Scientists in Sweden studied what four types of wild deer eat by analyzing their droppings using DNA technology. They found that moose, roe deer, red deer, and fallow deer eat very different plants depending on the season and where they live. The research shows that deer are flexible eaters and can adapt their diets based on what’s available. This matters because as deer populations grow in areas near humans, understanding what they eat helps us manage forests and farmland better. The study looked at over 2,500 samples across two different Swedish landscapes to understand how these animals share food resources.

The Quick Take

  • What they studied: What different types of wild deer eat throughout the year in Swedish forests, and whether they compete for the same foods
  • Who participated: Four deer species (moose, roe deer, red deer, and fallow deer) living in two different Swedish regions with different amounts of forest, farmland, and deer populations. Scientists collected 2,568 droppings to study
  • Key finding: Deer eat plants from over 70 different plant families, but usually stick to fewer than 10 favorite foods. Moose eat lots of pine trees, while smaller deer prefer shrubs and plants. What they eat changes by season and location
  • What it means for you: If you live near deer populations or manage forests, this research suggests that deer are flexible eaters who can adapt to different environments. This helps explain why deer populations can grow in areas near human farms and towns

The Research Details

Scientists collected droppings from four different deer species across two Swedish landscapes over multiple seasons. They used DNA technology called metabarcoding to identify exactly which plants were in each sample. This is like using a genetic fingerprint to identify plants the deer had eaten. The two study areas were different: one was mostly forest near the coast, and the other mixed forest with farmland. This allowed researchers to see how different environments and deer population sizes affected what the animals ate.

The researchers compared how much diet overlap existed between different deer species and within the same species across seasons. They looked at whether deer in areas with more farmland ate differently than deer in pure forest areas. They also examined whether areas with more deer had more competition for food, which might change what each species ate.

Understanding what wild deer eat is important because deer populations are growing across Europe and moving into new areas. When many deer live close together and near human farms, they can damage crops and forests. By knowing what each deer species prefers to eat and how flexible they are, forest managers and farmers can better predict problems and plan solutions. This research helps answer whether different deer species can peacefully share the same forest or if they compete too much

This study is strong because it examined a very large number of samples (2,568 droppings) across multiple seasons and two different landscapes. Using DNA technology to identify plants is more accurate than trying to identify plants by looking at droppings under a microscope. The researchers tested their predictions with real data rather than just guessing. However, the study only looked at two Swedish regions, so results might be different in other parts of Europe or the world

What the Results Show

The research confirmed that different deer species eat different things, which helps them share forest resources. Moose are heavy pine eaters, especially in spring and winter, eating more than 35-50% pine depending on location. In summer and fall, moose eat less pine (around 15%). Smaller deer like roe deer and red deer prefer shrubs, especially Vaccinium (a blueberry-like plant), and various forbs (soft plants). Birch and willow trees were important foods during growing season for all species.

The study found that red and fallow deer are very flexible eaters with diverse diets, while moose and roe deer are more specialized. This dietary flexibility of red and fallow deer could mean they compete more with other species when food becomes scarce. Diet overlap between different deer species changed with the seasons—it was lowest during summer and fall, suggesting deer spread out their eating habits when food is most abundant.

Interestingly, in areas where humans feed deer supplementary food like hay or silage, smaller deer ate more forbs in winter. This shows that human feeding practices change what wild deer eat. The research also found that areas with more farmland and higher deer populations had different patterns of food sharing compared to pure forest areas.

Spruce trees were used very little by the deer studied. Vaccinium shrubs were consistently important year-round for all species, making them a key resource. The diversity of plants eaten varied between species—moose had the highest overlap with itself across seasons (meaning moose individuals ate similar diets), while fallow deer showed the lowest overlap (meaning individual fallow deer ate quite different things from each other). Habitat diversity and the amount of farmland in an area influenced how much different deer competed for food, though these effects were different for each species

This study builds on previous research showing that different deer species can coexist by eating different foods. The findings support the idea that deer are adaptable eaters. The research adds new detail by showing exactly which plants matter most and how these patterns change with seasons and landscapes. Previous studies suggested this flexibility existed, but this is one of the first to document it so thoroughly across multiple species and seasons

The study only examined two Swedish landscapes, so results might not apply to other regions with different climates or plant types. The research couldn’t directly measure how much food was available, only what deer actually ate. Some plant families might be easier to detect with DNA than others, which could bias results. The study didn’t track individual deer over time, so it’s unclear whether specific deer change their diets or if different individuals just prefer different foods. Finally, the research focused on wild deer but noted that human supplementary feeding affects diets, making it harder to understand purely natural eating patterns

The Bottom Line

Forest and wildlife managers should recognize that different deer species have different food preferences but can adapt their diets based on availability. In areas with multiple deer species, management should focus on maintaining diverse plant communities rather than assuming deer will compete equally for all resources. Where human supplementary feeding occurs, managers should understand this changes natural eating patterns. Regular monitoring of deer diets using similar methods can help track how populations adapt to changing landscapes (Confidence: Moderate to High)

Forest managers, wildlife biologists, and farmers in areas with growing deer populations should pay attention to this research. Hunters and outdoor enthusiasts interested in understanding deer behavior will find this useful. Policymakers deciding on deer management strategies should consider these findings. This research is less directly relevant to people in urban areas without deer populations, though it provides interesting ecological context

Changes in deer populations and their impacts on forests happen over years to decades, not weeks or months. If management strategies change based on this research, effects on forest health and crop damage would likely become visible over 2-5 years. Understanding deer diet patterns helps predict long-term ecosystem changes

Want to Apply This Research?

  • If tracking wildlife observations, users could record which plants they see deer eating in different seasons and locations, then compare their observations to this research’s findings
  • For hunters or wildlife watchers, use this information to predict where different deer species will be found based on seasonal plant availability and landscape type
  • Over months and seasons, track observations of deer in your area and note which plants are being eaten or damaged, comparing patterns to seasonal predictions from this research

This research describes what wild deer eat in Swedish forests and should not be interpreted as dietary or health advice for humans. The findings apply specifically to European deer species in northern climates and may not apply to other regions or deer species. This study is observational research and shows patterns of deer feeding, not cause-and-effect relationships. Anyone making wildlife management decisions should consult with local wildlife experts and consider additional research specific to their region. This information is for educational purposes and should not replace professional wildlife management guidance.