Major decline in marine and terrestrial animal consumption by brown bears (Ursus arctos)

Historical Field Records Reveal Habitat as an Ecological Correlate of Locomotor Phenotypic Diversity in the Radiation of Neotropical Geophagini Fishes

AbstractPhenotypic macroevolutionary studies provide insight into how ecological processes shape biodiversity. However, the complexity of phenotype-ecology relationships underscores the importance of also validating phenotype-based ecological inference with direct evidence of resource use. Unfortunately, macroevolutionary-scale ecological studies are often hindered by the challenges of acquiring taxonomically and spatially representative ecological data for large and widely distributed clades. The South American cichlid fish tribe Geophagini represents a continentally distributed radiation whose early locomotor morphological divergence suggests habitat as one ecological correlate of diversification, but an association between locomotor traits and habitat preference has not been corroborated. Field notes accumulated over decades of collecting across South America provide firsthand environmental records that can be mined for habitat data in support of macroevolutionary ecological research. In this study, we applied a newly developed method to transform descriptive field note information into quantitative habitat data and used it to assess habitat preference and its relationship to locomotor morphology in Geophagini. Field note-derived data shed light on geophagine habitat use patterns and reinforced habitat as an ecological correlate of locomotor morphological diversity. Our work emphasizes the rich data potential of museum collections, including often-overlooked material such as field notes, for evolutionary and ecological research.

Brown bear digging decreases tree growth: Implication for ecological role of top predators in anthropogenic landscapes

Large carnivores have recently increased in number and recolonized in human-dominated landscapes; however, their ecological roles in these landscapes have not been well studied. In the Shiretoko World Heritage (SWH) site, brown bears have recolonized a previously abandoned mosaic landscape of natural forests and conifer plantations after land abandonment. We previously reported that the bears had recently begun to dig for cicada nymphs in association with the creation of larch plantations. As a result, this digging activity decreased soil nutrients. To deepen the understanding of the novel ecological role of brown bears within human-modified landscapes, we examined the impacts of brown bear digging on the growth of larch trees. We found that brown bear digging decreased fine root biomass of larch, soil water, and nitrogen availability. Brown bear digging negatively affected needle nitrogen content, but not carbon isotope ratios, a water stress index of trees. Tree ring data suggest that digging negatively affected the radial growth of larches. The results imply that digging decreases tree growth due to limited soil nitrogen uptake. Our findings indicate that the ecological roles of large carnivores may differ between natural and anthropogenic landscapes.

Seed dispersal function of the brown bear Ursus arctos on Hokkaido Island in northern Japan: gut passage time, dispersal distance, germination, and effects of remaining pulp

Megafauna are important seed dispersers because they can disperse large quantities of seeds over long distances. In Hokkaido, Japan, the largest terrestrial animal is the brown bear (Ursus arctos) and other megafauna seed dispersers are lacking. Thus, brown bears are expected to have an important function as seed dispersers in Hokkaido. In this study, we, for the first time, evaluated the seed dispersal function of brown bears in Hokkaido using three fleshy-fruited trees and studied: (1) gut passage time (GPT) in feeding experiments, (2) seed dispersal distance using tracking data of wild bears, and (3) the effect of gut passage and pulp removal on germination rate. Most seeds were defecated intact, and less than 6% were broken. The average GPT without pulp was 3 h and 56 min to 6 h and 13 min, depending on the plant and trial. Each plant's average simulated seed dispersal distance was 202-512 m. The dispersal distance of Actinidia arguta seeds with pulp was significantly longer than those without pulp because of their longer GPT. The germination rate of defecated seeds without pulp was 19-51%, depending on the plant, and was significantly higher or not different comparing with that of seeds with pulp. We concluded that brown bears in Hokkaido are effective seed dispersers. In managing brown bears in Hokkaido, such ecological functions should be considered along with conserving the bear population and reducing human-bear conflicts.

Coupled social and ecological change drove the historical extinction of the California grizzly bear (Ursus arctos californicus)

Large carnivores (order Carnivora) are among the world's most threatened mammals due to a confluence of ecological and social forces that have unfolded over centuries. Combining specimens from natural history collections with documents from archival records, we reconstructed the factors surrounding the extinction of the California grizzly bear (Ursus arctos californicus), a once-abundant brown bear subspecies last seen in 1924. Historical documents portrayed California grizzlies as massive hypercarnivores that endangered public safety. Yet, morphological measurements on skulls and teeth generate smaller body size estimates in alignment with extant North American grizzly populations (approx. 200 kg). Stable isotope analysis (δ13C, δ15N) of pelts and bones (n = 57) revealed that grizzlies derived less than 10% of their nutrition from terrestrial animal sources and were therefore largely herbivorous for millennia prior to the first European arrival in this region in 1542. Later colonial land uses, beginning in 1769 with the Mission era, led grizzlies to moderately increase animal protein consumption (up to 26% of diet), but grizzlies still consumed far less livestock than otherwise claimed by contemporary accounts. We show how human activities can provoke short-term behavioural shifts, such as heightened levels of carnivory, that in turn can lead to exaggerated predation narratives and incentivize persecution, triggering rapid loss of an otherwise widespread and ecologically flexible animal.

Mammal communities of primeval forests as sentinels of global change

Understanding the drivers and consequences of global environmental change is crucial to inform predictions of effects on ecosystems. We used the mammal community of Białowieża Forest, the last lowland near-primeval forest in temperate Europe, as a sentinel of global change. We analyzed changes in stable carbon (δ13 C) and nitrogen (δ15 N) isotope values of hair in 687 specimens from 50 mammal species across seven decades (1946-2011). We classified mammals into four taxonomic-dietary groups (herbivores, carnivores, insectivores, and bats). We found a significant negative trend in hair δ15 N for the mammal community, particularly strong for herbivores. This trend is consistent with temporal patterns in nitrogen deposition from (15 N depleted) industrial fertilizers and fossil fuel emissions. It is also in line with global-scale declines in δ15 N reported in forests and other unfertilized, non-urban terrestrial ecosystems and with local decreases in N foliar concentrations. The global depletion of 13 C content in atmospheric CO2 due to fossil fuel burning (Suess effect) was detected in all groups. After correcting for this effect, the hair δ13 C trend became non-significant for both community and groups, except for bats, which showed a strong decline in δ13 C. This could be related to an increase in the relative abundance of freshwater insects taken by bats or increased use of methane-derived carbon in food webs used by bats. This work is the first broad-scale and long-term mammal isotope ecology study in a near-primeval forest in temperate Europe. Mammal communities from natural forests represent a unique benchmark in global change research; investigating their isotopic temporal variation can help identify patterns and early detections of ecosystem changes and provide more comprehensive and integrative assessments than single species approaches.

Trichinella T9 in wild bears in Japan: Prevalence, species/genotype identification, and public health implications

In Japan, the recent series of sporadic outbreaks of human trichinellosis caused by Trichinella (Nematoda: Trichocephalida) has occurred owing to the consumption of raw or insufficiently cooked meat from wild bears. However, the infection status and molecular characteristics of Trichinella larvae in Japanese wild bears remain poorly understood. This study investigated the prevalence of Trichinella spp. in brown bears (Ursus arctos) from Hokkaido, and Japanese black bears (Ursus thibetanus japonicus) from three prefectures (Aomori, Akita, and Iwate) in northern Japan, between April 2019 and August 2022. Trichinella larvae were detected in 2.5% (6/236) of the brown bears and 0.9% (1/117) of the Japanese black bears. Sequence analysis using two genetic loci, the internal transcribed spacer region of nuclear ribosomal DNA and the mitochondrial cytochrome c oxidase subunit I gene, revealed that the larvae collected from the seven infected bears were identical to one of the two haplotypes of Trichinella T9. The prevalence of Trichinella T9 is low but is maintained in bears in the Hokkaido and Iwate prefectures suggesting that undercooked meat from these animals could cause human infection. Thus, continued health education campaigns are needed to raise awareness of the potential risk of trichinellosis among hunters, meat suppliers, consumers, and local governmental health agencies.

Clair CC. Inter-population differences in coyote diet and niche width along an urban–suburban–rural gradient

Many generalist species thrive in urban environments by supplementing their diets with anthropogenic food, which creates numerous challenges for managing urban wildlife. Management could be advanced with more information on how spatial and temporal variation in habitat use by urban animals predicts variation in their dietary ecology. In this study, we used stable isotope analysis complemented with GPS collar location data to determine how diet composition and the dietary niche of coyotes (Canis latrans) varied across a sample of 169 individuals collected along an urban-to-rural gradient in Alberta, Canada. We further categorized urban individuals as either matrix (frequent use of developed areas) or greenspace (use of natural areas) via GPS locations. Matrix coyotes were isotopically distinct from all other coyote populations: they had the largest dietary niche, exhibited the most among-individual variation in diet, consumed the most anthropogenic food and fruit, and consumed the least amount of prey. Greenspace coyotes consumed more anthropogenic food than rural and suburban coyotes but otherwise exhibited similar niche width, among-individual heterogeneity, and prey consumption. We further tested for seasonal dietary variation and found that urban coyotes had a larger dietary niche during the summer, when they also consumed more anthropogenic food. Our conclusions were robust to our choice of mixing model parameters, including discrimination factors, suggesting that these methodological choices have limited effect when discerning relative trends among populations. Overall, our results suggest that management of urban coyotes should target the food sources accessible to coyotes in the urban matrix to reduce human–coyote conflict.

Community Ecology and Conservation of Bear-Salmon Ecosystems

Apex predators play keystone roles in ecosystems through top-down control, but the effects of apex omnivores on ecosystems could be more varied because changes in the resource base alter their densities and reverberate through ecosystems in complex ways. In coastal temperate ecosystems throughout much of the Northern Hemisphere, anadromous salmon once supported abundant bear populations, but both taxa have declined or been extirpated from large parts of their former ranges with limited research on the consequences of diminished or absent interactions among species. Here we review the biogeography of bear-salmon interactions and the role of salmon-subsidized bears in (1) resource provisioning to plants and scavengers through the distribution of salmon carcasses, (2) competition among bears and other large carnivores, (3) predation of ungulate neonates, (4) seed dispersal, and (5) resource subsidies to rodents with seed-filled scats. In addition to our review of the literature, we present original data to demonstrate two community-level patterns that are currently unexplained. First, deer densities appear to be consistently higher on islands with abundant brown bears than adjacent islands with black bears and wolves, and moose calf survival is higher at low bear densities (<∼25 bears per 100 km2) but is constant across the vast majority of bear densities found in the wild (i.e., ∼>25 bears per 100 km2). Our review and empirical data highlight key knowledge gaps and research opportunities to understand the complex ecosystem effects related to bear-salmon interactions.

Testing for a predicted decrease in body size in brown bears (Ursus arctos) based on a historical shift in diet

A recent study found a historical decline in the proportion of meat in the diet of brown bears (Ursus arctos L., 1758) in the Hokkaido Islands, Japan. Because feeding habits are strongly correlated with the body size of animals, the shift in diet should have led to a decrease in the size of these bears. To predict the effects of this dietary shift on the skeletal size in bears, we correlated the femur length in Hokkaido brown bears with the carbon and nitrogen stable isotope values from bone samples and predicted the historical change in their body size. The variation in the femur lengths of the male and female subpopulations was positively correlated with their δ15N values, but not with their δ13C values, and the explanatory power of the constructed model was higher in males than in females. Based on the model and the δ15N values for historic and modern bears, the skeletal size of bear subpopulations in eastern Hokkaido was estimated to have decreased by 10%–18% for males and 8%–9% for females. Our results suggest that a historical dietary shift caused the decrease in the size of the Hokkaido brown bears.