Strontium-87/86 Ratio
Definition
The ratio of two strontium isotopes in a sample, which mirrors the ratio in local bedrock and water. Because strontium substitutes for calcium in bone and dentine, the ratio measured in ivory reflects the geological substrate where the elephant lived.
- Isotopes measured
- Strontium-87 and strontium-86
- Substitutes for
- Calcium in bone and dentine
- Reflects
- Local bedrock and water geology
- Applied to
- Ivory provenance in wildlife forensics
Common questions
Why does the ratio measured in ivory reveal where an elephant lived?+
Strontium enters an animal's diet through local plants and water and is incorporated into growing tissue in place of calcium, so the ratio locked into the ivory reflects the isotopic signature of the geological substrate the animal fed on.
How is an ivory sample's ratio turned into a location estimate?+
The measured ratio is compared against a reference database or isoscape of known 87Sr/86Sr values across candidate regions, narrowing the plausible origin to areas whose bedrock signature matches the sample.
Related terms
- Delta-C13 / Delta-N15
- Stable carbon and nitrogen isotope ratios in tissue, expressed as deviation from a reference standard (delta notation). They reflect diet composition and...
- Isoscape
- A map of isotope ratio variation across a geographic area, derived from systematic sampling of soil, water, plant, or mineral material; used...
- Population Structure
- The non-random distribution of genetic variation across subpopulations caused by limited gene flow between them. Different elephant herds separated by geography or...
- SNP (Single Nucleotide Polymorphism)
- A position in the genome where the nucleotide base differs between individuals. Genome-wide SNP panels are more powerful than STR panels for...
- STRUCTURE / ADMIXTURE
- Software tools that infer population structure by estimating each individual's fractional ancestry (membership coefficient) across K genetic clusters. Used to assign unknown...