Use of stable-carbon and -nitrogen isotopes to assess weaning and fasting in female polar bears and their cubs
Bibliographic record
Abstract
In some species, stable-isotope techniques can provide insights into dietary regimens where there are temporal shifts in trophic level or feeding frequency. We determined stable carbon (δ 13 C) and nitrogen (δ 15 N) isotope values for plasma and milk proteins and δ 13 C values for milk lipids from female polar bears (Ursus maritimus) and cubs to (i) ascertain whether cubs are at a higher trophic level than their mothers as a result of nursing and whether we can determine when weaning occurs, and (ii) determine the impact of seasonal fasting on δ 13 C and δ 15 N values. The plasma δ 13 C values for mothers and cubs were similar to milk-protein δ 13 C values and were significantly enriched in 13 C compared with those for milk lipid. Plasma from cubs of the year (COYs) in spring, when milk was their only diet, was isotopically enriched in 15 N by 1.0 over that of their mothers (δ 15 N = 21.5 ± 0.8 (mean ± SD) for cubs and 20.5 ± 0.5 for mothers) and depleted in 13 C by 0.8 (δ 13 C = 19.6 ± 0.5 for cubs and 18.8 ± 0.8 for mothers). For bears who fasted between summer and fall (34 months), plasma became depleted in 13 C by 0.5 and in 15 N by 1. Plasma from females, who had fasted from summer to spring (78 months) and given birth to cubs, became enriched in 13 C by 0.7 and in 15 N by 2. By using stable-isotope analyses we were able to show that (i) young cubs were at a higher trophic level than their mother when milk was their only food source, and (ii) seasonal fasting influenced δ 13 C and δ 15 N values. However, we were not able to use stable-isotope analyses to determine the exact time of weaning.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".