DOI: 10.5061/dryad.5qfttdzfd
title: Data from: Consequences of repeated sarcoptic mange outbreaks in an endangered mammal population

description: Diseases and parasites are important drivers of population dynamics in
 wild mammal populations. Small and endangered populations that overlap
 with larger, reservoir populations are particularly vulnerable to diseases
 and parasites, especially in ecosystems highly influenced by climate
 change. Sarcoptic mange, caused by a parasitic mite (Sarcoptes scabiei),
 constitutes a severe threat to many wildlife populations and is today
 considered a panzootic. The Scandinavian arctic fox (Vulpes lagopus) is
 endangered with a fragmented distribution and is threatened by e.g., red
 fox (Vulpes vulpes) expansion, prey scarcity and inbreeding depression.
 Moreover, one of the subpopulations in Scandinavia has suffered from
 repeated outbreaks of sarcoptic mange during the past decade, most likely
 spread by red foxes. This was first documented in 2013 and then again
 2014, 2017, 2019, 2020 and 2021. We used field inventories and wildlife
 cameras to follow the development of sarcoptic mange outbreaks in this
 arctic fox subpopulation with specific focus on disease transmission and
 consequences for reproductive output. In 2013-14, we documented visual
 symptoms of sarcoptic mange in about 30% of the total population. Despite
 medical treatment, we demonstrate demographic consequences where the
 number of arctic fox litters plateaued and litter size was reduced after
 the introduction of S. scaibei. Furthermore, we found indications that
 mange likely was transmitted by a few arctic foxes travelling between
 several dens, i.e., “super-spreaders”. This study highlights sarcoptic
 mange as a severe threat to small populations and can put the persistence
 of the entire Scandinavian arctic fox population at risk.
description: <strong>Study population</strong>
 The sarcoptic mange epizootic occurred in the Swedish
 subpopulation Borgafjäll (65.05N 14.33 E) located at the border between
 Jämtland and Västerbotten counties in Sweden (Fig. 1a). The area consists
 of 1676 km<sup>2</sup> sub-Arctic tundra and is surrounded by
 valleys with boreal forest. The arctic fox population in Borgafjäll has
 been under conservation actions since 2001, including supplementary
 feeding and red fox culling (Angerbjörn et al. 2013). Feeding stations
 containing commercial dog pellets are placed in close connection to active
 den sites. Since the conservation actions started, the number of litters
 has increased two-fold from early in the century until today (Wallén et
 al. 2021). <strong>Disease appearance and
 monitoring</strong>  The first suspected case of
 sarcoptic mange was observed the 14<sup>th</sup> of April
 2013. This individual was utilised and sent to the Swedish Veterinary
 Institute (SVA) for autopsy which confirmed the diagnosis of sarcoptic
 mange (U130513-0007). After the discovery of this first individual, we put
 out wildlife cameras on inhabited den sites (n=22) and combined this with
 intensive field monitoring in order to estimate the extent of the
 infection. During 2013 - 2015, we followed the population in a rather
 detailed way. However, for the period between 2016 - 2021 we only
 conducted ordinary inventories of most known dens and had some wildlife
 cameras out. We have therefore divided the data in three parts; i.e.,
 before the mange infestation 2004 - 2012, intensive monitoring 2013 -
 2015, and an extensive monitoring during 2016 - 2021.
 During all years the population was monitored by field
 inventories and the individuals at inhabited den sites were visually
 examined on distance using binoculars in order to detect symptoms of
 sarcoptic mange. Further the den sites were monitored for the occurrence
 of litters. The field inventories were combined with wildlife cameras at
 some dens in order to monitor the abundance of individuals with severe
 symptoms (Fig. 1b). In December 2013, a mountain rescue
 group reported a suspected case of sarcoptic mange that was observed at an
 old hut. Due to severe weather conditions, field work could not be
 initiated directly but new cases of sarcoptic mange was confirmed in
 January 2014. In January, two weeks of trapping was conducted in order to
 collect blood samples and monitor symptoms of infected individuals. In
 total, 6 individuals could be captured and sampled. Blood samples were
 collected on Nobuto blood sampling paper and was analysed by SVA using
 sarcoptic ELISA test. <strong>Wildlife
 cameras</strong> For the intensive period we
 tried to identify individuals with severe symptoms of sarcoptic mange
 (Fig. 1b), and we had wildlife cameras on all inhabited dens. The cameras
 were set to be triggered by motion and took 3 pictures every third minute
 when triggered. The pictures were analysed for red or arctic foxes with or
 without symptoms of sarcoptic mange. All pictures were then classified
 into visits in order to be able to compare the occurrence of infected
 individuals independent of the duration of the visit. A visit was
 considered as unique if no pictures with animals had been triggered during
 the last 20 minutes. By this, an individual that e.g., spent 6 h in front
 of the camera contributed to only one visit, despite several hundreds of
 pictures. During this intensive monitoring cameras were active during
 three periods; May-June 2013, September-November 2013 and February-April
 2014. Due to logistical restrictions and harsh climate, the cameras have
 not always been active for the same number of days, mainly dependent on
 the snow conditions. The minimum number of working days for a camera
 during one period were 20. During fur moulting in May,
 we could estimate the minimum number of individuals by fur characters and
 thereby determine the number of individuals at specific den sites. In
 July, no individual identification was possible due lack of individual
 markers in the fur. For the extensive monitoring 2016 -
 2021, the population was monitored by the county board administration
 through wildlife cameras. This recorded arctic fox activity, reproduction,
 litter size and foxes with visual signs of sarcoptic mange infection.
 However, data on the detailed dynamics of transmission across den sites
 has not been recorded in this period.
 <strong>Treatment regime</strong>
 The treatment was provided non-invasively through meat or sausage
 injected with Dectomax or Nexgard with the active substance doramectin or
 afoxolaner. A minimum of five pieces were put out on each den site hidden
 in the entrances or feeding stations. The pieces were hidden in order to
 avoid consumption by birds. The treatment was started immediately after
 the disease was detected and was repeated at the infected inhabited den
 sites every second to third week until no signs of mange was recorded,
 repeated one to six times. All treatment was conducted by the county board
 administration in Västerbotten and Jämtland. Dens or feeding stations that
 were supplied with medicine were monitored through wildlife cameras and
 directly by field personnel. <strong>Statistical
 analysis</strong> We tested for difference in the
 proportion of foxes with sarcoptic mange observed at visits between years
 using the General Linear Model (GLM). The relationship between geographic
 distance from the core area (i.e., the area where mange was first
 detected) was correlated to the proportion of visits from foxes with clear
 symptoms of sarcoptic mange. Based on the recorded
 number of litters over the study period, we calculated population growth
 rate, lambda = ln (Nt/Nt-1). Then, in order to decrease the sensitivity to
 rodent abundance, we used a three-year moving average. The difference in 3
 years average growth rate during years without mange compared with years
 with manage was tested for with a t test. To investigate if the litter
 size changed in response to sarcoptic mange outbreaks, we used linear
 mixed models (LMM) fitted with maximum likelihoods, using litter size as
 response variable and period (before vs. after) as a binary fixed effect
 explanatory variable. We accounted for prey abundance by including small
 rodent phase (classified as ‘low’, ‘increase’ and ‘peak’) as a fixed
 effect explanatory variable. Den site was included as a random variable.
 Further, we also tested for a difference in litter size between years with
 documented sarcoptic mange (2013-14, 2017, 2019-21) and years with no
 records of mange (2015-16, 2018) within the later time period (2013-2021).
 For this, we used the same approach as above, but used years with and
 without documented sarcoptic mange as a binary fixed effect explanatory
 variable.
description: # Data from: Consequences of repeated sarcoptic mange outbreaks in an
 endangered mammal population --- ### Description of the Data and file
 structure: Sheet 2004-2021 Column A: Borgafjäll area = den site Column B:
 2004 = number of cubs recorded at each den site (1 or higher = litter, 0 =
 no litter, - = no data) Column C: 2005 = number of cubs recorded at each
 den site (1 or higher = litter, 0 = no litter, - = no data) Column D: 2006
 = number of cubs recorded at each den site (1 or higher = litter, 0 = no
 litter, - = no data) Column E: 2007 = number of cubs recorded at each den
 site (1 or higher = litter, 0 = no litter, - = no data) Column F: 2008=
 number of cubs recorded at each den site (1 or higher = litter, 0 = no
 litter, - = no data) Column G: 2009 = number of cubs recorded at each den
 site (1 or higher = litter, 0 = no litter, - = no data) Column H: 2010 =
 number of cubs recorded at each den site (1 or higher = litter, 0 = no
 litter, - = no data) Column I: 2011 = number of cubs recorded at each den
 site (1 or higher = litter, 0 = no litter, - = no data) Column J: 2012 =
 number of cubs recorded at each den site (1 or higher = litter, 0 = no
 litter, - = no data) Column K: 2013 = number of cubs recorded at each den
 site (1 or higher = litter, 0 = no litter, - = no data) Column L: 2014 =
 number of cubs recorded at each den site (1 or higher = litter, 0 = no
 litter, - = no data) Column M: 2015 = number of cubs recorded at each den
 site (1 or higher = litter, 0 = no litter, - = no data) Column N: 2016 =
 number of cubs recorded at each den site (1 or higher = litter, 0 = no
 litter, - = no data) Column O: 2017 = number of cubs recorded at each den
 site (1 or higher = litter, 0 = no litter, - = no data) Column P: 2018 =
 number of cubs recorded at each den site (1 or higher = litter, 0 = no
 litter, - = no data, ? = arctic fox activity, litter could not be
 confirmed or unconfirmed) Column Q: 2019 = number of cubs recorded at each
 den site (1 or higher = litter, 0 = no litter, - = no data, ? = arctic fox
 activity, litter could not be confirmed or unconfirmed) Column R: 2020 =
 number of cubs recorded at each den site (1 or higher = litter, 0 = no
 litter, - = no data) Column S: 2021 = number of cubs recorded at each den
 site (1 or higher = litter, 0 = no litter, - = no data) Column T:
 Monitored years = the number of years the den has been monitored Column U:
 Inhabited = the number of times the den has been inhabited by arctic fox
 Column V: Relative inhabited = Inhabited / Monitored years ### Description
 of the Data and file structure: LS\_stat Column A: Year = the year data
 was collected Column B: Before_after = if data was collected before (i.e.
 2004-2012) or after (2013-2021) the first appearence of sarcoptic mange
 Column C: Mange = if mange was recorded on the den site (N = no, Y = yes)
 Column D: Phase = the phase of the small rodent cycle, where
 'Increase' = Small rodent abundance is higher than the low phase
 but lower than the peak phase; 'Peak' = The highest small rodent
 abundance over the cycle, appearing after the increase phase and before
 the low phase; 'Low' = A distinct decline in small rodent
 abundance relative to the other phases Column E: Den = den site Column F:
 Litter size = the number of cubs observed at the den site