Diet analysis of David’s deer (Elaphurus davidianus) based on stable isotope analysis

Supplemental feed for free-ranging deer is often advocated by managers to
compensate for winter survival. However, providing extra food has great
costs so it is important to know how essential supplemental feed is for
deer populations. In our study, supplemental feed is supplied year round
for free-ranging Père David’s deer (Elaphurus davidianus) since
early 2019 to help them survive food shortages in the Jiangsu Dafeng Milu
National Nature Reserve. To understand use of supplemental feed, we
quantified the biomass contributions of C3 plants, C4 plants, and
supplemental feed consumed by free-ranging deer by assessing their faecal
carbon and nitrogen stable isotope values in May, July, October and
December. The diet-faeces trophic shift of deer was assessed using
semi-captive animals. Faeces in both areas were collected and faecal δ13C
values revealed more variable diets of free-ranging deer than semi-captive
deer in different months. MixSIAR model showed that C4 plants contributed
greatly to deer diet biomass (75.1%, 82%, 64.3%,79.4%, respectively in
May, July, October and December) compared with C3 plants and supplemental
feed. We suggest that managers should consider the efficiency of long-term
supplemental feed and consider the selection of C3 and C4 plants during
restoration.