RE-EXAMINATION OF LIFE HISTORY PARAMETERS
OF LONG-FINNED PILOT WHALES IN
THE NEWFOUNDLAND WATERS*TOSHIO KASUYA**, DAVID E. SERGEANT*** AND KENJI TANAKA****
ABSTRACTAge dependent life history parameters of the long-finned pilot whale
were analyzed using recent technique of aging which allowed accurate age
estimate for old individuals and materials taken in 1954 from the drive
fishery off Newfoundland and once used by Sergeant (1962). In both sexes
mean growth ceases at ages between 21 and 25 years, when natural mortality increases. Males live to age 36 years or about 10 years shorter thanfemales. Natural mortality is dependent on age in both sexes, and malemortality exceeds that of females of the same age, thus causing age related
decline of male proportion in the population. Pregnancy rate is notapparently dependent on age of females and the possibility of a large
proportion of postreproductive females is rejected, which is different fromfeature known on the short-finned pilot whale. Additionally, long-finned
pilot whales differ from short-finned pilot whales in the younger age atmaturation, shorter longevity and higher proportion of adult males,suggesting less specialized reproductive strategy and difference in thesocial structure.
INTRODUCTION

A study on life history and reproductive biology of the long-finned pilot
whale, Globicephala melaena (Traill, 1809), was published by Sergeant (1962)
using materials obtained from the drive fishery off Newfoundland. This was
the first delphinid biology based on reliable age determination. However, as
recognized by himself, the age of older individuals tended to be under
estimated due to the decrease of readability of dentine layers or cessation of
the deposition at an age between 8 and 16 years, and reliable life history
parameters were not available for older individuals. Recent study of Martin(1987) on long-finned pilot whales mass stranded on the British coast probably retained similar problem (IWC, 1987).
• Early version of this manuscript was submitted to the 38th annual meeting of the Scientific Committee of theInternational Whaling Commission in Bournmouth in May 1986 with document no. IWCISC/38/SMll•• Far Seas Fisheries Research Laboratory, 5-7-1, Orido, Shimizu-ski, Shizuoka-ken, 424 Japan••• Arctic Biological Station, 555 St. Pierre Blvd. Ste. Anne de Bellevue, Quebec, H9X 2W1 Canada•••• Faculty of Oceanography, Takai University, 3-20-1, Orido, Shimizu-ski, Shizuoka-ken, 424 Japan
Sci. Rep. Whales Res. Inst.,
No. 39, 1988, 103-119

104

KASUYA, SERGEANT AND TANAKA

After Sergeant (1962), there was a progress in age determination
technique of toothed whales (Perrin and Myrick, 1981), and Kasuya andMatsui (1984) established age determination method for the short-finned
pilot whale, G. macrorhynchus Gray, 1846, using annual growth layers in dentine
and cementum apparent in decalcified and haematoxylin stained longitudinal
section of the tooth. Based on this aging technique, Kasuya and Marsh (1984),
Marsh and Kasuya ( 1984) and Kasuya ( 1986) analyzed the life history andreproductive biology of short-finned pilot whales taken by the drive fishery or
small-type whaling with harpoon gun off the Pacific coast of Japan. Thesestudies showed that the short-finned pilot whale exhibits a large longevity
difference between males (46 years) and females (63 years), age dependentchange in the pregnancy rate, and post-reproductive life time of females
extending over 20 years. Marsh and Kasuya (1986) indicated further need to
examine the presence of postreproductive females in g. melaena.
We reanalyzed in the present study some of the life history parameters of
the long-finned pilot whale using materials of Sergeant (1962) and age determination method of Kasuya and Matsui (1984), and compared them with theresults of short-finned pilot whales off Japan to find difference of the reproductive strategy between the two pilot whale species.
MATERIALS AND METHODSThis study is based on teeth of 437 long-finned pilot whales obtained fromthe drive fishery off Newfoundland and some accompanying biological data
(Table 1). They were collected in June to October 1954 and were the major
portion of the materials used by Sergeant ( 1962) for the study of age andgrowth. The teeth had been preserved in glycerin with a tag having specimen
number, body length (measured to a nearest inch), sex and date on it.
Information was not available for male maturity. The reproductive status
data of females (usually pregnancy and lactation only) were available for some
limitted number of individuals. Although these data did not seem to be biased
to certain body length classes (Fig. 2), our data contained high proportion of
females of unknown reproductive status and very low number of restingfemales (adult females neither pregnant nor lactating), the former being close
to the sum of the females in pregnancy or in lactation, and the latter amounts
only 16% of the pregnant females (Table 2). This was because only females
which were obviously pregnant or lactating were fully recorded and mature
females of another reproductive status (resting) were underrecorded in thesample (Sergeant, 1962: p.56). Therefore mature females of unknown reproductive status were more likely to be in the resting status rather than pregnant
or lactating.
The teeth had been cut transversely near the cingulum for the previous
age determination. For the present age determination, we usually used only
the root portion of the tooth. The crown side of old individuals did not usually
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

105

LONG-FINNED PILOT WHALESTABLE 1. MATERIALS USED IN THE PRESENT STUDY

Sex

Month*

With ageandbody lengthWith age
but without
body length**

Male

July
August
Sept.
Oct.
Total
July
August
Sept.
Total

43
101
8
0
152
67
200
8
275

0
1
0
0

Female

1
6
2
9

Total

43
102
8
0
153
68
206
10
284

* All the materials were collected in 1954.

** Used for only age composition and age dependent sex ratio analysis.

have the most recent layers due to sawing off. The few exceptions were for 0
to 2 years old young tooth where the crown side of the tooth was used because
the root was too short and thin. Either root or crown portion of the tooth was
firstly rinsed in running water for one to two nights to remove the glycerin,
longitudinally half sectioned, glued on a plastic plate, polished to a thicknessof about 30 to 40 µ,m, decalcified in 5% formic acid for several hours, stainedwith Mayer's haematoxylin and mounted with Canadian balsam (Kasuya andMatsui, 1984).
Kasuya aged all the individuals without referring to any data of thespecimen (including the date of sampling) and using method of Kasuya andMatsui (1984) outlined below:(1) To have three independent counts for both cementum and dentine.
(2) To choose the middle figure as the best for each tissue.
(3) To use the best dentinal count if the pulp cavity is wide and the deposition of dentine was considered to be continuing on the entire
pulp wall (open pulp cavity) or on part of the wall (closing one), or to
use the best cemental count if the pulp cavity was narrow and linedby thin uniformly stainable dentine suggesting cease of the deposition (closed pulp cavity).
(4) A pair of stainable and unstainable layer was assumed to represent
one year as deduced by Sergeant (1962), and any age between n and
n+l year was expressed by n+0.5 (n being an integer).
After aging all the individuals, the body length was plotted on age, andfive individuals (two females and three males, see Figs 3 and 4) were found in
the body length/age relationship to be apart from rest of the individuals.
These individuals were excluded from the subsequent analyses, but ages ofrest of the individuals were accepted as they stand (including 10 individuals
having no body length data).
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

106

KASUYA, SERGEANT AND TANAKA

Males• OpenoIii,/

Femalesc

Closing• Closed

20

:;::;

~ 30

cloo

"'C

•

/.

• 0/0

.....

• •o/ •• ••• • .:Cl.I

o o..f ~

.D 20

E

• • •
o "" •
eo •ce

~

o.

:I

0

z

o

-

o

o ./o~

a.I..::..

• .t• ..

•

•

•

•

•

•

.

•
•

•

•

•

• o
o

-5(••

:-:;/:"~

.~7-=

.

,..
:.;,t.-

10.. 9/•... 6"•.

• g'
•• 7"

-· ./{
10

20

30

40

50

Number of cementa! growth layers
Fig. I. Scatter plot of number of dentinal growth layers on that of cementa! layers inthe same tooth slide. Symbols distinguish the condition of pulp cavity. Numerals
represent the number of individuals having open pulp cavity, and each of othermark represents one individual. The solid line represent equal deposition of layers
in both issues.

RESULTS

Comparison between dentinal and cemental layer counts
Fig. 1 compares the number of growth layers in cementum and that in
dentine of the same teeth. Since these tooth had been cut transversely toremove a piece of thin section for the previous age determination (Sergeant,1962), we could not confirm on most of the present preparations if all thecementa! or postnatal dentine layers were present (neonatal line in dentine
could be identified only on the slide of juveniles prepared from the crownportion of the tooth). Although this did not necessarily imply loss of the first
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

LONG-FINNED PILOT WHALES

107

postnatal growth layer in either of the tissues, we were uncertain on tooth
showing disagreement of counts in the two tissues if it came from the error ofreading or from the deficit of the preparation. The readability of cemental
and dentinal layers was slightly inferior to that of the short-finned pilot
whales studied by Kasuya (1986) and Kasuya and Matsui (1984).
Admitting possible minor disagreement expected from the above deficit,
we considered that growth layer counts in the two different tissues in a toothslide were similar on most of the teeth having open or closing pulp cavity, but
the correlation was lost on teeth with closed pulp cavity. The number of
cemental layers exceeded that of the dentinal layers after ages between 15 to
20 years, and the magnitude of the disagreement increased with increasingage (Fig. 1).
We conclude therefore that growth layers in the two dental tissues aredeposited at a same rate on young individuals, but on older individuals only
the cemental layers continue deposition. And we assumed without direct
evidence that the rate of cemental layer deposition stays same (annual) for theentire lifetime after the start of its deposition in early postnatal time (Kasuya
and Matsui, 1984).
Body length composition and neonatal length
Body lengths of the 152 males ranged between the half-foot length
groups of 5.5-6.0 feet (l.68-l.83m) and 19.5-20.0 feet (5.94-6.lOm) (Fig. 2).
A peak of large individuals was present between 17 .5 and 19.0 feet (5.33 to
5.79m)
Body lengths of the 275 females were found between length groups of
6.0-6.5 feet (l.83-l.98m) and 16.0-16.5 feet (4.88-5.03m). A peak of larger
individuals was present at lengths between 14.0 and 15.0 feet (4.27 to 4.57m),
which was about 1 m smaller than that of the male. These features are similar
to the body length frequencies presented by Sergeant (1962).
We had five (three female and two male) postnatal individuals having no
neonatal layer in dentine, an indication of newborn calves (Kasuya andMarsh, 1984). Their body lengths were 175 and 198cm in males, and 173,
183, and 183cm in females (Figs 3 and 4). Mean of the five body lengths was
182.4cm. The range was nearly within the range of neonatal lengths of both
sexes (165 to 191 cm) reported by Sergeant (1962), and the mean was close to
the mean neonatal lengths (174 cm in females and 178 cm in males) estimatedby him. We found no reason to change the neonatal length estimate ofSergeant (1962).
Male growth
The correlation between body length and age was very good before age
20 years, with most of the plots within the range of 70 cm, but it was apparently lost after an age between 21 and 25 years (Fig. 3). The male growth is
rapid till the age of 2.5 years, or the body length of 2.7 to 3.3 m. After thisSci. Rep. Whales Res. Inst.,
No. 39, 1988

108

KASUYA, SERGEANT AND TANAKA
2
20

3

5

/,

6

Males

15
10
5
0
5

1!!.

r1J
:J

:2
>

'ii
c

0
.....
Cl.I

0
10
5
0
20
15

.0

E 10

:J

z

5
0
5
0
20

Unknown

15
10
5
0

5

10

15

20

Body length in feetFig. 2 Body length frequency of materials used in the present study. Scale at the top
indicates body length in meter.

age, males grew at a slower but almost constant rate till the age of about 20
years. The inconspicuous secondary growth spurt probably started at about
12-13 years.
Although the mean body length seemed to stop increasing at an age
between 21 and 25 years, and the mean body length of males over 25 years
was 557 cm (n=5), we were unable to consider this figure as a reliable estimate of the mean asymptotic length of males due to the small sample size
(Appendix Table 1).
The age at the start of secondary growth spurt (12-13 years) probably
corresponds to the mean age at the attainment of breeding maturity 12 years
estimated by Sergeant ( 1962). Due to the lack of adequate number of samples
on age and maturity, Sergeant (1962) firstly estimated the mean age of breeding maturity (12 years) from a limited number of samples with good age
estimate, then he read the mean body length of 4.88 mat breeding maturity
on his mean growth curve corresponding to the age at the attainment of
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

109

LONG-FINNED PILOT WHALES
6
(•)

..
I•

.: .
E
c

A•

••I•

-

£. 4
OI

I•
y

c

~
:>.

(•)

u

0

(•)

ID

. ~:
t'
I

0

10

20

30

40

Age in years
Fig. 3. Scatter plot of body length on age, males. Each mark represents one individual. Marks in parentheses indicate ages that were not used in the present
alalyses.

breeding maturity. If the same method was adopted to the growth curve
constructed in the present study, males were estimated to attain the length of
4.3 to 4.9 m at the mean age of breeding maturity (12 years). The middle
value of this range, 4.6 m, was about 30 cm smaller than the estimate ofSergeant (1962). We consider that the difference is significant in view of thenarrow individual variation of body length (see above).
This disagreement probably came from the overestimation of malegrowth by Sergeant ( 1962) due to the underestimation of age of many individuals over 8 to 16 years. Therefore, the present estimate of 4.6 m can be abetter estimate of the mean male length at age 12 years (age at breeding
maturity estimated by Sergeant (1962)). However, in view of slow and complicated procedure of maturation of males of the short-finned pilot whale(Kasuya and Marsh, 1984) and rather limited number of samples available forthe long-finned pilot whale study (Sergeant, 1962), we feel that parameters
relating to male maturity of the latter species require further investigation.
Female growth curve
Female body length increased almost at the same rate as that of theSci. Rep. Whales Res. Inst.,
No. 39, 1988

110

KASUYA, SERGEANT AND TANAKA.. .. ... ··i. :.
:

..

., .

•.

·.··i
. ........
• . • ?:=:.•··
. I
:• •.

fll

•

Me

•

• •
• • .f • • • •··-·1•.:.·.
:! , ....

I •

E 4

•

,.

.

-=' j -· .

• ; .i. .•. .

c~~r?l·~·
i ~i

>i 3
-0
0

: ....
T

CD•:Matureo: Immature•:Unknown
(•)

0

10

20

30

40

50

60

Age in years
Fig. 4 Scatter plot of body length on age, females. Each mark represents one individual. Marks in parentheses indicate ages that were not used in the present
analyses.

males till the age of 6 years (mean age of females at sexual maturity, see
below) as indicated by Sergeant ( 1962) (Fig. 4), then the growth rate declined
rapidly with increasing age, and the mean body length apparently ceased toincrease at an age between 21 and 25 years. The mean body length of females
over 25 years was 488.8cm (n=53, sd= 18.6). This is the mean asymptotic
length of females of this population.
Both mature and immature females were present at the body lengths
between 11.0 and 13.0 feet (3.35 and 3.96m), and at the ages between 4 and 8
years (Figs 4 and 5). These ranges did not differ from corresponding figures
estimated by Sergeant (1962). His estimation of the mean age and bodylength of females at the attainment of sexual maturity were 6 years and 12
feet (3.66m), respectively.
Age related change in female reproductive activity
Three resting females identified as senile by Sergeant ( 1962) were agedby us at 22.5, 30.5, and 41.5 years, and they were not always old. Marsh andKasuya ( 1984) indicated the difficulty of identifying postreproductive females
by macroscopic observation of ovaries. The oldest females of the present
study at the pregnant, lactating, or resting status were aged at 39.5, 39.5 and41.5 years, respectively (Fig. 5), which were close each other. Ages of three
resting femals having corpus luteum of ovulation were 4.5, 24.5, and 25.5
years, and the age of a lactating female having corpus luteum of ovulation
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

111

LONG-FINNED PILOT WHALES

Males

20
15
10
I/)

Iii

:J
"'O

>
"'O

.£

5
5
Immature

05Prngnant

0

.....

0

Cll

Lactating

.D

E 5
:J

z

0
5

Resting0
Unknown

10

5

10

20

30

40

50

Age in years
Fig. 5. Age composition and reproductive status of the long-finned pilot whale sample. White square at the bottom indicates sum of the females of known reproductive status.

was 31.5 years. These ages are younger than that of the oldest confirmed
pregnancy.
Table 2 lists two kinds of pregnancy rates; (1) proportion of pregnant
females in sexually mature females of known reproductive status, and (2)proportion of pregnant females in all the females including both immatureand unknown reproductive status. Since females of unknown reproductive
status in our sample probably tended to include more resting females thanthe pregnant or lactating ones (see above), the former figure will overestimatelevel of the apparent pregnancy rate of the sample, and this underrepresent,
if it exists, the age dependent decline in the pregnancy rate. To the contrary,
the latter will underestimate the apparent pregnancy rate (the degree of
which will depend on the number of pregnant females classified to the unknown category), but will better reflect the age dependent change in the
pregnancy rate if it exists.
None of the two pregnancy rate series in Table 2 showed significant age
dependent change (Chi-square tests for ages over 10 years, p > 0.5). Thus, wewere unable to conclude that the females of long-finned pilot whales off
Newfoundland exhibit age dependent decline of reproductive activity, which
was very distinct in the short-finned pilot whale populations off Japan andSci. Rep. Whales Res. Inst.,
No. 39, 1988

112

KASUYA, SERGEANT AND TANAKATABLE 2. AGE DEPENDENT CHANGE IN APPARENT PREGNANCY RATE INGLOBICEPHALA MELAENA.
Age(years)Immatu re

0-10
10-20
20-30
30-40
40-50
50-60
Total

No.
data

Pregnancy rate(%) **
(1)

(2)

1
0

15
55
36
16
1
0

75
28
20
10
4

53.3
30.9
38.9
37.5
0

8.8
20.5
25.0
23.l
0
0

7

123

138

36.6

16.5

Mature*
p

L

11
0
0
0
0
0

8
17
14
6
0
0

6
37
19
9
0
0

11

45

71

R

3

T

• P=pregnant, L=lactating, R=resting, T=total.
** (1) indicates proportion of pregnant females in mature females of known reproductive status, and (2)that in total females including females of immature and unknown maturity.

was an indication of the presence of postreproductive females (Kasuya andMarsh, 1984; Marsh and Kasuya, 1984; Kasuya, 1986).
The uncertainty that surrounds above analysis comes from the adultfemales of unknown reproductive status. If a 39.5 years old pregnant female
is excluded, then all the 18 females over 33.5 years are non-pregnant or of
unknown reproductive status (Appendix Table 2). Females of the latter category has high probability of not being pregnant, and might leave a possibility
for postreproductive females. However, even under extreme assumption thatthey were all in the resting status, the number of pregnant females in the total
females over 35 years (1/15) was not significantly different from that at 10-35
years (36/119) (Chi-square test, 0.2>p>O.l), making it impossible to conclude
the presence of significant number of postreproductive females in the population.
From the above analyses we conclude that the population of long-finned
pilot whales has high reproductive capacity till the observed oldest age,although a larger sample may perhaps prove the presence of some postreproductive females among old females.
Sex ratio, age composition and mortality rate
The proportion of females in the sample increased from parity at ages
below 10 years to 100% at age over 36 years (Table 3 and Appendix Table 2),
or about 5 years earlier than the corresponding age for the short-finned pilot
whale populations off Japan (Kasuya and Marsh, 1984; Kasuya, 1986). The
decline of male proportion with increasing age will reflect the sexual difference of mortality rates and longevity (see below).
Sergeant ( 1962), using cementum age of limited number of selected individuals, showed that males lived to age of only 36 to 40 years while females
did to age of 46 to 50 years. Ages of the oldest individuals of the present
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

113

LONG-FINNED PILOT WHALESTABLE 3. AGE RELATED CHANGE OF THE SEX RATIO INGLOBICEPHALA MELAENA.
Age(years)No. females

0- 5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60

55
51
46
44
34
22
16
10
5
0
0

Total

284

No. males

Total

Females
(%)

56
37
23
19
13
2
2
I

0
0
0
0
153

Ill

88
69
63
47
24
18
11
5
0
0

49.5
58.0
66.7
69.8
72.3
91.7
88.9
90.9
100.0

100.0
437

65.0

material were 35.5 years in males and 56.5 years in females. However, the ageof the oldest female seemed to be an outlier, and the ages of the next oldest
male and female were 33.5 and 42.5 years, respectively (Appendix Table 2).
Thus reasonable longevity difference between sexes of the long-finned pilot
whale will be about 10 years as suggested by Sergeant ( 1962).
Age frequencies plotted on a logarithmic scale (Fig. 6) showed an apparent gradient change in both sexes at an age between 21 and 25 years. Additionally, there was observed in the male age composition a slight depression atages between 8 and 17 years or at the age of puberty, suggesting a possible
segregation of some pubertal males from the breeding schools. The similarfeature was indicated for short-finned pilot whales off Japan (Kasuya andMarsh, 1984).
Ignoring the slight underrepresentation of pubertal males indicatedabove, we estimated the apparent annual mortality rate of males as about 0.07
at ages below 25 years (Table 4). The corresponding figure for ages between
21 and 36 years (the oldest male age) was calculated to be about 0.15 using
very limited number of samples. For females, we estimated the corresponding
figure of the mortality rates to be slightly over 0.02 (< 25 years) and about 0.1(from 21 to the oldest individual). The male apparent mortalities are always
higher than that of the females of the same age, as observed on the short-finned
pilot whale off Japan (Kasuya and Marsh, 1984; Kasuya, 1986).
DISCUSSION

We re-examined several biological parameters of long-finned pilot whales off
the Newfoundland waters using materials once used by Sergeant (1962) and
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

114

KASUYA, SERGEANT AND TANAKA
30r-~~~~~~~~~~~~~~~~--,

Males

20
10

5

3
2
1.___~'---~'---~'---~'---~'---~+--~'---~+--~
40
30
0
10
20

Age in years
Fig. 6. Age frequency of long-finned pilot whale samples plotted on logarithmic
scale. Straight line indicate linear regression of the frequency on age (see Table 4).

recently improved age determination method, which could give higher ages
for many of individuals aged over 10 years by the previous method of aging
using only dentinal layers. Among biological parameters examined, we foundno reason to alter the previous estimate of Sergeant ( 1962) on neonatal bodylength, longevity, female age at the attainment of sexual maturity, andjuvenile sex ratio. The growth curves of both sexes were altered slightly, andthe mean asymptotic length of females and the age at the length were newly
estimated in the present study.
In particular, we obtained new estimate of age composition of the catchand biological parameters derived from it. These allowed us to compare somelife history parameters of long-finned pilot whales in the Newfoundlandwaters and those of short-finned pilot whales off Japan studied by Kasuya andMarsh (1984), Marsh and Kasuya (1984) and Kasuya (1986).
Apparent mortality rates calculated above are sums of natural mortality
rate, fishing mortality rate and annual change in recruitment. Effect of thefishery on the latter two components is probably significant in the populationof long-finned pilot whales, which had long history of hunting of relatively
small scale (probably less than 500 individuals per year) by highly selective
harpoon fishery and 3 years large scale harvest just prior to the commencement of present sampling (about 3,000 individuals per year) by less selective
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

115

LONG-FINNED PILOT WHALESTABLE 4. APPARENT ANNUAL MORTALITY RATES OF GLOBICEPHALA MELAENAESTIMATED FROM AGE COMPOSITION.
MethodFemaleMale

0-25 years
21-43 years
21-57 years
0-25 years
21-36 years

AB

0.0231
0.06960.0201 ±0.0090
0.0682 ±0.0160
0.0985 ±0.0122
0.0716 ±0.0115
0.1497 ±0.0507

0.0683

A: From the gradient of the linear regression in Fig. 6.
B: By segment analysis (Robson and Champman, 1961), best point estimate and standard error.

(Kasuya and Marsh, 1984) drive fishery (Sergeant, 1953; 1962; Mercer,1975).
We consider that the drive fishery could have decreased absolute numberof recruitment in the last 2 years preceding the sampling, but did not cause
severe change in the age composition of older individuals. Thus we feel thatthe present age composition data are not suitable for the analysis of age dependent change in juvenile mortality rate.
To the contrary, the history of harpoon fishery over 7 years could haveselectively killed larger individuals and changed the age composition and sex
ratio of older individuals as observed on the short-finned pilot whales off
Japan (Kasuya and Marsh, 1984). This causes difficulty to make meaningfulcomparison of apparent age dependent mortality rates between sexes. However, we consider that the present sample size is probably large enough togive a rough estimate of the maximum age which is allowed physiologicallyfor the species, and that our finding of the shorter longevity of males allows
our deduction of above result that males will have natural mortality rate
exceeding that of the females of same age.
Ages of the oldest individuals in the sample of long-finned pilot whales
were younger than those of short-finned pilot whale populations off Japan by
6 (including an outlier) or 20 years (excluding an outlier) in females or by 10
years in males, and were close to those of less specialized delphinid species
such as striped dolphin, Stenella coeruleoalba, and spotted dolphin, S. attenuata,studied by Kasuya (1985). The difference of longevity between the two pilot
whale species was in parallel with that of the age at sexual maturity (G.
melaena of shorter life matures younger). Although reliable estimates ofnatural mortality rate are not available for either of the two pilot whale
species, above longevity difference suggests a higher natural mortality of thelong-finned pilot whale.
Although there remains a possibility that a larger sample may find somepostreproductive females in old age classes, we have been unable to confirm
age dependent decline of pregnancy rate in the long-finned pilot whale. This
is in clear contrast with the life history observed on the short-finned pilot
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

116

KASUYA, SERGEANT AND TANAKA

whale populations off Ja pan, where the confirmed pregnancy occurred below
age of 36 years and lactation below 51 years while females lived for 63 years,
and additionally their pregnancy rate declined with increasing age for all theage range over 8 years (Kasuya and Marsh, 1984; Marsh and Kasuya, 1984;
Kasuya, 1986). We conclude therefore that female long-finned pilot whales
have a shorter lifespan and breed till older age at a more constant rate than
the short-finned pilot whale. We do not have data to compare the absoluteannual pregnancy rates of the two species. Not denying the possibility that theabove features of reproduction of long-finned pilot whale could have beenenhanced in some degree by the continued expolitation, we suggest that thedifferences indicated between the two pilot whale species are principally
species specific.
In a short-finned pilot whale population off Japan, individuals become
reproductive at the mean ages of 9 years (female) and 17 years (male), andthe sex ratio of adult individuals is 0.27 (adult males/adult females) (Kasuya
and Marsh, 1984). In the population oflong-finned pilot whales, males mature
at a lower age (probably at 12 years) relative to the age of female maturity (6years), and the natural mortality rate of both sexes appear to increase at asimilar age (21-25 years) while there is large difference in the short-finned
pilot whale off Japan (28 years in males and 46 years in females). These resulted in the higher adult male ratio of 153/220=0.70 (estimated from the age
composition), which is closer to those of more generalized delphinids, e.g.
0.77 of Stenella attenuata (Perrin, Coe and Zweifel, 1976), 0.91 of S. longirostris(Perrin, Holts and Miller, 1977) and 1.1 (=1278/1191) of S. coeruleoalba(Miyazaki and Nishiwaki, 1978)
Above analyses indicate that the long-finned pilot whale has life history
parameters which are apparently less specialized than those of the shortfinned pilot whale, and that its reproductive strategy and social structure will
not be the same with those of the short-finned pilot whale. The cohesive
matrilineal school structure and long maternal care of the latter species(Kasuya and Marsh, 1984) may not be so pronounced in the long-finned pilot
whale population off Newfoundland.
ACKNOWLEDGEMENTS

We thank Dr S. Ohsumi for reviewing manuscript, and Mr T. Miyashita andMrs M. Ikeya for the help in statistics and drawings.
REFERENCES
IWC, 1987. Report of the sub-committee on small cetaceans. Rep. int. Whal. Commn, 37: 121-128.
KsuvA, T., 1985. Effect of exploitation on reproductive parameters of the spotted and striped dolphins off
the Pacific coast of Japan. Sci. Rep. Whales Res. Inst., 36: 107-138.

Sci. Rep. Whales Res. Inst.,
No. 39, 1988

LONG-FINNED PILOT WHALES

117

KsuvA, T., 1986. Comparison of life history parameters between two stocks of short-finned pilot whales off
the Pacific coast of Japan. IWC/SC38/SMIO. 32 pp.
KASUYA, T. and H. MARSH, 1984. Life history and reproductive biology of the short-finned pilot whale,
Globicephala macrorhynchus, off the Pacific coast of Japan. Rep. int. Whal. Commn (special issue 6):259-310.
KASUYA, T. and S. MATSUI, 1984. Age determination and growth of the short-finned pilot whale off the
Pacific coast of Japan. Sci. Rep. Whales Res. Inst., 35: 57-91.
MARSH, H. and T. KASUYA, 1984. Change in the ovaries of the short-finned pilot whale, Globicephalamacrorhynchus, with age and reproductive activity. Rep. Int. Whal. Commn (special issue 6): 311-335.
MARSH, H. and T. KASUYA, 1986. Evidence for reproductive senescence in female cetaceans. Rep. int. Whal.
Commn (special issue 8): 57 - 74.
MARTIN, A. R., P. REJTBIKDS and M. G. RICHARDSON, 1987. Aspect of the biology of pilot whale (Globicephalamelaena) in recent mass strandings on the British coast.]. Zool., Land., 211: 11-23.
MERCER, M. C., 197 5. Modified Leslie-DeLury population models of the long-finned pilot whale (Globicephalamelaena) and the annual production of the short-finned squid (Illex illecebrosus) based upon their interaction at Newfoundland.]. Fish. Res. Bd Can., 32 (7): 1145-1154.
MIYAZAKI, N. and M. NISHIWAKI, 1978. School structure of the striped dolphin off the Pacific coast ofJapan. Sci. Rep. Whales. Res. Inst., 30: 65-115.
PERRIN, W. F., J.M. COE and J. R. ZWEIFEL, 1975. Growth and reproduction of the spotted porpoise, Stenella
attenuata, in the offshore eastern tropical Pacific. Fish. Bull., 74(2): 229-269.
PERRIN, W.F., D.B. HoLTs and R.B. MILLAR, 1977. Growth and reproduction of the eastern spinner
dolphin, a geographical from of Stenella longirostris in the eastern tropical Pacific. Fish. Bull., 75(4):725-750.
PERRIN, W. F. and A. C. MYRICKJR (eds), 1981. Age determination of toothed whales and sirenians. Rep. int.
Whal. Commn (special issue 3). 229 pp.
ROBSON, D.C. and D.G. CHAPMAN, 1961. Catch curves and mortality rates. trans. Am. Fish. Soc., 90: 181-189.
SERGEANT, D.E., 1953. Whaling in Newfoundland and Labrador waters. Norsk Hvalfangst-Tid., 12: 687-695.
SEGREANT, D. E., 1962. The biology of the pilot or pothead whale Globicephala melaena (Traill) in Newfoundland waters. Bull. Fish. Res. Bd. Can., 132: 1-84 +I-VII.

Sci. Rep. Whales Res. Inst.,
No. 39, 1988

118

KASUYA, SERGEANT AND TANAKAAPPENDIX TABLE 1. AGE-LENGTH KEY OF GLOBICEPHALA MELAENA (CM).
Age(years)
0.5
1.5
2.5
3.5
4.5
5.5
6.5
7.5
8.5
9.5
10.5
11.5
12.5
13.5
14.5
15.5
16.5
17.5
18.5
19.5
20.5
21.5
22.5
23.5
24.5
2'.25.5

safliples
4
13
23
9
7
10
13
7
2
5
4
2
6
4
6
4
5
5
3
2
3
4
1
4
5

Males
mean
207.8
264.3
303.0
319.7
332.9
360.1
387.7
393.l
405.0
416.8
425.0
471.5
448.3
474.3
481.8
495.3
508.2
544.4
559.3
553.5
560.3
554.0
561.0
582.3
556.0
557.2

sd

no.
samples

23.0
11.4
17.<:J
12.3
10.6
15.0
17.9
11.7
14.0
26.9
6.3
6.5
12.1
22.8
23.0
41.8
16. l
19.7
4.7
15.5
13.8
15.6

10
11
8
10
15
8
4
14
13
9
10
10
8
9
5
6
14
12
7
4
6
5
9
4
10
53

15.8
19.8

Females
mean

sd

199.3
270.6
302.0
327.1
333.5
358.9
376.5
379.5
398.4
389.4
401.1
422.2
421.9
413.4
415.0
426.2
436.4
435.9
441.7
434.5
445.3
464.6
451.2
444.0
444.8
448.8

21.4
16.7
15.4
11.9
17.9
14.5
19.4
19.4
22.2
11.2
11.0
21.9
18.4
12.3
18.0
17.2
21.4
18.0
13.6
16.5
13.3
18.3
18.0
12.3
18.9
18.6

Sci. Rep. Whales Res. Inst.,
No. 39, 1988

119

LONG-FINNED PILOT WHALESAPPENDIX TABLE 2. AGE AND REPRODUCTIVE STATUS OF GLOBICEPHALA MELAENA.
Age(year)

immat.
preg.

0.5
1.5
2.5
3.5
4.5
5.5
6.5
7.5
8.5
9.5
10.5
11.5
12.5
13.5
14.5
I5.5
16.5
17.5
18.5
19.5
20.5
21.5
22.5
23.5
24.5
25.5
26.5
27.5
28.5
29.5
30.5
31.5
32.5
33.5
34.5
35.5
36.5
37.5
38.5
39.5
40.5
41.5
42.5
56.5
Total

Femalesmature
!act.
rest.

4

2
2
2

I*

3
3
2
I
2
3
3
3
2

I
2
I
3
2
3

I
2
3
3
5
5
6
4
6
4
4
2
2
I**
4

6
II
9
8
11
7
3
8
10
6
8
4

10
II
9
10
15
9
4
14
13
11
12
II
9
9
5
6
14
12
8
4
6
5
9
4
10
2
3
6
7
4
3
6
3

I
2
6
7
3
3
2
2
4
2
2

2*

I
2

2
2

I**
I
3

total

l
2
3
2
I
3

4
3

2

11

46

71

• Includes one female having corpus luteum of ovulation.
** Classified as "senile" by Sergeant (1962).

Sci. Rep. Whales Res. Inst.,
No. 39, 1988

l*
l*

Males
unknown

4
I3
23
9
7
10
I3
7
2
5
4
2
6
4
7
4
5
5
3
2
3
4
4

2

3
4

4
I**

I
2

3

7

l
I49

I
284

153