Glossary of rat behavior terms
Informal, illustrated definitions of rat behavior
Allogroom, head and body: One
rat grooms the other, frequently around the neck or head (especially
eyes, mouth, chin and ears). Somewhat less frequently, one rat may
groom the flanks of another.
Allogrooming of the neck occurs in an agonistic context and is called aggressive neck grooming.
Grooming consists of rapid little nibbles, in one spot or moving slowly
to one side. Slow motion video analysis reveals that the groomer
seizes folds of neck skin between his teeth (Miczek and Boer
2004). The groomed rat remains immobile, and may even be pushed
into different positions. The groomed rat may peep or squeak
softly. Any sudden movement by the groomed rat may trigger a bite
and a kick from the rear legs of the groomer (Miczek and Boer 2004).
Grooming of the
head and neck may be an olfactory investigation of the sebum from the
back of the animal.
Barber: Excessive grooming in
which the fur is nibbled off. Rats may barber each other, in
which case frequent areas of barbering and subsequent bald spots on
other rats are the head, face, neck and shoulders. Dominant rats may
barber subordinates (e.g. Bresnahan 1983). Lactating
mothers may have barbered stomachs, either as the result of
nibbling by the babies once their teeth have erupted, or by the dam
herself in response to irritation from the nursing.
Self-barbering is also found in non-lactating rats, in
which case the rat may nibble off fur from its forearms and chest.
Barbering is sometimes caused by Demodex mites, or as a result
of mutual grooming when the rats' diet contains more than 20% fat.
Other possible causes include skin ulcers (pyoderma), other external
parasites, genetic disorders, caloric or protein deficiencies,
abrasion on rough surfaces, hormonal imbalances, chronic renal
disease, ringworm (dermatophytosis), and intensive breeding (Harkness
and Wagner 1995).
Behavioral Estrus (female
in heat): Phase of the female rat's ovarian cycle during
which she displays reproductive behavior. Behavioral estrus
corresponds to vaginal proesturs, the 12 hour period before
During behavioral estrus, the female solicits
the male to prompt him into mounting her. She darts towards him and
runs or hops away. She may repeat this approach-retreat sequence
several times, sometimes wiggling her
ears. She may also pause near him or run by him, and may
intercept him in his pursuit of another female. The male finds these
solicitation behaviors very attractive, and follows the female. If he
mounts her, the pressure he exerts on her flanks, lower back, and
anogenital area triggers lordosis,
the female mating posture (Nelson 1995).
Belly-groom or "power grooming":
One rat grooms a recumbent rat's belly. May be an attempt to reach
the nape, which is the goal of play fighting. See also "Belly-up
roll" and allogrooming.
Belly-up roll (pin): Juvenile-type
defense tactic in which one rat rolls onto his back before another,
sometimes after receiving a nip or bite on the rump. The top rat may
then step on the supine rat, sometimes orienting himself
perpendicular to the long axis of the supine rat (thus avoiding the
whiskers), and pinning him down. The top rat may groom the supine
rat's belly (see also belly-groom, or
"power groom"), perhaps as an attempt to gain access to the nape or
rump. Rolling on one's back tends to prevent further attack for
several reasons: play fighting is directed at the nape, and serious
offensive bites are directed at the lower back and flanks, so a roll
hides these areas. Also, the rolled rat becomes motionless, and
motion is an important stimulus for attack (Thor et al. 1981).
Lastly, the recumbent rat may track his opponent's face with his
teeth and whiskers, which may actively inhibit attacks as well
(Blanchard and Blanchard 1977).
So, the belly-up roll is probably not a signal of submission or
defeat that inhibits further attack, because the attaker may continue
to press his attack. The belly-up roll is instead a defensive
strategy: the subordinate rat can escape being bitten insofar as he
can interpose his belly between the attacker and his own vulnerable
target areas of rump and nape.
Bite: Piercing contact with the
that scratches or breaks the skin. Damage ranges from a superficial
scratch to a deep puncture to a slash. For a deep bite, the rat
touches the object with its upper incisors and brings the lower
incisors powerfully upward. Rats are also capable of voluntarily
separating their lower incisors into a "V" shape that may increase
the damage from a bite.
Social biting: In a social context, rats may bite each
other, particularly during fights.
Offensive bites tend to be directed at the lower back and
flanks. Defensive bites tend to be directed at the face.
Defensive bites are sometimes delivered in a lunge-and-bite sequence.
The bite to the head is characteristic of hurt, frightened, or
Note that lunging bites directed at the face may also be used
offensively, especially by females toward intruders (DeBold and
Miczek 1981). Check out RatRaisins, Inc. for more
discussion of rat bites.
Predatory biting: During a predatory sequence, rats may
also bite their prey with their incisors and kill it. For example,
rats may bite the head, neck or upper back of mice (Hsuchou et
al. 2002). Rats may bite the heads off of crickets prior to
Food biting: While eating, rats bite off small chunks of
food with their incisors. The food is passed back into the mouth
where it can be chewed between the molars.
Box: Two rats stand on their hind
face to face and nearly nose to nose, and push or paw at each other
with their front legs and paws, usually around the head, neck,
shoulders and front legs of their opponent. In high intensity boxing
the rats stand erect on their hind feet and rapidly push, paw, and
grab at each other. In low intensity boxing the rats squat on their
haunches and paw at each other gently. If no contact is involved, the
encounter is a nose-off. Boxing is a defensive
strategy: as long as the subordinate rat maintains whisker-to-whisker
contact, the dominant rat cannot bite his rump. The dominant rat may
respond to the boxing tactic with a sidle
(Blanchard et al. 1977).
Bound (ricocheting jump): Rat
advances with leaps: it pushes off with both hind feet, lands on both
front feet, brings forward the hind feet and pushes off again. The
rat spends 3/4 of its time in the air: in one beat, the forefeet hit
the ground followed quickly by the hind feet, which push the rat into
the air, and three beats later the forefeet hit the ground again. The
back arches when the hind feet are brought forward, making bounding
very conspicuous. The rat may also thump at each bound when it hits
Brux : Soft, repetitive grinding
the incisors against each other. Serves the sharpen the incisors and
may be given in times of relaxation or stress (Rosales et al
2002, Pohto 1979). Also see chatter.
To read more about bruxing and to hear rat sound samples, go to
the Norway Rat Vocalizations
Caching, or Stashing: The rat
up a food item in its mouth, runs elsewhere, and deposits the food
item. The rat frequently leaves the item there and returns for
another load. The place a rat chooses to cache food in is usually a
protected, hidden or semi-hidden location, such as a nestbox, a
dead-end passage, or a dark corner.
Cephalocaudal groom ("CCG"): Grooming
sequence of face and body (common to all rodents). The rat starts by
licking the paws, then rubs them over the head. This is followed by
licking and rubbing the side of the body, the anogenital region, and
the tail. The sequence may be anywhere from loosely organized to very
stylized, performed in a similar or identical fashion each time. In
rats, most sequences appear to be loosely organized. The grooming
sequence may be interrupted at any point, and it seems that rats
usually stop before grooming their tails.
Chase, or pursuit: Running
in which a rat pursues a target individual. If the chase occurs in a
social context, the pursuer may deliver a nip to the fleeing rat's
rump if he gets close enough. Rats may also pursue prey.
grinding of the incisors against each other. May be given during
intense agonistic encounters, and may represent an internal conflict
(dual activation) of attack and flight tendencies (Lammers et
al. 1988). May be louder and may contain more sharp crackling
sounds than bruxing in a relaxed context.
To read more about chattering and to hear rat sound samples, go to
the Norway Rat Vocalizations
Chew (mastication): Grinding
shredding of food between the molars. The lower jaw is in the back
position, such that the molars are in contact with each other and the
incisors are not. Chewing is involved in processing food prior to
ingestion, and is quite different from gnawing.
For details on the exact biomechanics of chewing, see Weijs (1975);
Weijs and Dantuma (1975).
Climb: Vertical locomotion up or
a vertical surface. Rats may scale just about any vertical or slanted
surface with a sufficient handhold. They use both forefeet (pull) and
hind feet (push) to grasp footholds and haul themselves up. They may
use their claws if they can't use their toes, as when climbing a
screen or fabric. Rats climb up more easily then they descend. They
descend head first, and appear to have some difficulty controlling
their weight and speed on descent. A rat may start a descent and may
then jump or fall the rest of the way.
Crawl: Ineffecient, nonpostural
shown by baby rats between days 3 and 10.
Crawl-over: One rat
approaches the flank side of another rat and maintains close body
contact as it crawls over the other animal. Urine marks are deposited
during the crawl-over, but not all crawl-overs are accompanied with
urine marking. There appears to be no favored body part to mark,
urine is distributed over most of the back (Taylor et al.
Communal nesting (nest
sharing): two or more females combine their litters in a
single nest and raise them together. The mothers may be related or
unrelated, and the litters may be the same or different ages. Often
includes communal nursing.
For more, see article entitled Communal
nesting and nursing in Norway rats.
(allonursing): the sharing of milk with the young of another
For more, see article entitled Communal
nesting and nursing in Norway rats.
Dig: Rats dig by pulling
of dirt backwards with their front paws, making a pile under their
stomachs. Sometimes the rat uses its whole forebody to pull a load
backwards. Periodically they clear the accumulated pile by kicking it
backwards with their hind feet. Rats may clear tunnels by pushing
dirt with their forepaws and head.
Dorsal Immobility, or
immobility response: Freezing or "going limp" behavior that
occurs when rats are picked up by the scruff of the neck. The
response is triggered by constriction of the skin at the nape
(Mileikovsky and Nozdrachev 1997). Dorsal immobility is seen
primarily in juveniles when their mother picks them up and transports
them from place to place (e.g. retrieving
pups back to the nest) (Wilson and Kaspar 1994). Going limp
probably helps the mother carry the baby, and the dorsal immobility
response is seen in the juveniles of many different altricial
species. The response persists into adulthood in rats, as adult rats
may continue to freeze when picked up by the scruff (Webster
Drag (another rat): A rat graps
another rat's skin in its teeth and attempts to pull the rat in a
Dragging may be seen in mother rats. Price and Belanger (1977)
examined the behavior of mother rats toward intruders and found that
33% of females dragged or pulled intruders, usually toward the nest.
The mother rats targeted the neck 61.4% of the time, the side 28.3%
of the time, the tail 8.7% of the time, and the ear 1.6% of the time.
Dragging adult rats may be a component of maternal aggression.
Wiesner and Sheard (1933) observed that lactating female rats may
drag their mates and adult offspring toward the nest. Lactating rats
may even drag young rabbits or kittens as well. This dragging tends
to decrease as lactation wanes, which suggests that dragging is
linked with normal pup-carrying. Adult rats may simply be a
"supernormal" stimulus for the retrieval response, and the mother may
drag them because they are too big to be lifted and carried.
Drink: Most domestic rats
from water bottles, licking the water off the metal ball at the end
of the waterspout. Rats may also lap standing water from a dish.
Ear wiggle: Female vibrates
ears rapidly. Ear wiggling is part of a suite of solicitation
behaviors in which the female initiates and maintains mounting
behavior by the male. Ear wiggling occurs when the female is in
behavioral estrus, about every 4-5
Eye-boggle (eyeboggle, boggle):
Eyeball vibrates rapidly in and out of the socket. Occurs during
high-intensity bruxing (soft, repetitive grinding
of the incisors). The rat's masseter muscle, which passes through the
eye socket behind the eyeball, moves the jaw rapidly up and down
during bruxing. When bruxing is intense, the contractions of the
masseter vibrate the eye in and out of the socket in time with the
incisor grinding. Usually considered to indicate pleasure and
Feed (eat): Consumption of
Rat takes bites out of food item with its
incisors. The morsel of food is then passed deeper into the mouth
where it is chewed between the molars and
Fight, or wrestle: This is an
escalated form of conflict, in which two rats wrap around each other
into a tight ball, rolling around together and biting, frequently
shrieking. According to Blanchard et al. 1975, the attacking rat
jumps or lies across the back of his opponent and attempts to bite
the opposite flank.
Flank Mark: Flank marking is
scent marking behavior involved in olfactory communication, in which
scent from the flank (presumably from the flank sebaceous glands,
Ebling 1963) is rubbed onto objects in the environment. Typically,
the rat leans sideways into a vertical structure (like a wall or the
edge of a burrow entrance) and pushes its side against the surface
while pulling itself forward. Males flank mark more than females.
Flank marking tends to be performed in familiar environments (Peden
and Timberlake 1990).
Flight: One rat runs away from
other, the second rat may or may not pursue.
Forequarter pivot: Adult defense
tactic, in which the defending rat stands on its hind legs and pivots
its forequarters to face the attacker, but leaves its hindquarters in
contact with the ground. The forequarter pivot enables the rat to
launch a counterattack. The more juvenile defense is the belly-up
roll, in which the hindquarters follow the forequarters and the
rat ends up on its back.
Gallop: limbs of both sides
nearly in synchrony (e.g. left and right front legs move nearly
together, left and right hind legs move nearly together). The gallop
is a fast, asymmetric gait, with a period of free-flight (all four
limbs off the ground).
In an extreme form the gallop may become a bound
or ricocheting jump, in which the forefeet hit the ground,
then the hindfeet hit the ground, then three beats later the forefeet
hit the ground again (Gambaryan 1974, mentioned in Golubitsky et
Gnaw: The rat pulls its lower
forward with its jaw muscles, such that its incisors touch each other
and its molars do not. The upper incisors hold the object, and the
lower incisors are pulled powerfully upward to cut against it.
Gnawing is a rodent's speciality, and their specialized jaw muscles
and jaw atriculation give the rodent a very effective, powerful
gnawing action. Gnawing is quite different from chewing,
which is used to process food prior to ingestion.
- Gnawed pen
closeup,1.1 MB). Look for the marks of the incisors. The top
incisors cut a small, semicircular slice in the object, the lower
incisors cut a deep gouge.
Head Bob (sway):
the head up and down or side to side. May precede a jump over a gap.
Rats bob their heads in order to gain a sense of visual depth
(distance between themselves and a far away object) using motion
parallax cues. Albinos may sway more frequently than pigmented rats
because albino vision is very poor. For more on depth perception and
the vision of pigmented and albino rats, see What
do rats see?
Hide: One rat retreats to a safe
preferably far away from the aggressive rat. He may stay there,
sitting quietly for a long time, sometimes up to an hour.
Hiss: Vocalization made during
escalated agonistic encounters, typically when rats are very close to
or in contact with each other. Such escalated conflicts tend to occur
when the rats are confined and cannot escape each other, as escape
takes precedence over fighting and hissing. Hisses tend to last about
1 second and have no discrete begining or end, which makes
identification of the hissing rat difficult. Hisses also have an
ultrasonic component Berg and Baenninger 1973). The two hisses I have
heard were emitted by the defensive rat. To read more about rat
vocalizations, go to the Norway
Rat Vocalizations Page.
- Hissing during open mouth tooth display by Snip (inside cage)
toward Widget (outside)
Killing the young of one's own species. Infanticide may be followed
by cannibalism, but this is not always the case. Infanticide may be
committed by mother rats, by unrelated female rats, by unrelated male
rats, or by father rats. Each commits infanticide under different
conditions and for different reasons.
The targets of infanticide are usually newborn pups. Rarely, older
pups may be killed. Newborn pups are usually simply eaten
(picked up and consumed like a food item). Older pups tend to be
killed by predatory attack (chase,
lunge, bite, kill sequence).
To read more about infanticide, visit the Infanticide
in Norway rats page.
Kick: May occur when a sidling rat
approaches another very closely. The hind foot closest to the second
rat kicks out, and may contact the second rat on the flank or higher
on the the back.
Offensive kick: The rat's offensive kick looks more like a
hind-foot grab which pulls the two rats into a close encounter,
perhaps enabling the kicker to position himself just prior to a
kick. During a close sidle with Cricket, Widget lashes out with a
hind leg. Notice also how Widget has grabbed Cricket's belly fur with
his front paw
Defensive kick: The rat raises a hind foot and uses it to
keep off or push away another rat
kick. During a close approach by Henry (black and white rat,
standing), Harvey (black rat facing camera) pushes Henry with his hind
foot and tail. Photo courtesy of Jon Lyman.
Lordosis (female arched back):
Female mating posture. Female stands immobile, with her back arched
downward toward the floor, her rump pushed upward and tail deflected
to the side. Her vulva, which normally faces the floor, rotates
almost 90 degrees to the vertical, backward-facing position. Without
lordosis, copulation would be impossible.
Lordosis is a reflexive behavior that is triggered by a touch on
the lower back, flanks, or genital region. The female may also
solicit mounting behavior by the male,
which in turn triggers lordosis.
Manipulate food (process
food): Rats may process their food before consuming it.
Processing may include removing a hard cover from a soft, edible
center: gnawing the shell off a nut, peeling
the skin off a pea. Processing may also include orienting a prey item
with the paws until it is positioned correctly: for example, rats
rotate crickets until the insect's head points upward, and the rat
proceeds to bite off the head, thus killing the
prey. Rats further process crickets by pulling off the legs and wings
before eating the thorax and head (Ivanco 1996).
Once the food is procesed, the rat typically holds its food by
squatting on its hind legs and holding it between the two front paws,
or, more rarely, with just one front paw. Rats may also take bites of
food directly without holding it up, though the rat may steady a
large edible object with a forepaw. This usually happens when a food
item is too large to pick up (e.g. chicken bone or corncob), or when
the food is pureed (e.g. soup, syrup) or too fine to pick up (e.g.
Attacks by a mother rat with a young litter. Typically, such attacks
consist of a lunge and bite attack, and are
directed at any animal approaching the mother's nest and young.
Mothers may also sidle, box
and drag intruders. Such attacks may discourage
other animals from approaching and possibly harming her offpsring
(e.g. predators, unfamiliar rats).
Mount: One rat places its
forequarters on another rat's rump from behind. Mounting is the male
copulatory position, and is seen when a male mounts a female prior to
mating. Mounting is also sometimes seen between rats of the same sex,
usually in an aggressive context.
Nestbuild: Rats may drag
carry desirable nesting material in their mouths into their chosen
sleeping spot, such as a nestbox or burrow. In captivity they may
choose bedding such as fabric pieces, tissue paper, paper towels,
toilet paper, and shredded cardboard. Wild rats may use leaves and
grass. Rats shred the material into smaller sizes, and line the
bottom of their nestbox with it.
Rats build several types of nest:
- pad: simplest kind of nest. Consists of just a few flat
objects (leaves, bits of paper) which elevate one rat just above the
- "cup-shaped" nest: larger nest may with a cup shape. Made
with finer texture grass or shredded paper interwoven a bit to form the
walls of the cup. The cup is lined with flat objects. Three to five
rats can sit comfortably in one of these. Nest elevates them 2-6 inches
from the floor.
- Hooded nest: Organized nest in which the walls grow so
high they form a ceiling, and the nest becomes a hollow sphere with
just one opening. These nests are sometimes built by mothers for
Nibble: Rats may nibble their
skin or that of other rats with their teeth. Under normal
circumstances they do not bite off the fur, but rather appear to be
combing the fur with their teeth and nibbling the skin underneath. If
nibbling is excessive it may become self-barbering or barbering of
Nip: Light pinching contact with
teeth, skin unbroken. May elicit a squeak.
Nose-off: Two rats stand
facing each other. The rats may have all four paws on the ground, or
may have one or both front paws up (in which case a nose-off may
segue into boxing). Sometimes one rat leans in toward the other while
the second rat leans away from him (the rat who leans in is usually
the dominant rat). Generally, the closer the rats are to each other,
the more intense the encounter. The nose-off may be accompanied with
the open-mouth tooth display from the
subordinate rat. Nose-offs are a defensive strategy: as long as the
subordinate rat maintains whisker-to-whisker contact, the dominant
rat cannot bite him. Nose-offs may escalate into boxing.
The dominant rat may respond to the nose-off or boxing tactics with a
sidle (Blanchard et al. 1977).
Nose-offs may escalate into boxing.
crouching posture of a mother rat over her offspring, which allows
them to nurse and provides them with protection and warmth. The
nursing posture may also be performed by non-lactating females and
even males who have been repeatedly exposed to foster pups.
Open-mouth tooth display: Facial
expression in which the mouth is open, revealing the base or all of
the bottom incisors. The more intense the expression, the wider the
mouth and the more you can see the teeth. In a very intense version
(seen during a nose-off), the mouth is wide open and lower incisors
are spread apart into a "V" shape, and the rat may squeak
or hiss. Also, the forehead fur appears flattened
and ears may be pulled slightly down and rotated forward. This "flat
foreheaded" look was useful to me in the past, with my now deceased
female rat Paint, because it was a good predictor of an impending
lunge-and-bite onto my hand.
- Open mouth tooth display and hissing by Snip (inside cage) to
Overmark: Deposit of a scent
over the scent mark of another rat. The topmost scent mark is known
as the top-scent, and the animal who puts it there is called
the top-scent-male or top-scent-female.
Peep: Brief (0.1 sec) high pitched
note that sweeps steeply upward in pitch. Sounds like a soft "bwip."
Heard during head and body allogrooming. To read more about peeps and
listen to peep samples, go to the Norway
Rat Vocalizations Page.
Pica: The consumption of
substances like clay, kaolin (a type of clay), or even bedding. Pica
is the rat's response to nausea, as rats cannot vomit.
rat's body hair stands on end. May occur when the rat is cold, or
when stressed, such as during or after an intense altercation.
of behaviors used to hunt and kill prey. A common sequence includes:
detection of prey --> chase --> bite
--> kill --> manipulate -->
eat. More on predation
Pup retrieval: Carrying
behavior in which a mother rat picks up a straying pup in her mouth,
usually by the neck, and brings it back to the nest. May be
facilitated by the pup's transport
Push: May occur when a sidling rat
makes physical contact with another rat. Using the broadside of its
body, the sidling rat presses against the second rat. The sidling rat
may tuck his head town, sometimes as far down as between his front
paws (possibly to protect it), or under the second rat (possibly to
gain leverage). The second rat may reciprocate, such that both rats
push against each other. Alternatively, the second rat may be pushed
back. If the encounter happens on a ledge, the pushing rat may
maneuver the second rat off the ledge.
Scratch: Rats may raise a
foot and scratch themselves, usually with rapid movements of the hind
foot and claws. They can reach their head (eyes, ears etc.), neck,
front leg and side with their hind foot.
Shriek: Loud scream that covers
frequencies at once, from 0.2 to 20 kHz and perhaps up into
ultrasound. Heard during fights, or when rat is in pain, or in strong
protest. To read more about shrieks and to hear shriek samples, go to
the Norway Rat Vocalizations
Sidle (lateral display, crab walk,
crowd): Threatening posture in which one rat (usually but not
always the dominant one) approaches another rat sideways or broadside
("crab walks"), with his back strongly arched, and crowds the second
rat. Sidling may a successful strategy to counter boxing
and acheive a rump bite. If physical contact is
made, the sidle may become a push. The sidling
rat may also kick.
Sleep: Periodic suspension of
Sniff: cluster of movement
in which (1) the rat probes its snout along and around surfaces in a
series of discrete head movements, (2) the tip of the snout and the
whiskers are in brisk motion, (3) the rat breathes in and out rapidly
(Welker 1964). Sniffing is often a component of exploratory behavior.
Through sniffing, the rats sample their surroundings by smell and
initiation of sexual interaction. A female rat in behavioral
estrus will attempt to initiate and maintain mounting behavior by
soliciting the male. She darts towards him, then runs or hops a short
distance away. She may wait a bit, move back, wiggle
her ears, and repeat the sequence. This is called full
solicitation. In partial solicitation she pauses in front
of the male (touchback) or runs past him (runby). In an
interception, she darts in front of a male who is following
another female and distracts him.
The male rat finds these behaviors very attractive, and he may be
motivated to follow and mount the female. The
touch on her back triggers lordosis in her,
the female arched-back mating posture that enables copulation. For
more, see Nelson 1995.
Squeak, long: Loud, high
0.2-0.3 sec note that stays relatively constant in pitch. Given by
subordinate rat during belly-grooming, during other tense encounters,
or in strong protest. A variation is the broken long squeak, which is
a long squeak that is broken into two notes. To read more about long
squeaks and to hear squeak samples, go to the Norway
Rat Vocalizations Page.
Squeak, short: High pitched, 0.2
note that sweeps slightly upwards in pitch. Heard during head
grooming and mild social interactions. Variations include the chirrup
(broken, double-note short squeak), and the squeak-churr (sqeak that
ends in a broad-band vocalization that sounds like a soft "churr").
To read more about short squeaks and their variants, and to hear
squeak samples, go to the Norway
Rat Vocalizations Page.
Tail carry: rats may pick up
their tails in their mouths and carry them. May be a form of
displaced maternal behavior by mother rats. Pregnant rats who are
deprived of all nesting material still attempt to build nests by
carrying their tails again and again to the chosen nest site. Mother
rats with nursing litters may retrieve
their own tails to the nest.
Tail writhe (tail wag, tail
swish): Tail moves sinuously on the ground, and may bang on
the floor. The movement may involve the entire tail, or as little as
the tail tip. Tail writhing is frequently seen during nose-offs.
I have also been able to elicit tail writhing by covering the rat's
head with my cupped hand and pressing down gently.
The function of tail writhing is unknown. Tail writhing may
indicate a high degree of tension or excitement, possibly negative
excitement. For example, lactating females may swish their tails
during aggressive encounters with each other (Adams and Boice
Tonic Immobility (also:
immobility, paroxysmal inhibition): Freezing behavior seen
when pressure is applied to the upper back/nape of a rat (Grant and
Mackintosh, 1963; Lehman and Adams 1977; Meyer 1990; Tikal 1991;
Webster et al. 1981).
Tonic immobility may be seen when a rat performs a belly-up roll
during an agonistic encounter. In this position, when the rat is
completely prone, his upper back may contact the floor and the
pressure may trigger a tonic immobility response which keeps the rat
immoble for some time. Tonic immobility tends to last longer in
subordinate rats (Tikal 1991). Tonic immobility may also serve to
reduce the probability of an attack during a conflict, as animals
prefer to attack moving targets (Thor et al. 1981). Immobility
will not, however, inhibit all attacks as Blanchard et al.
(1977) has shown that a motivated resident rat will attack an
Tonic immobility can be artificially triggered by humans who apply
pressure to the upper back. Tonic immobility may be related to
dorsal immobility, in which a rat
freezes when picked up by the scruff.
Tonic immobility may be related to "playing dead" or "animal
hypnosis" in other species (e.g. guinea pigs, rabbits, chickens,
quail etc.). For example, chickens who are manually restrained by a
human may go limp and stay that way for some time.
Trot: Gait in which legs within
girdles step in alternation (the two front legs alternate between
themselves, and the two back legs alternate between themselves), and
diagonal pairs of legs move in synchrony (front left and back right
move together). This gait is intermediate in speed between the walk
and the gallop.
Urine mark, or scent mark:
rat deposits tiny droplets of urine on the surfaces and objects he
walks on. Considered an advertisement of the rat's presence and a sex
attractant. Urine may be deposited by: (1) anogenital drag:
rubbing hindquarters over top of object, leaving a trail of urine as
the rat steps over it; or (2) leg-lift: lifting hind leg
nearest the object and urinating on one corner while standing, or
walking beside the object with one hind foot on top of it, leaving a
trail of urine along the entire length of the object (Brown 1975).
Rats may urine mark each other using the (3) crawl-over.
Visit the urine marking in Norway rats
page for more.
Ultrasonic vocalizations (USVs):
Vocalization above 20 kHz. Rats emit different USVs in a variety of
contexts. Different types of ultrasonic vocalizations include:
* Infant distress calls: Infant rats, who cannot
regulate their own body temperature, emit high pitched, 40 kHz distress
calls when they are cold (Allin and Banks 1971; Carden and Hofer 1992).
* Long distress USVs: Rats emit long 20 kHz vocalizations
when they are unhappy or stressed. For example, these calls are emitted
when an adult or juvenile is defeated socially (Thomas 1983), sees a
predator (Blanchard 1991), experiences pain (Cuomo 1988, Tonue 1986) or
anticipation of pain (Antoniadis 1999).
* Short, chirping USVs: these calls are shorter and higher
pitched (50 kHz) than the negative SVUs (Knutson 1999), and are thought
to be positive. Adults and juveniles emit them during play (Knutson
1998), courtship (Barfield 1979), and in anticipation of feeding
(Burgdorf 2000). Here's an article on "laughing
in rats" as well as a summary
article written by the researchers.
For more, see What do Rats Hear?
Walk: Lateral sequence gait,
no period of free-flight (all four legs off the ground). Walking is
the slowest of rat gaits.
Yawn: Deep intake of breath
wide open mouth. Frequently associated with stretching. For some
wonderful photos of rat yawns, check out the Dapper Rat Gallery
of Yawns page.