Roger Bergström

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.

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.

Felled Scots pine (Pinus sylvestris) as supplemental forage for moose (Alces alces): Browse availability and utilization

Abstract Old trees felled by forestry actions or natural disturbances can supply large herbivores with a substantial amount of forage and thereby potentially affect browsing patterns. To explore the felling of mature Scots pine (Pinus sylvestris L.) as a management practice (and potentially divert moose from young pine forests) this study identified how much browse there is available on felled trees and to what extent this browse is used by moose (Alces alces L.). Pine trees were surveyed in two study areas in Sweden and one in Norway. Pine crowns from thinning-stage trees held on average 8 kg of potential moose forage (dry weight). Corresponding figures for mature trees and seed trees were 29 kg and 12 kg, respectively. When the trees were processed during commercial felling, much of the potential forage became unavailable, and only approximately 1.5 kg per tree was available for moose after processing. The utilization of the forage on felled trees ranged between 5 and 15%. No significant difference in utilization between tree ages or between tops and bases within the tree crowns were found. However, the bite diameters on twigs differed between parts and age stages of the trees. This study illustrates that felling of trees can influence the availability of winter forage for moose and thereby has the potential to decrease browsing pressure on young forest stands. The substantial effect that storms can have on short-term forage supply for moose is also emphasized.

Response of moose hunters to predation following wolf return in Sweden.

Background Predation and hunter harvest constitute the main mortality factors affecting the size and dynamics of many exploited populations. The re-colonization by wolves (Canis lupus) of the Scandinavian Peninsula may therefore substantially reduce hunter harvest of moose (Alces alces), the main prey of wolves. Methodology/Principal findings We examined possible effects of wolf presence on hunter harvest in areas where we had data before and after wolf establishment (n = 25), and in additional areas that had been continuously exposed to wolf predation during at least ten years (n = 43). There was a general reduction in the total number of moose harvested (n = 31,827) during the ten year study period in all areas irrespective of presence of wolves or not. However, the reduction in hunter harvest was stronger within wolf territories compared to control areas without wolves. The reduction in harvest was larger in small (500-800 km2) compared to large (1,200-1,800 km2) wolf territories. In areas with newly established wolf territories moose management appeared to be adaptive with regard to both managers (hunting quotas) and to hunters (actual harvest). In these areas an instant reduction in moose harvest over-compensated the estimated number of moose killed annually by wolves and the composition of the hunted animals changed towards a lower proportion of adult females. Conclusions/Significance We show that the re-colonization of wolves may result in an almost instant functional response by another large predator—humans—that reduced the potential for a direct numerical effect on the density of wolves’ main prey, the moose. Because most of the worlds’ habitat that will be available for future colonization by large predators are likely to be strongly influenced by humans, human behavioural responses may constitute a key trait that govern the impact of large predators on their prey.

Summer browsing by moose on Scots pine

Abstract Moose (Alces alces L.) browse Scots pine (Pinus sylvestris L.) mainly during the winter. There is a growing concern also regarding summer browsing by moose on Scots pine. We studied summer browsing on Scots pine during two consecutive years. In a survey of 47 stands in 2003, current summer browsing was found for 20.4% of the Scots pine main stems, and on almost half of them (9.8%) the top shoot was browsed. This indicates that the pine damage causing reduced wood quality was as serious during summer as during the preceding winter. There was significantly more summer browsing on previously browsed pines, compared to a random use, both at tree and stand level, and summer browsing was also spatially clumped within stands. Browsing on top shoots occurred up to a height of 2.8 m, whereas side shoot browsing was recorded for pines with a height up to 4.8 m. In 2004, 11 of the 47 stands were randomly selected for a more detailed study of pines browsed during that summer. The summer browsed trees contained, on average, 114 current shoots tree−1, and 10.5 shoots tree−1 (9.2%) were browsed. In this area, summer browsing may explain a considerable part of the moose-related forest damage recorded. The proportion of pines subjected to summer browsing did not change with availability of pines. Hence, increasing the number of Scots pine trees in young stands may be a way to increase the number of unbrowsed pine trees at a given moose population density.

Browsing by large herbivores on Scots pine (Pinus sylvestris) seedlings in mixture with ash (Fraxinus excelsior) or silver birch (Betula pendula)

Abstract Food selection by large herbivores occurs at a hierarchy of scales, for example landscape, patch or plant. Several hypotheses regarding food plant selection on patch or plant level have been developed. In this cafeteria-type design field experiment, conducted during one winter immediately after planting, we tested the effect of species mixture on browsing by large herbivores (mainly roe deer) on Scots pine seedlings in mixture with seedlings of ash (highly preferred) or silver birch (less preferred). Browsing on Scots pine was not affected by species mixture, neither in terms of the number of browsed pines nor browsing intensity. Instead, browsed biomass was positively and significantly correlated to the total biomass available for browsing. Also, there were differences due to species, with ash being most browsed (44.6%), followed by Scots pine (18.9%) and silver birch (11.6%). Browsed biomass per browsed seedling, however, was largest for Scots pine. In addition, browsed seedlings were initially taller compared to unbrowsed seedlings for all species. The main management implication in this study is that the species mixture did not influence large herbivore browsing on Scots pine seedlings. Hence, removing or discouraging more (or less) attractive browse species in early stages of pine regeneration activities seems unnecessary from the point of large herbivore browsing.