Detecting the effects of predator-induced stress on the global metabolism of an ungulate prey using fecal metabolomic fingerprinting

Azzurra Valerio,Luigi Boitani,Robert B Wielgus,Alessandro Giuliani,Stephanie L Simek,Mariacristina Valerio,Luca Casadei,C Steven Borrego

doi:10.1038/s41598-021-85600-z

Abstract

Few field tests have assessed the effects of predator-induced stress on prey fitness, particularly in large carnivore-ungulate systems. Because traditional measures of stress present limitations when applied to free-ranging animals, new strategies and systemic methodologies are needed. Recent studies have shown that stress and anxiety related behaviors can influence the metabolic activity of the gut microbiome in mammal hosts, and these metabolic alterations may aid in identification of stress. In this study, we used NMR-based fecal metabolomic fingerprinting to compare the fecal metabolome, a functional readout of the gut microbiome, of cattle herds grazing in low vs. high wolf-impacted areas within three wolf pack territories. Additionally, we evaluated if other factors (e.g., cattle nutritional state, climate, landscape) besides wolf presence were related to the variation in cattle metabolism. By collecting longitudinal fecal samples from GPS-collared cattle, we found relevant metabolic differences between cattle herds in areas where the probability of wolf pack interaction was higher. Moreover, cattle distance to GPS-collared wolves was the factor most correlated with this difference in cattle metabolism, potentially reflecting the variation in wolf predation risk. We further validated our results through a regression model that reconstructed cattle distances to GPS-collared wolves based on the metabolic difference between cattle herds. Although further research is needed to explore if similar patterns also hold at a finer scale, our results suggests that fecal metabolomic fingerprinting is a promising tool for assessing the physiological responses of prey to predation risk. This novel approach will help improve our knowledge of the consequences of predators beyond the direct effect of predation.

Highlights

Few field tests have assessed the effects of predator-induced stress on prey fitness, in large carnivore-ungulate systems
In our study we used NMR-based fecal metabolomic fingerprinting as a novel non-invasive approach to detect the effects of predator-induced stress on the fecal metabolome of a prey
This metabolic difference was statistically significant with both principal component analysis (PCA) and orthogonal projection to latent structure discriminant analysis (OPLS-DA), the predictive ability of both models in site C (Q2 = 0.33; Q2 = 0.35) were relatively low compared to site A (Q2 = 0.71; Q2 = 0.53) and B (Q2 = 0.63; Q2 = 0.73)

Summary

Introduction

Few field tests have assessed the effects of predator-induced stress on prey fitness, in large carnivore-ungulate systems. While the precise mechanisms whereby the gut microbiome modulates stress response have not been clearly established (but see30), recent studies suggest that the temporal changes of the gut microbial metabolism in response to early life stress in chickens Gallus gallus domesticus[31], mild-prolonged stress in mice Mus musculus[32], and restraint and separation in cattle Bos taurus[33] may aid in identification of stress This detection function is possible because the gut microbial metabolism is directly linked to the host metabolism: low-molecular weight compounds (metabolites) produced by the host after metabolism and conjugation in the liver, are excreted in the intestine where they are further metabolized by the gut microbes[34]. The recent development of high-throughput techniques such as fecal metabolomics have become increasingly popular to non-invasively detect these subtle phenotypic c hanges[37]

Methods

Results

Conclusion