Moose on the Run

I LOVE moose. I have a moose necklaces, shirts, and art. I always stop to take a picture whenever I see one grazing on the side of the road, which happens fairly often since I live on a forested mountain. I love that they’re gentle giants, for the most part. They are one of the few fairly benign charismatic megafauna residing in Alaska, unless they’re provoked. I love springtime when a normally solitary new mother carefully escorts her sweet, wobbly calves through my neighborhood in search of the tastiest morsels.

Moose are a reminder that humans do not occupy this world alone and that there is wilderness in all of us. Humans and animals share this world and we both deserve to use the space. I love that I’m not so far removed from nature in my day-to-day life that I can’t still interact, even in a small way, with a gentle giant. Living in a city surrounded by concrete and high-rise buildings makes it so easy to forget that other animals inhabit our space alongside us.

I’ve seen significantly more moose this summer than usual so I was inspired to share one my favorite moose essays this week. It’s adapted from an essay I wrote for my Global Change and Natural Resources course. (The name is a fancy, liberal-arts way of saying we learned about weather systems and the mechanics of climate change.) The assignment was to explore how climate change would affect a natural resource in any location, so of course I chose to investigate moose in Alaska.

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Over the course of my college career, I have written three research papers about moose for various classes. I liked this essay the best, so this is the one I’m sharing. Because this was a scientifically written paper, I include my citations. They can all be accessed through Jstor, a digital library for scholarly writings.

Please comment below if you have any moose stories you’d like to share or if you want to hear about the friendly moose that has been making my front yard her home this summer!

 

How Climate Change Impacts Alaskan Moose

Introduction

One of the primary effects of the current human-induced climate change is rising atmospheric temperatures which often results in cascading, unpredictable changes across ecosystems, usually to the detriment of the native species. This change is happening all over the globe, but it is especially pronounced above the Arctic Circle as organisms are unable to move any farther north to reach cooler climates. As temperatures rise, there will be a significant northern shift in moose’s traditional habitat given that temperature primarily controls their distribution. Moose are extremely sensitive to changes in temperatures because of their inability to thermoregulate (Lenarz et al, 2009).

The direct effect of heat stress has multiple repercussions – an increase in the energy expended to stay cool, reduced foraging capabilities (Lenarz et al 2009); their ability to sufficiently care for their calves (Bowyer et al 1998); and their susceptibility to being infected by diseases and malnutrition (Murray et al 2006). While moose in Alaska don’t frequently experience heat stress due to the perennially cooler climate, (especially near the coasts) they will begin to undergo more stress as the Arctic regions’ temperatures are expected to soar.

Climate change has a number of direct and indirect effects on moose, the effects of which often result in a cascade of changes for other species as well. Increased heat stress and thermoregulating challenges lead to decreases in neonatal survival and increases in malnutrition and disease rates. Moose are preferential foragers so they effect the density of certain trees and bushes, and they are also an excellent food source for predaotrs due to their large body size.

The migration of moose can have negative effects for the ecosystems in which moose play a vital role, and for the Alaskan people that depend on their presence as a food source. This is a significant issue because moose play not only a large role in ecosystem dynamics, but also culturally and spiritually for the Alaskans that depend on moose as a part of their subsistence lifestyle.

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Distribution

Globally, moose occupy the northern forests of North America, Europe, and Russia because the mammals are “superbly adapted” to cold temperatures (Lenarz et al, 2009). Around 1750,000 – 200,000 moose inhabit almost the entire interior of the state of Alaska – from the Colville River on the Arctic Slope, to the Seward Peninsula, to the Alaska Peninsula, to Mount Fairweather (Alaska Department of Fish and Game). Though moose are fairly strong swimmers, they are not able to swim the miles necessary to establish a sustainable population on the Aleutian Islands and Alexander Archipelago, which would not be a large enough area to provide for many moose, regardless. Alaskan residents hunt about 30% of the moose every year, though this percentage is much higher for the indigenous Alaskans that practice a subsistence lifestyle (Alaska Department of Fish and Game). The moose is primarily hunted because the animals offer around 900 pounds of usable meat and organs. It also has a cultural significance to the native Alaskan populations, not only as a spiritual experience but also as a mechanism to reinforce familial bonds through hunting (McIlwraith, 2008). This percentage is likely to be smaller than the actual amount of moose hunted because acquiring permits is an expensive and time consuming process, so illegal hunting often occurs, and because some hunters fail to report their all of their game. Yet the moose is not currently in danger of being overexploited through hunting means.

The primary control of moose distribution is temperature, though other factors do have an affect. Summer temperatures are a major limiting factor of the distribution of moose because temperatures upwards of 14ºC cause an increase in metabolism and bodily stress that can lead to poor survival rates if experienced for extended amounts of time (Lenarz et al, 2009). However, warmer temperatures are not completely detrimental. Fire frequency increases in hotter temperatures, which promotes the growth of moose favorites – willow, aspen, and birch trees (VanStone, 1976) – and thus moose density can be partially offset by this surge in food availability. In areas with too much winter precipitation, moose were not able to break through the snow to migrate to new habitats and to find preferred forage options (Bowyer et al 1998). The presence of wolves also affects the density and numbers of moose present in an ecosystem. When wolf populations are reduced artificially via human control, there was a substantial increase in the moose population, a proliferation that continued even after the wolf population recovered (Boertje et al 1996). The risk of predation also influences the moose’s foraging ability, as they have to constantly monitor their surrounding for potential danger. When the threat of predation is high, moose browse less selectively and ingest lower quality forage than if they were not concerned about either bear or wolf predation (Molvar and Bowyer, 1994).

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Primary Global Change Components Expected to Impact Moose

Moose are relatively intolerant of heat and respond to increases in heat by seeking thermal refuge in conifer swamps or aquatic refuges. With a predicted increase in temperatures, especially in Arctic regions, moose will be expected to move their southern-most distribution towards more northerly latitudes to combat the increasing temperatures. Moose experience an increase in metabolism, heat and respiration rates, reduced foraging efficiency, and reduced body weight when summer temperatures reach just 14ºC (Lenarz et al 2009). When temperatures exceeded 20ºC, moose resort to panting to regulate their internal temperatures, so they needed to expend a significant amount of energy to stay cool (Lenarz et al 2009). As climate change progresses, climbing temperatures are predicted to continue, so moose will spend an increasing amount of time and energy trying to keep cool, which will reduce their energy available for other activities such as foraging or reproducing. As a result in decreasing foraging time and efficiency, moose body fat reserves will decrease which is especially problematic for higher latitude moose, who heavily rely on their fat reserves to survive the long, cold winters (Lenarz et al 2009).

Climate influences reproductive capabilities of adult moose and the survival of neonates. Harsh weather can lead to hypothermia in newly born moose, and can affect females that have to deal with deep snow (Bowyer et al 1998). Snow above 70 cm impedes adult movement and 90+ cm reduces calf survival (Hayes et al 2003). Adult females can have a reduced maternal investment and lactation abilities after experiencing either diminished amounts of browse in the winter months or delayed spring forage opportunities due to climatic variation. Weather can also affect the quantity and quality of forage, which can influence the timing of reproduction and the twinning rate (Bowyer et al 1998). The more nutrients available to moose to consume, the higher the rate of twinning. Neonates born later in the spring might suffer higher mortality rates, in part because they are typically underweight due to the lack of easily obtainable nutrition available to them, and in part because of the predation. As spring starts earlier and earlier due to climate change, the nutritious plants bloom sooner that the moose are born a trophic mismatch occurs.

Climate change also leads to indirect effects – an overall decrease in body condition makes moose more susceptible to predation and disease. In a 40-year study of moose in northern Minnesota, pathogens were the cause 62% of deaths of adult moose, mostly caused by liver fluke, though meningeal worm was also a factor (Murray et al. 2006). The moose were more prone to be infected by the pathogen because their bodies were already under severe stress due to malnutrition and an increase in number of days above the thermoregulation threshold as the growing season was longer and warmer than the typical (Murray et al. 2006). Murray et al. also found that malnutrition played a significant role as well, as indicated by bone-marrow fat levels and blood profiles, which were different for moose dying of natural causes compared to those killed by anthropogenic factors (2006). Also a change in temperature regimes will allow diseases to shift their boundaries north and inhabit larger ranges, perhaps causing an increase in incidences of infection.

There are a variety of ways in which moose could be affected by a changing climate, some of which are negative and some of which are positive. If the fall is warmer than usual, the soils will stay warmer and the plants will be able to be productive for longer, given that there is sufficient sunlight for them to continue photosynthesizing (Cooper, 2014). The warmer temperatures would mean a delay in the beginning of winter, which could have myriad effects and is challenging to predict. If there is more snow during the year, moose will have a harder time moving around, but the plants will be better insulated in warmer soils and might be more able to start being productive sooner which would benefit the moose. The longer the snow remains, the higher the likelihood of death by predation for calves as the snow is not able to camouflage them as the spring earth does (Hayes et al 2003). If there’s less snow during a winter, then the moose will have an easier time migrating but the plants will have much less insulation which might lead to frost-damage; however then there will probably be an earlier snowmelt which would minimize the damage to the plants (Cooper 2014). Also if there’s less snow then there is less water stored in the icepacks that supplies water to rivers, which might lead to a drier summer, which would directly impact the plants and moose.

Fire has been a significant driver of habitat change benefitting moose because it is relatively frequent, burns massive tracts of land, and preferred browse species quickly regenerate afterwards. The main fire starter is lightning, which is pretty common throughout the state. The majority of the interior has been burned within the past 250 years (VanStone, 1976). Anthropogenically induced fires have also been a source of huge source of fire recently, mostly used in the process of land clearing. Moose move into areas relatively recently burned because the forests have opened up and are not as dense with understory shrubs which can make it challenging to easily move around for these big creatures. Birch, willow, and aspen can quickly recolonize a burned area, often changing it from its original hardwood dominated composition to something moose prefer (VanStone, 1976). With increasing temperatures predicted in Alaska as a result of global climate change, fires are probably going to become more common as in some areas. It is challenging to predict a response because there are a variety of factors, though the result will affect the moose population.

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Time Frame for Climate Change Related Impacts to Occur

With global climate change, the average temperatures Alaska will experience are predicted to increase by several degrees. The rate of change for Arctic regions is much faster and more severe than for lower longitudes, so the moose will have to rather quickly adapt to living in warmer conditions. Given that extended temperatures above 14ºC can be problematic for moose and that those temperatures are already frequently reached, the increase will be quite detrimental to their health. As can be seen, there are already demonstrable effects of climate change on not only populations of moose in Alaska, but worldwide. Moose are well adapted to cold temperatures and their range will most likely shift northward to accommodate the increasing temperatures found in southern latitudes. This shifting range will have a large impact on ecosystems and might result in a trophic cascade.

 

Conclusion

Moose are heavily impacted by climate as it influences their foraging opportunities, their overall health (especially as it relates to disease and malnutrition), and their reproductive success. While there are many negative impacts of the current climate change, there are some benefits and it is challenging to predict which will have the largest influences on moose populations. Researchers so far have done a good job analyzing how moose respond to primary stimuli such as temperature or predation, but there are several ways to expand on this research and to explore new topics. Can moose rapidly evolve either smaller body sizes or a better cooling mechanism so that they are not overly stressed in the rising temperatures? Will the timing of parturition begin to coincide more with the new beginning of spring and the growth of plants? Are the populations viable with this level of disruption occurring? These are questions that researchers should address because they will provide valuable insight into the future of the Alaskan moose.

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Literature Cited

Alaska Department of Fish and Game                                                  http://www.adfg.alaska.gov/index.cfm?adfg=moose.main

Boertje R. D., Keech M. A., Young D. D., Kellie K. A., and Seaton, C. T. (2009) Managing for Elevated Yield of Moose in Interior Alaska. The Journal of Wildlife Management 73, 314-327.

Bowyer R. T., van Ballenberghe V., and Kie J. G. (1998) Timing and Synchrony of Parturition in Alaskan Moose: Long-Term versus Proximal Effects of Climate. Journal of Mammalogy 79, 1332-1344.

Cooper, E. J. (2015) Warmer Shorter Winters Disrupt Arctic Terrestrial Ecosystems . Annual Review of Ecological and Evolutionary Systems 45, 271-295.

Hayes R. D., Farnell R., Ward R. M. P., Carey J., Dehn M., Kuzyk G. W., Baer A. M., Gardner C. L., and O’Donoghue. M. (2003) Experimental Reduction of Wolves in the Yukon: Ungulate Responses and Management Implications. Wildlife Monographs 152, 1-35.

Lenarz, M. S., Nelson, M. E., Schrage M. W., and Edwards A. J. (2009) Temperature Mediated Moose Survival in Northeastern Minnesota. The Journal of Wildlife Management 73, 503-510.

Molvar E. M., and Bowyer R. T. (1994) Costs and Benefits of Group Living in a Recently Social Ungulate: The Alaskan Moose. Journal of Mammalogy 75, 621-630.

McIlwraith, T. (2008) “The Bloody Moose Got up and Took off”: Talking Carefully about Food Animals in a Northern Athabaskan Village. Anthropological Linguistics 50, 125-147.

Murray D. L., Cox E. W., Ballard W. B., Whitlaw H. A., Lenarz M. S., Custer T. W., Barnett T., and Fuller T. K. (2006) Pathogens, Nutritional Deficiency, and Climate Influences on a Declining Moose Population Wildlife Monographs 166, 1-30.

VanStone, J. W. (1976) The Yukon River Ingalik: Subsistence, the Fur Trade, and a Changing Resource Base. Ethnohistory 23, 199-212.

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