The DOI matches its Crossref record; 56 of the 56 references it cites were found in a registry or an index.
Latitudinal effects on weight and age-dependent survival of red fox Vulpes vulpes
Open accessAbstract
Age-dependent survival is central to understanding population dynamics and life-history evolution. We analysed carcass weight and age-at-harvest data from 6 022 red foxes ( Vulpes vulpes ) collected across Sweden between 1967 and 1971 to evaluate latitudinal effects on body mass and age-dependent survival. Carcass weights decreased from south to north in both adults and sub-adults, contrary to Bergmann’s rule, with southern foxes weighing approximately 1.27 times more than northern foxes. The latitudinal weight gradient exceeded the sex difference in both age classes, and no sex × region interaction was detected. The decrease in weight with latitude is consistent with reduced prey availability and harsher winter conditions in the north, which limit growth and body size during development. Using a Bayesian age-at-harvest model with region-specific population growth rates ( λ ), we estimated age-dependent survival probabilities for four latitudinal regions and both sexes. Despite the strong latitudinal gradient in weight, survival did not show a corresponding pattern — regional differences were uncertain, with all credible intervals spanning zero. Regional population growth rates were consistent with slight decline in the north and near-stability in the south-central region, which suggests that body condition and population dynamics are coupled at the regional scale despite no survival gradient. The decoupling of body condition and survival across regions suggests that mortality patterns are similar across the latitudinal gradient. We discuss these patterns in terms of latitudinal productivity gradients, prey availability, and life-history trade-offs in a widely distributed carnivore.
Overview
CoChat Summary
TL;DR
Carcass weights of 6,022 Swedish red foxes declined from south to north in both adults and sub-adults, contradicting Bergmann's rule, yet age-dependent survival showed no matching latitudinal gradient. The authors argue body condition and regional population dynamics are coupled even though mortality patterns appear similar across latitudes.
Key findings
- Carcass weight decreased from south to north in both adults and sub-adults, contrary to Bergmann's rule, with southern foxes weighing approximately 1.27 times more than northern foxes.
- The latitudinal weight gradient exceeded the sex difference in both age classes, and no sex × region interaction was detected.
- Survival showed no corresponding latitudinal pattern: regional differences in age-dependent survival were uncertain, with all credible intervals spanning zero.
- Regional population growth rates were consistent with slight decline in the north and near-stability in the south-central region.
Methods
- Analysis of carcass weight and age-at-harvest data from 6,022 red foxes (*Vulpes vulpes*) collected across Sweden between 1967 and 1971.
- A Bayesian age-at-harvest model incorporating region-specific population growth rates (λ) was used to estimate age-dependent survival probabilities for four latitudinal regions and both sexes.
- No further methodological detail (e.g., model priors, weight measurement protocols) is available in the provided text.
Limitations
- The paper states no limitations in the provided text (the abstract and repository page contain no limitations section).
- Evident from the text: the data are from 1967–1971, so the patterns describe a historical period and may not reflect current conditions.
- Evident from the text: the article is a preprint that "has not been certified by peer review," and only the abstract is available here, so the full analytical detail cannot be assessed.
Model-written summary. Check it against the paper before relying on it.
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Verification
Claims the paper makes
0 Valid · 0 Not valid · 0 Not checked · 9 Own results and interpretations
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The latitudinal weight gradient exceeded the sex difference in both age classes, and no sex × region interaction was detected.”
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Carcass weights decreased from south to north in both adults and sub-adults, contrary to Bergmann’s rule, with southern foxes weighing approximately 1.27 times more than northern foxes.”
plainstates an association- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The latitudinal weight gradient exceeded the sex difference in both age classes, and no sex × region interaction was detected.”
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The decrease in weight with latitude is consistent with reduced prey availability and harsher winter conditions in the north, which limit growth and body size during development.”
plainstates a cause- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The decoupling of body condition and survival across regions suggests that mortality patterns are similar across the latitudinal gradient.”
hedged- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- Rests on an assumption not shown here.
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Citations
Cites
TOWARD A METABOLIC THEORY OF ECOLOGY
Brown, J. H., Gillooly, J. F., Allen, A. P., Savage, V. M., & West, G. B. (2004) · Ecology · doi:10.1890/03-9000 · Cited by 7,779
Temporal Variation in Fitness Components and Population Dynamics of Large Herbivores
Gaillard, J.-M., Festa-Bianchet, M., Yoccoz, N. G., Loison, A., & Toïgo, C. (2000) · Annual Review of Ecology and Systematics · doi:10.1146/annurev.ecolsys.31.1.367 · Cited by 1,729
Early development and fitness in birds and mammals
Lindström, J. (1999) · Trends in Ecology & Evolution · doi:10.1016/s0169-5347(99)01639-0 · Cited by 1,695
The Evolution of Body Size: What Keeps Organisms Small?
Blanckenhorn, W. U. (2000) · The Quarterly Review of Biology · doi:10.1086/393620 · Cited by 1,277
Geographic gradients in body size: a clarification of Bergmann's rule
Blackburn, T. M., Gaston, K. J., & Loder, N. (1999) · Diversity and Distributions · doi:10.1046/j.1472-4642.1999.00046.x · Cited by 899
State-dependent life histories
McNamara, J. M., & Houston, A. I. (1996) · Nature · doi:10.1038/380215a0 · Cited by 848
Life history evolution: successes, limitations, and prospects
Stearns, S. C. (2000) · Naturwissenschaften · doi:10.1007/s001140050763 · Cited by 820
On the Ecological Significance of Bergmann's Rule
McNab, B. K. (1971) · Ecology · doi:10.2307/1936032 · Cited by 634
Heppell, S. S., Caswell, H., & Crowder, L. B. (2000) · Ecology · doi:10.1890/0012-9658(2000)081[0654:lhaepp]2.0.co;2 · Cited by 566
AGE-SPECIFIC SURVIVAL IN FIVE POPULATIONS OF UNGULATES: EVIDENCE OF SENESCENCE
Loison, A., Festa-Bianchet, M., Gaillard, J.-M., Jorgenson, J. T., & Jullien, J.-M. (1999) · Ecology · doi:10.1890/0012-9658(1999)080[2539:assifp]2.0.co;2 · Cited by 455
Research works printed but not linked: 8
- 2001, Food Habits and Trophic Niche Overlap of the Red Fox, European Wild Cat and Common Genet in the Peneda-Gerês National Park, Galemys, 13, 39
- 1965, Studies on Food Ecology of the Red Fox (Vulpes v.) in Sweden, Viltrevy, 3, 377
- 1970, Some Aspects of Reproduction and Mortality Rates in Swedish Foxes (Vulpes Vulpes), 1961-63 and 1966-69, Viltrevy, 8, 1
- 1998, The Red Fox in Norway: Morphological Adaptation or Random Variation in Size?, Zeitschrift fur Saugetierkunde, 63, 16
- 10.2307/177239 · doi:10.2307/177239
- Plummer, M. et al. (2003). “JAGS: A Program for Analysis of Bayesian Graphical Models Using Gibbs Sampling”. Proceedings of the 3rd International Workshop on Distributed Statistical Computing. Vol. 124. 125.10. Vienna, Austria., pp. 1–10.
- 2000, Animal Home Ranges and Territories and Home Range Estimators, Research techniques in animal ecology: controversies and consequences, 442, 65
- 10.1111/j.13652907.2007.00101.x · doi:10.1111/j.13652907.2007.00101.x
Cited by
Still being checked.
Metadata
- Authors
- Willebrand, T., Odden, M., Samelius, G., Walton, Z., Østbye, K., Englund, J., & Spong, G.
- Affiliations
- University of Inland Norway (NO)
- Snow Leopard Trust, Seattle, Washington, USA
- Inland Norway University of Applied Sciences, Norway
- Kattfotsbacken, Hässelby, Sweden
- Swedish University of Agricultural Sciences (SE)
- Corresponding author
- Willebrand, Tomas
- Venue
- bioRxiv (Cold Spring Harbor Laboratory)
- Publisher
- openRxiv
- Published
- 2026-06-29
- OpenAlex
- W7166518371
- Cited by
- 0
- References
- 56
- Type
- posted content
- Language
- en
- Open access
- green
- doi.org
- Licence
- Locations
- bioRxiv (Cold Spring Harbor Laboratory) (submittedVersion, cc-by-nc-nd)
- Topics
- Physical Sciences › Environmental Science › Ecology › Wildlife Ecology and Conservation
- Physical Sciences › Environmental Science › Ecology › Animal Ecology and Behavior Studies
- Physical Sciences › Earth and Planetary Sciences › Paleontology › Evolution and Paleontology Studies
- Keywords
- red fox, latitudinal gradient, body mass, age-dependent survival, Bergmann's rule, carcass weight, harvest age, population growth rate, prey availability, winter harshness, body condition, life-history trade-offs, sex differences
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- CoChat. (2026). Citation check: Latitudinal effects on weight and age-dependent survival of red fox Vulpes vulpes. https://app.cochat.ai/papers/10.64898/2026.06.29.735157
- The paper
- Willebrand, T., Odden, M., Samelius, G., Walton, Z., Østbye, K., Englund, J., & Spong, G. (2026). Latitudinal effects on weight and age-dependent survival of red fox Vulpes vulpes. bioRxiv (Cold Spring Harbor Laboratory). https://doi.org/10.64898/2026.06.29.735157
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