Saturday, March 9, 2024

Bald eagles eat prairie dogs?

We all know that bald eagles like fish. Few of us, however, picture them soaring over grasslands seeking out prairie dog snacks. In a new paper from the Journal of Raptor Research, lead author Courtney Duchardt and coauthors make the case that prairie dogs are an important resource for at least four species of raptors overwintering in the Southern Great Plains, bald eagles included. Their paper, titled “Overwintering Raptor Abundance and Community Composition in Relation to Prairie Dog Colonies in the Southern Great Plains,” explains the first broad scale look into the relationship between prairie dogs and their aerial predators, and illuminates an important trophic interaction with implications for raptor conservation through the lens of climate change.

 

Grasslands across North America have shrunk significantly since the 1970’s, and for those remaining, habitat quality is a far cry from what it used to be. Since the ‘90’s, the total population of grassland birds across North America has decreased by 53%, illustrating the link between grassland health and bird abundance. Grassland raptors, with their large spatial requirements, likely suffer graver consequences from these reductions in habitat quality than other birds.

 

Duchardt, from the Department of Natural Resource Ecology and Management at Oklahoma State University, and her colleagues, provide strong evidence that the stability and predictability of prairie dog colonies provides an important prey source for overwintering raptors across the Southwest Great Plains. Between 1998 and 2002 the research team conducted winter road surveys in Arizona, Colorado, New Mexico, Texas, and the Mexican state of Chihuahua. Their results were illuminating — nine raptor species occurred in tandem with prairie dog colonies. Notably, bald eagles and rough-legged hawks were included in this pattern, even though they don’t often encounter prairie dogs on their breeding grounds. However, as Duchardt points out, “prairie dogs are perfectly sized raptor-snacks,” so it makes sense that both species would see them as caloric jackpots.

 

Climate change could alter cycles of prairie dog reproduction. Already, variation in climate norms has increased the occurrence of plague among colonial breeding rodents like prairie dogs. If raptors feed on prairie dogs as often as this new study suggests, these shifts in prairie dog availability could push raptors to range further for food. The further they range, the more often they encounter dangers like wind turbines, which have been shown to negatively affect golden eagles and ferruginous hawks. This is of special concern for juvenile raptor which have a hard enough time during their first year of life without added stressors.

 

An obvious next step is to prioritize protection of prairie dog colonies in areas where raptors are associating with them as a prey source. However, supporting prairie dogs for the sake of raptor health is politically tricky. “Prairie dogs are contentious and seen as pests in most parts of their range. However, their role as a keystone species helps to demonstrate that, even though there are conflicts, they are important,” says Duchardt. “To support raptors wintering in the Southern Plains, we need to consider prairie dog management.”

 

Raptors are bioindicators, meaning they serve as proxies for habitat health, and they play a key part in naturally supporting ecosystem functioning as top predators on the landscape. Even with the reality of human-prairie dog conflict, there are pathways forward. “Ranching can be compatible with diverse wildlife communities because many of the wildlife co-evolved with bison, and sustainable ranching can replicate that,” says Duchardt. Using innovative management tools and educating the public on the importance of prairie dogs and raptors in these regions, Duchardt is optimistic that a middle ground can be found — one that allows bald eagles to munch on prairie dogs for years to come.

Tuesday, January 23, 2024

Yellowstone - wolf pack v bison standoff

 


Final results:



Wolves and elk are (mostly) welcome back

 


In Poland and Germany’s Oder Delta region, survey shows

Survey shows positive attitudes towards rewilding in the Oder Delta region, but finds locals’ feelings are mixed.

Peer-Reviewed Publication

GERMAN CENTRE FOR INTEGRATIVE BIODIVERSITY RESEARCH (IDIV) HALLE-JENA-LEIPZIG

Oder Delta 

IMAGE: 

THE ODER DELTA AREA COMPRISES DIVERSE NATURAL HABITATS AND IS PARTICULARLY SUITABLE FOR THE NATURAL COMEBACK OF WILDLIFE.

view more 

CREDIT: SANDEEP SHARMA

An online survey conducted in Germany and Poland shows that large parts of the participants support the return of large carnivores and herbivores, such as wolves and elk, to the Oder Delta region, according to a study published in People and Nature. Presented with different rewilding scenarios, the majority of survey participants showed a preference for land management that leads to the comeback of nature to the most natural state possible. Locals, on the other hand, showed some reservations.

In recent years, the concept of rewilding has captured the attention of conservationists, who see it as a promising and cost-effective tool to combat biodiversity loss and restore ecosystems. The Oder Delta area, which spans the northern border between Germany and Poland, is particularly suitable for the natural comeback of wildlife. It comprises diverse natural habitats, like riparian forests, standing- and flowing waters, open and semi-open inland dunes, and heathlands, and is surrounded by diverse landscapes of forests, rivers, and wetlands.

To measure public sentiment towards rewilding in the Oder Delta, a team of researchers led by the German Centre for Integrative Biodiversity Research (iDiv) and the Martin Luther University Halle-Wittenberg (MLU) carried out an online, choice experiment survey. Given the geographic position of the area across both Germany and Poland, the survey offered a unique opportunity to investigate differences in attitudes between the two countries. Approximately 1,000 respondents from each country were presented with different scenarios describing the ecological status of the Oder Delta in 2050 as a result of various management interventions. The scenarios included, for example, the conditions of rivers and forests and the presence of large animals such as elk, lynx, or wolves. Beyond the “status quo” option, an intensification of land use in the region, respondents were presented with two alternative scenarios with varying biodiversity benefits.

Importantly, only the status quo option came at no additional cost. The two alternative options were associated with tax payments to fund the necessary interventions, meaning that respondents were faced with a trade-off: an increase in nature benefits went hand in hand with an increase in taxes. “This allowed us to calculate the respondents’ willingness to pay for different management interventions in the Oder Delta region”, says lead author Rowan Dunn-Capper from iDiv and MLU. “This helps us understand broader preferences for rewilding”.

Strong preferences for rewilding

The study revealed a significant appetite for rewilding initiatives at the national scale, particularly for the presence of large animals, such as wolves, lynx, elk, and bison in the Oder Delta. Willingness to pay for scenarios in which large animal species were present was almost three times larger than for restoring the most natural landscape elements. “To find such preference was surprising given the often-negative portrayal of large animal species, notably the wolf, in the popular media”, says Dunn-Capper. “It suggests the public may be more welcoming of wildlife return than first thought”. This preference was also true for forests and agriculture: respondents in Germany as well as in Poland had a strong preference for the most natural rewilding levels with minimum human intervention on the ecosystem. Additionally, the fact that results for Germany and Poland were broadly comparable indicates that preferences for rewilding hold across political and cultural contexts.

Locals are less enthusiastic about rewilding

Survey participants living near the Oder Delta (within 100km) did not show the same appetite for rewilding initiatives. Local respondents showed a preference for large herbivores, such as elk and bison, but were less enthusiastic about the presence of large carnivores, like wolves. Similarly, local respondents showed contrasting preferences for certain rewilding interventions in rivers and agricultural landscapes compared to the national sample. For example, a significant share of local respondents were not willing to pay for scenarios in which flooding regimes were fully restored in the Oder Delta. “This underscores the intricacies of conservation planning and highlights the importance of local input to foster biodiversity democracy, this is the management of natural resources as a democratic process”, says senior author Professor Henrique Pereira, head of Biodiversity Conservation at MLU and iDiv. “Generally, our findings support rewilding as a novel ecosystem restoration approach that has public acceptance to become mainstream across Europe.”


Thursday, January 11, 2024

Red deer populations in Europe: more influenced by humans than by wolves and other predators

 

Alongside the occasional bison and elk, red deer are Europe's largest native wild animal. An international study led by wildlife ecologists from the University of Freiburg has now investigated the factors that affect the red deer population in a particular area. The researchers were able to show that the population density of the animals in Europe is primarily influenced by human hunting and land use and not by large predators such as wolves, lynx and brown bears. “While large carnivores are often considered key factors in controlling prey populations in undisturbed ecosystems, this is less visible in human-dominated landscapes. Our study illustrates that these interactions are context-dependent,” says Dr. Suzanne T. S. van Beeck Calkoen, former PhD student at the Chair of Wildlife Ecology and Management at the University of Freiburg and first author of the study.

The researchers collected data on the population density of red deer at over 492 study sites in 28 European countries and analysed the influence of various factors such as habitat productivity, the presence of large carnivores, human activities, climatic variables and the protection status of the area. The evaluation of the data showed that human hunting reduced red deer density more than the presence of all large carnivores. Human land use, on the other hand, led to an increase in red deer density. In most cases, the presence of large carnivores had no statistically significant effect on the red deer population. Only when the three predators wolf, lynx and bear occurred together in one area did the number of red deer decrease. However, the study published in the Journal of Applied Ecology did not investigate how the presence of predators affects the behavior of red deer.

The return of the wolf
The study also sheds new light on the ongoing debate about the return of the wolf to Central Europe, notes Prof. Dr. Marco Heurich, Professor of Wildlife Ecology and Conservation Biology at the Faculty of Environment and Natural Resources at the University of Freiburg and initiator of the study. “Our research shows that the return of a large carnivore such as the wolf alone does not have a major impact on the occurrence of red deer. This is because in Central Europe, human influences predominate both indirectly through interventions in the red deer’s habitat and directly through the killing of the animals.” In addition, the mortality rate of wolves in Central European landscapes is very high, mainly due to road traffic, which further limits their influence on prey populations. “However, we also found a high variability in red deer densities, which indicates that there may be specific situations in which large carnivores do have an impact. Investigating this will be the task of future studies,” states Heurich.


    Wednesday, December 13, 2023

    Boosting beaver populations could have toxic consequences

     


    Study suggests boosting beaver populations could have toxic consequences 

    IMAGE: 

    CLIFFORD ADAMCHAK'S BOAT WITH SAMPLING EQUIPMENT IN A BEAVER POND IN CRESTED BUTTE, COLORADO. 

    view more 

    CREDIT: CLIFFORD ADAMCHAK/CU BOULDER

    Beavers are influential animals in ecosystems. These dam-building, tree-chewing rodents change streamflow with their wooden barriers and create rich wetland habitats by diverting water into soils near rivers. They help conserve water and improve biodiversity. 

    But a preliminary study by CU Boulder researchers suggests that beaver activities in the Western U.S. may exacerbate the spread of mercury-containing toxins in rivers and the surrounding habitats. Clifford Adamchak, a Ph.D. student in the Department of Ecology and Evolutionary Biology presented the team’s findings Tuesday at the 2023 meeting of the American Geophysical Union in San Francisco.

    “In a world where beavers are increasingly being seen as an effective means to achieve various conservation and restoration goals, there is a possibility that we would see an abnormally large flush of methylmercury if we were to reintroduce beavers in the Western U.S. on a larger scale,” said Adamchak.  “So it is important to better understand the impacts of their activities.”   

    Beavers were once ubiquitous in North American streams before Europeans arrived in the region. The animal’s population then plummeted because of hunting and habitat loss. 

    Research has shown that beavers change the environment significantly, especially over longer timescales, and can provide various environmental benefits. By building dams and trapping water in their ponds, they help to replenish groundwater supplies and maintain wetland habitats for other species. Beaver ponds also help cool the water and mitigate the spread of wildfires, some increasingly significant benefits as climate change heats up the planet and intensifies wildfires in the Western U.S. As a result, several states, including California, Colorado and Oregon are exploring the idea of releasing more beavers to boost populations.

    But beaver ponds, because they lack oxygen, are a hot spot for bacteria that can generate mercury-containing neurotoxins. 

    “A stream that flows smoothly with nothing stopping it would have very different biological chemical and geological processes than a stream that has cascading beaver dams and ponds,” said Adamchak. “Beaver activities also impact the surrounding landscape, because the animals forage for woody vegetation on land.” 

    Human activities, including coal burning and mining, emit mercury into the atmosphere. The mineral then gets into lakes and streams through rain and snow. In water, chemical reactions and certain bacteria transform the mineral into methylmercury, a toxic organic compound that can build up in organisms and travel down the food chain. For example, when a bear eats a fish containing methylmercury, the neurotoxin will accumulate in the bear’s body. Studies have shown consuming large amounts of methylmercury-containing food can lead to mercury poisoning and nervous system damage in humans. 

    While atmospheric mercury levels in the Eastern U.S. have decreased over the years because of emission reduction efforts, the levels in the Western U.S., have remained constant or even slightly elevated. 

    Adamchak and the team set off to investigate whether increased beaver activities—partly due to reintroduction efforts—have led to a rise in methylmercury levels in the Western U.S. water. 

    Over the past summer, Adamchak visited several beaver ponds in California and Colorado, taking more than 300 samples of water and sediment from the ponds and their surrounding environment. He found that the methylmercury levels in the water of beaver ponds were very low, whereas the levels in the sediment— the soil and sand at the bottom and around the ponds—were very high. This suggests that the toxins might be accumulating in the sediment, rather than the water. 

    In addition, Adamchak found that the sediment around the ponds, where water periodically submerges, had the highest methylmercury levels. This implies that beavers could spread the mercury-containing neurotoxin in the surrounding landscape. 

    The research is still in its early stages, and Adamchak said it’s unclear to what degree methylmercury can affect the wetland ecosystem as a result of beaver activities. But researchers are concerned that as beavers move around the river corridor across their lifespans and abandon old ponds, more vegetation may grow in areas with high methylmercury concentrations in the soil and get passed on to organisms that feed on them.  

    Fortunately, previous studies have shown beaver ponds tend to have higher methylmercury concentrations when they are new, and the levels decrease significantly with age. “That suggests beavers probably don’t have overwhelmingly negative effects on the ecosystem. But at this point it’s very hard to say if more beaver activities are good or bad in terms of mercury levels,” Adamchak said.

    Adamchak planned to revisit these ponds next year to collect more data. He will also investigate if the age of the ponds or seasons influence the methylmercury levels in the ponds.
     

    Friday, November 17, 2023

    The return of the grey wolf (Canis lupus) to Germany,

    The return of the grey wolf (Canis lupus) to Germany, which began 23 years ago in the region of Lusatia in Eastern Germany, is a process of great ecological and social significance. Therefore, a precise understanding of the recolonisation of the original habitat by the grey wolf and a reliable prediction of its future potential distribution are highly valuable. A detailed comparison of different approaches to spatial modelling using 20 years of distribution data now unravelled the complexity of the recolonisation process. A team led by scientists from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) shows in a paper in the scientific journal Diversity and Distributions that grey wolf habitat selection changed from the early (when they cherry-pick the finest locations) to late phases of recolonisation (when they are much less selective) in a particular area. These results are a refinement of the team’s earlier habitat modelling from 2020, originally published by the Federal Agency for Nature Conservation.

    Grey wolves prefer habitats with plenty of cover at a substantial distance from people, their settlements and roads. These preferences were demonstrated during their return to Germany in the 21st century, when they recolonised the habitat from which they had been extinguished 200 years earlier. Knowledge of such habitat requirements and associated preferences also allows predicting the further expansion of their current range in Germany in the future. In 2020, the Federal Agency for Nature Conservation (BfN), in collaboration with a scientific team from the Department of Ecological Dynamics at the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW), published a study on modelling suitable habitats.  In this study, the team calculated that there could potentially be space for around 700 to 1,400 wolf territories in Germany's natural areas. The scientists have now taken a closer look and tested a variety of approaches to spatio-temporal modelling with regard to different phases of recolonisation.

    “There is reason to believe that the recolonisation of Germany by the grey wolf is not a so-called stationary process, but is characterised by changing framework conditions”, explains Prof Stephanie Kramer-Schadt, Head of the Department of Ecological Dynamics at the Leibniz-IZW. “Stationary processes in this case would mean that the wolves find the same or very similar environmental conditions in the regions into which they newly enter – and that they respond to the environmental conditions in the same way during all phases of the process.” Both assumptions appeared to be doubtful in the case of the recolonisation of Germany by the grey wolf. On the one hand, eastern Germany and the Rhine-Ruhr area in the west, for example, considerably differ in terms of the density of human infrastructure. On the other hand, wolves may show different or varying degrees of habitat preferences depending on whether they move in during the early, first phase or during the late, saturation phase of recolonisation.

    “These questions are highly relevant for the quality of the predictions”, says first author Dr Aimara Planillo, a scientist at Kramer-Schadt's department at the IZW. “If models are developed on the basis of the specific environmental conditions of a particular region, they could underestimate the suitability of another, very different region to which such a model might be applied. At the same time, models created with data from early recolonisation phases may underestimate the suitability of habitats during the late phases – because the wolves during the early phase have a free choice to cherry-pick particular places and habitats and thus appear to be considerably more selective than they will be during the later phases. The reverse is also true: data from late recolonisation phases might suggest that wolves appear to be less selective, which is why the selectivity of their choice and use of habitats in newly colonised areas would probably be underestimated.”

    This investigation was conducted by a team led by Dr Planillo and Prof Kramer-Schadt, in collaboration with scientists from LUPUS – the German Institute for Wolf Monitoring and Research –, the Eberswalde University for Sustainable Development, the Technical Universities of Dresden and Berlin, the Humboldt University Berlin, the Federal Agency for Nature Conservation and the University of Veterinary Medicine Vienna. They tested a variety of modern modelling methods and algorithms with data from more than 20 years of wolf monitoring in Germany with particular attention to the potential pitfalls arising from the actual dynamics of the recolonization process. They developed the models on the basis of a combination of radio telemetry and observation data and tested how well they could predict subsequent phases of the colonisation process. “The new models confirmed our previous work in two ways”, conclude Planillo and Kramer-Schadt. “On the one hand, our projections from 2020 were proven to be largely accurate. Secondly, the sometimes significant differences to model forecasts of the various spatial phases of the process show that it is indeed non-stationary”, say the authors. “When recolonising an area, wolves always secure the best habitats first. It therefore appears that they are considerably more sensitive to environmental variables. Neighbouring second class sites are colonised just as reliably in later phases, as we were able to demonstrate in many regions of eastern Germany.” The team was thus able to validate their predictions and refine them in a more differentiated manner. “Spatio-temporal projections of habitats of expanding species should be carried out with great caution”, they conclude.

    The most important factors for habitats to be suitable for wolves are close proximity to forests or cover-rich areas and a large distance from roads. The best habitats for wolves are found in the north and northeast as well as in the south of Germany, whereas habitats of lower quality tend to be found in the west. In the south of Bavaria and in some forest areas of central Germany (in the Harz Mountains as well as in the Spessart, Odenwald and Rhön), larger habitats of high quality are still unoccupied by wolves at the time the team ran the analysis. It is likely that the first wolves to arrive there will first settle in prime locations – which by now has already happened according to the most recent data – and colonise medium-quality locations over time. “With regards to our latest modelling and similar experiences from other European countries, where habitats of lower quality are also used permanently when wolf densities are high, previous habitat modelling tends to be too conservative”, says Kramer-Schadt. “However, they provide a good spatial forecast for the initial colonisation of new habitats.”

    Wednesday, November 1, 2023

    Wolves hunting and killing sea otters and harbor seals on Alaska’s Katmai coast


    Peer-Reviewed Publication

    OREGON STATE UNIVERSITY

    Wolf and otter 

    IMAGE: 

    WOLF WITH A SEA OTTER ON ALASKA'S KATMAI COAST.

    view more 

    CREDIT: KELSEY GRIFFIN

    CORVALLIS, Ore. – Firsthand observations of a wolf hunting and killing a harbor seal and a group of wolves hunting and consuming a sea otter on Alaska’s Katmai coast have led scientists to reconsider assumptions about wolf hunting behavior.

    Wolves have previously been observed consuming sea otter carcasses, but how they obtain these and the frequency of scavenging versus hunting marine prey is largely unknown. Scientists at Oregon State University, the National Park Service and Alaska Department of Fish and Game are beginning to change that with a paper just published in Ecology.

    In the paper, they describe several incidents they observed involving wolves and marine mammals in Katmai National Park that they believe haven’t been previously documented:

    • In 2016 the researchers witnessed a male wolf hunt and kill a harbor seal. The wolf was positioned near the mouth of a creek when it charged into the water, grabbing the tail of the harbor seal. The wolf continued to tear into the flesh of the seal’s tail and after an approximate 30-minute struggle, the seal appeared to tire, straining to lift its head above water. The wolf dragged the seal onto the exposed sandbar and began to tear into the existing wound and consume the tail.
    • On three separate days in 2016, 2018 and 2019 the scientists and others observed wolves carrying sea otter carcasses.
    • In 2021, the researchers watched three wolves hunt and eat an adult sea otter on an island during a low tide. They watched the wolves travel to the island, then lost sight of them for about one minute and then saw them reappear carrying a limp sea otter. They fed on the carcass for about 60 minutes. Once the wolves left, the researchers examined the kill site and found an area of concentrated blood where the sea otter was likely killed. The presence of blood indicates the sea otter had been alive when ambushed by the wolves, as opposed to being scavenged, the researchers note. 

    “This is really exciting documentation of behaviors we believe have never been directly observed by scientists,” said Ellen Dymit, a doctoral student at Oregon State. “It kind of forces us to reconsider the assumptions that underlie a lot of our management decisions and modeling around wolf populations and populations of their prey, which often assume that wolves depend on ungulates, like moose and elk.”

    The research project originated in 2016 when Kelsey Griffin, a National Park Service biologist, and some of her colleagues stopped for lunch on the beach during a day of conducting marine debris and bird mortality surveys at Katmai National Park.

    “Seemingly out of nowhere, we are sitting there, we just see this white wolf carrying an otter just trotting by,” Griffin said. “What? I was just blown away. I have never seen anything like that before.

    “Then I was asking my co-workers: ‘Has anyone seen this before? Do wolves often eat sea otters?’ I was just asking a bunch of questions about the wolves and it just seemed like there was not a whole lot of information about them. That was the initial observation. I just got lucky. Wolves on the Katmai coast have never been studied and our research highlights the unique role wolves play in nearshore ecosystems in Alaska” 

    Griffin connected with Gretchen Roffler, a biologist with Alaska Department of Fish and Game, who introduced Griffin to Taal Levi, a professor at Oregon State and Dymit’s advisor.

    The project builds on work by Roffler, Levi and others on wolves and sea otters on Pleasant Island, an island landscape adjacent to Glacier Bay about 40 miles west of Juneau and hundreds of miles east of Katmai across the Gulf of Alaska.

    In a paper published earlier this year, they found wolves on Pleasant Island caused a deer population to plummet and switched to primarily eating sea otters in just a few years. They believe this is the first case of sea otters becoming the primary food source for a land-based predator.

    Future papers will include analysis of wolves and sea otters from Lake Clark National Park, Glacier Bay National Park and Kenai Fjords National Park, in addition to Katmai. The research team plans to look at how sea otter density impacts the diets of wolves and variations of wolf diet on a pack level versus and individual level.