Social ‘meltdown’ in the demise of an island endemic: Allee effects and the Vancouver Island marmot
Bibliographic record
Abstract
1. More than 75 years have passed since W.C. Allee proposed that breakdowns in sociality may shift animal populations to inverse density dependence at small sizes and thereby hasten spirals to extinction. Despite decades of attention, empirical evidence of this 'Allee effect' in wild populations remains scarce. 2. Here, we report on findings from a multi-year study of the population ecology and behaviour of the critically endangered Vancouver Island marmot (Marmota vancouverensis) and present quantitative evidence of an Allee effect and highlight the mechanisms that drive it. 3. The V.I. marmot is a large, social rodent endemic to Vancouver Island, Canada, and its population has declined by 80-90% since the 1980s. The species currently is represented in the wild by roughly 200 individuals. 4. This study compared characteristics of contemporary V.I. marmots (2002-2005) with (i) animals in the same population at an earlier time period (1973-1975) and (ii) congeners. Specifically, data on time allocation, social activity and ranging behaviour of animals in colonies in the late stages of decline were compared with historical data collected from colonies under more stable demographic conditions. 5. We found that contemporary V.I. marmots had home ranges that were 10-60x larger than historic animals and congeners, interacted with conspecifics at 10% of the historic rate, devoted 10x more time to anti-predator vigilance, and abandoned the bi-modal activity patterns previously described for this and other marmot species. Contemporary marmots also showed an 86% decline in feeding rate, and entered hibernation on average 20 days later than animals in historic populations. 6. Combined with results showing reduced per capita survival and reproduction in contemporary marmots, these findings suggest a strong role for Allee effects in the current plight of the Vancouver Island marmot. A positive link between aspects of fitness and population size emphasizes the need to identify threshold colony sizes and densities necessary to promote recovery. We discuss this and other implications of this species' social 'meltdown'.
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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 | 0.001 | 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".