THE PATTERN OF BEHAVIOUR
OF
RABBIT
PUPS
IN
THE
NEST
by
R. HUDSON and H.
DISTEL1)
(Institut
für Medizinische
Psychologie, Ludwig-Maximilians-Universität
München,
F.R.G.)
(With
6
Figures)
(Acc.
10-XII-1981)
INTRODUCTION
Rabbit
pups
are born after 31
days gestation
in a rather immature
state.
They
are
naked,
have sealed
eyes
and outer
ears,
are ectothermic
and
have
poor
motor coordination.
By day
7
they
are
capable
of limited
orienting
responses
to
auditory
stimuli
(GOTTLIEB, 1971),
and
may
also
perceive light
changes
(RIPISARDI Bt
al.,
1975) although they
do
not
begin
to
open
their
eyes
before
day
10.
Pups
start to leave the nest when 13
to
18
days
old
(ZARROW et
al., 1965;
IVIYKYTOWYCZ
&
DUDZINSKY,
1972).
By
this time
they
are able
to
maintain a stable
body temperature
physiologically
(WISHAW et
al.,
1979)
and have much
improved
motor
coordination.
When
given
the
opportunity,
doe domestic rabbits
construct
a
fur-
lined
nest
of
grass
in
an
underground
burrow
for
their
young
(DEUTSCH,
1957).
They
leave their
pups
almost
immediately
after birth
and,
with oc-
casional
exceptions, only
return
to
feed them once
approximately every
24
hours
(VENGE,
1963;
ZARROW et
al.,
1965).
The
daily
nursing period
is
very
short,
varying
between does from
2
to 4 minutes
(LINCOLN,
1974).
Rabbits
apparently
make little other
provision
for
their
young,
and even
fail to
retrieve
pups
which
stray
from the nest
(ZARROw et
al.,
1962).
While various
aspects
of
the
pups' physiological development
and of
rabbit maternal behaviour have been
investigated,
little attention has
been
given
to the behaviour of the
pups
in
the nest. Yet accounts
of
rabbit
maternal
behaviour
suggest
that
the
pups
must maintain an
adequate
1)
We would like to
express
our thanks to Prof.
J.
ASCHOFF,
Prof. E.
PÖPPEL,
Dr W.
FRIES and T. ROENNEBERG for
critically reading
the
manuscript
and for
helpful
discussions,
and
to
the Deutsche
Forschungsgemeinschaft
for
supporting
this
work
(Di 212/2-1).
256
body temperature
without
being
brooded,
and must obtain sufficient
nourishment
during
brief,
once
daily nursing periods.
It
is
the
purpose
of this
study
to
report
on
the
behaviour
of
rabbit
pups
during
the time
they
are confined to the nest. Their
daily
cycle
of
pre-
nursing aggregation
and
exposure
from the nest material
and
post-
nursing digging
and
dispersal
will
be described and its
adaptive
significance
discussed.
ANIMALS AND METHODS
Rabbits,
Oryctolagus
cuniculus
(L),
of an
established chinchilla strain
(Chbb)
were
ob-
tained from
Thomae
(BIBERACH, F.R.G.),
and bred
in
our facilities.
Twenty-two
litters
reduced
to
six
pups
each
were
used. Six litters
were
observed with
minimal
interference
until
post-natal
day
14 to establish the normal
pattern
of the
pups'
behaviour. Sixteen ad-
ditional litters raised under the same basic conditions were used
for
behavioural tests.
The
pups
were
raised
in a
plexiglass
nest
box which was connected
by
a
plexiglass
passage
to a standard rabbit
cage (Fig. 1). Passage
and nest box floors were lined with
porous plaster
board 1 cm
thick,
which
absorbed the
pups'
urine
readily.
This was re-
newed
for each
litter.
A
sliding
door between the
passage
and
home
cage
served to
separate
the mother from her
young.
The animals were
kept
under a constant 12 hour
light/dark cycle. Hay,
water and food
pellets
were
provided
ad libitum. The
ambient air
temperature
was
20°C ±
1°C,
and
the relative
humidity
fluctuate between
40 and
60%.
However,
the
air
temperature
in the nest
box
was
2-3°C
higher
due
to the heat
produced
by
the
pups,
and
repeated
local measurements indicated a variation of air
temperature
within the
box
as shown in
Fig.
1.
Does
were allowed at
least
one
week
to
become
accustomed to
the
new environment
and to
build a
nest.
After
they
had
given
birth
and left the
nest
for one hour the does were
locked out
by
closing
the
sliding
door.
All
litters were born
in
the afternoon or
during
the
night,
and
the
following
day
was counted as
day
1. For the next two
weeks the
experimen-
tal method of ZARROW et al.
( 1965)
was
followed,
and does were allowed access
to
the nest
box
only
twice a
day;
in
the
morning
one hour after
the
lights
went
on,
and
in
the
evening
one hour before
they
went off. The
passage
door was closed
again
after 10
minutes,
or
if
the doe
nursed,
5 minutes after
her
return to
the home
cage.
Obseraational litters
(1
to
4).
To
record
the
behaviour
of
the
pups
a Video
system
was
installed
with the camera view-
ing
the nest box
from above. The behaviour was filmed for ten 10-minute
periods
each
day:
12,
6,
2
and 1 hour before
nursing,
5 minutes
before,
during
and 5 minutes after
nursing,
and
1,
6 and
10 hours after
nursing.
Births were
also
filmed.
Nursing always
oc-
curred in the
morning
when
the doe
was
given
access
to
the nest box
by
the
experimenter.
The second access was
given
10 hours later. Two minutes of each
recording
were used for
quantitative analysis
of the
degree
of
exposure
of
the
pups
from
the nest material. This
was
estimated
by allocating
a
visibility
value to various
parts
of the
pups'
bodies
(one
ear =
1,
entire head =
2,
back or
belly
=
2,
tail =
1)
and
adding up
the values
of
visible
body
parts
of the whole litter.
The
location
of
the
pups
in
the nest was also
analysed
over
the first
12
days.
For
this
the
nest box floor was divided into six
equal
areas 15
by
13
cm
(Fig. 1),
and
points
were
allocated
in
the middle of each area and
in
the center
of
the
nest
where
the
area borders
met.
The
presence
of a
pup
at
any one
of the
resulting eight points
was scored.
If
a
pup
was between
points
the score was
shared,
and
if it
was
near the
corner
or
edge
of
the box
257
the nearest
point
received the score.
When the
pups
were
totally
covered,
local
movements of the nest material
were used to estimate the
position
of the
pups.
The
approximate
milk
consumption
was also measured
in
the observational
litters and
in some of the test litters.
To minimize
disturbance,
the
pups
were
weighed
1 hour before
and 1 hour after
nursing.
The data from the observational
litters
provided
the base
line
against
which the
performance
of
test litters was
analysed using
the t-test
for
dependent
samples
(HAYS,
1963).
Fig.
1. Ground
plan
of
the observation
cage.
The dashed
line
between
passage
and home
cage represents
the
sliding
door,
and arrow heads the
air holes near the
top
of the nest
box.
Dotted lines show the
areas
into which the nest box floor was divided
for
recording
the location of the
pups.
Local variation of the air
temperature
within the nest is indicated.
258
In two additional litters
(5
and
6)
the behaviour of
pups
and
doe
was
observed and
recorded from
beneath
through
the
plexiglass
after the
plaster
floor
was removed.
7>st litters.
The
behaviour
of
pups
before
nursing
was further
investigated
in
five litters. In two of
them
(A, B),
a
different
pair
of
pups
was moved each
day
20 cm
away
from the
littermates
immediately
before
nursing.
In three
more litters
(C,
D,
E),
the effect
of
covering
the
pups
with
nest
material
immediately
before
nursing
was
observed,
and in
one litter
(C)
tested
every
second
day. Daily
milk
intake was measured
in
litters
A,
B and
C.
In
five more litters
(F to J),
the
post-nursing
behaviour of
pups
was
investigated
under
various stimulus
conditions, i. e. ,
limited
contact with the
doe,
covering
the
pups
with
nest
material,
exposure
to the smell of
urine,
and
contact
with
urine,
water
or
a cold surface.
The influence of local
variables
in
the nest was tested in four litters
(K
to
N).
In
two
of
them the
plaster
floor with
covering
nest material
was
rotated 180°
immediately
after
nursing
on
day
5
and turned back
again
on
day
8.
In two other
litters
temperature
dif-
ferences
in
the
nest
(Fig. 1)
were
eliminated
on
day
4
by blocking
the air
holes
and en-
trance.
Finally,
the nest boxes of two litters
(K, L)
were detached from the doe's home
cage
and
the
pups
raised in a
separate
room in the
dark. The does were
brought
in
every day just
before
nursing,
except
on
days
5
and 8 when the
pups
were not allowed to nurse.
On
these
and
the
following days
(6
and 9
respectively),
the
exposure
of
the
pups
from
nest material
was recorded on Video
following
a schedule similar to that described
above.
Pups
were
only exposed
to
light
on these
days during
Video
recording.
RESULTS
Behaviour
of
the doe.
All does built a
fur-lined
nest of
hay
in
the nest boxes. Parturition
lasted about
10 minutes
only,
and the does
rapidly
licked each
pup
as
it
was born. After
giving
birth the does nursed their
pups
for less than a
minute,
and
then
abruptly
left the nest box without
returning during
the
following
hour.
The next
morning,
as soon as the
dividing
door was
raised,
the does
entered
the
nest and
spent approximately
5
to
10
minutes
nursing.
However,
on
subsequent days
does
only
ever
spent
between
2.3
and
2.9
minutes
nursing.
During
the 10 minutes
of
evening
access
they
sometimes
entered
the
nest box
briefly
but
paid
no
attention
to the
pups.
While
nursing,
does
kept
their
body very
still. Even when
they
trod
on
a
pup
they
did not
adjust
their stance
despite vigerous
wriggling
and
vocalization
by
the
pup.
Does stood hunched over their
litter,
their
hind
feet and tail
pressed firmly
to
the
floor,
enclosing
the
pups
within
a small
area.
As
the
pups grew
this
posture
altered.
By day
7 or
8,
does raised
their
hindquarters
off the
ground
and stretched
out more
(Fig. 2).
They
occasionally
nuzzled nest material
away, especially
from
very young
pups,
and sometimes
briefly
licked
them.
259
Fig.
2.
Schematic
representation
of the
nursing postures
of the doe viewed
from beneath.
Hatched
areas indicate the
body parts
in contact with the
floor,
and arrows the
gaps
allow-
ing
access to the doe's
belly. (a)
Hunched
posture
before
day
7 or
8,
(b)
extended
posture
after
day
7
or
8.
Just
before
leaving,
does
deposited
a few faecal
pellets
in
the nest
box,
and sometimes
made an
attempt
to clean the nest box entrance
by
pushing
scattered material back into the nest.
Behaviour
of
the
pups.
After birth
the
newborn
pups
were
very
active
and
vocal,
and
im-
mediately
tried to suckle. As soon as
their mother
left,
they very
quickly
burrowed under
the nest material
and
became well covered.
Apart
from some variation
between
litters on
day
1,
the
pattern
of
behaviour
of the
pups
remained
essentially unchanged
until
day
13,
when
they
started to leave
the nest box. This
pattern
was
clearly
associated
with the time of
nursing
and divided
naturally
into four main
periods: nursing
itself,
a
post-nursing
period
of about 15
minutes,
a
period
of about
22
hours between
nursings,
and
a
pre-nursing period
of
one to two hours.