GCE Announcement
Publication News
New GCE paper on how grazing by large mammals affects marsh invertebrates
Lugar and Pennings (2025, Estuaries and Coasts 48:105) looked at how grazing by cows, horses and humans (mowing) affected marsh invertebrates (snails, insects, spiders) in GA Spartina marshes. Heavy grazing by cattle reduced plant abundance, the abundance of Littoraria snails, and the abundance of most arthropods. Moderate grazing by horses had variable effects depending on invertebrate species, and mowing increased densities of some arthropods, probably because regrowing plants were high in nitrogen. Katydids (Orchelimum) were always reduced by grazing, and individuals grew poorly on leaves from grazed plots. Because grazing type (cattle, horses, people) and intensity and location were confounded in this study, we can't be sure which was the most important factor, but it's likely that grazing intensity was the reason that cattle grazing had strong negative effects on the marsh food web. In contrast, moderate levels of mammalian grazing, as exemplified by horses on Cumberland Island, probably do not have a large effect on marsh invertebrates, especially given the patchy nature of mammal grazing (horses and cattle won't cross creeks, and so are limited to marshes adjacent to upland habitat).
This study leveraged work by Kate Davidson, John Griffin and the Angelini lab at Cumberland Island, and we're grateful to all of them.
(Contact Steve Pennings for additional information)
submitted May 01, 2025
