Deer feeding damage to crops is found all over the world, including Japan.Agricultural crops are nutritious and a good food for deer, but the effect of crop feeding on deer growth and reproduction was unknown.Deer generally begin to breed when their bodies grow above a certain size.Therefore, knowing the effects of crop feeding on body size and pregnancy rate is important for accurately predicting fluctuations in the number of deer inhabiting the region and developing effective damage control methods.

　This time, we targeted 152 female wild sika deer captured in the survey areas of Nagano and Gunma prefectures, where deer damage many crops.First, when the plants mainly eaten outside the farmland and the crops (grass, vegetables) that are harmful to the deer are collected and the stable nitrogen isotope ratio (δ15N value) is measured, the crops show a higher δ15N value. rice field.In addition, when the δ15N value of bone collagen contained in deer bone was measured, the body of a young deer under 4 years old with a higher δ15N value of bone collagen was larger.This indicates that long-term crop feeding may cause young deer to "prematurely ripen", increasing pregnancy rates and increasing populations.

　From this result, it was found that measures to prevent deer from invading agricultural land and extermination of individuals that eat crops are useful for controlling agricultural damage.In addition, since the δ15N value was effective as an index of deer's dependence on crops, it is expected that the δ15N value will be used to elucidate the characteristics of individuals that feed on crops and to develop deer damage control methods.

Paper information:[Ecosphere] Agricultural crop consumption induces precocious maturity in deer by improving physical and reproductive performance