Coping with Intense Reproductive Aggression in Male Arctic Ground Squirrels: The Stress Axis and Its Signature Tell Divergent Stories
Bibliographic record
Abstract
We tested the adaptive stress hypothesis that male arctic ground squirrels (Urocitellus parryii) exhibit a stress response over the course of the breeding season that is characterized by increasing free cortisol concentrations, increasing mobilization of stored energy, and decreasing physical condition. We assessed the functioning of the hypothalamic-pituitary-adrenal axis by measuring cortisol levels in response to the stress of capture and in response to a hormone challenge protocol (dexamethasone suppression and adrenocorticotropic hormone stimulation). We measured blood glucose levels, free fatty acids, white blood cells, and hematocrit to assess the downstream physiological responses to cortisol. Immediately after spring emergence, male arctic ground squirrels had ample free abdominal fat and few signs of wounding. By the end of the breeding season 3 wk later, visible fat reserves were almost entirely gone, and most males had extensive wounds. Total plasma cortisol concentrations increased over this period, but so did corticosteroid-binding capacity, resulting in no change in the free cortisol response to capture. We found no significant changes in how the animals responded to our hormone challenges, contrary to our prediction that the stress axis should increase free cortisol production. Even though we found no change in the functioning of the stress axis, all of the downstream measures suggested that male arctic ground squirrels are chronically exposed to high cortisol concentrations. Over the breeding season, blood glucose increased, fat stores and circulating free fatty acids were depleted, and both hematocrit levels and white blood cell counts decreased significantly. Our data suggest that a more complex relationship between the stress axis and downstream measures of stress exists than that proposed by the adaptive stress hypothesis. We propose several nonexclusive, testable mechanisms that could explain our observations.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".