A test of reactive scope: Reducing reactive scope causes delayed wound healing

Area of Science:

• Physiology
• Ecology
• Animal Behavior

Background:

• The reactive scope model posits animals possess adaptive stress responses (reactive homeostasis) before pathological effects occur (homeostatic overload).
• Previous research has interpreted wildlife stress effects using this model, but direct experimental testing was lacking.

Purpose of the Study:

• To experimentally test the reactive scope framework by manipulating reactive homeostasis ranges in house sparrows.
• To investigate how chronic stress, mediated by corticosterone, affects subsequent stressor responses and pathology.

Main Methods:

• House sparrows were subjected to chronic stress with manipulated corticosterone levels (elevated, blocked, or unmanipulated) to alter allostatic load.
• Following chronic stress, birds received a superficial wound challenge to assess pathological effects.
• Measurements included weight changes and wound healing rates.

Main Results:

• Birds with elevated corticosterone (high allostatic load) showed the most pathology: weight loss and slower wound healing.
• Unmanipulated birds (medium allostatic load) experienced weight loss but normal healing.
• Birds with blocked corticosterone (low allostatic load) exhibited minimal weight loss and normal healing.

Conclusions:

• Increased allostatic load reduces the reactive homeostasis range, making individuals more susceptible to homeostatic overload.
• Findings support the reactive scope framework, demonstrating a direct link between stress exposure, coping capacity, and pathology.