Measuring salivary cortisol in wild carnivores

Area of Science:

• Behavioral endocrinology
• Wildlife biology
• Animal physiology

Background:

• Non-invasive hormone analysis is crucial for studying wild animals.
• Salivary hormone assays offer a promising alternative to traditional methods.
• Spotted hyenas (Crocuta crocuta) exhibit complex social structures, making them ideal for behavioral studies.

Purpose of the Study:

• To develop and validate a non-invasive salivary cortisol assay for juvenile spotted hyenas.
• To investigate the relationships between salivary cortisol levels and temporal/social variables in wild hyenas.
• To provide a methodological framework for salivary cortisol analysis in other wild carnivores.

Main Methods:

• Collection of over 260 saliva samples from nearly 70 juvenile spotted hyenas.
• Validation of a salivary cortisol assay for use in this species.
• Analysis of cortisol levels in relation to daily rhythms, dominance, age, sex, social rank, and social behaviors.

Main Results:

• Evidence of a bimodal daily rhythm in salivary cortisol, with concentrations decreasing around dawn and dusk.
• Dominant littermates exhibited lower cortisol levels compared to singleton juveniles.
• Cortisol levels did not significantly vary with age, sex, or maternal social rank.
• Inflicting aggression on others was associated with lower salivary cortisol concentrations.

Conclusions:

• Salivary cortisol analysis is a viable tool for studying behavioral endocrinology in wild spotted hyenas.
• Social dynamics, particularly dominance and aggression, influence cortisol levels in juvenile hyenas.
• The described methods can be adapted for salivary cortisol measurement in other wild carnivore species.