Polar Biol (2008) 31:1137–1141

DOI 10.1007/s00300-008-0446-8

SHORT NOTE

Fetus presentation and time taken for parturition in Antarctic fur seal, Arctocephalus gazella, at Cape ShirreV, Antarctica

Jorge Acevedo · Anelio Aguayo-Lobo · Daniel Torres

Received: 3 August 2007 / Revised: 7 March 2008 / Accepted: 10 March 2008 / Published online: 22 May 2008© Springer-Verlag 2008

Abstract We document the inXuence of fetus orientationin the time invested in the birthing process of Antarctic furseals at Cape ShirreV, Antarctica. Our results show thatbreeching was signiWcantly higher than cephalic orientationon the order of 1.5:1. The average duration of the birthingprocess was 37.26 min, and the average duration consider-ing the fetus orientation was 27.22 and 49.39 min for thecephalic and breech, respectively. The average time wassigniWcantly diVerent only in the phase from the appearanceof the amniotic-allantoids sac to the complete expulsion ofthe pup. Possible explanations for this diVerence are: thefriction between the opposite hair direction with the uterus-vaginal wall after the rupture of amnio-allantoid sac duringthe transit of the fetus in breech position, and/or the factone or both front Xippers would increase the scapular diam-eter and make the Wnal step of fetus delivery more diYcult.

Keywords Birth · Cephalic and breech births · A. gazella · Cape ShirreV · Antarctic

Introduction

All pinniped species spend part of their life history at seafor feeding and part on land or ice for breeding and rearingof oVspring. The breeding process in Otariids alwaysoccurs on land (sand, rock and pebble beaches), includingbeaches covered by snow fallen in the previous winter, asoccurs in Arctocephalus gazella (Peters 1875).

Although most aspects of the reproductive biology areknown in diVerent pinniped species, the fetus orientation atbirth and the time spent giving birth has been poorly docu-mented. Previous studies have focused mainly on ecologicalaspects and population trends post-explotation. In general,giving birth in many pinniped species seems to be relativelyshort (Slijper 1956; Bowen 1991). The scarce data availableabout fetus orientation in pinnipeds are contradictory with,some suggesting that pups are normally born in a cephalicposition and others in either cephalic or caudal position(Harrison 1969; Sweeney 1986; Bowen 1991). On the otherhand, Harrison (1969) pointed out that fetus orientation inpinnipeds may have little eVect on the process of birth,however, it is uncertain whether or not fetus orientationmay inXuence the duration of birth. In part this uncertaintyis due to the small sample sizes used in previous studies. Inthis study we want to examine the fetus orientation at birthand time spent in birth in the Antarctic fur seal using largersample sizes.

Birthing in Antarctic fur seals is highly synchronized(Lunn and Boyd 1993). Females give birth to a single pupbetween mid-November and late December (Knopf 2002),but nonetheless twin pups have been reported (Doidge1987; Acevedo unpublished data). The scarce availablerecords for this species show that the time from the Wrstappearance of the pup to its Wnal emergence is rarely morethan a few minutes, and sometimes even only a matter of

J. Acevedo (&) · A. Aguayo-LoboFundación Centro de Estudios del Cuaternario (CEQUA), Av. Bulnes 01890, Punta Arenas, Chilee-mail: jacevedo@inach.cl

A. Aguayo-Loboe-mail: aaguayo@inach.cl

A. Aguayo-Lobo · D. TorresScientiWc Department, Chilean Antarctic Institute, Plaza Muñoz Gamero 1055, Punta Arenas, Chilee-mail: dtorres@inach.cl

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seconds. The placenta is generally delivered a few minutesafterwards. Moreover, the duration of cephalic birth isslightly less that for breech birth, and cephalic orientation isslightly more common than breeching (Bonner 1968).

In this paper, we analyze the labor process in the popula-tion of Antarctic fur seals at Cape ShirreV, LivingstonIsland, Antarctica. We provide new information on the timetaken for the complete labor process and examine thepotential eVects of fetus orientation on duration of laborgiven the life cycle and evolutionary process of the speciesbetween terrestrial to aquatic habitat.

Materials and methods

Labor duration and fetus orientation of Antarctic fur sealpups were recorded during two consecutive austral summerseasons at the Antarctic Specially Protected Area (ASPA)N°149 “Cape ShirreV and San Telmo Islets” (62° 28�S, 60°48�W), as part of the Weld work of the INACH-018 Project“Ecological studies on the Antarctic fur seal, Arctocephalusgazella”. Periodical observations were carried out eachsummer season between November and December in 1999/2000 and 2000/2001 on the main breeding beaches (Fig. 1).

We deWned birthing as the physiological process fromthe appearance of the amniotic-allantoids sac to the deliv-ery of the fetus and placenta from the uterus through the

vagina. For comparative purposes we divided the process oflabor into three phases: (1) From the appearance of theamnio-allantoid sac until fetus delivery, also called “birth”;(2) from birth to placenta appearance to the outside; (3)from the placenta presentation to complete delivery(Fig. 2).

Observation of the complete birthing process and itsdiVerent phases were timed, and the fetus orientations atbirth were recorded as either breech or cephalic (Fig. 3).Additional records were made for females that were notobserved for the entire process. In these cases, time wasrecorded only for the complete Wrst phase and/or fetusorientation was recorded birth.

A chi square test was used to compare the rate of birthbetween the two orientations (cephalic and breech). Dura-tion of the complete labor process and all three phases weretested by Mann–Whitney non-parametric tests (U). A sig-niWcance level of 0.05 was used for both tests (Zar 1984).

Results

Fetus orientation at birth

Eighty-two observations were recorded of which 60% werebreech births, and all pups were alive. The overall cephalic/breech ratio was 1:1.5, which was signiWcantly diVerent

Fig. 1 Study area showing the main breeding beaches (black) where the observations were made at Cape ShirreV, Living-ston Island, Antarctica

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(X2 = 4.00; df = 1; P < 0.05) than the hypothesis of 1:1.Moreover, signiWcant diVerences were obtained whenbirths were pooled into 15-day groups (X2 = 6.49; df = 2;P < 0.05) (Fig. 4). In this analysis the cephalic/breech ratioin December was signiWcantly diVerent from the hypothe-sized value of 1:1 (X2 = 4.00 and 4.94; df = 1; P < 0.05).

Duration of the birthing process

Thirty-Wve complete labor processes were recorded. Dura-tion of the complete process ranged from 6 to 186 min witha high frequency (25.7%) taking place between 16 and20 min. Similarly, the complete labor duration for cephalicbirths ranged from 6 to 76 min with a high frequency

(29.4%) occurring between 6 and 10 min, and for breechpresentation the time ranged from 10 to 186 min with thegreatest proportion (38.9%) taking between 16 and 20 min(Fig. 5). The average for total labor, without considerationof the position of fetus presentation, was 37.26 min (conW-dence limit 95% = 25.17–49.00 min); however, signiWcantdiVerences (U0.05,(1)17,18 = 204; 0.025 > P > 0.01; n = 35)were obtained between the average duration with cephalic(mean 27.22 min; conWdence limit 95% = 16.41–37.24min; n = 17) versus breech births (mean 46.39 min; conW-dence limit 95% = 26.01–67.16 min; n = 18).

When all three phases of the complete birthing processwere analyzed separately according to fetus orientation atbirth, it was observed that the average time of cephalic

Fig. 2 Sequence of a complete parturition in Antarctic fur seals by phases. Phase 1 (a–f), Phase 2 (g) and Phase 3 (h–i)

Fig. 3 Cephalic (left) and breech (right) presentation of a fetus in Antarctic fur seals

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orientation in the Wrst phase was signiWcantly less thanbreech (Z = 6.34; P < 0.001; n = 67). The following phases,however, showed similar average duration between bothclasses (Table 1). Additionally, the mean time between therupture of the amnio-allantoid sac and the complete expul-sion of the fetus in both cephalic and breech births was 3(range: 1–6 min, n = 30) and 25 min (range 2–172 min,n = 36), respectively.

Discussion

Typically, birth in terrestrial mammals is cephalic (Slijper1962) while in aquatic mammals, such as cetaceans, births

with a Xuke orientation are more often successful (Slijper1962; Harrison 1969). In pinnipeds the fetus orientation issuggested to be normally cephalic as are terrestrial mam-mals (Sweeney 1986), although Harrison (1969) reportsthat pup presentation may be either cephalic or caudal.Similarly, Bowen (1991) states that both cephalic andbreech births occur with equal probability (for all specieswhere n > 10 records). Our Wndings on fetus presentation atbirth show the occurrence of cephalic and breech births, butthe ratio between both pup orientation were signiWcantlydiVerent from the hypothesized ratio of 1:1 (Bowen 1991),suggesting that the breech orientation is much morecommon in this species.

High frequency of breech births has been also reportedfor another three otariids species with more than 30records. Crawley and Wilson (1976) reports 60% of breechbirth for A. forsteri Lesson 1828 at Snares Island. SimilarWndings have been reported for Eumetopias jubatus (Schre-ber 1776) with 61% breech births (Gentry 1970), and inOtaria Xavescens (Shaw 1800) 72% of births were reportedto be breeched from 36 records in rookeries from northernChile (Acevedo 1999; Acevedo et al. 2003).

In relationship with the duration of the birthing process,the labor process in many pinniped species has beenreported to be relatively short (Slijper 1962; Bowen 1991).Moreover, Harrison (1969) pointed out that fetus orienta-tion in pinnipeds may have little eVect on the process ofgiving birth.

The duration of complete birthing in Antarctic fur sealsranged from 6 to 186 min (average 37.26 min); however,the average for cephalic orientation births was signiWcantlyless than those of breech births, indicating that fetus orien-tation had an eVect on the length of labor. Moreover, thissigniWcant diVerence occurred only in the Wrst phases oflabor.

Our Wndings are also observed in another seven speciesof Otariids, where breech births take longer, with a timediVerence of 3–49.4 min (Rand 1955; Bonner 1968; Gentry1970; Stirling 1971; Marlow 1975; McNab and Crawley1975; Odell 1975). We suggest that this diVerence in dura-tion of the Wrst phase between both orientations could beexplained in terms of hydrodynamics; the greatest friction

Fig. 4 Cephalic and breech ratios by 15 days period and overall studyperiod at Cape ShirreV. The cephalic/breech rate are shown at the top

Fig. 5 Frequency of the complete parturition duration recorded inAntarctic fur seals, during the two seasons at Cape ShirreV

Table 1 Duration of each parturition phase recorded in Antarctic fur seals, considering the position of fetus presentation

Presentation Phases n Average (min)

Standard error

Minimum (min)

Maximum (min)

Cephalic Phase 1 30 6.00 0.54 2 14

Phase 2 17 17.35 5.33 0 68

Phase 3 17 3.35 1.36 1 15

Breech Phase 1 37 30.08 5.26 5 176

Phase 2 18 17.06 5.30 0 64

Phase 3 18 2.00 1.18 1 15

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would occur where hair direction was opposite to the direc-tion of movement through the uterus-vaginal wall after therupture of amnio-allantoid sac during the transit of fetus inbreech position to the outside. However, other observationsmay explain this diVerence. For example, during breechbirths front Xippers are often extended toward the head(n = 18 cases), while the position of both pectoral Xippersin all cephalic presentation were toward the tail end. Thisposition change of pectoral Xippers in the breech positionwould increase the scapular diameter and make the step ofexpelling the fetus through the uterus-vaginal channel morediYcult.

On the other hand, the scarce data regarding the birthingprocess for Antarctic fur seal have been reported by Bonner(1968) at South Georgia. He noted that the birth duration(from the amnio-allantoid sac to the complete full termfetus expulsion) was no more than a few minutes (1–7 min)and sometimes only a matter of seconds (<0.5 min), whilethe placenta is delivered generally between 6 and 10.5 minafter the pup’s birth. The diVerence in the time spent incomplete birth (from the amnio-allantoid sac to the placentadelivery) between Bonner’s data (mean 10.2 min) and thosereported here (37.26 min) could be due to the low numberof cases observed (n = 5) by Bonner (1968).

In other Otariid species, the only information availableon complete birthing time is for: A. forsteri with times thatvary from 2 s to 6.5 min from the appearance of amnio-allantoid sac to the complete full term fetus expulsion(n = 24), and placenta delivery between 3 and 163 min afterthe pup birth (McNab and Crawley 1975); Zalophus cali-fornianus Lesson 1828 with birth times of 2.5–16.1 min(average 7.3 min) (Peterson and Bartholomew 1967; Odell1975) and placenta delivery between 17 and 60 min (n = 2)(Peterson and Bartholomew 1967); and Phocarctos hookeri(Gray, 1844) and Neophoca cinerea (Péron, 1816) withbirth times of 10 min and 12–170 min and placenta deliveryat 50–360 min after the birth, respectively (Marlow 1975).

On the basis of our Wndings, it is possible to concludethat the time spent in the complete birthing process isgreater than that previously reported for the Antarctic furseal, and the fetus orientation has a signiWcant eVect on thelength of the Wrst phase of the birthing process, a trend thatis also observed in other Otariid species. Our data are validfor Antarctic fur seal, and further study is required in pinni-peds to allow for a more detailed examination and explana-tion of the high proportion of breech orientations and theireVect in the birthing process, in the evolutionary paradigmfrom terrestrial to aquatic life.

Acknowledgments Thanks are given to the Director of the InstitutoAntártico Chileno (INACH) for the continuous support of our scientiWcresearch. Thanks are also extended to Chilean Navy for the logisticsupport during the Antarctic seasons 1999/2000 and 2000/2001.

Thanks to our colleagues of INACH 018 Project who helped us in theWeld, and Carlos Olavarría and Emma Newcombe for the critical revi-sion of this manuscript.

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