Moose as a vector for non-indigenous plant species in Alaska

Authors: Seefeldt, Steven; COLLINS, WILLIAM - Alaska Department Of Fish And Game; Kuhl, Joseph; CLAUSS, MARCUS - University Of Zurich

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/30/2010
Publication Date: N/A
Citation: N/A

Interpretive Summary: White sweetclover and narrowleaf hawksbeard are two widespread non-indigenous plant species that are rapidly expanding in Alaska. White sweetclover is expanding most rapidly along roadsides, river flood plains and in disturbed urban areas. Narrowleaf hawksbeard, with a wind-blown seed has been found in recently burned natural areas. There was concern that moose could be a vector for the spread of these two species after ingesting viable seed. A study was conducted to determine whether and for how long viable seed could be found in moose feces after ingestion. Narrowleaf hawksbeard is not a species of concern for moose mediated dispersal as only 5 seedlings were produced after the ingestion of over 50,000 live seed. Sixteen percent of viable white sweetclover seed survived mastication and digestion in moose and seedling-producing seed were found 11 days after feeding. Management programs will need to be developed to limit the availability of white sweetclover seed for moose. Management could include techniques such as mowing after flowering so that any seed will be covered in snow during the winter or use of herbicides to prevent seed production. Scouting for new infestations of white sweetclover spreading from established populations will need to factor in moose trails and the distance moose can move over several days.

Technical Abstract: White sweetclover and narrowleaf hawksbeard are non-indigenous invasive plant species in Alaska that are rapidly spreading, including into areas that are otherwise free of non-indigenous plants. There has been concern that native moose could be dispersing viable seed from these plants after ingestion. To address this concern, a seed-viability study was conducted involving tame moose at the University of Alaska Fairbanks Agriculture and Forestry Experiment Station, Matanuska Experiment Farm, Palmer, Alaska. Objectives were to determine if seeds from these two plant species could survive mastication and digestive passage through moose, whether this passage impacted seed viability, and whether seed passage rates were the same as similar sized Cr-mordanted fiber. In this study, narrowleaf hawksbeard seed rarely survived mastication and digestion with only 5 seedlings recovered from 42,000 live seed fed to the moose. About 16% of live white sweetclover seed (3,595 of 22,000) fed to the moose produced seedlings. Most of the sweetclover seedlings came from feces produced 2 and 3 days after feeding. In 2 moose, sweetclover seedlings were grown from fecal material that was passed 11 days after feeding, raising the possibility that seeds could be transported long distances after ingestion. Cr-mordanted fiber passage did not closely follow seedling producing seed, possibly because time in the rumen may reduce seed viability. Once roadsides in Alaska become infested with white sweetclover, moose may then serve as a transport vector of these weeds into river channels and floodplains which are distant from roads. This information will impact white sweetclover management programs and alert land managers to the potential for other instances of wildlife-mediated seed dispersal.