Data from: Caching for where and what: evidence for a mnemonic strategy in a scatter-hoarder

Scatter-hoarding animals face the task of maximizing retrieval of their
scattered food caches while minimizing loss to pilferers. This demand
should select for mnemonics, such as chunking, i.e. a hierarchical
cognitive representation that is known to improve recall. Spatial
chunking, where caches with the same type of content are related to each
other in physical location and memory, would be one such mechanism. Here
we tested the hypothesis that scatter-hoarding eastern fox squirrels
(Sciurus niger) are organizing their caches in spatial patterns consistent
with a chunking strategy. We presented 45 individual wild fox squirrels
with a series of 16 nuts of four different species, either in runs of four
of the same species or 16 nuts offered in a pseudorandom order. Squirrels
either collected each nut from a different location or collected all nuts
from a single location; we then mapped their subsequent cache
distributions using GPS. The chunking hypothesis predicted that squirrels
would spatially organize caches by nut species, regardless of presentation
order. Our results instead demonstrated that squirrels spatially chunked
their caches by nut species but only when caching food that was foraged
from a single location. This first demonstration of spatial chunking in a
scatter hoarder underscores the cognitive demand of scatter hoarding.