Yellowstone wolf study reveals how to raise successful offspring

What are the key ingredients to raising successful, self-sufficient offspring? A new life sciences study using 14 years of data on gray wolves in Yellowstone National Park indicates that cooperative group behavior and a mother's weight are crucial. "A female's body weight is key in the survival of her offspring, and cooperation in the protection and feeding of young pups pays off in terms of the production of offspring," said Robert Wayne, a professor of ecology and evolutionary biology at UCLA and co-author of the new research, published this week in the online edition of the Journal of Animal Ecology. Wolves are social carnivores that live in territorial, kin-structured packs. Female wolves depend on other adults in the pack to help them provide food for their pups and defend the youngsters from predators — mainly, competing packs of wolves. The greater the group cooperation, the researchers say, the better the pack's survival advantage. "Consequently, larger packs tend to get larger and win the 'arms race' of holding territories against the aggressive actions of other packs," Wayne said. "Large packs get better at building armies of soldiers to defend their turf, and cooperative behavior and sociality are maintained by natural selection." Wolves were re-introduced into Yellowstone Park in the mid-1990s and are rapidly becoming one of the best-studied carnivore populations in the world; they are turning out to be an excellent model for the study of sociality and cooperation, Wayne said. Over many years of intensive collaborative study, former UCLA graduate student Dan Stahler (now a biologist with the National Park Service) and former UCLA postdoctoral scholar Bridgett vonHoldt (who worked in Wayne's laboratory and will soon become an assistant professor at Princeton University) analyzed genetic and life-history data on more than 300 gray wolves. They assessed survivorship and reproductive success, as well as the factors that influenced them, including body weight and pack size, among other variables. They found a striking association between pack size, body weight and offspring survival. "We discovered that mother wolves' body weight and pack size play a crucial role in enabling pups to survive and thrive from birth to young adulthood," said Utah State University assistant professor of wildlife resources Dan MacNulty, a co-author of the study. The research was funded by the National Science Foundation, the National Park Service and the Yellowstone Park Foundation, as well as private donors. Environmental conditions that impact wolf reproduction, the researchers say, include resource availability, population density and disease prevalence — especially deadly canine distemper, caused by a contagious virus to which pups are especially vulnerable. In addition to body weight and pack size, the researchers examined the effects of maternal age and color (gray or black coat) and wolf population size on reproductive success. "Each of these factors affects reproduction, but, overwhelmingly, female body weight and pack size are the main drivers of litter size and pup survival," said Stahler, the study's lead author. "Bigger females produce bigger litters; bigger packs are better equipped to hunt and defend pups and resources from competitors."

Group Dynamics of Yellowstone Pronghorn

The American pronghorn in the Yellowstone region have proven to be gregarious animals. Observations of group dynamics have found their interactions to be influenced by social, reproductive, and environmental factors. Pronghorn were also found to be somewhat unpredictable, making it more challenging to develop conservation strategies for this species. A study published in the Journal of Mammalogy reported about tracking the locations of 53 adult female pronghorn fitted with VHF and GPS radio collars in Yellowstone National Park for nearly 6 years. The Yellowstone population of pronghorn is a native species of special concern. They number fewer than 300, and are one of only a few pronghorn migrations remaining in the greater Yellowstone region. Observing changes in how animals behave as groups can give clues to the influence of environmental and human factors on their survival. The American pronghorn displays flexibility in behaviors of grouping and mating that could indicate resilience to changes in the environment, but this flexibility can make it difficult to create management strategies for the population. Grouping patterns of pronghorn change due to availability of food, density and demographic variables within the group, and human factors such as fencing and hunting. In this study, females switched groups frequently, and groups became smaller when females were giving birth and rearing their young. Snow pack and the number of predators also affected group sizes and cohesion, but habitat and vegetation had less influence. Examination of Yellowstone pronghorn found that they favor lower elevations during the winter, avoiding deep snow. Building on this information, the National Park Service has undertaken restoration efforts to ensure that native vegetation and migration routes to these favored areas are re-established. Conservation efforts seek to control disease, protect or restore key habitat, regulate harvests, and limit adverse effects of development and recreation. When planning the timing and location for conservation actions, biologists must consider what this grouping behavior can reveal about the species. Full text of “Group Dynamics of Yellowstone Pronghorn,” Journal of Mammalogy, Vol. 93, No. 4, 2012, is available at http://asmjournals.org/.

Wolf mange part of nature's cycle

Mange and viral diseases have a substantial, recurring impact on the health and size of reintroduced wolf packs living in Yellowstone National Park, according to ecologists.

Following the restoration of gray wolves to Yellowstone in 1996, researchers collected blood from the animals to monitor parasite-induced disease and death. They also tracked the wolves in each pack to follow their survival and allow additional data-gathering.

"Many invasive species flourish because they lack their native predators and pathogens, but in Yellowstone we restored a native predator to an ecosystem that had other canids present that were capable of sustaining a lot of infections in their absence," said Emily S. Almberg, graduate student in ecology, Penn State. "It's not terribly surprising that we were able to witness and confirm that there was a relatively short window in which the reintroduced wolves stayed disease-free."

The researchers found that within a year after the wolves were reintroduced to Yellowstone, 100 percent of the wolves tested had at least one infection, but mange did not infect wolves living in the park until 2007.

"We can look at the biology of the diseases and predict which ones will come in first," said Peter J. Hudson, Willaman Professor of Biology and director of the Huck Institutes of the Life Sciences, Penn State. "What was surprising was that so many diseases came in so fast, but those were the ones we expected to come in first. It wasn't really a sequence, they were almost there immediately. That's very interesting in itself. "

The diseases that infected the wolves quickly were all viral, including canine distemper and canine parvovirus -- both contractible through bodily secretions. Mange, however, is a skin infection, caused by scabies mites, that makes the wolves scratch and lose fur. An infected wolf can lose enough body heat in the winter to freeze to death. Mange is spread by direct contact with another mite-infected animal or by contact with the mites themselves, as they can survive away from a host for several days, depending on the temperature.

"Where did those diseases come from?" asked Hudson. "Most of them initially came from other canid species, like coyotes or foxes. Wolves are animals that disperse far and move around fast, and once the wolves were established the diseases were spread from pack to pack."

Almberg and Hudson tracked how quickly mange spread from pack to pack after the disease entered the population. The number of infected wolves in a pack did not affect the likelihood of a neighboring pack to contract mange, but distance was a factor -- for every six miles of distance between an infected pack and an uninfected pack, there was a 66 percent drop in risk for the uninfected pack. Some wolves and packs were not severely affected by mange, while other packs were decimated, the researchers report in the current issue of Philosophical Transactions of the Royal Society B.

In January 2007, Mollie's pack was the first in Yellowstone to show signs of mange infection. As of March 2011, they had recovered. The Druid pack, which had been one of the most stable and visible packs in the park, according to Almberg, started to show signs of mange in August 2009.

"It was in a very short amount of time that the majority of the animals [in Druid] became severely infected," Almberg said. "The majority of their hair was missing from their bodies and it hit them right in the middle of winter. The summer before it got really bad, we saw that many of the pups had mange."

The Druid pack was gone by the end of the winter in 2010.

The researchers note that the wolf population in Yellowstone experienced several phases -- from 1995 to 2003 the wolves experienced rapid growth, from 2003 to 2007 the number of wolves stabilized, and the most recent data from 2007 to 2010 shows a decline.

"We're down to extremely low levels of wolves right now, we're down to [similar numbers as] the early years of reintroduction," said Almberg. "So it doesn't look like it's going to be as large and as a stable a population as was maybe initially thought."

Do beavers benefit Scottish wild salmon?

Reintroduced European beavers could have an overall positive impact on wild salmon populations in Scotland, according to a study by the University of Southampton.

Representatives of recreational fisheries interests north and south of the border are concerned that beavers can harm economically important fish stocks due to their dam building activities and potential to block migratory life phases. However, results of a study conducted by scientists at the University of Southampton, funded by Scottish Natural Heritage, indicate that beavers can also have substantial beneficial effects which may outweigh those that are negative.

The study's findings highlight that while the activities of beavers can result in localised and often temporary negative impacts on fish, primarily due to dams impeding their movements and reducing the availability of suitable spawning habitat, these can be at least off-set by the benefits of increased habitat diversity and resulting abundance and productivity of fish, including salmon.

Dr Paul Kemp, a researcher in freshwater fish ecology and fisheries management from the University's International Centre for Ecohydraulics Research, who lesd the study comments that, "the positive findings were more frequently based on quantitative evidence, while discussion of negative impacts was often speculative."

Dr Kemp and his colleagues were surprised that the "weight of evidence" tended to indicate an overall positive effect considering the background of those who participated in the survey. "Most participants were from a fisheries background and whom you might expect would tend to side with the fish, but based on their experience of beaver and fish interactions tended to be positive towards beaver," he says.

Beaver reintroduction has been a contentious issue in Scotland ever since a total of 16 individuals from Norway were released in Argyll in 2009 and 2010 as part of a scientific trial conducted by the Scottish Wildlife Trust, The Royal Zoological Society of Scotland, and the host partners, the Forestry Commission Scotland.

Even more controversy surrounds the establishment of a breeding population of escaped beavers on the River Tay. This has had ramifications south of the border as the Angling Trust has written to Richard Benyon, the UK minister for Fisheries and the Natural Environment, requesting that trapping and destruction of the beavers be urgently undertaken to prevent their spread to England where it is claimed they could damage fisheries.

Researchers carried out a critical view of over 100 sources of peer-reviewed information in which benefits were cited 184 times compared to 119 for the negative effects. Analysis of existing literature indicates that beaver activity can have both positive and negative effects on fish. Negative effects relate to the construction of beaver dams which can temporarily impede the movement of some fish, particularly in narrow rivers and streams, while siltation can cause loss of spawning habitat immediately upstream of dams. But beavers can also have beneficial effects on fish by increasing the variety and area of habitats in streams, and due to the presence of dams and ponds by increasing the abundance of invertebrates, which form the main component of the diet of many stream-dwelling fish, and providing refuge during periods of high or low water flows.

The study, which was published in the leading international fisheries journal Fish and Fisheries, also reports the findings of an expert opinion survey of 49 fisheries managers, scientists, and beaver ecology experts, from Europe and North America, where most of the research has been conducted. More than half (58 per cent) of those who responded believed that the overall impact of beavers on fish populations was positive.

Professor Roger Wheater, the Chair of the Beaver-Salmonid Working Group, says: "I would be very surprised if biodiversity were not increased but our concern continues to be the impact on salmonid spawning areas and the management required to deal with situations where salmonids in any particular system are at risk."

Bears, scavengers count on all-you-can-eat salmon buffet lasting for months

Salmon conservation shouldn't narrowly focus on managing flows in streams and rivers or on preserving only places that currently have strong salmon runs.

Instead, watersheds need a good mix of steep, cold-running streams and slower, meandering streams of warmer water to keep options open for salmon adapted to reproduce better in one setting than the other, new research shows. Preserving that sort of varied landscape serves not just salmon, it provides an all-summer buffet that brown bears, gulls and other animals need to sustain themselves the rest of the year.

"In any one stream, salmon might spawn for two to four weeks," said Peter Lisi, a University of Washington doctoral student in aquatic and fishery sciences, who studies the Wood River watershed in southwest Alaska.

"Animals like coastal brown bears and Glaucus-winged gulls gorge themselves at one stream for a few weeks and then just move to another stream that might have water temperatures a few degrees warmer and therefore support salmon populations that spawn at a later time," he said. "It's easy for animals to move when such streams are as little as a mile or two apart."

"A whole network of streams, some colder and some warmer, provides what Lisi and Daniel Schindler, UW professor of aquatic and fishery sciences, call "hydrological diversity." Such diversity more than triples the time predators have access to salmon in a summer, from just a few weeks to more than three months in the watershed studied.

The researchers' paper on landscape attributes that influence spawn times will be presented Aug. 8 in Portland, Ore., during the Ecological Society of America's annual meeting.

"Both Glaucus-winged gulls and brown bears have very short growing seasons at high latitudes. Salmon are a key resource that allows these species to fatten up and achieve the necessary annual growth in this short period of time," Schindler said. "A complex landscape results in streams of differing temperature so salmon populations don't spawn at the same time. Predators and scavengers have a much longer window of accessibility."

"We knew that salmon are an important seasonal resource for lots of predators and consumers. However, there is little appreciation for the importance of biological diversity within salmon for these consumers."

The response of salmon to hydrologic diversity is what makes stocks viable over time and will probably make them better able to respond to climate change, Lisi said. Instead of focusing narrowly on flow regimes or trying to decide which individual streams and rivers to protect, a better goal would be to protect a wide range of hydrologic conditions, the co-authors said.

""Biological diversity within salmon stocks has important benefits to terrestrial ecosystems," Schindler said. "This scale of variation in hydrology, geomorphology and biological diversity is often swept under the rug and dismissed as unimportant in activities such as river restoration, projections of climate impacts and fishery management."

The paper, part of a session on linkages between aquatic and terrestrial systems, also describes how biological diversity in returning salmon are linked to the pollination of a flowering plant, something no other group has described.

Populations of kneeling angelica, 3-to-6-foot plants loaded with clusters of tiny white blossoms, don't all bloom at the same time, even though sun and weather conditions might be uniform across a watershed. Instead, these streamside plants have evolved to bloom approximately 10 days after salmon typically arrive at a particular stream.

It takes about that long for salmon to start to die, many of which are killed by bears or die naturally after spawning. Blowflies lay eggs on the carcasses and the result is a population boom of maggots to take advantage of all the dead salmon. Those maggots emerge as adult blowflies the next summer just in time for the salmon run. Before laying their eggs, the blowflies swarm kneeling angelica flowers to feed on nectar, spreading pollen at the same time.

Previous research has looked at direct connections to plants, such as roots taking up nutrients when salmon carcasses decay, Lisi said. This is an indirect consumer pathway.

"Kneeling angelica are among the last plants to bloom. It's fall, everything else is dying, most of the insects are gone but these plants hold out for the arrival of salmon," Lisi said.

Study: Wolverines need refrigerators

Will insects and bacteria consume more of the wolverine's food if the climate warms?

Wolverines live in harsh conditions; they range over large areas of cold mountainous low-productivity habitat with persistent snow. The paper suggests wolverines take advantage of the crevices and boulders of the mountainous terrain, as well as the snow cover to cache and "refrigerate" food sources such as elk, caribou, moose and mountain goat carrion, ground squirrels and other food collected during more plentiful times of year. These cold, structured chambers provide protection of the food supply from scavengers, insects and bacteria. In addition, the refrigerated caches increase the predictability of available food resources, reduce the energy spent by females searching for food while in lactation phase, and decrease the time mothers spend away from cubs.

The paper appears in the current edition of the Journal of Mammalogy and was co-authored by Robert M. Inman of WCS, Audrey J. Magoun of Wildlife Research and Management, Jens Persson of the Swedish University of Agricultural Sciences, and Jenny Mattisson of the Norwegian Institute for Nature Research.

"People don't normally think of insects and microbes as being in competition for food with wolverines," said lead author Robert Inman of the Wildlife Conservation Society's North America Program. "But in fact, bacteria will devour an unprotected food source if that source is available."

Through an extensive literary review, the authors noted that wolverine reproduction is confined to a brief period of the year, and the lactation phase in females (February through April) corresponds to a period of low availability of food resources. Wolverines, which are opportunistic foragers, have adapted by amassing food caches during the preceding winter months when food is more readily available. Without the cached food supply or an unforeseen alternative (such as a winter-killed ungulate), early litter loss occurs.

Inman said, "Understanding why and how wolverines exist where they do and the various adaptations they have evolved to eke out a living will better inform population management strategies and conservation of the species."

Climate change will play a key role in management planning for the conservation of wolverines, the authors say.

In a study published in 2010, wolverine biologists demonstrated a relationship between the areas where wolverines exist (their distribution) and persistent snow cover. The first theory advanced was that wolverines must have deep snow available in springtime so that they can give birth to their small cubs in a warm, secure den. The newly released study suggests that other factors related to climate and snow pack, such as competition for food, may also be involved in explaining the limits to wolverine distribution.

Because of their dependence on snow pack, wolverines were recently listed as warranted for protection under the Endangered Species Act due in large part to the threat of climate change reducing distribution and habitat connectivity. The authors say that a deeper understanding of how and why wolverines use snow pack the ways they do is critical to understanding how climate change will impact survival and reproductive rates.

"Shedding light on the specific mechanism of how climate will affect wolverines is important in order to know what to do to help them hold on," said WCS's North America Program Director, Jodi Hilty.

Inman and co-authors published a study in December of 2011 on the spatial ecology of wolverines in the Journal of Wildlife Management. This latest paper represents the second of several that will help to inform a conservation strategy for the species.

The Iberian wolf lives close to humans more for refuge than for prey

The Iberian wolf lives in increasingly humanised landscapes, with limited food resources and its presence is not always welcome. But, according to Spanish researchers, food availability plays a secondary role compared to landscape characteristics, which can offer refuge and allow wolves to remain in human-dominated environments in Galicia.

The habitat of the Iberian wolf (Canis lupus signatus) varies greatly across the Iberian Peninsula and its diet revolves around what is available, ranging from wild animals to domestic waste. In contrast, this predator is able to survive in humanised landscapes where characteristics provide them refuge from humans.

"Although the wolf boasts highly adaptable strategies for survival, landscape is the factor we have analysed that best explains their distribution across Galicia," as explained to SINC by Luis Llaneza, researcher at Asesores en Recursos Naturales (A.RE.NA.) and lead author of the study published in the 'Diversity and Distributions' journal.

His research has allowed for the analysis of the relative influence of landscape attributes, human presence and food resources and the existence of wolves over an area of 30.000 km2 in the north-west of the Peninsula.

The scientists concentrated on indirect signs of the animal to identify their distribution in Galicia. In total, 1,594 excrement samples were analysed, which were then verified using DNA molecular analysis to locate them in the territory.

The results revealed that landscape properties are decisive in terms of animal safety at a level of 48%, whereas the presence of humans (buildings and roads) is influential at a level of 35% and food availability as 17%. Llaneza says that "as long as tolerated by humans, the wolf can be found in any place where there is refuge and food."

According to the scientists' model, the presence of wolves would increase if there were more semi-wild horses and wild ungulates. As the authors outline, "the amount of semi-wild horses in Galicia could be a key factor determining the presence of wolves in areas where wild prey or other food sources area not so abundant."

A safe refuge for the wolf

After studying the effect of altitude, land orography and refuge availability, researchers demonstrated that these mammals require their habitat to be a plant mosaic containing vegetation of more than 50 centimetres in height (bushes and shrubs) to hide in.

"These animals remain in Spain and little by little we are beginning to understand how they survive in human-dominated areas," says Llaneza. The study reveals that wolves choose high places that are difficult to access, such as areas where vegetation provides refuge from humans.

"The density of vegetation allows wolves to go unnoticed by humans", adds the researcher, who recalls that humans are the known cause of wolf death in 91% of instances. Some 65% of wolves are killed on the road, 20% by poaching and 6% by legal hunting.

With the participation of the University of Santiago de Compostela and the Doñana Biological Station (EBD-CSIC), the research team concludes that a set of variables and data analysed explains only 20% of wolf distribution in Galicia. Their next undertaking will be the study of other factors that influence wolf survival in humanised areas, such as the extent to which they are tolerated.