Effects of population density and snow depth on the winter diet composition of sika deer

Diet composition and selection of Père David's deer in Hubei Shishou Milu National Nature Reserve, China

Hubei Shishou Milu National Nature Reserve is an ideal place to restore the wild population of Père David's deer (Elaphurus davidianus). Understanding foraging ecology and diet composition is essential for assessing population development or establishing long-term effective conservation measures for endangered species. However, little is known about the diet composition of Père David's deer and its diet selection mechanism. In this study, we used stable isotope technology to investigate the diet composition of Père David's deer according to various tissues (i.e., fur, muscle, liver, heart, and feces) and seasons, and evaluated the correlation between the nutrient composition of plants and diet composition. Bayesian isotope analysis showed that the autumn and winter diet estimated by fur and fecal samples indicated a diet dominated by C3 grasses (42.7%-57.2%, mean), while the summer diet estimated by muscle and liver samples was dominated by C3 forbs (30.9%-41.6%, mean). The Pearson correlation test indicated that the contribution of winter diet composition reflected by fur and fecal samples was associated with correlations with crude protein (r = .666, p < .01) and soluble sugars (r = .695, p < .01). The results indicated that crude protein and soluble sugars were important factors influencing the winter diet selection of Père David's deer. In the context of the current reintroduction facing many challenges, such as habitat fragmentation, wetland degradation, and human disturbance, comprehensively evaluating the diet selection mechanism of Père David's deer under different resource specificities and temporal changes should be considered in the future.

Long-term stability in the winter diet of the Japanese serow (Artiodactyla, Caprinae)

The winter diets of northern ungulates are sensitive to changes in environmental conditions and ungulate population densities. We hypothesized that the winter diets of smaller browser ungulates might not readily change in response to fluctuating environmental conditions. We analyzed long-term trends in the winter diet of the Japanese serow (Capricorniscrispus) by analyzing rumen contents of 532 individuals over a span of 16 years among five populations along with changes in the population densities of sika deer (Cervusnippon) in Nagano Prefecture, central Japan. The winter diet composition of the serow was stable over the long term despite the increase in deer population density. The little-flexible nature of the serow diet may explain the long-term stability in the winter diets.

Seasonal resource selection of an arboreal habitat specialist in a human-dominated landscape: a case study using red panda

Human dominated landscapes provide heterogeneous wildlife habitat. Conservation of habitat specialists, like red pandas Ailurus fulgens, inhabiting such landscapes is challenging. Therefore information on resource use across spatial and temporal scales could enable informed-decision making with better conservation outcomes. We aimed to examine the effect of geo-physical, vegetation, and disturbance variables on fine-scale habitat selection of red pandas in one such landscape. We equipped 10 red pandas with GPS collars in eastern Nepal in 2019 and monitored them for one year. Our analysis was based on a generalized-linear-mixed model. We found the combined effect of geo-physical, vegetation and disturbance variables resulted in differences in resource selection of red pandas and that the degree of response to these variables varied across seasons. Human disturbances, especially road and cattle herding activities, affected habitat utilization throughout the year whereas other variables were important only during restricted periods. For instance, geo-physical variables were influential in the premating and cub-rearing seasons while vegetation variables were important in all seasons other than premating. Red pandas selected steeper slopes with high solar insolation in the premating season while they occupied elevated areas and preferred specific aspects in the cub-rearing season. Furthermore, the utilized areas had tall bamboo in the birthing and cub-rearing seasons while they also preferred diverse tree species and high shrub cover in the latter. Our study demonstrates the significance of season-specific management, suggests the importance of specific types of vegetation during biologically crucial periods, and emphasizes the necessity to minimize disturbances throughout the year.

Occurrence patterns of crop-foraging sika deer distribution in an agriculture-forest landscape revealed by nitrogen stable isotopes

Conflicts arising from the consumption of anthropogenic foods by wildlife are increasing worldwide. Conventional tools for evaluating the spatial distribution pattern of large terrestrial mammals that consume anthropogenic foods have various limitations, despite their importance in management to mitigate conflicts. In this study, we examined the spatial distribution pattern of crop-foraging sika deer by performing nitrogen stable isotope analyses of bone collagen. We evaluated whether crop-foraging deer lived closer to agricultural crop fields during the winter and spring, when crop production decreases. We found that female deer in proximity to agricultural crop fields during the winter and spring were more likely to be crop-foraging individuals. Furthermore, the likelihood of crop consumption by females decreased by half as the distance to agricultural crop fields increased to 5-10 km. We did not detect a significant trend in the spatial distribution of crop-foraging male deer. The findings of spatial distribution patterns of crop-foraging female deer will be useful for the establishment of management areas, such as zonation, for efficient removal of them.

Dietary resource use and competition between white-tailed deer and introduced sika deer

Content Native communities of herbivores have evolved fundamental dietary niches that avoid or minimise competition; the introduction of exotic species can change dietary niches, cause overlap in resource use, and result in competition for resources. Aims We compared niche breadth, overlap in diet, and quality of diet between introduced sika deer and native white-tailed deer in Maryland, USA. We investigated these changes in free-ranging populations where both species are allopatric as well as when they are sympatric. Methods We used microhistological analysis of faecal samples to determine the percentage of resources used by sika deer and white-tailed deer, as measured between geographical areas of similar habitat quality. We compared resource use specifically by controlling for harvest pressure and resource availability, which are known to alter resource use other than the presence of an additional deer species. Key results We observed a significant resource overlap (range 63–88%) between species. In the presence of sika deer, white-tailed deer displayed an increased niche breadth (108%) and a lower diet quality (17%). Sika deer consumed the same resources that comprised 78% of white-tailed deer diet. Unlike other native ungulates that have dietary overlap with white-tailed deer, sika deer is neither temporally nor geographically segregated in habitat use. Conclusions Resource overlap and changes in niche breadth and diet quality during sympatry strongly denote dietary competition between sika deer and white-tailed deer. This competition results in white-tailed deer altering the dietary selection, thereby consuming lower-quality forage. Implications White-tailed deer are concentrate selectors and require higher diet quality than do sika deer, which can tolerate diets higher in fibre, consistent with their classification as intermediate feeders. A decrease in the nutritional quality of resources used by white-tailed deer could contribute to the decline of white-tailed deer over time and allow the continued spread of sika deer.

Long-term deer exclosure alters soil properties, plant traits, understory plant community and insect herbivory, but not the functional relationships among them

Evidence of the indirect effects of increasing global deer populations on other trophic levels is increasing. However, it remains unknown if excluding deer alters ecosystem functional relationships. We investigated how sika deer exclosure after 18 years changed soil conditions, the understory plant community, the traits of a dominant understory plant (Sasa palmata), herbivory by three insect-feeding guilds, and the functional relationships between these properties. Deer absence decreased understory plant diversity, but increased soil organic matter and ammonium concentrations. When deer were absent, S. palmata plants grew taller, with more, larger, and tougher leaves with higher polyphenol concentrations. Deer absence led to higher leaf area consumed by all insect guilds, but lower insect herbivory per plant due to increased resource abundance (i.e., a dilution effect). This indicates that deer presence strengthened insect herbivory per plant, while in deer absence plants compensated losses with growth. Because plant defenses increased in the absence of deer, higher insect abundances in deer absence may have outweighed lower consumption rates. A path model revealed that the functional relationships between the measured properties were similar between deer absence versus presence. Taken together, deer altered the abiotic and biotic environment, thereby changing insect herbivory, which might impact upon nutrient cycling and primary productivity. These results provide evidence that deer can alter interactions between trophic levels, but that functional relationships between certain ecosystem components may remain constant. These findings highlight the need to consider how increasing global deer populations can have cascade effects that might alter ecosystem dynamics.