Rangifer

Are trampling effects by wild tundra reindeer understudied?

2019-04-17T09:42:06+02:00

Grazing and trampling by the wide-ranging wild tundra reindeer may have major top down landscape effects by causing vegetation changes. Grazing, as the collective effect of eating, trampling, defecation, and urination, has been studied extensively. In contrast, trampling effects per se are rarely studied, and almost never quantified, even though considered very important. The main reason appears to be methodological; effects of trampling imprints are difficult to measure and quantify systematically. In particular, in winter reindeer may largely subsist on slow-growing ground lichens. They grow in habitats with little snow cover and extensive soil frost, and dry lichen may be particularly susceptible to trampling, generating a likely substantial forage loss.

Does connectivity exist for remnant boreal caribou (Rangifer tarandus caribou) along the Lake Superior Coastal Range? Options for landscape restoration

2019-04-17T09:42:05+02:00

Genetic analysis can provide important information on the dynamic and spatial structure of groups of animals or populations. Little is known of the genetic population structure of caribou that inhabit the Lake Superior Coastal Range (LSCR) and the level of gene flow between individuals within the range and beyond. From a landscape perspective, this range is spatially isolated and genetic connectivity within the range is presumed limited due to large water crossings on Lake Superior. This study aims to answer if animal movement can be discerned, using genetic population and relatedness analyses, within and beyond the LSCR. Faecal and hair samples collected between 2005 and 2015 in Pukaskwa National Park were analyzed for genetic markers and compared to 131 unique genotypes previously obtained from both within the LSCR and in the two next closest ranges. Animals from one nearshore island (i.e. Otter) were more closely associated with offshore islands than other mainland caribou, likely a result of past movement and translocation rather than ongoing movement. Conversely, on another nearshore island (i.e. Pic), individuals assigned to a different genetic cluster and were related to animals further north outside the range, demonstrating some connectivity through the discontinuous distribution to the coast. Long-term population declines have been observed in the LSCR range despite genetic connectivity within the range and relatively low total habitat disturbance. Restoring connectivity of the LSCR so that it is not isolated from populations to the north is required for the recovery of the mainland portion of the coastal range. These genetic analyses provide some insights on where movements may occur and where landscape restoration efforts may best be directed to enhance connectivity.

Early fall and late winter diets of migratory caribou in northwest Alaska

2019-04-17T09:42:03+02:00

Lichens are the primary winter forage for large herds of migratory caribou (Rangifer tarandus). Caribou select for lichens more than they are available across the landscape and they generally avoid, during winter, habitat that has been burned by wildfires for decades while lichen abundance recovers. However, the relative importance of lichens in the diet is subject to debate. From 2010-2013, we conducted one of the largest microhistological studies of the early fall (58 samples from 1 site) and late winter (338 samples from 58 sites) diets of barren-ground caribou. Lichens constituted ~ 71% of the late winter diets of caribou in northwest Alaska, whereas moss (11%) and shrubs (9%) were the next most common forage items. Early fall diets were very similar to late winter, perhaps because deciduous vegetation is senescent during both periods. Diets of males, non-pregnant females and pregnant females were not significantly different. Pregnancy was not associated with the abundance of any forage type during winter but was associated with higher physiological stress. This result was expected as fall body condition dictates conception, caribou are ‘capital’ breeders, and gestation can be energetically demanding. Caribou that migrated south (i.e., wintered south of 67.1°N) had lower levels of nutritional stress, higher levels of lichen in the diet, and lower levels of moss and shrubs compared to caribou that did not migrate south. Future investigations into the potential connection between lichen abundance in the winter diet and survivorship, as well as linking the late summer diets of individuals to their reproductive success, should be undertaken.

Estimates of caribou herd size using post-calving surveys in the Northwest Territories and Nunavut, Canada: A meta-analysis

2019-04-17T09:42:02+02:00

Post-calving surveys to estimate herd size of barren-ground caribou (Rangifer tarandus groenlandicus, R. t. granti, and R. t. caribou) have been used for caribou herds in Alaska, Yukon, Northwest Territories, Nunavut, and Québec/Labrador. The main field procedure uses relocation of collared caribou to locate aggregated groups of hundreds or thousands of caribou during times of high insect harassment that usually occur in July. These groups are then photographed to obtain a count of the caribou in the aggregated groups. Often some caribou are missed, and the count of caribou may be a negatively biased estimate of total herd size, unless a high proportion of the herd is found and photographed. To address this, some previous studies have used the Lincoln-Petersen estimator, which estimates the proportion of the herd counted based on the percentage of available collared caribou found during the survey. However, this estimator assumes equal probabilities of all groups of caribou being found, regardless of group size and the numbers of collared caribou in the group. These assumptions may not be valid, as larger groups are more likely to be found than smaller groups, particularly if there are several collared caribou present. This may lead to estimates that are biased low, along with an estimate of variance that may also be biased low. A two phase estimator developed by Rivest et al., in 1998 became available in R statistical software in 2012. We analyzed 20 data sets from post-calving surveys in the NWT and NU carried out between 2000 and 2015 using the Rivest estimator to explore working characteristics of this estimator. We compared the Rivest estimates with Lincoln-Petersen estimates and total counts on each survey. We considered factors that influence precision of the Rivest estimator with a focus on sampling factors such as the proportion of collars found, the number of collars available, and natural factors such as the degree of aggregation of caribou in each survey (as indexed by the negative binomial dispersion parameter). In general, the Rivest estimator displayed acceptable precision when high proportions of caribou groups with collars were detected and counted, collar numbers were sufficient, and aggregation was adequate. Notable exceptions occurred in years of lower aggregation which resulted in many small groups with 0 or few collared caribou, and in these cases herd estimates had large variances and low precision. Estimates from the Rivest estimator, Lincoln-Petersen estimator, and total counts converged when sampling effort was high, collar numbers relative to herd size were high, and caribou were well aggregated in a limited number of groups. In other cases, estimates of the Rivest estimator were generally higher than Lincoln-Petersen estimates, presumably due to negative bias with the Lincoln-Petersen estimator. We provide a set of working recommendations to optimize field sampling to ensure reliable estimates of herd size using post-calving methods.

Eigil Reimers; Våre Hjortedyr – en bok til undring, glede og kunnskap

2019-04-17T09:41:59+02:00

Morten Tryland & Susan J. Kutz (Eds.); Reindeer and Caribou: Health and Disease

2019-04-17T09:42:01+02:00