Seed dispersal by white-tailed deer: implications for long-distance dispersal, invasion, and migration of plants in eastern North America

Abstract

For many plant species in eastern North America, short observed seed dispersal distances (ranging up to a few tens of meters) fail to explain rapid rates of invasion and migration. This discrepancy points to a substantial gap in our knowledge of the mechanisms by which seeds are dispersed long distances. We investigated the potential for white-tailed deer ( Odocoileus virginianus Zimm.), the dominant large herbivore in much of eastern North America, to disperse seeds via endozoochory. This is the first comprehensive study of seed dispersal by white-tailed deer, despite a vast body of research on other aspects of their ecology. More than 70 plant species germinated from deer feces collected over a 1-year period in central New York State, USA. Viable seeds included native and alien herbs, shrubs, and trees, including several invasive introduced species, from the full range of habitat types in the local flora. A mean of >30 seeds germinated per fecal pellet group, and seeds were dispersed during all months of the year. A wide variety of presumed dispersal modes were represented (endo- and exozoochory, wind, ballistic, ant, and unassisted). The majority were species with small-seeded fruits having no obvious adaptations for dispersal, underscoring the difficulty of inferring dispersal ability from diaspore morphology. Due to their broad diet, wide-ranging movements, and relatively long gut retention times, white-tailed deer have tremendous potential for effecting long-distance seed dispersal via ingestion and defecation. We conclude that white-tailed deer represent a significant and previously unappreciated vector of seed dispersal across the North American landscape, probably contributing an important long-distance component to the seed shadows of hundreds of plant species, and providing a mechanism to help explain rapid rates of plant migration.

Ecosystem and competition impacts of introduced deer

“…The role of deer and other ungulates as endozoochorous seed dispersers is now increasingly recognised (Malo and Suare 1995;Pakeman et al 2002;Myers et al 2004), with dispersal by deer implicated in long-distance plant dispersal (Myers et al 2004). Within the conifer forest landscape studied by Hemami et al (2004Hemami et al ( , 2005, less than a quarter of plant species persist in situ; the majority recolonise stands during the management cycle (Eycott et al 2006a), with the buried seed bank playing only a minor role (Eycott et al 2006b).…”

Deer Browsing Delays Succession by Altering Aboveground Vegetation and Belowground Seed Banks

“…This selectivity in diet could rapidly lead to depressed diversity of soil seed banks, which in turn is predicted to impact aboveground vegetation, especially early in secondary succession [4], [18]. A number of studies have assessed the impact of deer on aboveground plant communities, particularly in forests [1]–[3], [18]–[25], but few studies have considered how seed bank composition is affected by the presence of large herbivores such as deer. This is a critical link to understanding the long-term impacts of large herbivores as well as the regeneration potential of seed banks following disturbance such as heavy grazing [7], [26].…”

Decreasing deer browsing pressure influenced understory vegetation dynamics over 30 years

“…Moreover, through selective feeding, deer may affect species composition by avoiding unpalatable species or favouring species particularly resilient to browsing (Augustine and McNaughton 1998). Deer also enhance the dispersion of both epi-and endo-zoochorous species (Myers et al 2004) and, conversely, may alter the reproductive process of other plants by consuming flowers (Mårell et al 2009) or fruits, like acorns, that are preyed upon by deer (Picard and Gégout 1992). These effects of deer activity directly impact plant communities and more generally alter environmental conditions that could induce secondary changes in vegetation composition.…”