013;Olson & Allen, 2019). Similar to our observations, many of these records were from adult individuals, questioning the impact of leucism on hunting success and survival.
Although many of the known records of leucism in carnivores are from animals in museum collections, an increasing number of records are being collected using camera traps Cronemberger et al., 2018;Olson & Allen, 2019;Scrich et al., 2019). can be used to monitor badger sets to study the number of offspring and offspring survival of sets with or without leucistic badgers, to derive estimates of fitness consequences of fur coloration (Bernardi et al., 2021).
As there is little knowledge about the causes and consequences of color anomalies in wild mammals, it is important to get a better understanding of where and how often these anomalies occur (Caro, 2005;Łopucki & Mróz, 2010). Only then can we study the locations where the anomalies occur to get a better understanding of the underlying mechanisms and potential fitness consequences.
As the number of camera traps deployed by scientists, conservationists, and the general public is increasing (Burton et al., 2015;Rowcliffe & Carbone, 2008), these devices will pick up more and more rare events, such as color anomalies and rare behaviors (Cove et al., 2017). It is important to report these rare events to build up a larger number of scientific publications of color anomalies in wild mammals to better understand how often these anomalies occur and to provide a starting point for further studies.

ACK N OWLED G M ENTS
We want to thank the students and volunteers that helped with

CO N FLI C T O F I NTE R E S T
The authors declare no competing interests. data curation (equal); funding acquisition (lead); investigation (equal); methodology (equal); project administration (lead); writing-review and editing (equal).

DATA AVA I L A B I L I T Y S TAT E M E N T
All camera trap data from the Scandcam project (locations and images) are available on viltk amera.nina.no.