Moose and Cherry Trees
Moose browse lab: Are moose learning to eat wild cherry trees?
In the winter moose eat a variety of woody browse, primarily willow species. All of these woody plants produce secondary chemical compounds that often function to deter moose and other herbivores from browsing the plant to death. Some plants store the secondary chemical compounds in higher concentrations in the shoot tips and buds and respond to damage by increasing chemical concentrations. Plants can store these chemical compounds at higher concentrations when the plant is young and most vulnerable. In some instances the secondary chemicals can be deadly. The way a plant uses secondary chemical compounds varies between species, and herbivores in an area adapt to these strategies.
Three dead moose were found in Anchorage winter of 2010-2011 after consuming bird cherry trees (Prunus padus), which contain a plant secondary chemical compound called a cyanogenic glycoside (Woodford 2011). When an animal consumes such a plant the chewing and digestive actions break the cells releasing the cyanogenic glycoside (Francisco 2000). Enzymes come in contact with the released cyanogenic glycoside and facilitate the process of breaking the chemical down and releasing Hydrogen Cyanide (HCN) a toxic gas (Francisco 2000). The HCN is transferred to blood cells and is redistributed throughout the body where it has a primary toxic affect on the central nervous system (CNS) (Dirikolu 2003). The redistribution effectively prevents much of the HCN from coming in contact with the CNS, and allows large animals such as moose and horses to consume small amounts of toxic HCN without death or clinical signs (Dirikolu 2003). However, when high enough concentrations are reached in an animal poisoned with HCN the animal will show clinical signs such as erratic behavior, gasping for air, staggering and in some instances death.
The cherry trees responsible for the recorded deaths of the moose were all planted in private landscapes (Woodford 2011). These cherry trees are invading natural forests throughout Anchorage, and in some instances appear to be the dominant vegetation (Flagstad 2010). Other research on these trees affect to salmon habitat has shown that they do not support the quantity or diversity of insects as other tree species (Roon 2011). Fewer insects on the tree may be from the cyanogens contained in the tree preventing insects from eating the leaves.
Moose eat a variety of browse species in the winter, and all contain some toxic chemicals. Scientists believe that by eating a variety of species, moose are able to gain the nutrition they require while not building up high concentrations of toxic chemicals from a single browse species (Risenhoover 1989). Since the toxins act alone and not together this keeps moose from getting sick from the food it eats (e.g. imagine if you could only eat jalapeno, basil, coco and coffee beans). Moose may be learning to eat wild and domestic cherry trees, which may or may not have affects on the ecosystems ability to support the moose. Let’s explore the question: Are moose learning to eat wild cherry trees?
Study Questions:
1.From the data collected, which tree species do moose seem to prefer as browse?
2. Is there evidence that moose are significantly eating bird cherry trees?
3. What differences in consumption of cherry trees and other species are noticeable from this data?
4. From this data, what can you infer about cherry consumption, consequences or benefits to moose?
Vocabulary:
Woody Browse- (noun) Species of trees or shrubs that moose will eat.
Bud- (noun) part of plant that will flower during the growing season.
Enzyme- (noun) Protein that binds to specific chemicals to facilitate a reaction resulting in the chemical breaking down into different compounds.
Cyanogenic- (noun) Compound that releases hydrogen cyanide, a poisonous gas, when broken down.
Glycoside- (noun) Compound that plants often use to store toxins in a manner that keeps the toxin in a harmless state.
Works Cited:
Dirikolu, Levent, C. Hughes, D. Harkins, J. Boyles, J. Bosken, F. Lehner, A. Troppman, K. McDowell, and T. Tobin. 2003. The Toxicokinetics of Cyanide and Mandelonitrile in the Horse and Their Relevance to the Mare Reproductive Loss Syndrome. Toxicology Mechanisms and Methods. 13: 199-211.
Flagstad, L., H. Cortés-Burns, and T.L. Roberts. 2010a. Invasive plant inventory and Bird Cherry control trials. Phase II: Bird Cherry distribution, demography and reproduction biology along the Chester and Campbell Creek trails, Anchorage, Alaska. Prepared for The Municipality of Anchorage and The Anchorage Parks Foundation. Alaska Natural Heritage Program, University of Alaska Anchorage, Anchorage, AK. 61 pp. http://aknhp.uaa.alaska.edu/botany/akepic/publications/ Downloaded 2/16/2012.
Francisco, Ilza A. and M. H. Pimenta-Pinotti. 2000. Cyanogenic Glycosides in Plants. Brazilian Archives of Biology and Technology. 43(5): 487-492.
Roon, David A. 2011. “Ecological effects of invasive European bird cherry (Prunus padus) on salmonid food webs in Anchorage, Alaska streams.” M.Sc. Thesis, University of Alaska Fairbanks. http://aknhp.uaa.alaska.edu/botany/akepic/publications/ Downloaded 2/16/2012.
Risenhoover, Kenneth L. 1989. Composition and Quality of Moose winter Diets in Interior Alaska. Journal of Wildlife Management. 53(3): 568-577.
Woodford, Riley, and C. Harms. 2011. Cyanide-poisoned Moose Ornamental Chokecherry Tree a Devil in Disguise. Alaska Fish and Wildlife News. March 2011. http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=501&issue_id=96 Downloaded 1/27/12.
Go to Winter Tree Identification
For more information or to participate e-mail gagraziano@alaska.edu