Dive Performance and Aquatic Thermoregulation of the World’s Smallest Mammalian Diver, the American Water Shrew ( <i>Sorex palustris</i> )
Bibliographic record
Abstract
Allometry predicts that the 12–17-g American water shrew (Sorex palustris)—the world’s smallest mammalian diver—will have the highest diving metabolic rate coupled with the lowest total body oxygen storage capacity, skeletal muscle buffering capacity, and glycolytic potential of any endothermic diver. Consistent with expectations, and potentially owing to their low thermal inertia, water shrews had a significantly higher diving metabolic rate in 10°C water (8.77 mL O2 g−1 h−1) compared with 30°C water (6.57 mL O2 g−1 h−1). Unlike larger-bodied divers, muscle myoglobin contributed minimally (7.7%–12.4%) to total onboard O2 stores of juvenile and adult water shrews, respectively, but was offset by high blood O2 carrying capacities (26.4%–26.9% v/v). Diving was predominantly aerobic, as only 1.2%–2.3% of dives in 10°C and 30°C water, respectively, exceeded the calculated aerobic dive limits at these temperatures (10.8–14.4 s). The mean voluntary dive time of water shrews during 20-min trials in 3°C–30°C water was 5.0±0.1 s (N=25, n=1,628), with a mean maximum dive time of 10.1±0.4 s. However, the average dive duration (6.9±0.2 s, n=257) of radio-telemetered shrews exclusively foraging in a simulated riparian environment (3°C water) for 12–28 h suggests that mean (but not maximum) dive times of water shrews in the wild may be longer. Mean dive duration, duration of the longest dive, and total time in water all decreased significantly as water temperature declined, suggesting that shrews employed behavioral thermoregulation to defend against immersion hypothermia. Additionally, free-diving shrews in the 24-h trials consistently elevated core body temperature by ∼1°C immediately before initiating aquatic foraging bouts and ended these bouts when body temperature was still at or above normal resting levels (∼37.8°C). We suggest that this observed predive hyperthermia aids to heighten the impressive somatosensory physiology, and hence foraging efficiency, of this diminutive predator while submerged.
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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 | 0.000 |
| 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".