Transportation corridors can attract threatened wildlife via habitat enhancement and foraging opportunities, leading to collisions with vehicles. But wildlife may also be attracted to energy-dense food products that are spilled or discarded from moving vehicles, which is rarely studied. Therefore, we quantified train-spilled attractants in Banff and Yoho National Parks, Canada, where agricultural products (hereafter, grain) are transported along 134 km of railway and may contribute to wildlife mortality. We measured grain deposition from 2012 to 2015 at 19 sites and assessed the performance of three structures developed to measure spilled grain. We then modeled grain deposition with respect to four types of spatial and temporal variables: those related to grain shipment, physical habitat characteristic, train-related characteristics and variables specific to the study site. Grain was spilled at a mean rate of 1.64 g m À2 day À1 (SD = 3.60) from April to October (n = 3 years) and 1.52(SD = 2.37) from November to March (n = 1 year). Extrapolating annual deposition across the study area yielded enough grain (110 tons) to provide 4.77 9 10 8 kcal of gross energy, which is equivalent to the average annual caloric needs of 42-54 grizzly bears Ursus arctos horribilis; the regional population is estimated at 50-73 animals. Much of this energy will not be accessible or available to bears; however, their attraction to it could contribute to rising and unsustainable rates of mortality. Models explained 9-31% of the variance in deposition for each grain type, primarily via coarse temporal variables of shipping rates and month. The absence of more specific predictive variables suggests that mitigation should target broader policies, such as prompt reporting and repair of leaky hopper cars, and limits to train stoppage in protected areas. We encourage more global assessment of the under-studied issue of food attractants spilled by vehicles along transportation corridors.

Induction of the p21(WAF1) protein (hereafter called p21) following genotoxic stress is known to inhibit proliferating cell nuclear antigen (PCNA)-dependent DNA repair, downregulate apoptosis, and trigger a sustained growth-arrested phenotype called accelerated senescence. Studies with immortalized human and murine cell lines have revealed that exposure to ultraviolet light (UVC; 254 nm) results in the degradation of p21 to facilitate DNA repair and promote cell survival, or may lead to apoptotic cell death. The objective of the present study was to determine whether exposure of non-transformed human fibroblast strains to relatively low fluences of UVC (i.e., fluences typically used in the clonogenic survival assay) might induce sustained nuclear accumulation of p21, leading to accelerated senescence. We have evaluated the responses of normal human fibroblast (NHF) strains and nucleotide excision repair (NER)-deficient fibroblast strains representing xeroderma pigmentosum (XP) complementation groups A and G and Cockayne syndrome (CS) complementation groups A and B. We report that exposure of NHFs to < or =15 J/m(2) of UVC, and NER-deficient fibroblasts to < or =5 J/m(2) of UVC, results in sustained nuclear accumulation of p21 and growth arrest through accelerated senescence. With each fibroblast strain examined, exposure to UVC fluences that resulted in approximately 90% loss of clonogenic potential triggered significant (>60%) accelerated senescence, but only marginal (<5%) apoptosis. We conclude that nuclear accumulation of p21 accompanied by accelerated senescence may be an integral component of the response of human fibroblasts to UVC-induced DNA damage, irrespective of their DNA repair capabilities.

Transportation infrastructure can cause an ecological trap if it attracts wildlife for foraging and travel opportunities, while increasing the risk of mortality from collisions. This situation occurs for a vulnerable population of grizzly bears ( Ursus arctos ) in Banff National Park, Canada, where train strikes have become a leading cause of mortality. We explored this problem with analyses of rail-associated food attractants, habitat use of GPS-collared bears and patterns of past mortality. Bears appeared to be attracted to grain spilled from rail cars, enhanced growth of adjacent vegetation and train-killed ungulates with rail use that increased in spring and autumn, and in areas where trains slowed, topography was rugged, and human density was low. However, areas with higher grain deposits or greater use by bears did not predict sites of past mortality. The onset of reported train strikes occurred amid several other interacting changes in this landscape, including the cessation of lethal bear management, changes in the distribution and abundance of ungulates, increasing human use and new anthropogenic features. We posit that rapid learning by bears is critical to their persistence in this landscape and that this capacity might be enhanced to prevent train strikes in future with simple warning devices, such as the one we invented, that signal approaching trains. This article is part of the theme issue ‘Linking behaviour to dynamics of populations and communities: application of novel approaches in behavioural ecology to conservation’.

Citation: Pollock, S. Z., S. E. Nielsen, and C. C. . A railway increases the abundance and accelerates the phenology of bear-attracting plants in a forested, mountain park. Ecosphere 8(10):e01985. 10. 1002/ecs2.1985 Abstract. Vegetation enhancement along railways has not been well studied, despite high rates of mortality from train strikes across numerous species, including sensitive populations in protected areas. This situation describes grizzly bears (Ursus arctos) in the mountain parks of Canada, where train strikes have become the leading source of known mortality. We hypothesized that attraction by bears to railways occurs partly because of increases in the richness, diversity, cover, and maturation rate of plants consumed by bears relative to adjacent forest and that this effect may increase with elevation. We quantified and compared responses in plants used by bears to the railway (ballast), forest edge, and within adjacent forest for two growing seasons (May-October) at 19 locations spanning an elevational gradient in Banff and Yoho National Parks in the Canadian Rocky Mountains. Overall, richness, diversity, and total cover of plants consumed by bears were greatest at the forest edge. On the forest edge or ballast, flowering rates of some species were over three times higher and fruit occurrence was up to five times higher than 50 m into the adjacent forest. Enhancement of berry productivity along rail edges increased with elevation. Buffaloberry (Shepherdia canadensis), an important regional pre-hibernation resource, had more fruit, faster ripening, and higher sugar content for shrubs located within 15 m of the rail than within surrounding interior forest. Our results demonstrate that railway edges can increase the quantity and quality of palatable vegetation resources of both native and introduced species, potentially increasing strike risk for bears and other wildlife. Potential mitigation of this risk could include removal of attractants along the rail, particularly at locations where other factors increase the risk of collisions, and creation of forest openings, either through natural processes or through forest modification that would provide forage in less risky habitats.

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