Deer Preference and the Spread of Non-Native Invasive Plants
With the decline of natural predators, the population of white-tailed deer has exceeded historic levels and resulted in unprecedented browsing impacts to wild native flora.
A recent study published in the journal Biological Invasions entitled "Deer feeding selectivity for invasive plants" further expands our understanding in the role that deer play in non-native plant population dynamics.
The study documented the feeding preferences of eight mature does without fawns through three seasons; late summer, early autumn, and spring. 15 plant species were arranged in containers, and offered to deer so that they may browse among them. Game cameras were set along the study area, and were set to photograph when triggered by movement and inferred heat signatures. This allowed researchers to observe and measure the amount of biomass per plant species that deer consumed.
Based on this study, researchers found that deer had a taste for specific species and avoided others. Among the species deer actively avoided were non-native Japanese stiltgrass, Japanese barberry, and garlic mustard. They were also found to avoid the native hay-scented fern, which is regarded as a “native invader”.
Through the avoidance of these invasive species, deer are supplying a competitive advantage to undamaged invasive species which may contribute to their ability to aggressively spread. On the other hand, other invasive plants such as Oriental bittersweet, European privet, and Morrow`s honeysuckle were all found to be especially appetizing to deer, so deer may be suppressing the spread of these species.
Additional research may shed new understanding of how these plant-animal interactions further propagate through the ecosystem, as seed viability after digestion has not yet been fully investigated. Preference for invasive species could actually be bad news if seeds survive digestion and are able to disperse further distances via deer droppings. Regardless, ESA will keep an eye out for what researchers discover next on how to suppress non-native invasive plants.