Impacts of mute swans (Cygnus olor) on submerged aquatic vegetation in Illinois River Valley backwaters

By: , and 



Wetland loss in North America has been considerable and well documented, and the establishment of exotic species in remaining wetlands can further reduce their ability to support native flora and fauna. In the Chesapeake Bay and Great Lakes ecosystems, exotic mute swans (Cygnus olor) have been found to negatively impact wetlands through degradation of submerged aquatic vegetation (SAV) communities. Mute swan populations have expanded into many areas of mid-continental North America outside the Great Lakes ecosystem, but the environmental impact of these populations is not well known. Mid-continental wetlands in North America differ in physical characteristics (e.g., size, depth, and permanency) and aquatic vegetation species composition compared to wetlands in other areas where mute swans have been studied and, thus, may be more or less susceptible to degradation from swan herbivory. To investigate the impact of mute swan herbivory on SAV communities in mid-continent wetlands, we used exclosures to prevent swans from foraging in 2 wetland complexes in central Illinois. Above-ground biomass of vegetation did not differ between exclosures and controls; however, mean below-ground biomass was greater in exclosures (52.0 g/m2, SE = 6.0) than in controls (34.4 g/m2 SE = 4.0). Thus, although swan densities were lower in our study region compared to that of previous studies, we observed potentially detrimental impacts of swan herbivory on below-ground biomass of SAV. Our results indicate that both above-ground and below-ground impacts of herbivory should be monitored, and below-ground biomass may be most sensitive to swan foraging.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Impacts of mute swans (Cygnus olor) on submerged aquatic vegetation in Illinois River Valley backwaters
Series title Wetlands
DOI 10.1007/s13157-012-0316-6
Volume 32
Year Published 2012
Language English
Publisher SpringerLink
Contributing office(s) Coop Res Unit Leetown
Description 7 p.
First page 851
Last page 857
Country United States
State Illinois
Online Only (Y/N) N
Additional Online Files (Y/N) N