16 Ecology, Behavior, and ConservationScatter-Hoarding and Larder-Hoarding
Most species of squirrels, especially in temperate regions,
store energy to make it through periods of food shortages
and harsh conditions. Whereas hibernating squirrels usu-
ally store their energy in the form of body fat that enables
them to reduce their metabolic rates and activity during
these periods, many of the tree squirrels, in contrast, store
their food and remain active. In North America, numerous
studies on Tamia s c iur u s and Sciurus have been devoted to re-
search on two alternative strategies for storing food: larder-
hoarding and scatter-hoarding. At one extreme, larder-
hoarding involves the placement of all food reserves in a
single location that is then vigorously defended against all
other competitors. Tamiasciurus hudsonicus and T. douglasii
are the squirrels best studied and most well known for this.
Both species construct extensive larders (middens) contain-
ing hundreds of cones that ensure their survival through
periods of deep snowfall and low temperatures.
In contrast, many species of Sciurus—as well as other gen-
era (e.g., Sciurotamias)—in temperate, subtropical, and even
tropical regions engage in scatter-hoarding. This behavior, in
its most extreme case, involves the placement of each of
many items in individual, widely dispersed cache sites. Scat-
ter-hoarding is thought to decrease the detection of food
stores by competitors and thereby reduce the energy needed
to defend the stores. The tradeoff , of course, is the extent to
which the seeds can be spread before the costs of recovery
become prohibitive. Scatter-hoarding squirrels, such as the
eastern gray squirrel (S. carolinensis), appear to have mas-
tered this technique.
As was fi rst suggested by C. C. Smith for Sciurus and
Ta mia s c iur u s in North America, the type of plant food di-
rectly infl uences a squirrel’s food-storage strategy, and
this, in turn, can have a cascading eff ect on other aspects
of squirrel biology, such as social behavior and even popu-
lation dynamics. In coniferous forests, for example, cones
are best stored in central middens, where they are pro-
tected from other squirrels and where cool, moist condi-
tions prevent them from opening and releasing seeds.
However, these central larder-hoards must be vigorously
defended by an ever-vigilant owner. In Tamia s c iur u s this
has led to a social system involving extreme territoriality,
and a spatial system in which the habitat is divided evenly
among the squirrels. Mothers often bequeath these territo-
ries and middens to their daughters. In deciduous forests,
where several species of Sciurus reside, a diff erent behavior
is seen. Here squirrels scatter-hoard seeds and nuts in shal-
low pits just below the leaf litter. Scatter-hoards generally
require no defense. Consequently, many species of Sciurus
show overlapping home ranges and do not exhibit territo-
riality; their social system involves a dominance hierarchy
in which dominance is often established at dense patches
of food. Interestingly, where Tamia s c iur u s is found in mixed
forests, it often shifts its behavior and scatter-hoards.
However, in the coniferous forests of North America where
Sciurus is found, these squirrels generally neither scatter-
hoard nor larder-hoard. Hence the relationship betweena b(a) A red squirrel (Tamiasciurus hudsonicus) midden, mainly of spruce cones, in the White Mountains, Arizona. Photo courtesy
Melissa Merrick. (b) Another red squirrel (Tamiasciurus hudsonicus) midden, Mount Graham, Arizona. Photo courtesy Claire
Zugmeyer.