Bears are omnivores, and on Kodiak, they eat a large buffet of food items, including elderberries and salmon, two of their favorite foods. What happens, though, if a bear has a choice between elderberries or salmon? Which will he choose, or will he choose both? More importantly, why does it matter?
I’m sure you have controversies in your neighborhood. It may be a fight over a bill to fund a new school, a fight over a tougher crime initiative, or something as simple as whether or not to put a stop sign at the end of your street. In my neighborhood here in the wilderness, the recent research I’ll discuss in this post is what we call controversy. I’ve avoided writing about this scientific article until now because I know I will irritate several people, some of them friends. I finally decided, though, I couldn’t continue to avoid voicing my opinion on something this significant. I have invited some of the biologists involved in this study, other biologists, and local guides to read my blog, and I hope they will weigh in on the issue by leaving comments. I am sorry this post is long, but I didn’t want to break it into two parts.
The study I will discuss is titled, “Phenological synchronization disrupts trophic interactions between Kodiak brown bears and salmon.” It was published in the July 18th edition of the Proceedings of the National Academy of Sciences. I think it is an excellent study, and more importantly, other biologists must think it is an excellent study. The Proceedings of the National Academy of Sciences is a prestigious scientific journal, and to be accepted by this journal, a research paper must be peer-reviewed at the highest level. I do not disagree with the methods or the results of the study. What I do have a problem with are the broad, far-reaching conclusions drawn from what is, in my opinion, a preliminary field study.
Let me do my best to explain the focus and significance of this study. A large body of research concerns what happens due to global warming when coevolved species shift out of synch with each other. For example, consider a plant that is only pollinated by one bee species, and these two species co-evolved so the plant flowers at the exact same time the bee is ready to gather its nectar and pollinate it. What happens, if the bees hatch earlier each year due to a warming environment, but the flowers bloom at the same time because their cue for blooming is based on the amount of daylight, not temperature. The two species will slowly grow out of synch with each other, and the plant species may go extinct when the bees are no longer available to spread its pollen.
In this study, though, lead researcher William Deacy and his colleagues set out to investigate the opposite situation: what happens when warming temperatures cause climate-induced synchronization? In this case, when elderberries fruit several weeks earlier than usual on Kodiak Island during the middle of the sockeye salmon run, will bears choose to eat salmon or berries?
The Karluk River on Kodiak Island, where this research was done, supports a large sockeye salmon run lasting from June to early August. On a normal year, bears on the Karluk River feast on sockeye and other salmon until late August, when they begin eating elderberries and salmonberries which are just then ripening. Once the berries are gone, bears return to the river and side streams to eat other species of salmon.
When William Deacy worked on another research project in the Karluk area in 2013, he noted typical bear behavior. Throughout July, bears ate their fill of salmon and left the scraps for birds and other animals to scavenge. In 2014, after a warm spring, elderberries ripened two weeks earlier than usual, and plants produced ripe berries longer than normal. Deacy noted that bears in late July were eating berries instead of fish. Why, he wondered, would bears opt for elderberries over sockeye salmon? The winter and spring of 2015 were also warm, and Deacy again observed bears ignoring sockeye salmon while they ate berries.
Deacy and Kodiak National Wildlife Refuge biologist Bill Leacock gathered a team of scientists from several universities and organizations, including Oregon State University, the University of Montana, Washing State University, and the National Park Service, to examine this surprising bear behavior.
From meteorological records, the biologists determined the temperature on Kodiak is slowly getting warmer, and 2014 was the warmest year on record. When the winter and the spring are relatively warm, elderberries ripen earlier than normal, and when elderberries ripen earlier, bears seem to eat berries instead of salmon. What, they wondered, will happen when temperatures continue to warm? If the berries are ripe all summer, will bears only eat berries and ignore salmon? If this happens, what will the birds and small animals eat? They depend on bears to leave them scraps of salmon on the banks of streams. Not only do animals depend on bears for leftover salmon, but salmon carcasses provide fertilization for riparian vegetation. Another point of concern is if bears only eat berries and avoid salmon, will bears get enough nutrition?
Deacy and his colleagues headed for the lab to determine if elderberries are nutritious enough to sustain bears, and why bears like berries better than salmon. Fortunately, elderberries are protein-rich compared to other berries. They don’t have as much protein as a salmon, but a bear would do fine if he ate elderberries instead of salmon. I won’t discuss the part of the study suggesting why bears prefer elderberries over salmon because I believe this conclusion is based on a very shaky assumption.
Do bears prefer elderberries over salmon, and if provided with both, would they choose the berries? I don’t know the answer to this question, and neither does William Deacy or any other biologist. As I said earlier, I think this is a well-done, interesting, thought-provoking study, but let ’s not get carried away. This is a preliminary study consisting of three years of data taken over a fairly small geographical area. It is unprofessional for any biologist to draw sweeping conclusions from a limited, preliminary study.
I would like to believe the media is responsible for jumping to wild conclusions regarding this research. I corresponded with Dr. Deacy after the research was published and asked him if he was trying to say bears are now eating berries instead of salmon. I may have misunderstood him, but I thought he said he was only suggesting what might happen as our climate warms. Then I found articles titled, “Alaskan grizzly bears choose berries over salmon—thanks to climate change,” “Kodiak bears found to switch to eating elderberries instead of salmon,” “Grizzly bears go vegetarian due to climate change, “Climate change is luring Kodiak bears away from their iconic salmon streams,” and “As a warming climate changes Kodiak bears’ diets, impacts could ripple through ecosystems.” Deacy, himself, wrote this last article. In it, he claims, “climate change dramatically altered bear behavior.”
The researchers state the ecosystem on Kodiak Island has been disrupted. I have lived in the Kodiak wilderness and have helped my husband guide bear viewers for 35 years. My husband has lived in the Kodiak wilderness all his life. Warm springs and big berry crops are not unusual, and when the berries, especially salmon berries and elderberries, ripen, we know we will see fewer bears on the rivers feeding on salmon where we can show them to our eager bear viewers. The bears will instead be in the bushes eating berries. I seriously doubt bears prefer berries to salmon, though! Berries are an easier food source than salmon because all the bear has to do is sit on his rear end and eat them. He is required to expend energy to chase down a salmon.
I believe either from instinct or learned behavior, bears know that when berries ripen, they are usually only available for a short period. Salmon, though, can be eaten from June into November. One fact I feel these researchers did not stress enough is that five species of Pacific salmon return to spawn each year in the streams and rivers on Kodiak Island. Pink salmon, not sockeye salmon, are by far the most prevalent of these species, and I have thousands of photos to prove how much bears love to eat pink salmon. Pinks are in the rivers until late September, and Coho salmon remain in the rivers until November.
Yes, the spring and summer of both 2014 and 2015 were warmer than usual, and the berries were plentiful. Once the berries began to decline, though, bears were back on the rivers eating their fill of salmon and leaving scraps for the birds and other animals. I suspect when these warm springs and summers become the norm, bears will learn they have a longer period to eat berries and will split their time between berries and salmon. I may be wrong, and bears may choose berries, but I know it should take more than a two-year study before biologists begin telling reporters that Kodiak bears have abandoned salmon for berries.
The spring and summer of 2017 were cool. The berry crop was poor, and the salmon run on Kodiak was better than it has been in several years. Bears packed the salmon streams, and we wondered whether they would eat enough berries to gain the necessary calories they need to carry them through hibernation. A biologist arriving at Karluk Lake last summer observing abundant salmon and few berries might have designed a very different research study from the one I’ve been discussing in this post.
What worries me, is that as the planet warms, salmon populations will drastically decline because salmon are sensitive to even a small increase in water temperature. As this research suggests, though, when salmon are no longer available, perhaps bears will maintain a healthy diet by eating berries.
I would like to make one more comment before I get off my soapbox. Why must biologists live in a bubble? Why didn’t the researchers in this project talk to guides who have been watching bears for decades? I realize they can’t use anecdotal evidence in their study, but perhaps we could have offered possibilities in addition to the conclusions Dr. Deacy made.
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Robin Barefield is the author of three Alaska wilderness mystery novels, Big Game, Murder Over Kodiak, and The Fisherman’s Daughter. To download a free copy of one of her novels, watch her webinar about how she became an author and why she writes Alaska wilderness mysteries. Also, sign up below to subscribe to her free, monthly newsletter on true murder and mystery in Alaska.
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