Question · Mind
Why Do Ravens Hide Food?
[science] Ravens hide surplus food — a behaviour called caching — to protect it from competitors and to create a private food store for future use. Food is often unpredictable and competitive in raven environments; caching allows them to bank food when it is plentiful and retrieve it when scarce. The behaviour requires accurate spatial memory, an understanding of time, and — remarkably — an awareness that other ravens can steal caches.
What is Food Caching?
[science] Food caching (also called hoarding) is the act of storing food in a hidden location for later retrieval. Ravens typically carry food in their bill or throat pouch to a concealed spot — a crack in a rock, a patch of moss, a snow-covered hollow — and cover it with leaves, pebbles or other material. The behaviour is opportunistic: ravens cache most intensively when food is abundant (e.g., at large carcasses) or when they need to consume food without other ravens stealing it in the moment.1
The Memory Behind the Cache
[science] A series of experiments by Bugnyar, Heinrich, and colleagues demonstrated that ravens have exceptional spatial memory for cache locations and that this memory is episodic-like — encoding not just where but what and when:
- Ravens can accurately relocate caches several days after storing them, using landmarks rather than smell.1
- When ravens have cached both perishable and non-perishable items, they preferentially recover the perishable caches first — suggesting memory of the type and timing of each cache (Raby et al., 2007, using jays; comparable raven evidence in Bugnyar & Kotrschal, 2002).2
- Ravens distinguish their own caches from random locations, and from other ravens' caches.1
Deception and Counter-Deception
[science] One of the most remarkable aspects of raven caching is the social arms race it has produced. Because ravens observe each other caching and return to steal from those specific locations, cachers have evolved counter-strategies that imply an awareness of what other ravens know:3
- Re-caching: ravens that have been watched while caching often return later to move the cache to a new location, particularly if the observer was a dominant individual.
- False caching: ravens perform caching movements — digging, covering — without actually depositing food, apparently to mislead watching birds. This was documented by Bugnyar & Heinrich (2005).
- Screening: ravens choose cache sites behind objects that block the line of sight from other ravens.
- Audience monitoring: ravens cache in different ways depending on whether they are being watched and by whom — suggesting they track the knowledge states of specific individuals.
These behaviours have been interpreted as evidence that ravens understand that other ravens have knowledge they do not want them to have — a component of theory of mind. This interpretation is debated (see Raven theory of mind), but the behaviours themselves are well-documented.
Related Questions
Frequently Asked Questions
How do ravens remember where they hid food?
Ravens use spatial memory — encoding the precise location of each cache relative to landmarks — along with memory of what was cached and when (episodic-like memory). Studies show they can relocate caches accurately days to weeks later, distinguish more perishable from less perishable items, and prioritise recovering perishable caches first.
Can other ravens steal hidden food?
Yes, and this is a major driver of raven caching behaviour. Ravens observe each other and regularly steal caches (called "pilfering"). A raven that sees another caching will return later to steal from that specific location. In response, cachers have developed counter-strategies: re-caching after being watched, caching behind barriers, and using deceptive "false caching" movements.
How many caches does a raven make?
Individual ravens can make hundreds to thousands of caches over the course of a year. The exact number depends on food availability — a raven at a large carcass in winter may make dozens of caches in a single session. Each cache is typically a single food item buried in the ground or wedged in a crevice.
Sources
- Bugnyar, T. & Kotrschal, K. (2002). Observational learning and the raiding of food caches in ravens (Corvus corax): is it 'tactical' deception? Animal Behaviour, 64(2), 185–195.
- Raby, C.R., Alexis, D.M., Dickinson, A. & Clayton, N.S. (2007). Planning for the future by western scrub-jays. Nature, 445, 919–921. — episodic-like memory and future planning in corvids (scrub-jay study; raven evidence in Bugnyar & Kotrschal, 2002).
- Bugnyar, T. & Heinrich, B. (2005). Ravens, Corvus corax, differentiate between knowledgeable and ignorant competitors. Proceedings of the Royal Society B, 272, 1641–1646. — false caching and audience monitoring.
[science] peer-reviewed study or field-guide data