Number of Identified Specimens

Fragmentation breaks individual bones into multiple fragments, each of which is counted as a separate specimen if identifiable. Sites with bones broken into small pieces will have high NISP values relative to assemblages where bones are intact, even if the original number of animals was identical. This makes NISP particularly unreliable for comparing assemblages with different preservation or butchering patterns. Analysts should note fragmentation patterns and preferentially use metrics less sensitive to breakage.

NISP should be reported by taxon (species or genus) with clear documentation of identification criteria and methods. Associated information should include total number of specimens, number of unidentified fragments, mesh size of screening, recovery methods (hand collection, sieving, flotation), and excavation context. Reported NISP values are meaningful only when these methods and context are transparent, allowing readers to assess comparability with other assemblages.

NISP counts all identifiable bone fragments; MNI estimates the minimum number of animals. NISP is sensitive to fragmentation, while MNI is insensitive to it. For assemblages with many small fragments, NISP can be much larger than MNI, creating the false impression of dietary diversity. Best practice is to report both metrics. NISP is better for detecting temporal trends in faunal composition, while MNI is better for estimating the diversity of fauna.

Sites excavated with 1/4-inch screens will recover different proportions of small bones (fish, bird, small mammal) compared to sites with 1/2-inch screens or hand collection only. This affects NISP values for small fauna disproportionately. When comparing NISP across sites, it is essential to document and account for differences in screening mesh size, water flotation methods, and collection protocols. Ideally, assemblages should be subsampled to equivalent recovery standards before comparison.

Not reliably. NISP values for large animals (elk, cattle) and small animals (fish, birds) cannot be directly compared because individual large animals contribute more meat than individual small animals. To estimate dietary contribution, analysts typically convert NISP to bone weight or use published conversion factors relating bone counts to meat weight. However, such conversions introduce substantial uncertainty and are best used as rough approximations.