Caching behavior of woodrats (Neotoma lepida & Neotoma bryanti) through maturity

Abstract

Woodrats are known to cache a variety of items such as food, building and nesting material, as well as seemingly random objects, which they store in large structures called middens. The collecting and storing of items nonessential to survival is a unique behavior, being displayed in only a few other animal genera, and it is not well understood. This distinctive behavior is what gave these rodents the nickname of “packrats” and provided us with our research question. Does caching behavior change as woodrats mature? In our study, a group of 15 captive woodrats, 7 Neotoma bryanti and 8 Neotoma lepida, age 2-3 months were provided building/nesting items, food items, and nonessential items. Over five days, caching behavior was observed, and items cached were documented. Building/nesting items consisted of 5 popsicle sticks, 4 black pipe cleaners, 4 silver pipe cleaners, 2 pompoms, and 1 cardboard toilet paper roll. Food items consisted of 30g of rabbit chow, which was placed in a small glass jar and refilled daily. Nonessential items consisted of 3 small silver jingle bells and 2 medium gold jingle bells. Woodrats were tested again at 8-9 months, using the same methods as above. No significant differences were found between the age groups or species.

Full text

Caching behavior of woodrats
(Neotoma lepida & Neotoma bryanti)
through maturity
Chyanne Smith, Heather O’Donnell and Michele Skopec
Department of Zoology, Weber State University, Ogden, Utah
Introduction
Woodrats are known to cache a variety of items such
as food, building and nesting material, as well as
seemingly random objects, which they store in large
structures called middens. The collecting and storing
of items nonessential to survival is a unique behavior,
being displayed in only a few other animal genera.
This distinctive behavior is what gave these rodents
the nickname of “packrats”.
Study Objective
Woodrat caching behavior of non-essential items is
poorly understood. We hypothesize caching behavior
of non-essential items may be related to gaining
knowledge of their surrounds for future benefits.
Therefore, we predict less mature woodrats will
collect nonessential items more frequently to learn
about their surroundings. Additionally, as the
woodrats age, and are exposed to the same objects
again, we expect to see their collection methods
focus more on essential items for building/nesting
and food rather than non-essential items. We do not
expect to see any significant caching differences
between the two species, as they are closely related.
Methods
In our study, a group of thirteen captive born woodrats
(N. lepida n=8 and N. bryanti n=5), housed at Weber
State University, age 2-3 months were provided
building/nesting items, food items, and nonessential
items. Over 5 days, caching behavior was observed,
and items cached were documented. Items were
considered cached if they were moved from the top
shelf or if a nest was build on the top shelf which
incorporated those items. Once the woodrats reached
8-9 months individuals were tested again with the
same methods as above.
Conclusions
.
.
Results
Figure 1. Objects cached by species and age.
There were no differences between N. lepida (n=8)
and N. bryanti (n=5) as adults (t=-0.69 df=11 p=0.51
) or juveniles (t=-0.17 df=11 p=0.87 ). Additionally,
no differences between individuals were found in N.
lepida (t=-0.62 df=7 p=0.56 ) or N. byranti (t=0.20
df=4 p=0.85) as they matured.
Table 1. Caching non-essential items.
N. lepida (n=8) and N. bryanti (n=5) showed no
significant difference (χ2=0.44 p=0.51) in
caching of non-essential items as they aged.
Table 2. All objects cached by juveniles.
N. lepida (n=8) and N. bryanti (n=5) showed no
significant difference between juveniles (χ2=0.04
p=0.84) of both species, with regard to caching
all items presented.
Woodrats displayed no significant difference in caching of
non-essential items as they aged. Additionally, there were
no significant differences found between individual’s
average number of objects cached as they aged. As
predicted, there were no significant differences found
between species with regard to number of objects cached
and all objects cached. Future studies may be needed
which focus on the behavior of woodrats younger than
two months of age.
Neotoma lepida
Objects for caching
Neotoma bryanti
0
5
10
15
20
25
N. bryanti N. lepida
Average number of
objects cached
Juvenile
Adult
Species
Behavior
same at
maturity
Behavior
change at
maturity
N. lepida 5 3
N. byranti
4 1
Species
All objects
cached
Not all
objects
cached
N. lepida 2 6
N. byranti
1 4
Table 3. All objects cached by adults.
N. lepida (n=8) and N. bryanti (n=5) showed no
significant difference between adults (χ2=1.17
p=0.28) of both species, with regard to caching
all items presented.
Species
All objects
cached
Not all
objects
cached
N. lepida 4 4
N. byranti
1 4
Figure 2. Objects after caching.
Juvenile woodrats (N. bryanti) cage after five days
of being in the experiment. Pompoms have been
deconstructed to provide bedding. Food jar has
been completely removed from the top shelf (shelf
was removed for the picture), pipe cleaners and
popsicle sticks have also been removed and
cached in the bottom of the cage. Toilet paper roll
and hiding tubes were not considered in this study
as they are typical enrichment items placed in the
woodrats cages daily.
Object Category Quantity
Popsicle Sticks
Building 5
Pipe Cleaners Building/
Nesting
8
Pompoms Nesting 2
Jingle Bells
Non
-
essential
5
Rabbit Chow Food 1 jar, 30g
Acknowedgements
Special thanks to Susan Gurr and the woodrat crew for maintain the
animal facility and woodrat colony.