Table 1.

Potential mechanisms underlying resistance of the hypothalamic-pituitary-gonadal axis to stress (from Wingfield and Sapolsky, 2003).

Mechanism	Examples
A: Blockade at the CNS level: stressors are not perceived as stressful	Lekking species, breeding snow bunting
B: Blockade at the level of the HPA: failure to secrete glucocorticosteriods	Many avian species, breeding Lapland Longspurs, redpolls, garter snakes
C: Blockade at the level of the HPG: resistance of the gonadal axis to glucocorticosteriod actions	Male olive baboons, Arctic songbirds
D: Compensatory stimulatory inputs to the gonad axis to counteract inhibitory glucocorticosteriod actions	Male olive baboons, male Arctic ground squirrels, dark-eyed junco
E: Protection from the actions of glucocoticosteriods by, for example, steroid binding proteins	Tree lizards