An introduced competitor elevates corticosterone responses of a Native Lizard (Varanus varius)

Area of Science:

• Ecology
• Physiology
• Conservation Biology

Background:

• Glucocorticoid hormone profiles serve as physiological markers for species interactions.
• Understanding these interactions is crucial for animal fitness and population dynamics.

Purpose of the Study:

• To assess the impact of capture stress on lace monitor (Varanus varius) corticosterone levels.
• To compare basal and stress-induced corticosterone responses in lace monitors across varying densities of introduced European red foxes (Vulpes vulpes).

Main Methods:

• Measured plasma corticosterone in lace monitors before and after a 90-minute capture stress protocol.
• Compared corticosterone levels between lizards in high and low red fox density habitats.

Main Results:

• Lace monitors exhibited significantly increased plasma corticosterone post-capture.
• Lizards in high fox density habitats showed higher basal and stress-induced corticosterone levels.
• Fox density, time postcapture, and body condition interacted to influence corticosterone levels.

Conclusions:

• Competition with red foxes may induce physiological stress in lace monitors, potentially through nutritional stress or increased adrenocortical axis sensitivity.
• These stress responses could have adaptive or maladaptive consequences for lizard populations.
• Introduced competitors can significantly impact native biodiversity through physiological mechanisms.