13/08/2026
🚨NEW PAPER🚨
https://doi.org/10.1007/s10344-026-02127-2
How old is an otter cub? Determining cub age is important for identifying and protecting breeding sites and targeting seasonal surveys, but reliable ageing methods have been lacking.
In this new paper, led by researchers at Edinburgh Napier University in collaboration with the Cardiff University Otter Project, the authors present a novel method that estimates cub size relative to their mother using pixel measurements from camera-trap footage. The method was validated using domestic ferrets of known length, then applied to footage from an otter natal den to generate growth curves for three litters, from first emergence (ca. two months old) to at least seven months old.
The method was sufficiently accurate to estimate birth season, and the authors hope in future to collate crowd-sourced video and photographs of otter families from across the Eurasian otter range, to investigate regional variation in breeding seasonality.
Anecdotally, it has been suggested by field observers that tail: body length ratio might be used to indicate cub age. Data from CUOP were used to disprove this - analysis of length data from over three thousand individuals, from tiny foetuses recovered in utero, to adult otters, showed that the ratio remains remarkably constant as otters grow.
