Sea otters use objects to help open hard prey, but a universal story about every otter keeping the same favourite rock for days goes beyond the evidence cited in the earlier article. Tool choice and frequency vary among individuals.
What the research found
A 2024 study in Science followed 196 radio-tagged southern sea otters. Frequent tool use, particularly among females, helped animals access harder and larger prey and was associated with reduced tooth damage during food processing.
The researchers’ university account describes tools including rocks, shells and hard debris. The earlier account implied that characteristic tooth wear demonstrated damage from the tool-using habit; the study instead identified a protective benefit.
A tool does not have to be a lifelong possession
The Monterey Bay Aquarium describes rocks being used to open hard-shelled prey. Carrying and reusing an object during foraging is different from establishing that an individual has kept that same object across many days. A claim about long-term retention needs observations that identify and track the object.
Other marine mammals use carried tools
Sea otters are not the only marine mammals to carry foraging tools. Research in Shark Bay documents bottlenose dolphins carrying sponges during foraging. Tool use is specialised behaviour in both cases, rather than evidence that only one marine mammal can retain an object.
The useful distinction
A tool can help process food without being a treasured possession. The behaviour is interesting enough without attributing a human-style relationship to a particular stone.
To understand the animal, ask what the tool changes: which prey becomes accessible, how much effort is required, and whether the teeth avoid damage. Those questions can be investigated directly. A sentimental story about a lifelong favourite rock should not substitute for that evidence.
Correction, 3 October 2026: The earlier article overstated evidence for a favourite rock retained across days, described sea otters as the only marine mammals carrying tools, and implied tools cause characteristic tooth damage. Dolphins also carry tools, and the cited sea-otter study found reduced damage. Unsupported retention, archaeology and behavioural claims have been removed.
