Variability in deer diet and plant vulnerability to browsing among forests with different establishment years of sika deer

Abstract

Increased ungulate browsing alters the composition of plant communities and modifies forest ecosystems worldwide. Ungulates alter their diet following changes in availability of plant species; however, we know little about how browse selection and plant community composition change with different stages of deer establishment. Here, we provide insight into this area of study by combining multiple approaches: comparison of the understory plant community, analysis of records of browsing damage, and DNA barcoding of sika deer feces at 22 sites in forests in northern Japan varying in when deer were first established. The coverage of vegetation and number of plant species were only lower at sites where deer were present for more than 20 years, while the difference in plant coverage among deer establishment years varied among plant species. Deer diet differed across establishment years, but was more affected by the site, thereby indicating that food selection by deer could change over several years after deer establishment. Plant life form and plant architecture explained the difference in plant coverage across establishment years, but large variability was observed in deer diet within the two categories. Integrating these results, we categorized 98 plant taxa into six groups that differed in vulnerability to deer browsing (degree of damage and coverage). The different responses to browsing among plant species inferred from this study could be a first step in predicting the short- and long-term responses of forest plant communities to deer browsing.

Geographical and seasonal variation of plant taxa detected in faces of Cervus nippon yakushimae based on plant DNA analysis in Yakushima Island

“…In this analysis, DNA was extracted from undigested plant fragments in the feces. The DNA barcoding region was amplified by polymerase chain reaction (PCR), and the sequences were determined to identify the plant species eaten by individual deer (Matsuki et al, 2008; Nakahama et al, 2021; Sakata et al, 2021). Since this method does not require exterminated deer, it applies to deer populations in the western part and highlands of Yakushima, where deer are not managed.…”

“…Sika deer feed on hundreds of plants, but often selectively forage for their favorable plants (Anonymous, 2012;Hashimoto & Fujiki, 2014;Kato & Okumura, 2004; Research cooperation section of Kanagawa Prefectural Government Nature Conservation Center, 2016; Sakata et al, 2021;Takatsuki, 2009). In habitats where the populations of their favorite plants are reduced, deer change their feeding habits in two ways (Murata et al, 2009;Takahashi & Kaji, 2001).…”

“…To evaluate and predict the damage to vegetation caused by deer feeding and take effective measures against feeding damage, it is necessary to quantitatively evaluate which plants are used as food resources by deer. Recently, Matsuki et al (2008), Nakahama et al (2021), and Sakata et al (2021) have employed the plant DNA analysis of feces to evaluate the food species composition of sika deer. This method is expected to advance the study of deer food plants.…”

Chronic browsing by an introduced mammalian herbivore in a tropical island alters species composition and functional traits of forest understory plant communities

“…Ungulate browsers can structure understory vegetation in forests by affecting the survival, growth, and defense traits of plants within browse height. Ungulates may preferentially browse on palatable plants, potentially favoring species with unpalatable traits in the remnant plant community (Díaz et al, 2007; Sakata et al, 2021; Wigley et al, 2018). This may be especially true where plants respond to browsing by investing more in leaf defense traits (e.g., foliar fiber, phenolics content) (Carmona et al, 2011; Endara & Coley, 2011; Hallam & Read, 2006).…”