Mother deer's foraging of agricultural crops promotes growth of her offspring

A research team led by Professor Mayura Takada in Graduate School of Science and Engineering at Chuo University, and composed of Chuo University, National Agriculture and Food Research Organization, Forestry and Forest Products Research Institute, and National Institute for Environmental Studies announced on April 10 that they have found that foraging agricultural crops promotes skeletal growth of Japanese deer. The team also found that mother deer's foraging of agricultural crops promotes the growth of her offspring from the embryonic stage. Foraging of agricultural crops by female deer may lead to further population growth and increase in the feeding damage. In the future, the research group aims to establish the method to reduce agricultural damage caused by Japanese deer. The results were published in PeerJ.

In 2023, among wild bird and animal species in Japan, deer caused the highest damage to agricultural crops, amounting to approximately 7 billion yen (45 million USD) per year.

In large herbivores, body size of the animal at birth has a significant impact on the survival rate and subsequent reproductive success. Hind foot length, an indicator of body size, is also related to the mortality in the first winter.

In deer, which are a herbivorous animal, foraging agricultural crops that are more nutritious than wild plants may have a significant impact on its growing process. Furthermore, mother deer foraging high nutrient agricultural crops may affect the growth of her baby deer. On the other hand, the relationship between body size and foraging of agricultural crops, i.e., the relationship directly related to the survival rate and reproduction, has been unclear until now.

In this study, in order to quantify the effects of the foraging on the skeletal growth of the deer, the team analyzed specimens of 219 wild Japanese sika deer (145 females and 74 males) and 42 fetuses of the females (16 females and 26 males), the deer captured in Nagano Prefecture, where a lot of damage has been observed. They analyzed the relationship among the age of the specimen, diet history, skull size, and nitrogen stable isotope ratio (δ¹⁵N) of the bone sample as an indicator of long-term dependence on the agricultural crops.

The results showed that females with higher dependence on agricultural crops reached the maximum skull size at a maximum 1.4 years earlier, and that the deer from the mother deer with higher dependence on agricultural crops increased in its hind leg length at a maximum 15%. On the other hand, in male deer, the dependence on agricultural crops did not necessarily affect growth.

The study indicates that foraging of agricultural crops promotes skeletal growth in Japanese deer, and that mother deer's foraging has an effect on growth promotion in the next generation from the embryonic stage, resulting in a possible increase in the survival rate of the deer.

Female deer's foraging of agricultural crops may lead to the increase in population and feeding damage. The team aims to develop a countermeasure to the agricultural damage based on this study in the future.

Takada said, "Our study also showed that within the same group, there are deer that eat agricultural crops frequently and others who do not. We hope our further study on how this difference has occurred will lead to the development of more effective countermeasures to the agricultural damage by deer."

Journal Information
Publication: PeerJ
Title: Silver-spoon effect in agricultural crop consumers: crop consumption enhances skeletal growth in sika deer
DOI: 10.7717/peerj.19836