Anna Skarin

Summer habitat preferences of GPS-collared reindeer Rangifer tarandus tarandus

Abstract Reindeer Rangifer tarandus tarandus husbandry in Sweden commonly uses the Scandinavian mountain chain as grazing area during the snow-free season and the coniferous forests in the east during winter. Current knowledge of habitat use by reindeer is primarily based on traditional or local knowledge, or on investigations carried out on wild reindeer and caribou in other parts of the world. We identified spatial and temporal habitat use of free-ranging semi-domesticated reindeer by following 48 GPS-equipped reindeer in three summer ranges in the Swedish reindeer herding area. The GPS equipment registered positions every hour or every second hour, during two snow-free seasons. The GPS-collared reindeer were randomly chosen from herds with several thousand animals. Estimated home-range utilisation distributions were used to fit resource utilisation functions (RUFs) including various topographical features, vegetation types, and the vicinity to water and hiking trails. The GPS-equipped reindeer used different parts of the range throughout the snow-free season. Preferred vegetation types were consistently meadows, grass heaths, and other heaths. Avoided vegetation types were all types of forests, sparsely vegetated areas, and bare rocks. The reindeer were seemingly indifferent to hiking trails within their home ranges, which, however, usually coincided with preferred vegetation types, but they avoided areas with houses and holiday huts during early summer. Later in the season, the reindeer preferred higher elevated areas where human constructions were sparse. The home ranges of the GPS-equipped reindeer overlapped considerably during early parts of the season, indicating a dense use of the range by the entire herds. Crowding within the herds appeared to make individual reindeer select non-optimal habitats. However, in our study, we found a non-significant tendency of less predictable individual home ranges when there were large range overlaps. Vegetation types, direction of slopes, time within the season and the possibilities of avoiding insect harassment appear to be key factors for predicting valuable reindeer habitats in novel areas in a land management context.

Insect avoidance may override human disturbances in reindeer habitat selection

Habitat selection of semi-domesticated reindeer (Rangifer tarandus tarandus) was investigated through faecal pellet- group counts and by direct observations of reindeer from helicopter in the Langfjallet area in Idre reindeer herding district (62˚10’N) and in Mittadalen reindeer herding district (62˚50’N, aerial observations only). Reindeer pellets were found to be most abundant in habitats at high altitudes, and in some vegetation types. Pellet-group densities tended to be higher near the tourist trails, which often follow higher altitudes in the terrain. The aerial surveys showed that the reindeer moved towards higher altitudes when the wind speed was low and the temperature was high both in June and July. In June they moved towards lower regions when temperature was low and the wind speed was strong. The conclusion is that the reindeer use Langfjallet to escape insect harassment and warm weather, even though disturbance by tourism sometimes is high. Abstract in Swedish / Sammanfattning: Habitatval hos tamren (Rangifer tarandus tarandus) undersoktes genom att gora en spillningsinventering och genom att gora flygobservationer fran helikopter. Studien gjordes pa Langfjallet (62˚10’N) i Idre nya sameby och i Mittadalens samebys sommarbetesomrade (62˚50’N, endast flygobservationer). Pa Langfjallet finns det vandringsleder som ar frekventerade av vandrare fran juni manad fram till september. Spillningen visade att renarna foredrog hojderna i omradet samt en del av vegetationstyperna. Det var ocksa mer spillning narmare vandringslederna. Detta kan forklaras av att vandringslederna foljer hojderna i terrangen. Flyginventeringarna under bade juni och juli visade att renarna rorde sig mot hogre terrang nar det var varmt och lugnt vader. I juni rorde dom sig ocksa i lagre terrang nar det var stark vind och kallt vader. Slutsatsen ar att renarna valjer att vistas i hogre terrang for att undvika storningar fran insekter och for att finna svalka trots att det ar mansklig aktivitet i omradet.

Habitat use by semi-domesticated reindeer, estimated with pellet-group counts

Habitat selection theory predicts that herbivores should select for or against different factors at different spatial scales. For instance, quantity of forage is expected to be a strong factor influencing habitat choice at large scales, while forage quality may be important at finer scales. However, during summer, herbivores such as reindeer ( Rangifer tarandus tarandus ) can be limited in their grazing time by insect harassment, and do not always have the possibility to select for high quality forage. Human disturbances from hikers, etc., can also have a limiting effect on the possibility for reindeer to graze in high quality foraging habitats. Reindeer habitat selection at the landscape level was investigated through faecal pellet-group counts during the summers of 2002 and 2003 in two reindeer herding districts in Sweden. Resource utilization functions (RUFs) were developed using multiple linear regressions, where the pellet densities were related to vegetation types, topographic features, distances to tourist resorts, and distances to hiking trails. Validations of the models were performed through cross-validation correlations. Results show that high altitudes with high quality forage were important habitats. Areas that offer both snow patches and fresh forage plants for the reindeer were used in relation to their availability. The reindeer also seemed able to habituate to human intervention to a certain extent. The predictive capabilities of the RUF models were high and pellet-group counts seemed well suited to study how abiotic factors affect the habitat use at large temporal and spatial scales Abstract in Swedish / Sammanfattning: Renens anvandning av sommarbetesomradet, uppskattat med spillningsinventeringar Hierarkiskt habitatval innebar att djur valjer for och emot olika faktorer beroende pa den rumsliga skalan. Mangden bete kan t ex spela stor roll for en vaxtatares habitatval pa en stor skala medan kvaliten pa betet kan ha storre betydelse pa en mindre skala. For renar ( Rangifer tarandus tarandus ), kan betestiden och mojligheten att hitta bra bete sommartid begransas bade pa stor och liten skala pga. storningar fran insekter och mansklig aktivitet. Har studerades renarnas val av betesomrade pa landskapsniva med hjalp av spillningsinventering under somrarna 2002 och 2003 i tva samebyar i Sverige. Spillningstatheten for respektive omrade och ar undersoktes statistiskt med hjalp av multipel linjar regression eller sk ”resource utilisation functions” (RUF). Dar relaterades spillningstatheten till vegetationstyp, olika topografiska faktorer, avstand till vandringsleder, stugplatser och fjallstationer. Resultaten visade att omraden hogt upp i terrangen med hog beteskvalitet var attraktiva. Vegetationstypen moderat snolega som anses ha hog beteskvalitet anvandes av renarna i relation till dess forekomst. Daremot verkade renarna undvika omraden kring valbesokta fjallstugor och fjallstationer medan de daremot t o m foredrog omraden nara vandringsleder. Det kan bero pa att vandringslederna gar genom attraktiva vegetationstyper. RUF-modellerna hade en hog prediktiv formaga vilket visar att spillningsinventeringar ar anvandbara nar man onskar studera hur djuren anvander ett betesomrade i relation till olika faktorer pa en relativt stor rumslig och temporal skala.

Reindeer movement patterns in alpine summer ranges

To evaluate the movement rates of semi-domesticated reindeer (Rangifer tarandus tarandus) during the bare-ground season, we used successive GPS positions from 48 female reindeer. Data were collected during the summers of 2002 and 2003 in two Sámi reindeer herding districts in the Swedish mountains, Handölsdalen, and Sirges. The movement rates were analysed at five different time periods: over the whole season, and over the sub-seasons spring, and early summer, mid summer and early autumn. Variation in movements were analysed in relation to vegetation type, altitude, terrain ruggedness, temperature, wind speed, and proximity to hiking trails. We hypothesised that the foraging quality and different weather conditions is an important factor in determining movement rates. We found that reindeer movement rates were similar between study areas and were dependent on vegetation type and on weather conditions. Studying the circadian movements, in mid summer period when daytime oestrid activity are expected to be high, the reindeer stayed at higher altitudes where food quality was low, but moved to low altitudes at night where the food quality was higher. Therefore, we suggest that oestrid activity forces the reindeer to stay in low-quality vegetation types. Reindeer movements were linked to disturbance in areas of intermediate human activity. We found that in Handölsdalen, where hikers are abundant, the movement rates of reindeer decreased closer to the trails whereas in Sirges, where hikers are less abundant, the movement rates of reindeer increased closer to the trails.

Sea ice, rain-on-snow and tundra reindeer nomadism in Arctic Russia

Sea ice loss is accelerating in the Barents and Kara Seas (BKS). Assessing potential linkages between sea ice retreat/thinning and the regions ancient and unique social–ecological systems is a pressing task. Tundra nomadism remains a vitally important livelihood for indigenous Nenets and their large reindeer herds. Warming summer air temperatures have been linked to more frequent and sustained summer high-pressure systems over West Siberia, Russia, but not to sea ice retreat. At the same time, autumn/winter rain-on-snow (ROS) events have become more frequent and intense. Here, we review evidence for autumn atmospheric warming and precipitation increases over Arctic coastal lands in proximity to BKS ice loss. Two major ROS events during November 2006 and 2013 led to massive winter reindeer mortality episodes on the Yamal Peninsula. Fieldwork with migratory herders has revealed that the ecological and socio-economic impacts from the catastrophic 2013 event will unfold for years to come. The suggested link between sea ice loss, more frequent and intense ROS events and high reindeer mortality has serious implications for the future of tundra Nenets nomadism.

Decay rate of reindeer pellet-groups

Counting of animal faecal pellet groups to estimate habitat use and population densities is a well known method in wildlife research. Using pellet-group counts often require knowledge about the decay rate of the faeces. The decay rate of a faecal pellet group may be different depending on e.g. substrate, size of the pellet group and species. Pellet-group decay rates has been estimated for a number of wildlife species but never before for reindeer ( Rangifer tarandus ). During 2001 to 2005 a field experiment estimating the decay rate of reindeer pellet groups was performed in the Swedish mountains close to Ammarnas. In total the decay rate of 382 pellet groups in three different habitat types (alpine heath, birch forest and spruce forest) was estimated. The slowest decay rate was found in alpine heath and there the pellet groups persisted for at least four years. If decay was assumed to take place only during the bare ground season, the estimated exponential decay rate was -0.027 pellet groups/week in the same habitat. In the forest, the decay was faster and the pellet groups did not persist more than two years. Performing pellet group counts to estimate habitat use in dry habitats, such as alpine heath, I will recommend using the faecal standing crop method. Using this method makes it possible to catch the animals’ general habitat use over several years. Abstract in Swedish / Sammanfattning: Nedbrytningshastighet av renspillning Inom viltforskningen har spillningsinventeringar anvants under flera artionden for att uppskatta habitatval och populationstathet hos olika djurslag. For att kunna anvanda data fran spillningsinventeringar kravs ofta att man vet hur lang tid det tar for spillningen att brytas ner. Nedbrytningshastigheten ar olika beroende pa marktyp och djurslag. Nedbrytningshastighet pa spillning har studerats for bland annat olika typer av hjortdjur, men det har inte studerats pa ren ( Rangifer tarandus ) tidigare. I omradet kring Ammarnas genomfordes under aren 2001- 2005 ett faltexperiment for att uppskatta nedbrytningshastigheten av renspillning. Under tre somrar lades totalt 382 renspillningar ut i hagn i tre olika typer av habitat (fjallhed, fjallbjorkskog och granskog). Det visade sig att nedbrytningshastigheten var langsammast pa fjallheden, dar spillningshogarna fortfarande var kvar efter fyra ar. Den exponentiella nedbrytningshastigheten beraknades till -0.027 hogar/vecka om nedbrytningen antas ske under barmarksperioden. I skogshagnen gick nedbrytningen snabbare och alla hogar var borta inom tva ar. Vid spillningsinventeringar pa kalfjallsomradet eller omraden med liknande marktyp, dar syftet ar att studera djurens habitatval over en langre tid rekommenderas att anvanda den sa kallade ”faecal accumulation rate”-metoden, dar man inventerar orensade ytor. Det ger en generell bild av hur djuren anvant omradet under en langre period, eftersom nedbrytningen av spillning ar langsam i sadana habitat.

Modeling interdependent animal movement in continuous time.

This article presents a new approach to modeling group animal movement in continuous time. The movement of a group of animals is modeled as a multivariate Ornstein Uhlenbeck diffusion process in a high-dimensional space. Each individual of the group is attracted to a leading point which is generally unobserved, and the movement of the leading point is also an Ornstein Uhlenbeck process attracted to an unknown attractor. The Ornstein Uhlenbeck bridge is applied to reconstruct the location of the leading point. All movement parameters are estimated using Markov chain Monte Carlo sampling, specifically a Metropolis Hastings algorithm. We apply the method to a small group of simultaneously tracked reindeer, Rangifer tarandus tarandus, showing that the method detects dependency in movement between individuals.

Bayesian Inference for Continuous Time Animal Movement Based on Steps and Turns

Although animal locations gained via GPS, etc. are typically observed on a discrete time scale, movement models formulated in continuous time are preferable in order to avoid the struggles experienced in discrete time when faced with irregular observations or the prospect of comparing analyses on different time scales. A class of models able to emulate a range of movement ideas are defined by representing movement as a combination of stochastic processes describing both speed and bearing. A method for Bayesian inference for such models is described through the use of a Markov chain Monte Carlo approach. Such inference relies on an augmentation of the animal’s locations in discrete time that have been observed with error, with a more detailed movement path gained via simulation techniques. Analysis of real data on an individual reindeer Rangifer tarandus illustrates the presented methods.

Spatial modeling of data with excessive zeros applied to reindeer pellet‐group counts

Abstract We analyze a real data set pertaining to reindeer fecal pellet‐group counts obtained from a survey conducted in a forest area in northern Sweden. In the data set, over 70% of counts are zeros, and there is high spatial correlation. We use conditionally autoregressive random effects for modeling of spatial correlation in a Poisson generalized linear mixed model (GLMM), quasi‐Poisson hierarchical generalized linear model (HGLM), zero‐inflated Poisson (ZIP), and hurdle models. The quasi‐Poisson HGLM allows for both under‐ and overdispersion with excessive zeros, while the ZIP and hurdle models allow only for overdispersion. In analyzing the real data set, we see that the quasi‐Poisson HGLMs can perform better than the other commonly used models, for example, ordinary Poisson HGLMs, spatial ZIP, and spatial hurdle models, and that the underdispersed Poisson HGLMs with spatial correlation fit the reindeer data best. We develop R codes for fitting these models using a unified algorithm for the HGLMs. Spatial count response with an extremely high proportion of zeros, and underdispersion can be successfully modeled using the quasi‐Poisson HGLM with spatial random effects.

Reindeer habitat use in relation to two small wind farms, during preconstruction, construction, and operation

Abstract Worldwide there is a rush toward wind power development and its associated infrastructure. In Fennoscandia, large‐scale wind farms comprising several hundred windmills are currently built in important grazing ranges used for Sámi reindeer husbandry. In this study, reindeer habitat use was assessed using reindeer fecal pellet group counts in relation to two relatively small wind farms, with 8 and 10 turbines, respectively. In 2009, 1,315 15‐m2 plots were established and pellet groups were counted and cleaned from the plots. This was repeated once a year in May, during preconstruction, construction, and operation of the wind farms, covering 6 years (2009–2014) of reindeer habitat use in the area. We modeled the presence/absence of any pellets in a plot at both the local (wind farm site) and regional (reindeer calving to autumn range) scale with a hierarchical logistic regression, where spatial correlation was accounted for via random effects, using vegetation type, and the interaction between distance to wind turbine and time period as predictor variables. Our results revealed an absolute reduction in pellet groups by 66% and 86% around each wind farm, respectively, at local scale and by 61% at regional scale during the operation phase compared to the preconstruction phase. At the regional, scale habitat use declined close to the turbines in the same comparison. However, at the local scale, we observed increased habitat use close to the wind turbines at one of the wind farms during the operation phase. This may be explained by continued use of an important migration route close to the wind farm. The reduced use at the regional scale nevertheless suggests that there may be an overall avoidance of both wind farms during operation, but further studies of reindeer movement and behavior are needed to gain a better understanding of the mechanisms behind this suggested avoidance.