This column was published in the Cranbrook Daily Townsman Tuesday September 14, 2010.
Last week, I wrote about the trade-off that elk and other ungulates make between predation and forage. Many animals are forced to make decisions between accessing high quality food and exposing themselves to higher predation risk. Ungulate species around the world have evolved migration as a strategy to lower predation risk and access higher quality forage.
The issue of non-migratory or resident elk living year-round in the valley-bottom Trench has vexed wildlife managers and ranchers alike. The number of elk migrating to the high country each summer has declined significantly. As efforts continue to encourage elk to resume their seasonal wanderings, new challenges may arise in this effort.
Migratory ungulates in the Rockies follow a spring wave of green-up into the mountains, feeding on nutritious and highly digestible emergent vegetation. But constraints on food availability may hinder elk in the high country compared to their non-migratory cousins who stay put in the Trench. It all ties into plant growth.
Dr. Mark Hebblewhite at the University of Montana notes recent research that suggests changes in historical vegetation growth patterns may further disadvantage migrating elk. He notes that “climate change might potentially lead to reduced benefits for migration” (emphasis his).
If plants grow too quickly, forage quality is reduced. Slow-growing, cool springs keeps grasses lush, digestible and highly nutritious. Conversely, short, rapid-warming springs quickly dry out vegetation with a loss of nutritional value. Research on bighorn sheep and mountain goats in Alberta has shown that compressed green-up can directly reduce lamb and kid survival. It’s not a long stretch to other species using similar habitats and diets: elk and mule deer.
Evidence suggests changes are occurring in high elevation vegetative growth patterns. Global land plant growth increased 6% between 1982 and 1999, with the increase accredited to higher temperature, more rain and solar radiation; all key ingredients to plant growth. When University of Montana scientists Maosheng Zhao and Steve Running set out to update the research, they were astonished to find the same global terrestrial plant growth rate declined, albeit slightly at 1%, between 2000 and 2009. Their research, published in Science last month, found that drought has outpaced temperature increases, particularly in the southern hemisphere, and led to net declines in plant growth in many areas of the world. Elsewhere, including most northern latitude forests such as Canada, net plant growth is still increasing. But the work issues a warning that climate change can cause unexpected and rapid shifts in ecological systems.
A third issue is termed the “trophic mismatch hypothesis,” first described by Penn State’s Eric Post and colleagues for caribou in Greenland. There, changes in green-up time are creating a mismatch between calving times and food availability. In a harsh arctic or high elevation ecosystems where food is often scarce outside a short growing season, timing of birth is very important.
Some estimates place the energetic costs of lactation at some 200% more expensive to mothers than pregnancy. So having an abundant, nutritious food source while young are nursing is essential. Even slight shifts in forage availability is enough to lower calf survival. Whether the same phenomenon is occurring in alpine ecosystems is unknown. It’s a question Dr. Hebblewhite would like to test in the Rocky Mountains.
Timing of ungulate migration is a complex adaptation to various clues. Their ability to respond to change lags well behind plant growth responding to seasonal climate shifts. If changes are indeed occurring in high elevation montane forests, migrating local ungulates will be at a significant disadvantage compared to resident elk feeding on irrigated alfalfa fields in the Trench. Encouraging elk to vacate that food supply and resume traditional migrations from valley bottom to the high country faces its own uphill battle.
Wednesday, September 15, 2010
Wednesday, September 8, 2010
To eat or Be Eaten
This column was published in the Cranbrook Daily Townsman Tuesday September 7, 2010.
It’s that time of year again: men wear camo, wives are lonely and elk are nervous. Yes, elk season is open, this year with a twist. Anterless elk are in the sights in some parts of the Trench, a move to try to reduce their numbers in agricultural areas and convince them to hike for the high country come spring.
Ungulate migration has long been viewed as an evolutionary strategy to avoid predators and access good forage. For most animals, life is a trade-off: eat or be eaten. You can hide as long as you want, but eventually you’ll get hungry enough to venture out to that really tasty patch of grass. Biologists have tried to answer the question “when does predation risk outweigh foraging opportunities?” to identify a trigger point for migration. The answer isn’t easy.
Mark Hebblewhite is a Canadian biologist at the University of Montana who studiesthe movement of ungulates, especially elk in the Rocky Mountains. Recent work looked for differences between overlapping migratory and non-migratory elk populations in Banff National Park and the adjacent Ya Ha Tinda winter range.
In this system, wolves (elk’s main predator) are more numerous at low elevation, so the urge to migrate was driven by an understandable desire to avoid being eaten (especially strong for soon-to-be-moms). This strategy was effective: migration lowered predation risk by 70% compared to elk who chose to stay in the valley bottom. Freed from the threat of wolf predation, migratory elk’s movement decisions were based on finding quality feed. They were successful at that too, averaging 6% better forage than their non-migratory cousins. Better food was available to resident elk, but the high predation risk kept them from accessing it.
The question then is why would any elk in the Bow Valley choose not to migrate? Why stay and run a wolf gauntlet to access poorer food? Dr. Hebblewhite and his colleagues found that human activity “effectively decouples” the forage – predation risk trade-off. By selecting areas of high human activity where wolves fear to tread, resident elk lower their predation risk from 70% to 15% higher than migratory elk. The food around human activity may not be the best, but that’s more than compensated by volume: there’s lots of it.
Are there applications for this research to the resident vs migratory elk issue here in the East Kootenay? The Banff-Ya Ha Tinda situation is different. Here, elk predators (especially wolves) are in greater numbers at higher elevations. Lower predation rates in the Trench has likely helped drive the shift over the past 20 to 30 years into separate migratory and resident or homesteader elk populations, with the latter stubbornly refusing to leave the Trench in the summer.
Add in wide swaths of tasty alfalfa forage and one wonders why any elk would leave the Trench come spring. With elk now fenced out from many of those hay fields, if the predation risk side of the equation can be shifted to again favour the high country, perhaps elk will return to their migrations.
That predation is not likely to come from four-legged animals, unless we Trench-dwelling humans suddenly decide to co-exist with wolves and other predators. Increased hunting pressure is hoped to be a predation surrogate to help encourage elk to leave. This is part of the decision by the BC government to open an anterless elk season in the Trench. The hunt is based on sound science like Dr. Hebblewhite’s that increased predation risk may convince elk that the Trench is not such a safe place after all.
It’s that time of year again: men wear camo, wives are lonely and elk are nervous. Yes, elk season is open, this year with a twist. Anterless elk are in the sights in some parts of the Trench, a move to try to reduce their numbers in agricultural areas and convince them to hike for the high country come spring.
Ungulate migration has long been viewed as an evolutionary strategy to avoid predators and access good forage. For most animals, life is a trade-off: eat or be eaten. You can hide as long as you want, but eventually you’ll get hungry enough to venture out to that really tasty patch of grass. Biologists have tried to answer the question “when does predation risk outweigh foraging opportunities?” to identify a trigger point for migration. The answer isn’t easy.
Mark Hebblewhite is a Canadian biologist at the University of Montana who studiesthe movement of ungulates, especially elk in the Rocky Mountains. Recent work looked for differences between overlapping migratory and non-migratory elk populations in Banff National Park and the adjacent Ya Ha Tinda winter range.
In this system, wolves (elk’s main predator) are more numerous at low elevation, so the urge to migrate was driven by an understandable desire to avoid being eaten (especially strong for soon-to-be-moms). This strategy was effective: migration lowered predation risk by 70% compared to elk who chose to stay in the valley bottom. Freed from the threat of wolf predation, migratory elk’s movement decisions were based on finding quality feed. They were successful at that too, averaging 6% better forage than their non-migratory cousins. Better food was available to resident elk, but the high predation risk kept them from accessing it.
The question then is why would any elk in the Bow Valley choose not to migrate? Why stay and run a wolf gauntlet to access poorer food? Dr. Hebblewhite and his colleagues found that human activity “effectively decouples” the forage – predation risk trade-off. By selecting areas of high human activity where wolves fear to tread, resident elk lower their predation risk from 70% to 15% higher than migratory elk. The food around human activity may not be the best, but that’s more than compensated by volume: there’s lots of it.
Are there applications for this research to the resident vs migratory elk issue here in the East Kootenay? The Banff-Ya Ha Tinda situation is different. Here, elk predators (especially wolves) are in greater numbers at higher elevations. Lower predation rates in the Trench has likely helped drive the shift over the past 20 to 30 years into separate migratory and resident or homesteader elk populations, with the latter stubbornly refusing to leave the Trench in the summer.
Add in wide swaths of tasty alfalfa forage and one wonders why any elk would leave the Trench come spring. With elk now fenced out from many of those hay fields, if the predation risk side of the equation can be shifted to again favour the high country, perhaps elk will return to their migrations.
That predation is not likely to come from four-legged animals, unless we Trench-dwelling humans suddenly decide to co-exist with wolves and other predators. Increased hunting pressure is hoped to be a predation surrogate to help encourage elk to leave. This is part of the decision by the BC government to open an anterless elk season in the Trench. The hunt is based on sound science like Dr. Hebblewhite’s that increased predation risk may convince elk that the Trench is not such a safe place after all.
Wednesday, September 1, 2010
A life in nature: Ian McTaggart-Cowan.
This column was published in the Cranbrook Daily Townsman Wednesday September 1, 2010.
There was a quiet passing earlier this year that marked the end of a era in Canadian and British Columbia ecology. Dr. Ian McTaggart-Cowan died April 18, 2010, just a few months shy of his 100th birthday. There has been no greater contribution to our knowledge of nature in British Columbia than Dr. McTaggart-Cowan.
His parents emigrated to North Vancouver from Scotland with him as three-year old. Rod Silver, former head of the provincial Habitat Conservation Trust Fund, has written a thorough biography of Ian McTaggart-Cowan recounting his youth spent in the Lower Mainland of the teens and twenties, exploring the forests and haunts of what was a much wilder place.
There is a link to Dr. McTaggart-Cowan in almost everything we know today about birds and mammals in British Columbia. His list of accomplishments could well be unmatched in Canada: some 300 publications, definitive books on BC mammals and birds, approximately 100 graduate students (and influence on countless others who studied at UBC and elsewhere), including scientists who themselves went on to become internationally recognized experts in their field: Val Geist, Maurice Hornocker and C.S. (Buzz) Holling. Through his own work and those on whom he had direct influence, there are few areas in wildlife science today that cannot be traced directly back to Ian McTaggart-Cowan.
His awards are equally impressive: Officer of the Order of Canada, Officer of the Order of British Columbia, Fellow of the Royal Society of Canada, Leopold Medal of The Wildlife Society (the highest honour bestowed by the major international society for wildlife biologists) and others. For years, he was the honourary president of the Federation of BC Naturalists in recognition of his passion for and commitment to natural environment of this province.
The University of British Columbia was to become his second home. An undergraduate degree in 1932, followed by a brief sojourn abroad to complete his PhD at Berkley before returning home to Vancouver. His tenure took him from Professor to Department Head to Dean of Graduate Studies for the entire University.
As television emerged as a new medium in the 1950’s Ian McTaggart-Cowan was one of the first to embrace it as a means of public education. His CBC series, Fur and Feathers sought to introduce children to the wonders of nature and was followed by other television series, The Living Sea and The Web of Life.
I never had the honour of meeting Dr. McTaggart-Cowan. But I certainly knew of him. You can’t be a wildlife biologist in Canada without knowing. I recall the first time I came across one of his scientific papers as a young undergrad, deep in the depths of the University of Guelph library, far removed from the rainy west coast. I can’t remember what the paper was on, but the hyphenated name (as well as our common first name) struck me. I then soon found that for almost any topic I researched, be it bears, birds or mice, papers by the same McTaggart-Cowan would be discovered. He was the only Canadian to be so widely encountered.
There are few among us who can not only lead by example, but also inspire and raise others to levels not attainable on our own. The legacy of Ian McTaggart-Cowan, the museum collections named for him, the scholarships in his honour and numerous other awards speak of the unmatched contribution and selfless commitment of one man’s life to help us better understand the natural world, and British Columbia in particular.
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