* Corresponding author
1 These authors contributed equally to this work
Correspondence: Minghai Zhang Email: zhangminghai2004@126.com
Abstract: The foraging strategies of sympatric ungulates with similar ecological niches are important for understanding ecological niche differentiation, resource utilization, competition, and coexistence and for understanding the ecological impacts on plant communities in the ecosystem. The behavior of the wapiti (Cervus elaphus ) and Siberian roe deer (Capreolus pygargus ) foraging on Japanese yew (Taxus cuspidata ) has affected its succession and renewal in the northeastern forests of China, which has become an urgent problem for the relevant departments. This study analyzed the foraging strategies of the wapiti and Siberian roe deer on Japanese yew from July 2021 to January 2024 using field investigations and infrared camera monitoring in the Muling National Nature Reserve, Heilongjiang Province, China. It was found that the wapiti and Siberian roe deer have different foraging strategies in terms of time, space, and behavior. Temporally, they both preferred to forage for the saplings of the Japanese yew during the winter season, the degree of overlap in foraging rhythms was medium (Dhat1=0.67), and the diurnal foraging activity index (D RAI) of the wapiti was larger than that of the Siberian roe deer. Spatially, the suitable foraging habitat of the Siberian roe deer was twice that of the wapiti, and their overlap was low in the location and direction of saplings and the distance of the seed tree. Behaviorally, the foraging intensity of the wapiti was heavy, and Siberian roe deer was low. Foraging reduced the average primary branch height, number of new branches, and length of lateral branches of saplings, and the influence of the wapiti was significantly greater than that of the Siberian roe deer. This study provides a scientific basis for solving the conservation and management problems of the deer animals foraging on Japanese yew and contributes to further understanding of the competition-coexistence mechanism of sympatric species.
Keywords: Cervus elaphus ; Capreolus pygargus ;Taxus cuspidata ; foraging strategy; Kernel Density Estimation; Maximum Entropy Model
INTRODUCTIONThe foraging strategy of ungulates is a key link between primary production and food webs (Elsayed and Din, 2019). It influences the structure and trends of changes in the biome (Shoener, 1987; Wang et al., 2001), species distribution, resource utilization, and population dynamics (Heleno et al., 2012; Tylianakis et al., 2010; Zanni et al., 2021), and plays a major role in maintaining structural integrity and balance (Ge et al., 2012; Kasiringua et al., 2020; Wang et al., 2019a). Studies have found that the foraging of ungulates affects the growth of plants, seriously leads to the failure of renewal, and has a negative effect on interspecific competition (Bödeker et al., 2021; Konôpka et al., 2021; Kamler et al., 2010; Klopcic et al., 2010; Vacek, 2017), and spruce (Picea abies ) seedlings grow slowly when foraged by roe deer (Capreolus capreolus ) (Bergquist et al., 2003). Faced with this situation, plants will develop defense mechanisms; for example, sheep (Ovis aries ) reduce their intake when the flavonoid content of their food is too high (Sun, 2008). Interactions between sympatrically distributed animals and plants have been a classic proposition in evolutionary ecology, and the ecological impacts produced by animals on plants have been a popular topic of discussion in conservation biology and biodiversity conservation (Feng, 2022). In northeastern China, Japanese yew (Taxus cuspidata ) is a tertiary relict plant (Liu, 2007), which is a wild and endangered class I national protected plant. The wapiti (Cervus elaphus ) and Siberian roe deer (Capreolus pygargus ) are both protected animals and are the main prey of the Amur tiger (Panthera tigris ) and Amur leopard (Panthera pardus orientalis ). The wapiti, Siberian roe deer, and Japanese yew are, therefore, all the main protection species that need to be focused on for the protection and management of national parks and nature reserves. Previous studies have found that both the wapiti and Siberian roe deer foraged on Japanese yew under environmental stresses such as low temperatures, snow cover, and lack of food resources in winter (Feng, 2022). The Japanese yew accounts for 13% of the winter food composition of the wapiti, which leads to significant damage to the saplings (Zhu et al., 2019). As a result, their number and distribution range has declined sharply (Diao et al., 2020; Yang, 2018). On the other hand, the number of ungulates, such as the wapiti, is also decreasing in reserves due to human activities such as long-term forest logging, illegal poaching, and road construction in the past (Dixon et al., 2021; Sarula et al., 2019). Protecting wildlife like the wapiti, without affecting the succession and renewal of the Japanese yew forests has become an urgent problem for the management department of nature reserves. This study, therefore, analyzed the impacts of these two ungulates on Japanese yew by comparing their temporal and spatial strategies, and behavioral characteristics, to provide a scientific basis for solving the problem of their protection and management. The results not only contribute to further understanding of the competition-coexistence mechanism of sympatric species but also enrich the study of animal and plant interaction and co-evolution.
MATERIALS AND METHODS2.1 Study areaThe study area is located in the Muling National Nature Reserve, in the southern part of the Laoyeling, in the northern part of the Changbai Mountain (130°00′–130°28′E, 43°49′-44°06′N). The south is bordered by the Tianqiaoling Forestry Bureau of Jilin Province, the east is bordered by the Suiyang Forestry Bureau of Heilongjiang Province, and the west, north, and northeast are connected with the Gonghe Management Office, Shuangning Forest Farm, and Yangmuqiao Forest Farm of Muling Forestry Bureau, with a total area of 356.48 km2 (Feng, 2022). The mountains in this area are low, with altitudes ranging from 500m to 900m, and the landforms are distributed in bands. The climate is the typical temperate continental climate with an average annual temperature of approximately -2℃. The rainy season is short, and precipitation is concentrated, with an average annual rainfall of 514 mm and an annual frost-free period of 130 d (Tian et al., 2022). The forests in the reserve are primarily coniferous, broad-leaved forests, mixed coniferous and broad-leaved forests, and thickets, with 839 plant species belonging to 113 families and 373 genera. The dominant species are red pine (Pinus koraiensis ), purple linden (Tilia amurensis ), and red-barked spruce (Picea koraiensis ). There are 42 vertebrate species belonging to six orders and 14 families, represented by the Amur tiger, Amur leopard, wapiti, sika deer (Cervus nippon ), Asian black bear (Ursus thibetanus ), and wild boar (Sus scrofa ).2.2 Methods2.2.1 Field investigation
Areas with a relatively concentrated distribution of Japanese yew were selected for field investigations every winter from 2021 to 2024. The saplings were divided into foraging and control groups. During the survey, the saplings that were foraged on were labeled and their height, length of lateral branches, number of branches foraged, total number of branches, and information about the surrounding environment were recorded. Normal saplings were selected as controls in the corresponding areas, and the plant height and number of branches were recorded. The height of the primary branch growth, the number of new branches, and the length of lateral branch growth for each sapling were recorded every summer from 2021 to 2024.
The footprints and foraging traces were combined to distinguish saplings foraged by the wapiti or the Siberian roe deer. A total of 1947 foraging traces were observed. Among them, 1,235 were of the wapiti and 712 of the Siberian roe deer.
2.2.2 Infrared camera monitoring