Parturition in the rat (Rattus norvegicus): Normative aspects and the temporal patterning of behaviours

Behavioural Processes, 5 (1980) o Elsevier Scientific Publishing

21-37 Company,

Amsterdam

-

Printed

21

in Belgium.

PARTURITION IN THE RAT (R/i TTUS NOR VEGZCUS) : IJORMATIVE ASPECTS AND THE TEMPORAL PATTERNING OF BEHAVIOURS

MARK

J. DOLLINGER,

Department (U.S.A.)

WILLIAM

of Biobehavioral

R. HOLLOWAY

Sciences,

University

Jr.*

and VICTOR

of Connecticut,

*Present address: Department of Psychiatry, University and Dentistry, Rochester, N.Y. 14642 (U.S.A.)

of Rochester

H. DENENBERG

Storrs,

CT 06268

School

of Medicine

This research was supported in part by Research Grant HD-08195 from the National stitute of Child Health and Human Development, NIH. M.J.D. and W.R.H.Jr. (NIMH doctoral trainees) were supported by Training Grant MH-14278. (Accepted

26 September

Inpre-

1979)

ABSTRACT Dollinger, M.J., Holloway, W.R., Jr. and Denenberg, V.H., 1980. Parturition in the rat (Rattus norvegicusj : normative aspects and the temporal patterning of behaviours. Behav. Processes, 5: 21-37. The purpose of this paper was to present a quantitative analysis of parturition in the laboratory rat. In addition, the effects of parity were also investigated. Gestational length was 22-23 days (day sperm found was Day 1) in 95% of the pregnancies. The average length of parturition was 97.3 min. The mean litter size was 10.84 pups and the average weight of each pup at birth was 6.49 g. The effects of parity were limited to changes in two parturitional behaviours: Mount and Lordosis Contraction. These changes may reflect the conditioning of the uterus in response to a prior pregnancy. Pub births and placental expulsions did not occur at equidistant points throughout parturition. Following the birth of the first pup there was a characteristic lull in births. Indeed, almost two-thirds of the births occurred during the second half of parturition. The expulsion of placentas followed a similar time course though displaced to the right, reflecting the fact that placentas are expelled at some point following the birth of a pup. The main thrust of this paper was the temporal sequencing of parturitional behaviours. The 21 behaviours clustered into five phases which were defined in terms of their peak occurrence during parturition. The first phase -the Initiation Phase - was consonant with the birth of the first pup. During parturition, the female spent much of her time licking the first born, grooming her head, and sniffing in response to the novelty of the birth fluids. The second phase -the Contraction Phase - was marked by a lul in the pup births. During this phase the predominant contraction pattern shifted from Lordosis, the type of contraction seen prior to the birth of the first pup, to the transitional type (Intermediate) and finally to the Vertical Contraction. It was the Vertical Contraction which was closely associated with the birth of pups. The third phase - the Birth-Oriented Phase - included the second half of parturition, when the majority of the litter was born. The behaviours exhibited during this phase were intricately involved with pup births per se. The female spent much time grooming and pulling at the anogenital region, eating placentas, and grooming herself to clean the copious quantities of birth fluids. The fourth

22 phase -the Termination Phase - was marked by the birth of the last pup in the litter. Sniff Pup reached its highest levels during this phase. The fifth phase - the Nursing Phase - began after all the pups had been born, cleaned, stimulated, and clustered. The female then became quiescent over the young and nursing was initiated. A sixth cluster of behaviours exhibited low levels of occurrence and the absence of temporal patterning. Thus, parturition in the rat is characterized by an orderly progression of behaviours through the parturitional period. In addition, several naturally occurring behaviours such as Groom Dorsal and Eat-Drink are maintained at very low levels throughout the delivery.

Parturition is the culmination of the preparatory changes evidenced during gestation in the pregnant female’s behaviour and physiology. As gestation progresses, the pattern of pup retrieval changes from that of the virgin who takes about 7 days to sensitize (Rosenblatt, 1967), to a pattern where, by 16 days of gestation, the female retrieves and clusters pups after only 4 days (Lott and Rosenblatt, 1969). Changes in the characteristics of self grooming also occur. The virgin and early gestational female groom in a stereotypic fashion -they lick their forepaws, then begin grooming the head region, followed by each flank, the ventrum, and finally the anogenital region, with each area receiving about equal attention. But as gestation proceeds a larger proportion of the female’s time is spent grooming the nipple line and the anogenital region - areas associated with the care and birth of the young (Roth and Rosenblatt, 1967). Changes in the gestational female’s endocrine physiology begin immediately upon insemination. Estrous cyclicity is terminated as the pregnant female enters an endocrine state characterized by the dominance of progesterone. During the last week of pregnancy the blood titres of progesterone begin to decline, and estrogen becomes the predominant ovarian steroid ( Grota and Eik-Nes, 1967; Shaikh, 1971; Fuchs, 1974, 1978). A third hormone, prolactin, is low through pregnancy (Kwa and Verhofstad, 1967), and rises sharply on the day of parturition (Amenomori et al., 1970). While the preparatory events which lead up to parturition have been an active research area, parturition per se has received little attention. The only notable discussion of parturition in rat is a qualitative one of the events surrounding the birth of each pup (Rosenblatt and Lehrman, 1963), pattemed after a description of parturition in the cat by Schneirla et al. (1963). Four phases were described. The first - the Contraction Phase - immediately preceeds the birth of a pup, and is characterized by peristaltic waves of the uterine horns. The Contraction Phase may last several hours prior to the first birth, with much shorter durations prior to the birth of subsequent pups. The second - the Delivery Phase, - is consonant with the birth of a pup and consists of the expulsion of the pup. The pup’s birth initiates the start of the third phase -the Post-Delivery Phase - which is characterized by pup licking and placentaphagia by the parturient female. This is followed by a period of self grooming, nest building, and licking the pups that were previously born. These behaviours constitute the fourth phase - that of the Interval Between Births. The behaviour of the parturient female cycles

23

through these four phases in response to the multiple births. Following the birth of the last pup, the parturient female enters a prolonged quiescent state. While Rosenblatt and Lehrman’s work has provided a nice description of the events around the births of individual pups, it leaves unanswered the question of the nature of the temporal patterning of the behaviours through parturition, and how the behaviours are integrated with each other. Accordingly, the purpose of this paper is to provide a detailed description of parturitive behaviours in a quantitative framework sensitive to temporal patterning. In addition, we manipulated the variable of parity to see whether the same temporal patterning would be found with multiparous females as was found with primiparous ones. METHODS

Subjects Subjects were primiparae (100-130 days) and multiparae (15+180 days) of the Purdue-Wistar strain of Rattus noruegicus born in our closed colony. All multiparae had reared one litter of eight pups from birth to weaning and had been rested at least 30 days after the weaning of their first litter before being mated again. The room temperature was maintained at 21°C and the relative humidity was 40%. A 13 : 11 light : dark regimen was used with the lights on at 07.00.

Procedures

during gestation

Six females were placed in a cage with one male, and vaginal smears were taken daily (2-4 h after lights-on). When sperm were found in the smear (Day 1 gestation), the females were weighed, and housed in groups of six in suspended cages (66 X 25 X 18 cm). On Days lo-12 of gestation, the females were weighed again and assigned to one of three experimental conditions: unoperated controls, sham-operated, and bilateral olfactory bulbectomy. Those assigned to the bulbectomized group are the topic of another paper (W.R. Holloway, M.J. Dollinger and V.H. Denenberg, unpublished) and will not be discussed here. Females gaining less than 18 g were considered nonpregnant and were not assigned to an experimental group. Subjects assigned to the control condition were returned to their cages.

Operative procedures Sham-operated subjects were anesthetized with ether. The scalp was shaved and incised over the olfactory bulbs. A hole was drilled through the skull using a trefine with a 2.5-mm diameter. Following aspiration of blood from the opening, a piece of gelfoam was placed over the olfactory bulbs, and the incision was closed with g-mm wound clips. The females were placed into

24

large opaque plastic mouse tubs for 24 h following surgery and were then returned to their home cages. On Day 19 or 20 gestation, subjects were isolated into clear plexiglass maternity cages (30 X 27 X 24 cm). Food and shavings were on the cage floor, and water was available via an external bottle.

Behavioural

observation

On the morning of Day 23 - the expected day of birth for rats in our colony - subjects in the maternity cages were removed from the maternity rack and taken to an adjoining observation room. Each subject was observed periodically until abdominal contractions were frequent and vigorous, indicating that the first birth was imminent. Behavioural observations were then initiated. All behavioural observations were under ambient fluorescent illumination with the experimenter seated 2-3 feet (approx. 0.5-l m) from the cage. TABLE

I

The maternal

behaviours

_

observed

and their

definitions

Behaviour

Definition

Nurse Lick Pup Sniff Pup Pup Retrieval

Mother nurses one or more pups Mother licks one or more pups Mother sniffs one or more pups Mother moves a pup into the nest or if the pups are in the nest, picks them up either in the forepaws or mouth Mother out of contact with all pups at the beginning of a 10-s epoch Contractions characterized by arching of back and stretchingout of body Contractions characterized by an upward bulging of the flanks Any contraction which fits neither of the above descriptions. Mother pulls with her teeth at the anogenital region Mother eats placenta or umbilical cord

Zero Pup Contact Lordosis Vertical

Contraction Contraction

Intermediate Contraction Pull Placentaphagia Groom Anogenital Groom Head Groom Dorsal I Groom Ventral Sniff Mouth Nest Build Eat-Drink Twitch General Quiet

Activity

Mother

self grooms

specified

region

Any sniffing not directed at pups Any mouthing not involving eating Mother moves nesting material Mother eats the food pellets or drinks the water Mother exhibits a spontaneous jerk originating at her ventral surface Mother locomotes about cage Absence of all the above behaviours during the entire 10-s epoch, except for Nurse and Zero Pup Contact

25

The behavioural observation was divided into 10-s epochs with the beginning of each epoch signalled by an electronic beep in an earplug. The 21 behaviours observed are listed and defined in Table I. Behaviours were recorded as they occurred within each 10-s epoch, with the exception of Nurse and Zero Pup Contact which were scored at the beginning of each epoch. More than one behaviour could be recorded in a 10-s epoch. The behavioural scale items are totally inclusive of the parturient female’s behaviour. In addition to the 21 behaviours, the birth of each pup and the expulsion of each placenta were recorded. Each observation was begun prior to the birth of the first pup and was terminated 60 min following the birth of the last pup in the litter.

Normative

data

At the end of each behavioural observation, litters were removed from their mothers. The gestational length, parturitional length, litter size and body weights of the individual pups were recorded. Since these females were used as part of a larger experiment (W.R. Holloway, M.J. Dollinger and V.H. Denenberg, unpublished), a complete set of normative data could not be collected from each litter. This is reflected in different sample sizes for each measure (see below). RESULTS

Normative

data

Gestational

length

For the 188 litters in this part of the study, 31.9% were delivered on Day 22,63.3% on Day 23, and 4.8% on Day 24 (see Table II). Gestation length was not affected by Condition (x” = 4.62, df = 2), or by Parity (x2 = 3.09, df = 2).

TABLE

II

Gestational ____

length for all litters

~___

Day of birth Condition

Day 22

Day 23

Day 24

Sample size

Primip Primip Multip Multip

40 8 4 8

74 11 24 10

4 1 1 3

118 20 29 21

60

119

9

188

Control Sham Control Sham

Total Percentage

31.9 _~ ~_____~

63.3

4.8

26

Parturtional

length

The length of parturition (from birth of the first until and including the birth of the last pup) was obtained for 55 litters. The average time was 97.3 min (see Table III). This measure was not influenced by Condition or Parity (Condition: F1,51 = 0.51; Parity: F1,5r = 2.97; Condition X Parity: F1,51 = 1.53).

Litter size The mean litter size of 93 litters was 10.84 pups. The main effects of Condition (Fl,sg = 0.06) and Parity (Fl,ag = 1.91) were not significant, but the Condition X Parity interaction was significant (Fl,Bg = 6.09, P < .05). Multip Shams gave birth to the largest litters while Primip Shams gave birth to the smallest with the two Control groups intermediate (see Table III). TABLE

III

Parturitional

length,

litter size, and birth weights Primip Sham

Primip Control

-~ Parturitional length (mm) Litter size (n) Body weights (g)b

a96.16 11.09 6.48

k 6.13 + 0.50 ? 0.07

84.28 9.76 6.56

+ 15.7 f 1.02 + 0.15

for all litters Multip Control

Multip Sham

X

101.50 i 9.8 10.44 +0.83 6.36 ? 0.24

107.25 i 16.7 12.07 i 0.68 6.56 i 0.07

97.30 10.84 6.49

aX + standard error. hAverage weight of each pup in the litter.

Body weight The unit of analysis was the litter mean, determined by averaging the individual weights of each pup in the litter. For 30 litters the average Hour-l body weight was 6.49 g. It was not affected by Condition or Parity (Condition: F1,26 = 0.59; Parity: Fl,26 = 0.11; Condition X Parity: F1,26 = 0.11) (see Table III).

Parturition Statistical

behaviours analyses

The number of pups born and the length of parturition varied among mothers. In order to put them on a common baseline each parturition was divided into 10% blocks. This was done by determining for each female the time from the birth of the first pup until the birth of the last, and dividing that time into 10 equal intervals (Equivalent Time Units). The mean length of parturition was 97.3 min, so the average interval was 9.7 min. The 60min observation period following the end of parturition was divided into six, lo-min blocks, thus closely corresponding to the average parturitional time

27

intervals above. In all, there were 16 equivalent time units for each parturition (10 during parturition, six during the hour immediately following parturition). Within each equivalent time unit the number of epochs in which a particular behaviour occurred was obtained, and this value was divided by the total number of epochs in that time unit, thus yielding a percent occurrence statistic. This was the unit used for all subsequent analyses. To evaluate the data we used a three-way unweighted means factorial analysis of variance with orthogonal polynomials. The independent variables were Parity (primiparous and multiparous), Condition (control and shamoperated), and Time (16 intervals). The non-pooled error term was employed in evaluating each source of variance (Winer, 1971). Since the primary objective of this paper is a quantitative description of the parturitional behaviours, the results are presented in terms of the best fitting regression lines derived from the polynomial equations, thereby providing the purest picture of the temporal patterning of the behaviours. The regression equation consists of the significant components through the fourth power. The first four regression coefficients and their significance levels are given in Table IV (for the obtained values, see Dollinger, 1977). Whenever possible the data were pooled across treatment groups to increase sample size. Our analyses of variance found no Parity X Time interaactions, thus allowing us to pool the primiparous and multiparous control groups for all behaviours. When significant effects associated with Condition were found, the Sham groups were removed and the data were re-analyzed using only the primiparous and multiparous control groups (the sample analysed for each behaviour is defined in Table IV). The presentation of the results will mirror the chronological sequencing of the behaviours through parturition. Behaviours which exhibit their highest levels early in parturition will be discussed first, while those peaking during the 60 min following parturition will be presented last. This approach will facilitate the clustering of behaviours which exhibit similar temporal patterns. Parity effects. There were only two main effects of Parity, reflecting a marked consistency in parturitional behaviours across parity conditions. Primiparous females Mouthed more than Multiparous females (F1,37 = 5.11, P < 0.05)) and exhibited a greater number of Lordosis Contractions (F1,37 = 4.07, P < 0.05). There were no significant Parity X Time interactions. Birth of pups and expulsion of placentas. The birth of pups and the expulsion of placentas represent focal events in parturition, and convenient markers for the interpretation of the behavioural patterns. Pups are not born at equidistant time points throughout parturition. Instead, following the birth of the first pup there is a characteristic drop in the rate of births with the minimum occurring during the second equivalent time unit. The rate of pup births then increases through the birth of the last pup (Fig. 1). The expulsion of placentas follows a similar time course. However, because

-0.448*** -0.224** -0.262*** -0.444*** -0.187*** -0.264*** -0.350*** -0.218*** -0.290*** -0.289*** 0.116*** 0.456*** 0.655*** 0.612*** 0.083 -0.034 0.021 -0.036 -0.055 0.071 0.049

0.286 0.080 0.056 0.261 0.011 0.015 0.182 0.106 0.024 0.025 0.062 0.010 0.192 0.195 0.040 0.007 0.006 0.012 0.012 0.004 0.019

Lick Pup Sniff Groom Head Mouth Lordosis Contraction Intermediate Contraction Vertical Contraction Placentaphagia Groom Anogenital Pull Sniff Pup Twitch Quiet Nurse Nest Build Zero Pup Contact Eat-Drink Groom Dorsal Groom Ventral General Activity Pup Retrieval

*P < 0.05. **P < 0.01. ***p < 0.001.

1” Coeff.

0.207*** 0.144*** -0.119** -0.177*** -0.118 -0.191*** -0.355*** -0.284*** -0.286*“* -0.255*** -0.141* 0.112** 0.268*** 0.313*** 0.007 0.058 0.017 -0.028 -0.042 0.050 -0.041

2” Coeff

sample sizes, and groups included Y Int.

properties,

Behaviour

Regression

TABLE IV

-0.083** -0.040 -0.069 0.087** 0.156*** 0.163*** 0.057 0.051 0.203*** 0.103* -0.032 -0.107*** -0.040 0.051* -0.031 -0.042 -0.026 -0.008 -0.040 0.033 -0.014

3” Coeff.

0.129*** -0.054 0.142** 0.027 0.010 0.019 0.106*** 0.230*** 0.067** 0.146*** -0.010 -0.117*** -0.172*** -0.053 -0.088 0.013 0.014 0.017 0.054 0.011 -0.035

4” Coeff.

54 54 54 39 39 54 54 39 39 54 54 54 54 54 39 39 54 54 54 54 39

Sample size

All All All Controls Controls All All Controls Controls All All All All All Controls Controls All All All All Controls

Group included

29

c oo” ,

2

4

6

EQUIVALENT

8

TIME

‘p

12

14

I6

UNITS

Fig. 1. The percent occurrence of Pups Born and Placentas Expelled. The values are based on the data pooled across the four treatment groups. The two arrows designate the birth of the first and last pups, respectively.

the placenta is typically expelled several minutes after the pup is born, this curve is shifted to the right with respect to pup births (see Fig. 1). In the following figures which depict the time trends for the parturitional behaviours, the birth of an idealized litter of 11 pups (the average litter size) will be designated with circles at the top of each graph. Time trends for parturitional behaviours. There were three behaviours which exhibited their maxima at the time of birth of the first pup: Lick Pup, Sniff, and Groom Head. The orthogonal polynomial curves for these variables are shown in Fig. 2. Lick Pup Occurred in 65% of the epochs during the first time interval, and then dropped off sharply until about the fifth time interval when the drop became more gradual; the last two intervals were characterized by a slight increase. Sniff had a similar pattern to Lick Pup, though at a lower level of occurrence. Groom Head, unlike Lick Pup and Sniff, demonstrated a secondary maximum during the eight interval. Four other behaviours had parallel time courses with the peak centering around the third to fifth births. These were Mouth, Vertical Contractions, Intermediate Contractions, and Lordosis Contractions (Fig. 3). Following the fifth interval Mouth dropped gradually through the remainder of the epochs while the three contraction behaviours decreased through the birth of the last pup. The behaviours described above exhibited their peak occurrences during

30

0

4

2

4

6 EQUIVALENT

8 TIME

IO 4 UNITS

12

14

16

Fig. 2. The percent occurrence for Lick Pup (LP), Groom Head (GH), and Sniff(S). The two arrows designate the birth of the first and last pup in the litter, respectively. The circles at the top designate the births of an idealized litter of 11 pups.

EQUIVALENT

TIME

UNITS

Fig. 3. The percent occurrence for Mouth (M), Lordosis Contraction (LC), Intermediate Contraction (IC), and Vertical Contraction (VC). The two arrows designate the birth of the first and last pup in the litter, respectively. The circles at the top designate the births of an idealized litter of 11 pups.

31

60

Fig. 4. The percent occurrence for Groom Anogenital (GA), Placentaphagia (P), and Pull (Pu). The two arrows designate the birth of the first and last pup in the litter, respectively. The circles at the top designate the births of an idealized litter of 11 pups.

0

0

0

0

0

0

0

00

00

60-

SP

0

I 4

2i

4

6

0

12 ‘P

I4

I6

EQUIVALENT TIME UNITS

Fig. 5. The percent occurrence for Sniff Pup (SP). The two arrows designate the birth of the first and last pup in the litter, respectively. The circles at the top designate the births of an idealized litter of 11 pups.

32

EQUIVALENT

TIME

UNITi

Fig. 6. The percent occurrence for Nurse (N), Quiet (Q), and Twitch designate the birth of the first and last pup in the litter, respectively. designate the births of an idealized litter of 11 pups.

(Tw). The two arrows The circles at the top

the first half of parturition. An important point to note is that on the average only four pups (36% of the litter) were born during the first half of the delivery period. Three behaviours had their peak occurrence at the time of the sixth and seventh births: Groom Anogenital, Placentaphagia, and Pull (Fig. 4). A fourth behaviour, Groom Head, had its secondary maximum at the seventh birth (see Fig. 2). After peaking during the second half of parturition, these behaviours declined into the post-parturitional period. One behaviour, Sniff Pup, had gradually increasing values throughout parturition, and reached its highest value after the birth of the last pup (Fig. 5). There were three behaviours which achieved their maximal occurrences following the birth of the last pup: Quiet, Nurse, and Twitch (Fig. 6). All three had low levels of occurrence through the first seven births and began increasing between the eighth and last births. It is also interesting to note that two behaviours which had their maximal values early in parturition - Lick Pup and Sniff - also had modest increases postparturitionally (Fig. 2). Seven behaviours demonstrated no significant time trends: Groom Ventral, Groom Dorsal, Eat-Drink, General Activity, Zero Pup Contact, Pup Retrieve, and Nest Build. In addition, they all had low percentages of occurrence grand means from 3.7 to 0.5.

33

DISCUSSION

These results demonstrate that the parturitional behaviours cluster into five Phases based upon their temporal patterning (see Figs 2-6). Phase 1 - the Initiation Phase - is consonant with the birth of the first pup. The female exhibits her highest levels of Lick Pup, Sniff, and Groom Head (Fig. 2). Lick Pup subserves two important functions. Firstly, the licking acts to clean away the amnionic membranes and fluid thereby allowing the pup to begin aerobic respiration; secondly, licking constitutes the first interactions between mother and pup. Groom Head is often associated with the cleaning of birth fluids from the forepaw, while Sniff is a response to the altered olfactory properties of the environment, Thus, a distinctive feature of these behaviours is that they are a response to the change in the stimulus configuration of the environment; namely, the birth of the first pup and the elaboration of the birth fluids. It is interesting to note the high incidence of licking directed toward the first few pups born. These pups are stimulated considerably more than pups born later, suggesting a possible source of within-litter variability. Phase 2 -the Contraction Phase - is associated with a lull in the pup births (Fig. 1). Within the Contraction Phase, the three types of contractions succeed one another in prominence (see Fig. 3). Lordosis Contraction is the most common type of contraction early in Phase 2. This is the type of contraction which also predominates prior to the birth of the first pup, and may be associated with the movement of the pups into the birth canal. As the Lordosis Contractions begin to decline, the Intermediate Contractions reach their maxima, heralding the shift to the third type of contraction - Vertical Contraction. These contractions are closely associated with pup births; a pup is almost never born in the absence of the bulging of the female’s flanks, which distinguishes this type of contraction from the first two. The female often Mouths in conjunction with her contractions. An association between Mouth and Lordosis Contraction was found in the presence of Parity effects (and they were the only effects of Parity on the parturitional behaviours) and may reflect the conditioning of the uterus as a function of bearing a previous litter. These Phase 2 behaviours, taken together delineate a shift in the focus of the female’s attention from the pup oriented behaviour of Lick Pup to an increased responsiveness to the cues provided by the contracting uterus. This shift in attentiveness from pups which were previously born to the internal cues of the contracting uterus provides the transition to the second half of parturition, when the majority of the litter is born. Phase 3 - the Birth Oriented Phase - encompasses the second half of parturition when the majority of the litter is born. Four behaviours define the parturient female’s behaviour during this phase: Groom Anogenital, Pull, Placentaphagia, and Groom Head. These behaviours are intimately involved with the birth process per se.

34

Groom Anogenital is often seen between and following contractions, and is most closely associated with the cleaning of birth fluids from the anogenital region. Pulling at the anogenital region (Pull) typically occurs when a pup or placenta is lodged in the birth canal, and may facilitate its emergence. The high levels of Placentaphagia is consistent with the expulsion of the majority of placentas during this period - placentas are often consumed as soon as they emerge from the birth canal. There are two common sequences of placentaphagia. When the umbilical cord has been severed from the pup prior to the expulsion of the placenta, either by the mother or as a result of the contractions, the female will eat the placenta upon its emergence from the birth canal. Once the placenta has been consumed, she will engage in a bout of Groom Head to clean the fluids from her forepaws. When the umbicial cord remains attached to the pup either when the pup and placenta emerge together, or when the pup is expelled first and the placenta later but the cord is not severed, the female will commonly eat the placenta, then consume the umbilical cord, delicately severing the cord within l-2 mm of the pup. She then turns her attention to cleaning the birth fluids from the pup, and finally returns to her forepaws and self grooms. The above scenarios point to the integration of Groom Head into the Phase III behavioural patterns, and the regression properties of Groom Head point to a secondary maximum occurring during this phase (see Fig. 2). While the highest levels of Groom Head occur during Phase 1 in response to the novelty of the birth fluids, the secondary maximum seen during Phase III is a function of the large quantity of birth fluids associated with the great number of births occurring during this phase. Phase 4 -the Termination Phase - is marked by the birth of the last pup in the litter. Sniff Pup exhibits its highest levels during this period. This behaviour is often associated with Pup Retrieve and Nest Build (though neither of these behaviours exhibit significant trends). Thus, the female’s behaviour around the time of the last birth is in transition from the birth oriented behaviours to the nursing related behaviours. Phase 5 -the Nursing Phase - commences after the last pup in the litter has been born, and the pups have been cleaned, stimulated, and clustered. Phase 5 is characterized by the high occurrence of three behaviours: Twitch, Quiet, and Nurse (see Fig. 6). Twitch is associated with the initiation of nursing. When the pups first grasp the nipples, the female responds with this characteristic movement. Twitch reaches its maximal levels during the fourteenth time interval, suggesting that many of the pups in the litter have initiated suckling within 40 min following the birth of the last pup. An essential feature of the female’s behaviour following the birth of the last pup is her quiescence. During parturition the female is almost never Quiet, while in the fifteenth time interval, when Quiet reaches its maximum; she is Quiet during 52% of the epochs. The role of the female’s quiescence can clearly be seen when the time trend for Nurse is viewed. Nurse is a behaviour almost never exhibited during parturition. This was also found in the cat (Schneirla et al.,

35

1963). Concomitant with the absence of Nurse during parturition is the low level of Quiet. These results suggest that the female must be quiescent for nursing to be initiated. While the focus of the discussion has been on the importance of the temporal sequencing of the parturitional behaviours, there are also seven behaviours which exhibit no temporal patterning. Groom Dorsal, Groom Ventral, Zero Pup Contact, Pup Retrive, Nest Build, General Activity, and EatDrink are all characterized by the absence of significant time trends and low levels of occurrence. It may be important that during the parturitive period these naturally occurring behaviours be inhibited, and thereby not compete with the behaviours which are expressed in response to the events associated with parturition. ACKNOWLEDGEMENTS

Our thanks to the University of Connecticut of facilities and time. A special thanks to Jack Center for his friendly advice in the use of the Blanchette for his expert draftmanship, and to for his translation of the abstract into German.

Computer Center for the use Davis of Social Science Data statistical packages, to Ray Thomas Schmidt-Glenewinkle

REFERENCES Amenomori, Y., Chen, C.L. and Meites, J., 1970. Serum prolactin levels in rats during different reproductive states. Endocrinology, 86: 506-510. Dollinger, M.J., 1977. The importance of the early postnatal period in the rat (Rattus noruegicus). Unpublished Doctoral Dissertation, University of Connecticut, 188 pp. Fuchs, A-R., 1974. Regulation of uterine activity during gestation and parturition in rabbits and rats. In: E.M. Coutinho and F. Fuchs (Editors), Physiology and Genetics of Reproduction. Plenum Press, New York, N.Y., pp. 403-422. Fuchs, A-R., 1978. Hormonal control of myometrial function during pregnancy and parturition. Acta Endocrinol. Suppl. 221: l-70. Grota, L.J. and Eik-Nes, K.B., 1967. Plasma progesterone concentrations during pregnancy and lactation in the rat. J. Reprod. Fertil., 13: 83-91. Kwa, H.G. and Verhofstad, F., 1967. Prolactin levels in the plasma of female rats. J. Endocrinol., 39: 455-456. Lott, D.F. and Rosenblatt, J.S., 1969. Development of maternal responsiveness during pregnancy in the laboratory rat. In: B.M. Foss (Editor), Determinants of Infant Behaviour IV. Methuen, London, pp. 61+7. Rosenblatt, J.S., 1967. Nonhormonal basis of maternal behavior in the rat. Science, 156: 1512-1514. Rosenblatt, J.S. and Lehrman, D.S., 1963. Maternal behaviour of the laboratory rat. In: H.L. Rheingold (Editor), Maternal Behaviour in Mammals. Wiley, New York, N.Y., pp. 8-57. Roth, L.L. and Rosenblatt, J.S., 1967. Changes in self-licking during pregnancy in the rat. J. Comp. Physiol. Psychol., 63: 397-400.

36 Schneirla, T.C.;Rosenblatt, J.S. and Tobach, E., 1963. Maternal behavior in the cat. In: H.L. Rheingold (Editor), Maternal Behavior in Mammals. Wiley, New York, N.Y., pp. 122-163. Shaikh, A.A., 1971. Estrone and estradiol levels in the ovarian venous blood from rats during estrous cycle and pregnancy. Biol. Reprod., 5: 297-307. Winer, B.J., 1971. Statistical Principles in Experimental Design, Second Edition. McGrawHill, New York, N.Y., 907 pp. KURZFASSUNG Dollinger, Ratte

M.J.,

Holloway,

W.R.,

Jr. and Denenberg,

(Rattus norucgicus): normative Processes, 5: 21-37 (in Englisch).

Aspekte

V.H.,

1980.

und zeitliche

Der Geburtsablauf Verhastensmuster.

in der Behau.

Die Absicht der vorliegenden Veroeffentlichung war es, eine quantitative Analyse des Geburtsablaufs in der Laborratte zu geben. Zusaetlich wurde, in den Faellen wenn es sich urn eine Erstgeburt des Weibchens handelte, untersucht, ob dies von Einfluss auf geburtsspezifische Verhaltensweisen war. Die Tragzeit betrug 22-23 Tage in 95% aller Schwangerschaften (der Tag der Befruchtung wurde als Tag 1 bezeichnet). Der Geburtsvorgang dauerte durchschnittlich 97.3 Min. Die mittlere Wurfzahl betrug 10.84 Junge mit einem durchschnittlichen Geburtsgewicht von 6.49 g. Der Einfluss von Erst- oder Mehrfachgeburt des Weibchens beschraenkte sich auf zwei der beobachteten Verhaltsweisen: Kontraktionen des Maules sowie lordotische Kontraktionen (mouth and Lordosis Contraction). Diese Veraenderungen moegen eine Anpassung des Uterus auf Grund frueherer Schwangerschaften widerspiegeln. Die Geburt der Jungen sowie die Ausstossung der Placenta erfolgte nicht an zeitlich aequidistanten Punkten waehrend des Geburtsvorganges. Nach der Geburt des ersten Jungen trat eine charakteristische Ruhepause ein. Tatsaechlich fielen fast zweidrittel aller Geburten in die zweite Haelfte des Geburtsablaufes. Die ausstossung der Plazentas folgte einem aehnlichen, zeitlich jedoch nach rechts verschobenen, Ablauf, da diese nach der Geburt des Jungen erfolgte. Die Hauptzielrichtung unserer Untersuchung war es, die zeitliche Reihenfolge der waehrend der Geburt gezeigten Verhaltensweisen darzustellen. Die 21 beobachteten Verhaltens weisen gruppierten sich in fuenf Phasen. Jede Phase wurde durch das maximale Vorkommen bestimmter Verhaltensweisen waehrend des Geburtsablaufes definiert. Die erste Phase - die Einleitungsphase (Initiation Phase) - zeigte Uebereinstimmung mit der Geburt des ersten Jungen. Das gebaerende Weibchen verwendete vie1 Zeit mit dem Belecken des Erstgeborenen, dem Putzen ihres Kopfes, sowie allgemeinen Umherschnupperns als Reaktion auf das ungewohnte Vorhandensein der bei der Geburt sezernierten Fluessigkeiten. Die zweite Phase - die Kontraktionsphase (Contraction Phase) - war durch eine Verzoegerung im Geburtsablauf gekennzeichnet. Waehrend dieser Phase verschob sich das vorherrschende Kontraktionsmuster von lordotischen Kontraktionen, der Art von Kontraktionen wie sie vor der Geburt des ersten Jungen beobachtet wurden, zu einem Uebergangstyp (Intermediate), der endlich von Kontraktionen in fast vertikaler Position (Vertical Contraction) abgeloest wurde. Kontraktionen in letzterer Position waren eng mit der Geburt der Jungen verbunden. Die dritte Phase - die geburtsorientierte Phase (Birth-Oriented Phase) - schloss die zweite Haelfte des Geburtsablaufes ein, in der die Mehrzahl der Jungen geboren wurden. Die waehrend dieser Phase gezeigten Verhaltensweisen waren auf das engste mit der Geburt der Jungen per se verknuepft. Das Weibthen verwendete vie1 Zeit mit Putzen und Zerren in der anogenitalen Region, dem Verzehr der Placentas, sowie der eigenen Saeuberung von den in reichlichen Mengen abgeschiedenen Geburtsfluessigkeiten. Die vierte Phase - die Endphase (Termination Phase) - war durch die Geburt des letzten Jungen gekennzeichnet. Das Beschnuppern der Jungen (Sniff

37

Pub) als eine der untersuchten Verhaltensweisen erreichte waehrend dieser Phase sein Maximum. Die fuenfte Phase - die Saeugephase (Nursing Phase) - begann nachdem alle Jungen geboren, gesaeubert, stimuliert und in einem Haufen versammelt waren. Das Weibthen, dann ueber den Jungen ruhend, begann mit dem Saeugen. Eine sechste Gruppe von Verhaltensweisen zeigte nur geringe Haeufigkeit soweie Fehlen zeitlicher Organisation. Zusammenfassend laesst sich sagen, dass der Geburtsvorgang durch ein wohlgeordnetes Fortschreiten von Verhaltensweisen ueber seinen gesammten zeitlichen Ablauf gekennzeichnet ist. Waehrend des Geburtsvorganges wurde neben den spezifischen Verhaltensweisen eine Reihe von anderen natuerlichen Verhalten wie Putzen des Rueckens (Groom Dorsal), Nahrungsaufnahme und Trinken (Eat/Drink) beobachtet, allerdings mir geringer Haeufigkeit.