Reproduction and Survival of Yellowstone Bison

ABSTRACT The conservation of bison (Bison bison) from near extinction to >4,000 animals in Yellowstone National Park has led to conflict regarding overabundance and potential transmission of brucellosis (Brucella abortus) to cattle. We estimated survival and birth rates from 53 radiocollared adult female bison during 1995–2001, and we used calf:adult (C:A) ratios to estimate reproduction with the combined effects of pregnancy, fetal loss, and neonatal mortality during 1970–1997. Annual survival of adult females was high (0.92; 95% CI = 0.87-0.95) and constant. Birth rates differed by brucellosis status and age. Birth rates were 0.40 calves per female (95% CI = 0.15-0.65) for brucellosis-positive 3 year olds, 0.63 (95% CI = 0.39-0.87) for individuals testing negative, and 0.10 (95% CI = 0.00-0.24) for individuals contracting brucellosis that birth year (sero-converters). Birth rates were 0.64 (95% CI = 0.52-0.76) for brucellosis-positive individuals ≥4 years old, 0.81 (95% CI = 0.73-0.89) for brucellosis-negative individuals, and 0.22 (95% CI = 0.00-0.46) for sero-converters. Spring C:A ratios were negatively correlated with snow pack (β = −0.01 to −0.03, R² = 0.26-0.60, P < 0.05). Growth rate was highly elastic to adult survival (0.51), and juvenile survival (0.36) was 3 times more elastic than fecundity (0.12). Simulations suggested brucellosis eradication via vaccination would result in increased birth rates and a 29% increase in population growth (γ = 1.09), possibly leading to more bison movements outside the park. Our results will help park managers evaluate bison population dynamics and explore consequences of management actions and disease control programs.     

Hot spots for nitrous oxide emissions found in different types of permafrost peatlands

Recent findings on large nitrous oxide (N₂O) emissions from permafrost peatlands have shown that tundra soils can support high N₂O release, which is on the contrary to what was thought previously. However, field data on this topic have been very limited, and the spatial and temporal extent of the phenomenon has not been known. To address this question, we studied N₂O dynamics in two types of subarctic permafrost peatlands, a peat plateau in Russia and three palsa mires in Finland, including also adjacent upland soils. The peatlands studied have surfaces that are uplifted by frost (palsas and peat plateaus) and partly unvegetated as a result of wind erosion and frost action. Unvegetated peat surfaces with high N₂O emissions were found from all the studied peatlands. Very high N₂O emissions were measured from peat circles at the Russian site (1.40±0.15 g N₂O m^?2 yr^?1). Elevated, sparsely vegetated peat mounds at the same site had significantly lower N₂O release. The N₂O emissions from bare palsa surfaces in Northern Finland were highly variable but reached high rates, similar to those measured from the peat circles. All the vegetated soils studied had negligible N₂O release. At the bare peat surfaces, the large N₂O emissions were supported by the absence of plant N uptake, the low C : N ratio of the peat, the relatively high gross N mineralization rate and favourable moisture content, together increasing availability of mineral N for N₂O production. We hypothesize that frost heave is crucial for high N₂O emissions, since it lifts the peat above the water table, increasing oxygen availability and making it vulnerable to the the physical processes that may remove the vegetation cover. In the future, permafrost thawing may change the distribution of wet and dry surfaces in permafrost peatlands, which will affect N₂O emissions.     

Occurrence of Peronospora sparsa (P. rubi) on cultivated and wild Rubus species in Finland and Sweden

An outbreak of a dryberry disease caused by Peronospora sparsa (syn. P. rubi) occurred in plantations of arctic bramble (Rubus arcticus subsp. arcticus) in Finland in the middle of 1990s. The disease persists and is most severe in cool and rainy summers. The disease has not been encountered in northern Sweden where cultivars (R. arcticus nothosubsp. stellarcticus) different from those in Finland are used. The occurrence of P. sparsa in wild Rubus spp. is virtually unknown in both areas and it is not known whether they constitute a potential infection source. Therefore, the aim of this study was to investigate the occurrence of P. sparsa on wild Rubus spp. growing in the vicinity of cultivations of arctic bramble. Symptomatic plants were sampled in 1997–1999. P. sparsa was detected using a light microscope, preceded by incubation of the sample in vitro if necessary, and by a polymerase chain reaction (PCR) based method. Plants of cultivated R. arcticus subsp. arcticus were commonly infected by P. sparsa in Finland. P. sparsa was also found on the cultivated R. arcticus nothosubsp. stellarcticus in Finland and Sweden. However, the infected plants of the cultivars of nothosubsp. stellarcticus seemed to be much less damaged than the cultivars of subsp. arcticus. Plants infected with P. sparsa were found in the populations of wild R. arcticus subsp. arcticus in both countries, and in cloudberry (R. chamaemorus) in natural habitats in Finland. In addition, P. sparsa was detected on specimens of R. arcticus subsp. arcticus (collected in 1966–1985) and R. chamaemorus (collected in 1899–1981) in Finnish herbaria. The samples of R. idaeus and R. saxatilis collected from the field in this study or investigated in the herbaria were not infected with P. sparsa. These data show that P. sparsa has not recently invaded Finland but has become an economically significant pathogen during the rapid expansion of cultivation of the apparently sensitive clones of arctic bramble.     

Comparison of Endocrine Response to Stress Between Captive-Raised and Wild-Caught Bighorn Sheep

ABSTRACT Stress hormones in Rocky Mountain bighorn sheep (Ovis canadensis canadensis), produced in response to environmental changes, road development, or high population density, may impact their immune systems to a threshold level that predisposes them to periodic, large-scale mortality. We compared the stress response to a novel environmental situation and repeated handling between bighorn sheep born and raised in captivity (CR) and bighorn sheep born in the wild (WC) and brought into captivity. We measured plasma epinephrine, norepinephrine, cortisol, and fecal glucocorticoid metabolites (FGM). Three weeks after each group's arrival we used a one-time drop-net event to elicit an acute stress response, and we collected blood samples from each sheep over 35 minutes, as well as one fecal sample. We collected blood and fecal samples from both groups on 7 other occasions over the subsequent 6 months. We also collected fecal samples from the pen at approximately 24-hour intervals for 3 days following every handling event to monitor the stress response to handling. We found that CR sheep had a stronger autonomic nervous system response than WC sheep, as measured by epinephrine and norepinephrine levels, but we found a very similar hypothalamic-pituitary–adrenal axis (HPA) response, measured by cortisol levels, to the acute stress event of a drop-net restraint. We also found that once the WC sheep had acclimated, as indicated by the return to the initial baseline FGM levels within 12 weeks, the CR and WC groups' HPA responses to sampling events were not significantly different from one another. Fecal samples can provide a noninvasive mechanism for managers to monitor baseline FGM for a given herd. Using long-term monitoring of FGM rather than values from a single point in time may allow managers to correlate these levels to outside influences on the herd and better understand the impacts of management changes, population density, or increased human developments on the health of the sheep population.