The idea that wolves and other large carnivores cause a “trophic cascade” through their impact on elk has been challenged by a number of recent publications. Last week another study was released that puts a dent in the notion– it suggests human activities, not large predators, are primarily responsible for elk vigilance in human-dominated landscapes.

Briefly, trophic cascade theory holds that each trophic level is directly and inversely related to trophic levels above it. The trophic cascade described by Ripple and Beschta examines an interaction between wolves, elk, and a variety of plants on which elk feed (e.g., aspen, willow). It suggests wolves are indirectly responsible for an increase in woody browse in Yellowstone by (a) limiting elk densities through predation (direct effect) and (b) by changes in elk behavior (e.g. vigilance) associated with wolves’ presence (indirect effect; Ripple & Beschta 2011).

Mech (2012) recently pointed out that scientists looking at the same data have come to very different conclusions regarding the direct effect of wolf predation on the Northern Range herd in and near Yellowstone NP. These studies argue for the importance of other factors (e.g., drought, winter severity, human hunting, and other predators) in limiting elk densities on the Northern Range (see Mech 2012). Mech also argued that the effects of wolves on elk should be greatly diminished outside of areas where elk are largely protected from human activities (i.e., National Parks).

This new study, published in the open-access journal PLOS|one, examined how human activities and predator activities along with other environmental factors impact the behavior of elk in human dominated landscapes in Alberta, Canada.  It finds that three factors–land use type, vehicle traffic, and distance from roads–account for 80% of the variability in elk vigilance:

Elk decreased their feeding time when closer to roads, and road traffic volumes of at least 1 vehicle every 2 hours induced elk to switch into a more vigilant behavioural mode with a subsequent loss in feeding time. Other environmental factors, thought crucial in shaping vigilance behaviour in elk (natural predators, reproductive status of females), were not important. The highest levels of vigilance were recorded on public lands where hunting and motorized recreational activities were cumulative compared to the national park during summer, which had the lowest levels of vigilance.

Consistent with Mech (2012), they conclude that in human-dominated landscapes the the effects of various human disturbances on elk behavior far exceed those of predators:

Humans trigger increased vigilance and decreased foraging in elk. However, it is not just the number of people but also the type of human activity that influences elk behaviour (e.g. hiking vs. hunting).

This research highlights the increasingly complex picture that science paints regarding the relationship between large carnivores and their prey.  It also suggests that human beings and their activities must be accounted for when attempting to disentangle predator-prey relationships in human-dominated systems.  Ultimately, outside of wilderness areas, wildlife exist in complex socio-ecological systems, where humans may often be the dominant force shaping wildlife behavior and populations.

Suggested Reading

Ripple & Beschta. 2011. Biological Conservation, 145:205.

Mech. 2012. Biological Conservation 150:143.

Ciuti et al. 2012. PLOS|one, doi:10.1371/journal.pone.0050611.

 
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About The Author

Jeremy Bruskotter

Dr. Jeremy Bruskotter is an associate professor in the School of Environment and Natural Resources at the Ohio State University where his research interests are centered around the human dimensions” of wildlife conservation and management. Jeremy is passionate about wildlife–at one time or another, he has called himself hunter, angler, and wildlife photographer. Most of all, Jeremy is concerned with bringing the tools and techniques of the social sciences to bear on pressing issues in wildlife management.

34 Responses to Study Finds the Effect of Humans on Elk Behavior Exceeds the Effect of Natural Predators

  1. avatar Mark L says:

    “The cost of disturbance is a waste of time and energy”
    Zen-like wisdom…got to be one of my favorite quotes of all time.

  2. avatar WM says:

    JB,

    I have not read the study yet, but intend to later this week. What I would offer is that the following statement from the study is not universally true – “Elk decreased their feeding time when closer to roads.”

    I think we have all seen elk or deer for that matter, eating along roadsides, with little to no vigilence of humans around them, even in close proximity. The can become habituated to recognizing them not as a threat as much as eight to ten months out of the year. This is especially true in winter, at elk feeding stations in some areas – in WA, WY and ID, where I have visited. Or, for example, where the elk come into town in places like Banff, Canada (to avoid wolves), or Estes Park, CO, because they like the golf course grass, and where they become nuisances. I will suggest humans actually create conditions which encourage LESS vigilent behavior in these instances.

    I look forward to reading whether some of this is mentioned in the study, or whether it is omitted, further confusing what we see on the landscape and what is incrementally published by researcherss trying to find answers to complex animal behavioral questions.

    • avatar JB says:

      WM:

      The following quote speaks to your concern:

      “Although elk in Waterton Lakes National Park are not actively hunted within the park, animals are hunted along park boundaries when elk use lower-elevation areas during fall and winter due to shallow snow and higher forage availability. This is the reason why elk in this park do not show signs of habituation” (emphasis mine).

      They also discuss the importance of the different types of human activities in the discussion section:

      “We found the highest levels of elk vigilance on public lands during the hunting season, when hunting and intrusive recreational activities occurred cumulatively, whereas the lowest levels were found in the national park in summer – even when crowded with people – and on private lands during winter-spring – when human activities were almost absent after hunting season. Both public lands and national park were crowded with people in summer, but our study clearly showed that it was not just the number of people but above all it was the type of human activity that shaped elk behaviour.”

      And again discuss the possibility of habituation here (in the discussion):

      “High traffic volumes can have different impacts that depend on whether hunting is allowed or not (Fig. 4). If hunting is not permitted, then behavioural adaptations, such as habituation, can evoke a decrease in vigilance levels (Fig. 4; [72]). Human developments can affect the distribution of predators [73], [74].”

  3. avatar Immer Treue says:

    JB

    Read this last night. It’s sure to ruffle the feathers of many. But as WM writes, finding answers to complex animal behavior, is a work in progress.

  4. avatar Louise Kane says:

    JB thanks for posting this. These two observations are nto surprising in the least,” The highest levels of vigilance were recorded on public lands where hunting and motorized recreational activities were cumulative compared to the national park during summer, which had the lowest levels of vigilance.” and ” Humans trigger increased vigilance and decreased foraging in elk. However, it is not just the number of people but also the type of human activity that influences elk behaviour (e.g. hiking vs. hunting).”

    • avatar Ida Lupine says:

      I hate those ATV’s – the noise is awful.

    • avatar WM says:

      Louise,

      I will submit the behavior varies widely. For example, with Roosevelt elk (a slightly larger and more shy subspecies than the Rocky Mountain elk that inhabit coastal WA and OR), I have seen elk herds be much more vigilent and wary INSIDE Olympic National Park (season really doesn’t matter) than outside it, say near Sequim or Forks. So, let me just call
      BULL poop on your statement, and that of the researcher results if applied universally (instead of just to their study findings at that location). I bet the elk biologists at ONP might agree with me.

      • avatar Louise Kane says:

        so I would agree WM that applying or looking for an absolute from any study or research position, as it pertains to wildlife behaviour would be inappropriate. Yet why is it that this study/ researcher results are so easily poo pooed by you. You have not read the entire piece by your own admission. Why is it so hard to acknowledge that human hunting activities might impact elk behavior more – or say at least- as much as much as natural predators. How many hunting licenses are issued in a state? – how many hunters hunting elk from atvs or using roads and shooting at them? Depending on the state contrast the number of human hunters to 300- 700 or 800 wolves. Its a question of – what science do you prefer to back up your beliefs. You seem to consistently choose science that substantiates your status quo position when it comes to predators. Just an observation ,much like yours about bull poop

        • avatar JB says:

          Louise, WM:

          I think some folks want to make this into more than it is. The study challenges (in part) the notion that wolves and other carnivores are indirectly impacting elk populations (via their behavior)–at least outside of protected systems.

          As all studies do, this one leaves many questions unanswered. Still, it seems pretty clear that elk are cowering on unproductive mountain tops in fear of non-human predation–at least not in these systems. One more challenge to trophic cascades and one more challenge to the idea that the effects of wolves on elk are somehow profoundly different than the effects of other predators.

          I don’t care to “sanctify” the wolf (as Mech puts it). But neither do I think they should be vilified as some kind of super predator. More and more research is suggesting they are just one other predator on the landscape.

          These studies, taken together, raise the question of why western states have chosen to pursue wolves so aggressively relative to other predators?

      • avatar WM says:

        Actually, Louise, my comment was to respond to your obvious slam of hunters on public lands.

        There are two components to the vigilance issue. One is spatial – where the elk are at the time of observation, on public or private land and near or far from roads, or maybe trails. The second is temporal – when are people present, and what are they doing at that time on any particular owned land, as well as how frequently they are doing it, including whether the animals feel threatened by it(chasing elk to see, photographa or shoot them). A friend, who is an elk biologist, showed me some pictures a couple of years ago where he was taking photos of bull elk during the rut (in and outside a national park where roads were) and these horny bulls were not wary at all toward humans.

        The same spatial and temporal elements could be applied to predators, particularly wolves. Since a pack has a large area, sometimes as much as several hundred miles, they won’t be at the same place all the time (of course the land ownership is irrelevant to the prey and the predator). The question is how long does heightened vigil behavior for the prey remain (eating less, fleeing more quickly, occupying different habitat) when a risk is present, and IMPORTANTLY how long does it take for the behavior to fade away if the risk is no longer present. I have seen it change in a matter of days or weeks (before hunting season,abruptly changing during it, then transitioning to winter when elk will seek food wherever they can find it, even at a rancher’s hay stack or a sheltered apple orchard). Hunger can be an incredible motivator for all animals, and so can the quest for predator avoidance, whether the predator is a wolf, bear or human.

        I have also seen ATV’s or auto type vehicles go up a road, and have elk tracks over the top of theirs in a matter of minutes or hours. Ask loggers about elk or deer crossing or walking down the middle of the same access roads htey use, and into harvest areas. Sometimes a landing worked all day with heavy equipment like loaders, trucks and dozers, then left for night will have elk tracks in it when the crew shows up the next morning! They can be curious animals. Years ago, one of my hunting partners shot a mature 6 point bull elk, on a logging grade that had been graded by a bulldozer only the day before. So much for the noise and activity thing. This stuff is hard to study and even harder to draw meaningful conclusions.

        • avatar MAD says:

          All observable behavior of an animal species will be within the range of possible behaviors that are inherent within that animal. This is known as phenotypic plasticity. (Words like adapt and evolve are cavalierly thrown around but have specific Darwinian meaning that is very different than common usage)

          To summarily dismiss peer-reviewed scientific efforts due to your anecdotal experiences exposes your bias. Of course, these researchers are not claiming that every single elk on the planet(or wild animal for that matter) will react in exactly the same way that they are reporting. Anyone who believes this, or that the researchers are making those prognostications is foolhardy. What all wildlife researchers attempt to do is identify behavior that is quantifiably observed, document it, and draw some conclusions based on what was observed. Those conclusions can be very specific in relation to a subpopulation or situation, or more generally applied to larger subsamples of populations. Calling their work BULL poop (your word) is disingenuous.

          • avatar WM says:

            MAD,

            My comment (showing my bias) was directed to a previous statement of Louise Kane (clearly reflecting her bias). That my observations (or those of others with similar experiences) are anecdotal, does not make them invalid. They are examples of variation from what observed results MAY have been in this study, thus showing a range of different behavior than may have been reported in different field conditions involving different variables.

            And, importantly, my comment directed to Louise (this is an informal conversation afterall), stated that if these were universally applied they would not be accurate, and hence the term you find disingenuous and offensive. Your point is noted, however.

            And, yes, I understand scientific method. It is the extrapolation of a study result by either scientists or lay persons that find my skepticism – for example a hypothisis of “trophic cascade” benefits attributed to wolves as a means to justify increased numbers, based on research conducted solely in YNP, during a time when there was an over-abundance of elk from the fires of 1988.

            And, last, I am familiar with the term “phenotypic plasticity,” though I suspect most on this forum without a science background have not heard of it. I haven’t used it since grad school. From my recollections of long ago, it applied more to plants responding with adaptive change to their environment over a period of time. I would suggest some animals can be infinitely more plastic than plants, as individuals within their own lifetime (elk skittish in hunter presence > less so when not hunted even after a couple weeks) My anecdotal observations speak to that. I will add another, and that is that in the presence of the wolves where we hunt they are more skittish and out of sight all the time – for about five years now.

            • avatar MAD says:

              nope, you are absolutely incorrect as to phenotypic plasticity applying more to plants than animals. what I would suggest is that maybe you review some scientific research from the last 2 decades dealing with animal behavior to reaquaint yourself. grad school? I thought you were a retired lawyer who just greatly enjoys being the proverbial contrarian person who will to the death in opposition with what most on this site believe.

              • avatar MAD says:

                …will argue ’til the death…

              • avatar WM says:

                Yes, graduate school, and a retired lawyer. Mostly I remember phenotypic plasticity from plant ecology classes. Clearly terminology and applications change.

                As for the contrarian part, it would seem some here might benefit from exposure to differing points of view, because what some folks believe here deserves the occasional challenge.

              • avatar Mike says:

                ++ I thought you were a retired lawyer who just greatly enjoys being the proverbial contrarian person who will to the death in opposition with what most on this site believe.++

                The truth has been typed, lol.

            • avatar mikepost says:

              WM, I dont always side with you but I am in support of having group think challenged by educated comment. Some here think that their waste material has no odor. Keep it up…just don’t disagree with me….

  5. avatar Rachel says:

    Thanks for the article. I wrote a response to it, looking at the issue from another perspective. The study exemplifies a key dilemma: public support of national parks requires public access to wildlife for viewing, but increasing human interaction with wildlife in the parks is interfering with the parks’ abilities to maintain the integrity of affected species. As the study states, “quantifying human disturbance may be the highest priority for conservation”, despite the necessity of public access for retaining support.

  6. avatar mikepost says:

    See a related study: http://www.fs.fed.us/pnw/starkey/

    One of the specific studies this project has done is measure, over a period of years, the behavioral impacts on elk from human activity of various types. A little bit “apples & oranges” but I think the cumulative results of various studies are what is most valuable,

    • avatar WM says:

      mikepost,

      Footnote 7 of the current study which is the subject of this thread, is a reference to ATV (mountain biking, hiking)sensitivity of elk studies done at Starkey by Leslie Naylor, et al.

      7.Naylor LM, Wisdom MJ, Anthony RG (2009) Behavioral responses of North American elk to recreational activity. J Wildl Manage 73: 328–338.

      http://www.fs.fed.us/pnw/starkey/publications/pdf/Naylor%20et%20al._elk-recreation_JWM_April09.pdf

      From 2004 research elk aren’t too keen on ATV noise. But now I wonder, if the observed behavioral effects on elk might be even more amplified with wolf presence. Guess that may get some study as wolves reinhabit Eastern OR, where the Starkey Experimental Forest and Range is located, outside La Grande, OR. Starkey is only about 50 miles from Enterprise, OR where the Imnaha Pack and descendents (or other dispersers from ID) may reside.

      A perpetual backlog of studies for wolf and ungulate researchers awaits – talk about job security. LOL. :)

      • avatar mikepost says:

        WM, Starkey is a huge facility but it is fenced to keep the study herd intact. 8′ fencing in fact. I am not sure that any local wolves can do much more than salivate on the perimeter. You are correct though, we will never know enough…

    • avatar JB says:

      ” A little bit “apples & oranges” but I think the cumulative results of various studies are what is most valuable…”

      Thanks for the resource–resource(s) actually; there’s a lot of information here!

  7. avatar Richie G says:

    Why would elk be afraid on a golf course anyway,any animal would not be afraid. Would they be weary of a golf cart,it’s quiet and slow. As for golfers they are playing their game,so why should elk run away? As for hunting only seems natural if they see another elk get killed by a loud bullet,this could present itself as fear. Seems only common sense that if they are being killed by a loud noise,the association would create fear. I know this may not happem with Buffalo,but again I am not an authority on this subject matter. I do know when in the WALLOWA PARK you can walk up to deer,a ranger told me he has seen people put their kids on deer.People think of them like horses,because they were so clarm. But their were signs,do not get close to the deer,they are still wild animals.

    • avatar Savebears says:

      Richie,

      You perfectly illustrated the difference between the West and the East, you have no clue as to what happens in the west, and we all know that opinions are like…

      We all have them.

  8. avatar ma'iingan says:

    This study suggests that the trophic cascade effect of wolves in Northern Wisconsin is observable, but it’s certainly much more subtle than Ripple and Beschta’s observations in Yellowstone.

    http://ugakr-maint.libs.uga.edu/bitstream/handle/123456789/8205/callan_ramana_201012_phd.pdf?sequence=1

    • avatar JB says:

      Thanks for sharing, Ma’. Not sure if you’ve seen it yet, but the most convincing evidence I’ve seen for trophic cascades caused by large carnivores is Ripple & Beschta. 2012. Large predators limit herbivore densities in northern forest ecosystems. European Journal of Wildlife Research, 58:733-742.

  9. avatar Craig says:

    What’s a glaring problem is time of year! I’ve Hunted/ watched Elk my whole life. In Stanley Elk used to feed in all the open Meadows every evening,people drove the loop trails and watched. When wolves were added that slowly went down and now it’s rare to see them in a open meadow in the summer during the evening. Same goes for Yellowstone, time of year, morning,evening, and even places they hang around. They seem to know where there are people it’s safer at certain times of the year. I’ve not been able to get an Elk to Bugle for the last 8 years in Stanley during September. Where as before I had them Bugleing all night around our camp area.

    • avatar JB says:

      Craig:

      I did my masters’ work at Utah State, which is very near Hardware Ranch, a facility run by the Utah DWR that feeds otherwise wild elk in the winter. These are elk that were hunted outside of the feeding area, which acts as a sort of refuge. I remember local hunters were often upset because the elk seemed to “know” when hunting season was coming and would show up in the protected area shortly before the season started. These (again) otherwise wild elk could be approached very closely while at the ranch. You can see a few photos here: http://wildlife.utah.gov/hardwareranch/about.php.

      Anyway,your post reminded me of the experience.

      • avatar WM says:

        Hunger can be an incredibly strong motivator for changed behavior. What is observed at Hardware Ranch is repeated at a few state run elk feeding stations across the West, and many rancher haystacks and fruit orchards (where they are not so welcome). All of this because there is not so much quality winter range which they would otherwise occupy.

        Of course, they also learn some of those areas can be sanctuaries at other times of the year, as well. Knowledge is passed on from one generation of elk to the next, and the lead cow will often point the way. Guess we would call such behavior phenotypic plasticity.

  10. avatar Craig says:

    Also, I have called in over 80 Bulls over the years for fun,for friends bow hunting, and for myself. I know cow talk and all that goes into talking to elk. It’s a passion of mine, right beside Duck Calling.

  11. avatar Headwaters says:

    The paper accurately describes the behaviour of the Waterton elk which have been exposed for many years to a special hunting season that extends through most of the winter and was put in place to limit hay depredation. The whole herd is very conditioned to the hunting threat they face north and east if the park. My family’s eaten three or four of those elk over the years. It is a unique situation. A similar study in the Ya ha Tinda/Banff area, I suspect, would not produce the same findings as there is a good wolf population there and the elk have to factor wolves into their behaviour too. Wolves don’t survive long in the Waterton area as the same ranchers whose complaints about elk depredation got the extended hunting season put in place also have agate on for wolves and the road density there means wolves get lead poisoning pretty quick.

  12. avatar Richie G says:

    To sb; and you have no clue what happens in the east,let alone common animal behavior.p.s. opinions are like,and you have one too sb.

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‎"At some point we must draw a line across the ground of our home and our being, drive a spear into the land and say to the bulldozers, earthmovers, government and corporations, “thus far and no further.” If we do not, we shall later feel, instead of pride, the regret of Thoreau, that good but overly-bookish man, who wrote, near the end of his life, “If I repent of anything it is likely to be my good behaviour."

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