Search

Annual variation in phenology can have profound effects on the behavior of animals. As climate change advances spring phenology in ecosystems around the globe, it is becoming increasingly important to understand how animals respond to variation in the timing of seasonal events and how their responses may shift in the future. We investigated the influence of spring phenology on the behavior of migratory, barren-ground caribou (Rangifer tarandus), a species that has evolved to cope with short Arctic summers. Specifically, we examined the effect of spring snow melt and vegetation growth on the current and potential future space-use patterns of the Porcupine Caribou Herd (PCH), which exhibits large, inter-annual shifts in their calving and post-calving distributions across the U.S.-Canadian border. We quantified PCH selection for snow melt and vegetation phenology using machine learning models, determined how selection resulted in annual shifts in space-use, and then projected future distributions based on climate-driven phenology models. Caribou exhibited strong, scale-dependent selection for both snow melt and vegetation growth. During the calving season, caribou selected areas at finer scales where the snow had melted and vegetation was greening, but within broader landscapes that were still brown or snow covered. During the post-calving season, they selected vegetation with intermediate biomass expected to have high forage quality. Annual variation in spring phenology predicted major shifts in PCH space-use. In years with early spring phenology, PCH predominately used habitat in Alaska, while in years with late phenology, they spent more time in Yukon. Future climate conditions were projected to advance spring phenology, shifting PCH calving and post-calving distributions further west into Alaska. Our results demonstrate that caribou selection for habitat in specific phenological stages drive dramatic shifts in annual space-use patterns, and will likely affect future distributions, underscoring the importance of maintaining sufficient suitable habitat to allow for behavioral plasticity., (© 2021 The Authors. Global Change Biology published by John Wiley & Sons Ltd. This article has been contributed to by US Government employees and their work is in the public domain in the USA.)

The muskox ( Ovibos moschatus ) population inhabiting the eastern North Slope (ENS) of Alaska, US declined dramatically during 1999-2006, whereas populations in western Alaska (WA) were stable or increasing. To understand morbidity and mortality factors contributing to the decline, Alaska Department of Fish and Game conducted pathologic investigations of carcasses from 2005 until 2008. Additionally, archived sera from both ENS and WA muskoxen collected during 1984-92, before the documented beginning of the ENS decline; sera collected during 2000, near the beginning of the decline; and contemporary sera (from live capture-release, adult females) collected during 2006, 2007, and 2008 were analyzed to determine whether prevalence of antibody to potential pathogens differed in the two areas or changed over time. The pathogens investigated were those that were believed could cause lameness or poor reproduction or adversely affect general health. Furthermore, trace mineral levels, hemograms, and gastrointestinal parasites were evaluated in live adult females captured 2006-08. Pathologic investigations identified several comorbid conditions, including predation, polyarthritis caused by or consistent with Chlamydophila spp. infection, hoof lesions, copper deficiency, contagious ecthyma, verminous pneumonia, hepatic lipidosis suggestive of negative energy balance, and bacterial bronchopneumonia due to Trueperella pyogenes and Bibersteinia trehalosi . Pathogens suspected to be newly introduced in the ENS muskox population on the basis of serologic detection include bovine viral diarrhea, respiratory syncytial virus, Chlamydophila spp., Brucella spp., Coxiella burnetii , and Leptospira spp., whereas parainfluenza virus-3 antibody prevalence has increased in the WA population. Although multiple disease syndromes were identified that contributed to mortality and, in combination, likely limited the ENS muskox population, further holistic investigations of disease agents, trace mineral status, and nutritional factors in conjunction with intensive demographic and environmental analyses would provide a better understanding of factors that influence Alaskan muskox populations.

The desire to see free ranging large carnivores in their natural habitat is a driver of tourism in protected areas around the globe. However, large carnivores are wide-ranging and subject to human-caused mortality outside protected area boundaries. The impact of harvest (trapping or hunting) on wildlife viewing opportunities has been the subject of intense debate and speculation, but quantitative analyses have been lacking. We examined the effect of legal harvest of wolves (Canis lupus) along the boundaries of two North American National Parks, Denali (DNPP) and Yellowstone (YNP), on wolf viewing opportunities within the parks during peak tourist season. We used data on wolf sightings, pack sizes, den site locations, and harvest adjacent to DNPP from 1997-2013 and YNP from 2008-2013 to evaluate the relationship between harvest and wolf viewing opportunities. Although sightings were largely driven by wolf population size and proximity of den sites to roads, sightings in both parks were significantly reduced by harvest. Sightings in YNP increased by 45% following years with no harvest of a wolf from a pack, and sightings in DNPP were more than twice as likely during a period with a harvest buffer zone than in years without the buffer. These findings show that harvest of wolves adjacent to protected areas can reduce sightings within those areas despite minimal impacts on the size of protected wolf populations. Consumptive use of carnivores adjacent to protected areas may therefore reduce their potential for non-consumptive use, and these tradeoffs should be considered when developing regional wildlife management policies.

Migration is an important component of the life history of many animals, but persistence of large-scale terrestrial migrations is being challenged by environmental changes that fragment habitats and create obstacles to animal movements. In northern Alaska, the Central Arctic herd (CAH) of barren-ground caribou (Rangifer tarandus granti) is known to migrate over large distances, but the herd's seasonal distributions and migratory movements are not well documented. From 2003-2007, we used GPS radio-collars to determine seasonal ranges and migration routes of 54 female caribou from the CAH. We calculated Brownian bridges to model fall and spring migrations for each year and used the mean of these over all 4 years to identify areas that were used repeatedly. Annual estimates of sizes of seasonal ranges determined by 90% fixed kernel utilization distributions were similar between summer and winter (X̅ = 27,929 SE = 1,064 and X̅ = 26,585 SE = 4912 km2, respectively). Overlap between consecutive summer and winter ranges varied from 3.3-18.3%. Percent overlap between summer ranges used during consecutive years (X̅ = 62.4% SE = 3.7%) was higher than for winter ranges (X̅ = 42.8% SE = 5.9%). Caribou used multiple migration routes each year, but some areas were used by caribou during all years, suggesting that these areas should be managed to allow for continued utilization by caribou. Restoring migration routes after they have been disturbed or fragmented is challenging. However, prior knowledge of movements and threats may facilitate maintenance of migratory paths and seasonal ranges necessary for long-term persistence of migratory species.

We present a case of pericardial tamponade caused by hypothyroidism. A 66-year-old man presented with acute chest pain radiating to the back. Computed tomography ruled out an aortic dissection but revealed a large pericardial effusion, which was confirmed on transthoracic echocardiography showing features of tamponade. The effusion was drained and subsequent thyroid function tests showed profound hypothyroidism. No other cause of the pericardial effusion could be identified. Despite the prompt initiation of levothyroxine (T4) replacement therapy, the effusion re-accumulated over a period of 10 days and required further drainage. Following that, aggressive thyroxine replacement therapy using liothyronine (T3) was initiated and there was no further re-accumulation. Hypothyroidism should be suspected in any cases of pericardial effusion where the cause is not obvious. We should be vigilant of re-accumulation, and T3 replacement therapy should be considered in that situation.