California scrub-jays reduce visual cues available to potential pilferers by matching food colour to caching substrate

Some animals hide food to consume later, however these caches are susceptible to theft by conspecifics and heterospecifics. Many caching animals use protection strategies to minimise visual and acoustic cues available to potential pilferers, such as caching behind objects, in shaded areas and in quiet substrate. A widespread method of concealment in the animal kingdom is background matching, a camouflage strategy commonly used by prey animals where they match the colour or patterning of the visual background. Caching animals may also use this tactic to minimise the conspicuousness of caches, for example by hiding coloured food in a similar coloured substrate. We tested whether California scrub-jays (Aphelocoma californica) camouflage their food in this way by offering them coloured food to cache in substrates that either matched or did not match the colour of the food. We also determined whether this caching behavior was sensitive to social context by letting birds cache when a bird could be both seen and heard (visual and acoustic cue present), or heard but not seen (acoustic cues only). When caching events could be both heard and seen by a potential pilferer, birds cached randomly in both coloured substrates. However, they preferentially hid food in the substrate that matched the food colour when only acoustic, and not visual cues were present. These results reveal a novel cache protection strategy employed by a caching animal that is also sensitive to social context.L.A.K. received funding from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (FP7/2007-2013) under REA grant agreement PIIF-GA-2012-327423