A bookshelf cage can be enough space for a squirrel, but only if its stress system, not its snack bowl, drives the design. Heart rates that spike like sirens depend on a functioning hypothalamic pituitary adrenal axis, where brief surges of cortisol and catecholamines mobilize glucose, sharpen attention, then drop again.
The lazy assumption says more sunflower seeds equal better care. Biology disagrees. Constant treats without outlets for locomotor activity push insulin and lipid storage while leaving sympathetic activation unchecked, a recipe for chronic low grade inflammation and stereotypic pacing. What that animal needs is vertical complexity, objects to shred, branches to climb, and dark refuges that let the amygdala stand down.
Good captive design treats stress like a resource to budget, not a nuisance to erase. Short, predictable stressors, such as brief handling at fixed times, help maintain circadian rhythm of cortisol and prevent allostatic overload, while random noise, bright light, and human tapping flood the system with signals it cannot resolve. The bookshelf can work, but only when every inch answers a physiological question rather than a craving for seeds.
