Related Experiment Video
Updated: Jan 25, 2026

A Simple Critical-sized Femoral Defect Model in Mice
Published on: March 15, 2015
How many cubs can a mum nurse? Maternal age and size influence litter size in polar bears
Dorinda Marie Folio1, Jon Aars2, Olivier Gimenez1
11 CEFE, CNRS, Univ Montpellier , Univ Paul Valéry Montpellier 3, EPHE, IRD, Montpellier , France.
Abstract:
Life-history theory predicts that females' age and size affect the level of maternal investment in current reproduction, balanced against the future reproductive effort, maintenance and survival. Using long-term (30 years) individual data on 193 female polar bears ( Ursus maritimus), we assessed age- and size-specific variation on litter size. Litter size varied with maternal age, younger females had higher chances of losing a cub during their first months of life. Results suggest an improvement in reproductive abilities early in life due to experience with subsequent reproductive senescence. Litter size increased with maternal size, indicating that size may reflect individual quality. We also found an optimum in the probability of having twins, suggesting stabilizing selection on female body size. Heterogeneity was observed among the largest females, suggesting that large size comes at a cost.
Related Concept Videos
Cell Size
Surface Area
Cells can take in nutrients and water via diffusion through the plasma membrane itself or through specific channels in the membrane. The area of the membrane surrounding...
Brick Sizes
Modular bricks are the most common type and are sized to include the mortar joint, which is essential for...
Genome Size and the Evolution of New Genes
Genome Size and the Evolution of New Genes
Maximum Size of Aggregate
Sample Size Calculation
The sample size for the given experiment or sampling effort is fundamental to any study design. Sample size decides the number of...

