# Appraisal of Allostatic Load in Wild Boars Under a Controlled Environment

## TL;DR

This study measures stress in wild boars using cortisol levels in hair to understand how they adapt to controlled environments.

## Contribution

The study introduces cortisol in bristles as a novel method to assess long-term stress adaptation in wild boars.

## Key findings

- Young wild boars had higher cortisol levels than sub-adult and adult groups initially.
- Cortisol levels in young boars decreased over time, aligning with adult levels.
- Wild boars adapted to the controlled environment, maintaining physiological balance.

## Abstract

Mammals often experience stressful and life-threatening conditions; therefore, they implement neuroendocrine, metabolic or behavioral strategies aimed at survival and, if possible, returning to a physiological state. When the need for adaptation is long-lasting it may eventually lead to poor health conditions. Therefore, assessing allostatic load and resilience abilities is gaining attention in wild species, with the purpose of improving their welfare, even in different contexts, rather than their own ones. Wild boars (Sus scrofa) are attracting more negative attention nowadays because of urbanization and forest regrowth, which are causing them to spread across Europe. Thus, they represent a serious threat for farmers, crops and people in general. However, findings about the homeostatic control of stress in these wild species are still lacking. In the present study, we sought to investigate allostatic load of wild boars in a controlled environment through the evaluation of cortisol concentration from bristles collected at different time points. Our data highlighted the importance of adapting proper and effective strategies to monitor long-term stressful events, as well as preserve the physiological conditions of wild boars, and eventually find solutions to conflicts between humans and animal welfare.

Besides metabolic and cardiovascular parameters, fluctuations in endocrine and inflammatory biomarkers might be regarded as reliable indicators of allostatic load. Among them, glucocorticoids have been shown to correlate with social stress in animals, regardless of whether they are dominant or subordinate, thus highlighting the crucial role of physiological energetic costs, together with social challenges, in the onset and severity of allostasis. Therefore, in the present work, we evaluated and monitored monthly the concentration of cortisol in bristles (pg/mg) over six months in young (n = 8), sub-adult (n = 5) and adult female wild boars (n = 5), which were kept in a controlled State Forest in Southern Italy. Our data revealed higher concentrations of cortisol in young animals when compared to sub-adult (p < 0.01) and adult (p < 0.05) groups. Moreover, such an increase faded away over time, and cortisol concentrations were found to be overlapping those of sub-adult and adult groups, which did not display any significant variation throughout monitoring. Collectively, our findings suggest that the wild boars adapted to the controlled environment, thus preserving both a physiological state and animal welfare.