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REVIEW ARTICLE
CURRENT SCIENCE, VOL. 83, NO. 10, 25 NOVEMBER 2002 1210
e-mail: whale@md2.vsnl.net.in
Marine mammal research in India – a review and
critique of the methods
PL. Kumaran
Marine Mammal Consultant, #1329, 20th Main Road, Anna Nagar, Chennai 600 040, India
Indian research publications on marine mammals, in
most cases, are generally mediocre and misleading.
Published information ranges from reports of occa-
sional stranding to descriptions of fishery interac-
tions. Due to non-existence of a comprehensive
research programme and adequately trained research
teams in India, information available is fragmentary
and often of dubious scientific quality. Lack of under-
standing of the biology of most of the species and
absence of quantitative data on the anthropogenic
impacts are serious impediments to the conservation
of marine mammals in India. This review attempts to
identify the major gaps and provides recommenda-
tions in improving the research methodology for un-
derstanding the status of marine mammals and their
conservation.
ESTABLISHMENT of The Indian Ocean Cetacean Sanctu-
ary (IOCS) in 1979 by the International Whaling Com-
mission1 has given the necessary impetus for research on
the cetaceans of the Indian Ocean region. Available
information on the nature and number of cetacean species
reported from the Indian Ocean2 and records of whales
from Indian waters3,4 have been earlier documented.
Forty species of cetaceans have been recorded so far
from the Indian Ocean region, among which 25 species
are represented in the Indian waters. Of the 25 species,
according to the IUCN5, the status of 1 species is endan-
gered, 4 species is vulnerable and 20 species is insuffi-
ciently known. The dugong (Order: Sirenia) is considered
as vulnerable. However, Indian Wildlife Act (1972 and
amended in 1991)6 has listed only three species of ceta-
ceans (Irrawady dolphin, Ganges River dolphin and
sperm whale) and the dugong in Schedule I due to lack of
adequate scientific information.
Though there is steady increase in the number of pub-
lications on marine mammals of India in the last three
decades, most of the information pertains to the occa-
sional stranding or accidental entanglements in gill-net
fishery. In many incidences, the information is limited to
mere morphometric measurements of the animals and
photographs. In India, the quality of available literature is
inadequate to address the problems related to the biodi-
versity and conservation of the marine mammals. Despite
the fact that they occupy higher levels in the marine food
chain and compete with the fishermen to share the finfish
and shellfish resources, marine mammal research is of
poor quality in India.
It is unfortunate that the studies on marine mammals in
India, with the exception of a few publications, such as
the one on the evolutionary aspects7, gained no profes-
sional attention when compared to the publications from
Sri Lanka8. Published reports reflect the fact that the
study remained largely as pursuit of few interested indi-
viduals in one of the institutions engaged in marine fish-
eries research. The purpose of this review is to (1) survey
the papers published between the years 1800 and 2000 on
the marine mammals in the Indian waters; (2) assess the
methodologies adopted for studying the measurements;
(3) suggest improvements for future research; and (4)
suggest suitable research strategies for conservation of
the resources.
Material and methods
Reports on the Indian marine mammals, published by
more than 200 authors of 180 papers from 22 different
sources varying from conference abstracts to books dur-
ing the years 1800 to 2000 (including a record in 1748),
were considered for this survey. A total of 1452 records
of marine mammals, including stranding all along the ten
maritime states and two island groups, viz. Andaman and
Nicobar, and Lakshadweep, gear entanglements, sight-
ings in the Indian EEZ, specimens and photographs
archived in various museums in India and abroad during
the last 200 years were considered.
Whenever the available data permitted, the reports
were examined for the correctness of species identifica-
tion based on the FAO marine mammals species identifi-
cation guide9. However, even for the most frequently
reported genera like Sousa and Tursiops, the species
identification could not be confirmed based on the earlier
reports. Ganges River dolphins (Platanista ganetica) are
closely related to the marine cetaceans, and share similar
threats such as habitat degradation, fishery interaction
and pollution. Furthermore their status, research and
methods for conservation are different from those of
marine cetaceans and therefore not elaborately treated in
REVIEW ARTICLE
CURRENT SCIENCE, VOL. 83, NO. 10, 25 NOVEMBER 2002 1211
this review. For more details on the Ganges river dolphin,
readers can consult the works of Biswas and Bouruah10
and Kannan et al.11.
Results and discussion
Species diversity and abundance
A detailed list of the number of marine mammals recor-
ded from Indian seas during the years 1800 to 2000 is
presented in Table 1. The number of records between the
years 1800 and 1900 was only 47 and therefore it is
pooled together for that century. For the next hundred
years between 1901 and 2000, the records were shown in
ten-year intervals. Among the 1452 records, the exact
date/month/year could not be traced for 40 records and
for 32 records the species were not identified. Sixteen
species were recorded from 1800 to 1900 and eight spe-
cies were newly recorded during the last century. Among
the 24 species recorded, the blue whale was recorded
throughout the 20th century. There was not a single
record of rough-toothed dolphin after 1900. Likewise
there is a shift in the species composition among cetace-
ans during the last three decades. Open-ocean species
like sei whale, offshore species like Cuvier’s beaked
whale, oceanic dolphins like spotted, striped and Risso’s
dolphin were recorded for the first time during the last
three decades. Coastal species such as humpbacked dol-
phin and finless porpoise were incidentally caught in
large numbers in fishing gears due to increase in the
intensity of fishing. Significant rise in the number of
records as well as species during the last three decades
could be attributed to five separate12–15 monitoring stud-
ies on the impact of gill-net fishery on small cetaceans
and dugongs16. The observed trends in the number of
species from the southern states of Tamil Nadu (16) and
Kerala (13) could be attributed to the focus of research
on marine mammals in these states rather than to any
specific distribution pattern. For example, the number of
reported species (6) is low along the Gujarat coast. More
species could be expected from Gujarat because 18 spe-
cies of marine mammals have been recorded from the
neighboring Pakistan17.
The species diversity of marine mammals in India is
one among the richest in the Indian Ocean (Table 2).
Rough-bottom topography with deep submarine canyons
in some parts of the east coast facilitates the aggregation
of small cetaceans13. Twenty-six species of marine
Table 1. Marine mammals recorded from Indian waters from 1800 to 2000*
1800– 1901– 1911– 1921– 1931– 1941– 1951– 1961– 1971– 1981– 1991– Date not
Species 1900 10 20 30 40 50 60 70 80 90 2000 known Total
Blue whale 3 2 3 1 3 1 2 7 3 8 7 40
Fin whale 1 1 1 2 1 3 2 11
Sei whale 1 1 2
Bryde’s whale 1 4 2 7
Minke whale 2 1 3
Humpback whale 1 1 2
Sperm whale 1 7 13 1 1 23
Pygmy sperm whale 1 2 3
Dwarf sperm whale 3 1 1 5
Cuvier’s beaked whale 2 2
Short-finned pilot whale 13 1 152 166
Irrawady dolphin 2 2 4
Killer whale 1 6 8 1 16
False killer whale 1 2 2 9 3 1 3 21
Melon-headed whale 2 1 2 5
Indo-Pacific humpbacked dolphin 5 2 1 13 97 97 6 221
Rough-toothed dolphin 3 3 6
Risso’s dolphin 1 7 8
Bottlenose dolphin 2 6 58 28 11 3 108
Pantropical spotted dolphin 1 1
Spinner dolphin 1 92 144 21 2 260
Striped dolphin 1 1
Common dolphin 1 24 228 3 256
Finless porpoise 3 2 1 20 1 28 10 6 13 84
Dugong 1 1 1 6 2 149 1 4 165
Unidentified whales 1 1 10 2 2 1 17
Unidentified marine mammals 3 2 4 1 1 1 2 1 15
Total 47 14 3 8 5 10 34 25 544 561 161 40 1452
*Data after correcting the errors pointed out in Table 4.
REVIEW ARTICLE
CURRENT SCIENCE, VOL. 83, NO. 10, 25 NOVEMBER 2002 1212
Table 2. Species diversity of marine mammals
Species recorded in
Classification Total no. of species9 Species recorded from IOCS2 India (present study)
Order: Cetacea
Sub order: Mysticeti
Family: Balaenopteridae 6 6 6
Sub order: Odontoceti
Family: Physeteridae 1 1 1
Kogiidae 2 2 2
Ziphiidae 19 7 1
Delphinidae 32 16 13
Phocoenidae 6 1 1
Platanistidae* 2 1 1
Order: Sirenia
Family: Dugongidae 1 1 1
*Not considered in this study.
mammals are represented from two orders, viz. Cetacea
and Sirenia (Table 3). All the species of globally-
occurring baleen whales, sperm whales, porpoise and
dugong are represented in the Indian waters. About 37
and 75% of the known species from India represent the
beaked whales and dolphins respectively. Dolphins con-
tributed 74% to the total records, followed by dugongs
(11.4%), porpoise (5.8%) and baleen whales (4.5%).
About 92% of the records were during the last three dec-
ades between 1970 and 2000. Cetaceans and sirenians
recorded 86.4 and 11.4% respectively. Among the ceta-
ceans, 94% were Odontoceti (toothed whales), and
5% Mysticeti (baleen whales). Unidentifiable carcass
accounted for 1%.
Among the baleen whales, 62% of the records were
blue whales followed by 17 and 11% of fin and sei
whales respectively. Humpbacked whales and minke
whales were 3% each, and 4% were Bryde’s whales. In
the case of toothed whales, spinner (18%), common
(17.6%), humpbacked (15.3%), pilot whales (11.4%), and
bottlenose dolphins (7.4%) were recorded in higher num-
bers. All other toothed-whale species constituted less
than 2% each.
Fishery interaction and marine mammals
The large number of records during 1971–2000 was due
to mass stranding of pilot whales in 1972 (ref. 18) and
the subsequent awareness among researchers to report the
stranding/sighting/mass mortality of marine mammals.
Consequently, 23 species were reported to occur along
the Indian coast between 1971 and 2000. Another reason
for increase in the records is due to intensified fishing
activity along the Indian coast during the last three dec-
ades and the consequent increase in the number of inci-
dental/intentional capture of marine mammals, especially
by gill-net fishery. Among the total records (1452), 80%
was due to fishery interaction. Since the number of
marine mammals caught in the fishing gears is not prop-
erly monitored, the actual mortality due to fishing opera-
tion may be much higher. The damage caused by gill-nets
is more than that by any other gear. Moreover, it is
reported that cetaceans get entangled in other fishing
gears such as shore seines, travels and long lines, but
their impact is negligible compared to gill nets. Only
1.4% of the animals caught in the fishing gears had inju-
ries ranging from superficial cuts in the blubber to muti-
lation of the caudal fluke.
Among the large whales, blue19,20, fin21, minke22 were
caught alive and brought to the shore. Blue and fin
whales survived for a few hours. A blue whale20 and a
minke whale survived for three and two days respec-
tively. The same minke whale22, which survived for two
days in captivity, was released back into the sea. Due to
lack of awareness, the fishermen repeatedly land whales
with the hope of realizing good price, but in most cases
the animals are discarded in the shore. Dugongs were
kept under captivity23, but attempts to rear small cetace-
ans were not successful24,25 compared to that of dugongs.
Sightings of marine mammals
Next to the fisheries interaction, sightings (12% of the
total records) have helped to ascertain the distribution of
oceanic delphinids like killer whales. Sightings have also
provided information on the composition and structure of
dolphin schools. Based on sightings, Parsons26 reported
the age-related differences in the morphology and colora-
tion pattern in humpback dolphins off Goa. Sighting
cruises dedicated to marine mammals will bring valuable
information on the species composition, school structure,
and geographical and seasonal distribution. Based on
sightings it is possible to regulate gill-net fishery by
restricting or imposing seasonal ban on gill-net fishery, at
least in the geographical region where the small cetace-
ans are predominant.
REVIEW ARTICLE
CURRENT SCIENCE, VOL. 83, NO. 10, 25 NOVEMBER 2002 1213
Table 3. Inventory of marine mammals in India based on the present study@
Species English name IUCN status
Order: Cetacea
Sub order: Mysticeti
Family: Balaenopteridae
Balaenoptera musculus (Linnaeus, 1758) Blue whale Endangered
Balaenoptera physalus (Linnaeus, 1758) Fin whale Vulnerable
Balaenoptera borealis Lesson, 1828 Sei whale Vulnerable
Balaenoptera edeni Anderson, 1878 Bryde’s whale Insufficiently known
Balaenoptera acutorostrata Lacepede, 1804 Minke whale Insufficiently known
Megaptera novaeangliae (Browski, 1781) Humpbacked whale Vulnerable
Sub order: Odontoceti
Family: Physeteridae Sperm whale Insufficiently known
Physeter macrocephalus (Linnaeus, 1758)*
Family: Kogiidae
Kogia breviceps (de Blaninville, 1838) Pygmy sperm whale Insufficiently known
Kogia simus Owen, 1866 Dwarf sperm whale Insufficiently known
Family: Ziphiidae
Ziphius cavirostris Cuvier, 1823 Cuvier’s beaked whale Insufficiently known
Family: Delphinidae
Globicephala macrorhynchus Gary, 1846 Short-finned pilot whale Insufficiently known
Orcaella brevirostris (Gray, 1866)* Irrawady dolphin Insufficiently known
Orcinus orca (Linnaeus, 1758) Killer whale Insufficiently known
Pseudorca crassidens (Owen, 1846) False killer whale Insufficiently known
Peponocephala electra (Gray, 1846) Melon-headed whale Insufficiently known
Sousa species Indo-Pacific humpbacked dolphin Insufficiently known
Steno bredanensis (Lesson, 1828) Rough-toothed dolphin Insufficiently known
Grampus griseus (Cuvier, 1812) Risso’s dolphin Insufficiently known
Tursiops species Bottlenose dolphin Insufficiently known
Stenella attenuata (Gray, 1846) Pantropical spotted dolphin Insufficiently known
Stenella longirostris (Gray, 1828) Spinner dolphin Insufficiently known
Stenella coeruleoalba (Meyan, 1833) Striped dolphin Insufficiently known
Delphinus delphis Linnaeus, 1758 Common dolphin Insufficiently known
Family: Platanistidae
Platanista ganetica (Roxburgh, 1801)*,# Ganges River dolphin Vulnerable
Family: Phocoenidae
Neophocaena phocaenoides (Cuvier, 1829) Finless porpoise Insufficiently known
Order: Sirenia
Family: Dugongidae
Dugong dugon (Muller, 1776)* Dugong Vulnerable
@Data after correcting the errors pointed out in Table 4.
*Listed under Indian Wildlife Act.
#Not considered in detail in this study.
Reliability of earlier reports
Due to lack of expertise on marine mammals in India,
most of the published reports were not subjected to peer
review. Moreover, often reports on marine mammals
have been published in the in-house journals and
newsletters. Only 8% of the papers have been published
in international journals. Interpreting the available pub-
lished information in the light of recent developments in
marine mammal science is attempted, and a few common
errors found in the published reports are given as Table
4. In most of the reports, the central problem of conserva-
tion and management has been neglected. Among the
papers reviewed, hardly 2% of the papers had clearly
defined the purpose. Apart from this, few avoidable
errors such as misquoting the references were not
uncommon. For instance Chacko and Mathew’s work
(J. Bombay Nat. Hist. Soc., 1954, 52, 585) was misquoted
by Venkatraman and Girijavallaban27 and later by Lal-
mohan28 as J. Bombay Nat. Hist. Soc., 1954, 32, 347–353,
and ibid, 1954, 52, 538, respectively.
To overcome similar problems, published records were
analysed to identify the essential parameters for evolving
a suitable strategy for conservation of these resources. A
total number of 1173 records were studied in detail for 20
different factors varying from the availability of location,
date, sex, body measurement, species identification, and
also for the reasons for the cause of death, information on
anatomy, stomach content, etc. From the 20 factors stud-
ied, seven (Table 5) were identified as important based
on the following criteria: (1) the information should help
in understanding the distribution and for evolving a more
REVIEW ARTICLE
CURRENT SCIENCE, VOL. 83, NO. 10, 25 NOVEMBER 2002 1214
Table 4. Examples of few common errors found in published records on marine mammals of India
Species as reported Type/nature of errors reported by various authors Remarks
Measurements
Delphinus delphis73 Grows up to 8 m Size is too large for the reported species because the average
length is 2.3–2.6 m.
Balaenoptera physalus74 Total length 4.6 m Size is smaller for fin whale because the average reported length
at birth is 6.5 m. Based on the total length, the probability of sei
or Bryde’s whale cannot be ruled out. However large flipper ratio
(11.8% of the total length) is close to blue whales.
Sousa chinensis75 Tip of the upper jaw to the end of the Ventral grooves are found only in the baleen whales.
ventral grooves
Neophocaena phocaenoides76 Length of the throat grooves Throat grooves are found only in baleen whales.
Pseudorca crassidens77 Girth of the penis at two different points Not a useful measurement for species identification.
Physeter macrocephalus78 Girth of the penis at three different points Not a useful measurement for species identification.
Physeter macrocephalus4 Girth of the penis at three different points Not a useful measurement for species identification.
Misidentification
Balaenoptera borealis79 11% of the flipper indicates probable blue whale.
B. borealis80 12.2% of the flipper indicates probable blue whale.
B. borealis20 12.9% of the flipper indicates probable blue whale.
B. borealis81 12% of the flipper indicates probable blue whale.
Balaenoptera physalus82 11.8% of the flipper indicates probable blue whale.
B. physalus83 10.8% of the flipper indicates probable blue whale.
B. physalus84 10.6% of the flipper indicates probable blue whale.
Balaenoptera musculus57 7.6% of the flipper indicates probable fin whale.
B. musculus40 8.9% of the flipper indicates probable fin whale.
Sotalia species85 Probably misidentified Sousa species.
Stenella longirostris13 Photograph is clear enough to confirm identification as striped
dolphin.
Delphinus delphis43 Photograph is clear enough to confirm identification as
bottlenose dolphin.
Sousa chinensis44 Based on the stuffed specimen and photograph, it is probably a
spinner dolphin.
Balaena australis2–4,29–34 Misidentification and failure to verify Distribution of the reported species is limited to the southern
specimen or published report and therefore ocean. Moreover, the specimen is correctly identified as blue
repeated misquoting of the species for whale and the skeleton is mounted in Baroda museum.
more than 50 years
Sotalia fluvitils45 Distribution is limited to the part of northwestern South America.
Reproduction
S. chinensis48 Underdeveloped gonads in female Same species measuring 223.5 cm had foetus of 25 cm from the
specimen measuring 225 cm from the same geographical location.
Gulf of Mannar
Tursiops aduncus48 Underdeveloped gonads in a male specimen Same species measuring 163 cm had testis reported
measuring 221cm from the Gulf of Mannar from Parangipettai.
Misinterpretation
S. chinensis and S. longirostris50 Mass stranding Cannot be mass stranding because no information on pathology
or pollution is included and therefore this ‘mass mortality’ is
probably due to dynamite fishing.
Megaptera novaeangliae46 Reported ambergris and probable new Ambergris is found only in sperm whale and protrusion mistaken
mother \for a new mother was a normal postmortem change.
Inadequate/incorrect information
Dugong dugon42 Incorrect information and the record has Baleen whale washed ashore in 1849 was misquoted as dugong
been corrected after 52 years in Bombay City Gazetteer in 1909 and was corrected after
verification of the original newspaper report.
B. musculus86 Limited information No detailed measurements or clear photographs to support species
level identification and the report has only two sentences.
B. musculus87 Limited information Inadequate measurement and lack of clear photograph for species
level identification.
D. delphis13 Either date and/or position is incorrect Discrepancy in the position of the research vessel.
Sousa lentigosa88 Discrepancy in the sex In the plate, the sex is reported as male, but in the text as female
Balaenoptera edeni28 Incorrect information by the same author The specimen originally described by the author as Balaenoptera
with alteration in date, length and species borealis33 is 13.8 m in length and dated 18/3/1983. The skeleton
name is still kept at CMFRI, Mandapam, but the author has given
different lengths for the same specimen as 13 m (ref. 33), 13.5 m
(ref. 28) and 13.52 m (ref. 28) and two different dates.
REVIEW ARTICLE
CURRENT SCIENCE, VOL. 83, NO. 10, 25 NOVEMBER 2002 1215
complete inventory; (2) indicate the source for getting
specimens for future research; (3) point out thrust areas
for immediate attention; and (4) aid in designing a meth-
odology for the Indian context.
Problems in measuring the animals: Mostly, fishery
biologists undertake marine mammal research in India
and the scope is limited to reporting the various mor-
phometric measurements. These researchers have taken
as much as 60 morphometric measurements for the ceta-
ceans. Few measurements such as inter-orbital distance
(like in fishes), length of the throat grooves in toothed
whales (present only in baleen whales), thickness of pe-
nis at three different points, length of liver, lungs, eye,
largest tooth, width of eye, eye diameter, etc., are often
reported based on stranded and partially spoiled speci-
mens. Several of these measurements are not suitable for
the purpose of species identification in the case of ceta-
ceans. For instance, in the case of baleen whales, large
quantity of blubber is lost during migration, resulting in
the reduction of body girth. Similarly, the specimens
washed ashore bloat quickly in the tropical environment,
which considerably influences the girth measurements.
To overcome the constraints, 20 body measurements are
suggested for the small cetaceans (Table 6) based on an
earlier study on the tropical spinner and striped dolphins
from the Pacific Ocean29. These measurements are
proved to be growth-dependent and are sufficient to
answer questions pertaining to the species and growth.
For verification, detailed osteological measurement could
follow the morphometric measurements.
Repeated citation without verification of facts: Devkar30
corrected a report on the southern right whale
(Eubaleana australis) by Moses31 as blue whale. The
southern right whale is restricted to the southern latitude
from 20°S to 55°S. Moreover, the reported size of the
specimen by Moses31 was 21.4 m, which is higher by 3 m
than the maximum reported size for a southern right
whale. However, the FAO species identification guide9
has excluded Indian waters from the distribution of
southern right whales. But even today, based on the
report by Moses3, there are several such repeated wrong
citations2–4,32–36.
Misidentification: Lack of adequate field keys and reli-
able inventory has resulted in misidentification. About
25% of the reports on baleen whales were misidentified,
but the percentage for small cetaceans is less. However,
in the present analysis, hundreds of small cetaceans are
considered as reported by the authors because no detailed
measurement on them is available. In the present study
on baleen whales, the ratio of the outer margin of the
flipper to the total body length was considered as a key
character for identification, because this measurement is
available in most of the earlier reports. However, this
method has a limitation because the ratio for fin whale
(7.5–9.9%) and sei whale (9%) overlaps. Therefore it is
probable that the sei whale could be a fin whale and vice
versa due to failure to collect more information to con-
firm species identification. Even now, a specimen of
Balaenoptera musculus recorded during 1874 is still
labelled as Balaenoptera indica (earlier classification) at
the government museum in Chennai.
Baleen whales reported in this study are after correct-
ing the species level identification. Among the reports
surveyed, only two37,38 have attempted to correct
misidentification. In the first case the new identity of the
species was questioned39 and in the second, based on the
measurements, the specimen was corrected as fin whale
instead of blue whale after 12 years40. Another baleen
whale was identified up to species level based on the
Table 5. Few important aspects from published records on marine
mammals of India
Number Percentage in
Aspects of records total number of records*
Fishery interaction 1155 80
Sighting 180 12.4
Live stranding 83 5.7
Washed ashore 60 4.1
Stomach content 55 3.8
Injury 16 1.1
Human consumption 5 0.3
*Based on 1452 records.
Table 6. External measurements recommended for small cetaceans in
the Indian context*
Measurement
Length, total (tip of the upper jaw to the deepest part of notch between
flukes)
Length, tip of the upper jaw to centre of eye
Length, tip of the upper jaw to apex of melon (snout length)
Length of gape (tip of the upper jaw to angle of gape)
Length, tip of the upper jaw to external auditory meatus
Centre of eye to external auditory meatus
Centre of eye to angle of gape
Centre of eye to center of blowhole
Length, tip of upper jaw to blowhole along midline
Length, tip of upper jaw to anterior insertion of flipper
Length, tip of upper jaw to tip of dorsal fin
Length, tip of upper jaw to midpoint of umbilicus
Length, tip of upper jaw to midpoint of genital aperture
Length, tip of upper jaw to centre of anus
Length of flipper (anterior insertion of tip)
Length of flipper (axilla to tip)
Width, flipper (maximum)
Height of dorsal fin (fin tip to base)
Fluke span
Width of flukes (distance from nearest point on anterior border of fluke
notch)
*After Perrin29.
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CURRENT SCIENCE, VOL. 83, NO. 10, 25 NOVEMBER 2002 1216
stomach contents41 after 16 years38. Similarly, a baleen
whale recorded in 1849 was misquoted as dugong in
1909 and the same was corrected in 1961 (ref. 42). Pub-
lished keys fail to address the problems encountered in
the field conditions. For example, dolphins such as spin-
ner and striped have different colouration pattern, but
importance has not been given to these characters. In the
case of small cetaceans, teeth count is considered as a
primary character for species identification. At least three
species, viz. spinner (45–65 teeth), striped (40–55 teeth),
and common dolphins (40–61 teeth), have overlapping
range of teeth in each jaw. The likelihood of misidentifi-
cation between striped and common dolphins cannot be
ruled out. Even with differences in the teeth count, bot-
tlenose (18–26 teeth), and spinner have been misidenti-
fied as common43 and humpback dolphins44 respectively.
In the first case, the photograph is clear enough to iden-
tify the specimen as bottlenose dolphin and in the second
case, the photograph and stuffed specimen are adequate
for correcting the species identity. Jones45 mentioned
Sotalia fluviatalis as a commonly recorded small ceta-
cean in gill-net fishery. But the distribution of this spe-
cies is limited to northwestern South America9. In
another case13 a striped dolphin was misidentified as
spinner in spite of clear colour photograph. The report
has been corrected after 11 years. This is the first record
of striped dolphin from Indian waters.
Misinterpretation and partial information: Muthiah et
al.46 have reported a humpback whale with ambergris and
interpreted the protrusion of internal organ for a new
mother. But, ambergris was never reported from baleen
whales47. Protrusion of internal organs in the specimens
washed ashore is part of post-mortem changes. Unless
milk is found in the mammary glands, it is difficult to
externally infer feeding mothers.
A report by Lipton et al.48 on a male bottlenose and a
female humpback dolphin from the Gulf of Mannar
measuring 221 and 225 cm respectively, states that they
did not have developed gonads. According to another
report49 the humpback dolphin from the Gulf of Mannar
measuring 223.5 cm had a foetus measuring 25 cm. Simi-
larly, in an earlier study a male bottlenose dolphin meas-
uring 163 cm had a well-developed gonad measuring
30 cm, recorded from Parangipettai in the Tamil Nadu
coast13. It is possible that Lipton et al.48 missed the
gonads during necropsy or the humpback dolphin was
misidentified; photograph of the specimen was not
included in the report.
A report from Velapatty near Tuticorin on the sudden
death of spinner and humpback dolphins claims ‘mass
stranding’ as the cause50. However earlier incidents of
mass stranding involving small cetaceans are known to
be due to morbilivirus51 outbreak and/or due to alarm-
ingly high levels of xenobiotics52. In an earlier study53
the toxic load of spinner and humpback dolphins from
Parangipettai had only trace levels of xenobiotics. Fur-
thermore, the samples were not subjected to chemical or
pathological investigations to support mass stranding.
The ongoing illegal use of dynamite for coral fishing in
the vicinity50 could probably be attributed to the mass
mortality of dolphins.
Apart from the aforementioned problems, discrepan-
cies in reporting the position of ship, date, species length
and the use of blubber oil for treating respiratory com-
plaints are not uncommon.
Use of different species names: In the case humpback
dolphin or bottlenose dolphin, it is unclear as to how
many species inhabit the Indian waters. Humpback dol-
phins reported from the southeast and southwest coast of
India have a distinct morphological difference. Speci-
mens reported from Calicut (southwest coast) had a dis-
tinct hump and the same was absent in those reported
from Parangipettai (southeast coast). The humpback dol-
phins from Calicut have been reported by two specific
names, viz. Sousa plumbea54 and Sousa chinensis12,24.
From these reports which are by the same author, it is not
clear whether the specimens were actually two different
species. However many authors have considered hump-
back dolphins as S. chinensis along the east13,55 and west
coast15,26 of India. Similar differences in the hump have
been observed in the Indonesian waters; but irrespective
of the presence or absence of the hump, these dolphins
were considered as S. chinensis56. Morphological differ-
ence alone may not be useful for species identification of
humpback dolphins, and therefore it is treated here as
Sousa sp. The bottlenose dolphins have been reported
fewer than by ten different specific names along the
Indian coast. However, the taxonomy of the bottlenoses
is still unclear due to wide morphological variations
among different stocks, such as inshore and offshore
stocks of the same species. As it is difficult to assign a
specific name based on the earlier observations, it is
treated as Tursiops sp. in this review.
Anatomy and stomach contents
Incidental catches of mammals in the gill-net fishery
were used for studying the anatomy (mainly length and
weight of different organs) and stomach content. Infor-
mation on the anatomy of ten species of cetaceans, viz.
blue whale57, sei whale58, Cuvier’s beaked whale13, spin-
ner dolphin13,59, striped dolphin13, humpback dolphin13,
bottlenose dolphin13,57, false killer whale60, finless por-
poise61 and dugong62 is available. However it is difficult
to compare the data because they differ with sex, nutri-
tive condition and geographic location.
Information on the stomach contents is available for 11
species. Most of the small cetaceans are opportunistic
feeders and the stomach contents of the same species
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CURRENT SCIENCE, VOL. 83, NO. 10, 25 NOVEMBER 2002 1217
vary with space and time. Stomach contents of different
species observed during the same period at Parangipettai
(southeast coast) have shown differences in the prey,
although prawns were predominant in the stomach of the
spinner and humpback dolphins, and fishes in the bottle-
nose dolphins13. Commercially important fin and shell-
fishes such as Meglaspis cordyla, Saurida tumbil,
Sphyraena sp., Ilisha sp., Trichirus sp., Polynemus sp.,
Stolephorus spp., Tachysurus sp., carangids, barracudas,
sciaenids, conger eel, Loligo duvaucelli, Sepia spp. and
commercially less important ones such as Chiroteuthis
sp. and jelly fish have been reported in the stomach of
marine mammals. In addition, remains of crabs, pandalid
and penaeid prawns were also found in the stomach of
dolphins. Information on the nature and composition of
seagrasses fed by dugongs is also available.
Need for shift in research paradigm
Although the source of getting proper specimen in a
country like India to conduct quality research is difficult,
it is unfortunate that the available information is not sci-
entifically looked into, in most of the cases. However, in
recent years information on marine mammals in India has
attained quantitative progress. With the increase in
marine fishing activities all along the Indian coast, there
is good scope for qualitatively improving the research on
marine mammals, and thereby providing more informa-
tion for conserving the resources. In terms of quality of
data, vital information on the biology and ecology of
these animals is missing. The available information calls
for the need to collecting reliable data on marine mam-
mals. Studies on fishery interaction, biology, ecology,
genetics, loss of habitat and impact of pollutants are rele-
vant for conservation and management. Hence, it is time
for a shift in the entire approach and methodologies to
meet the conservation needs.
The following programmes are suggested for re-orient-
ing marine mammal research in India.
Taxonomy
It is still unclear how many species inhabit the Indian
waters. A survey of available literature indicates 26 spe-
cies (including the Ganges River dolphin), but it could
probably be more. The number of species recorded from
the Andaman and Nicobar islands is only nine, whereas
16 species have been reported from the Indonesian
waters2. A dedicated survey for the species of marine
mammals in the Andaman waters may reveal the occur-
rence of few beaked whales and oceanic dolphins. More-
over, it is important to study the available material in
various museums and private collections before expand-
ing these 26 species to a final inventory. The study of
archived material will not only bring unknown details of
the available type specimens, but also eliminate possible
repetitions. The probability of intra-specific variation
cannot be ruled out. Conventional approach such as de-
pendence on skeleton to answer questions pertaining to
taxonomy consumes more time and resource. Consider-
ing qualitatively superior results and cost effectiveness,
molecular approach with an effective tool like mitochon-
drial DNA (mtDNA) fingerprinting will be useful for
better understanding of inter and intra-specific variations
and management purposes63.
Non-invasive sampling techniques such as biopsy
and photo-identification
Biopsies could be taken using a dart from a research ves-
sel on a wild dolphin without injuring it64. Biopsy dart is
designed especially for collecting 3 g of skin and blub-
ber. Skin sample can be used for mtDNA analysis and
blubber for monitoring pollutant loads. It is possible to
collect samples from the same school of dolphins within
a short time. Biopsy dart causes minimum disturbance to
the animal and the wound normally heals within two
to three weeks. Results from biopsy sample serve as an
index for assessing the anthropogenic pressures and sex
composition in a population.
Another non-invasive technique is photo-identifi-
cation. The shape of the dorsal fin has inter- and intra-
specific variations, and the fin differs with age in some
species. Apart from this, wild dolphins will have distinct
individual markings in their dorsal fin such as nicks, cuts,
scars and body colouration. Photographs of dorsal fins
and flukes help in identifying individual animals65. This
technique is effective for studying the school structure
and species composition. A repeated photo-session from
the same geographical location for a protracted period of
time will help in monitoring the resident and migrant
populations as well as the reproductive success. Employ-
ing this technique on marine mammals inhabiting the
nearshore waters and island groups in the Gulf of Mannar
will provide valuable information.
Collection of samples from dead animals
Simple initiatives such as collection of skeletal remains
and teeth of stranded mammals will provide valuable
information on age. The growth layer groups (GLCs) in
the teeth can be used to determine the age of the ani-
mal66. The skull could be used for taxonomical purposes.
Collection of other organs such as kidney, liver, lung,
etc. can be undertaken whenever the specimen is fresh.
The collected samples, in the case of skeletal remains,
may be stored in carton boxes and polyethylene bags, and
the organs may be frozen whenever possible, for subse-
quent analysis.
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CURRENT SCIENCE, VOL. 83, NO. 10, 25 NOVEMBER 2002 1218
Analysis of stomach contents
The small cetaceans occupy the apex of the food chain
and they feed upon many commercially important fishes,
competing with the fisheries. Detailed studies on the
quantity and quality of food consumed by the cetaceans
are necessary to understand the interaction between them
and the major fish stock. In the case of the dugong, it is
necessary to estimate the quantitative and qualitative
requirements of the seagrasses to support the dugong
population in the Gulf regions of Mannar and Kutch. The
survival of the dugongs is dependent on the availability
of seagrass.
Field survey to monitor the impact of fishery
interaction vis-à-vis small cetaceans
The gill-net fishery has proved to be detrimental to the
small cetaceans off the coast of Sri Lanka67 and USA68.
However, the impact of gill-net fishery on the marine
mammals along the Indian coast is yet to be assessed.
This could be achieved by field surveys to monitor the
impact of fishery interaction vis-à-vis small cetaceans. In
the case of large whales, the fishermen deliberately bring
them to the shore, anticipating ambergris. Attempts like
this should be discouraged by awareness campaigns.
Moreover, surveys on incidental capture provide the
Information/sample to be collected Nature of study possible
Cause of death
Pregnant/lactating/
Foetus length/weight/sex
Testicle weight/length/sample
Ovaries weight/complete samples
Mammary thickness/uterus measurements
Thoracic vertebrae, skull and teeth
Adrenal glands weight
Blubber sample/adult/foetus/milk sample
Blubber and liver samples
Fishery interaction
Reproduction
Growth, skull morphometrics,
age determination
Xenobiotics pollution
MFO – Biomarker
Muscle, liver and kidney samples Heavy metals
Total weight
Weight of the heart, liver, spleen, kidneys Organ growth, Pathology, Pollution
Parasites in stomach, intestine, liver, muscle and
brain Parasites
Photograph of dorsal fin, nicks, cuts, and pattern of
mottling on the body, flukes Photo-identification
Population
Number/date/location/sex/length/photographs Identification/database establishment
Stomach contents/nature and composition of prey Trophic level prey–predator relationship
Figure 1. Schematic representation of sampling protocol recommended for marine mammals in India.
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CURRENT SCIENCE, VOL. 83, NO. 10, 25 NOVEMBER 2002 1219
much-needed evidence on the species distribution during
different seasons. The conflict between cetacean conserva-
tion and fisheries interest deserves immediate attention.
Biomarkers
Impact of xenobiotics such as PCB and DDT induces
undesirable changes in the reproductive physiology of the
cetaceans69. Earlier studies on the dolphins along the In-
dian coasts have detected trace level concentration of
these pollutants53,70. These chemicals are highly persis-
tent and the marine mammals that live for long years tend
to accumulate them. In recent years, the possibility of
using the skin biopsies for preliminary assessment of
Mixed Function Oxidase (MFO) as a biomarker71 has
evolved as a relatively inexpensive alternative to assess
the health of marine mammals.
Conclusion
Marine mammals are the poorly studied group of animals
in India. At present there is no major research pro-
gramme and none of the research institutions are concen-
trating on marine mammals. Expertise on marine
mammals is also lacking and research on marine mam-
mals has remained largely in the domain of fishery biolo-
gists. Wildlife Protection Act and creating awareness to
the public can only be a part of a larger effort towards
conservation. Marine mammals research in India should
gain a more professional approach. With the prevailing
trend, it is difficult to implement any meaningful meas-
ures to protect them. Data collection, of more than a cen-
tury, remains largely incohesive and purposeless. It is the
responsibility of scientists working in the field to ensure
that the quality of data is of international standards
before drawing attention of interested groups to join in
the conservation efforts. A schematic representation of
sampling protocol (Figure 1) involving broader issues for
quality data collection is suggested.
Marine mammal research should be given top priority
as given to the Antarctic programme because the conflict
between small cetaceans and gill-net fishery has direct
bearing on the economy of marine capture fishery. In-
formation on marine mammals is imperative to design
and implement meaningful conservation measures in the
existing marine parks and sanctuaries. Conservation of
dugongs cannot be delayed because their habitat is more
vulnerable to anthropogenic pressures such as destruction
of seagrass beds, illegal fishing using dynamite and pol-
lution. In an earlier study on Australian dugongs, 25
years have been predicted for the resilience of the popu-
lation to the pre-habitat destruction numbers72. There is
an indication based on the present review that dugongs
inhabiting our waters are relatively prone to extinction
than any other marine cetaceans. And research should
immediately focus more on the quantitative and qualita-
tive nature of seagrass beds and other antropogenic pres-
sures in the Gulf of Mannar and Kutch regions.
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ACKNOWLEDGEMENTS. I thank Dr E. Vivekanandan for sugges-
tions and improvement of earlier drafts and Drs A. Aguilar and
R. K. Rudhran for discussions. Curators Mr Jawahar and Mr Parmar of
the Chennai and Baroda museum respectively, are acknowledged for
permission to examine the whale skeleton. I thank M/s P. Thirumilu, J.
Carpenter and A. Gribling for literature collection and discussion. The
anonymous reviewer is acknowledged for constructive comments on
the manuscript.
Received 8 July 2002; revised accepted 17 September 2002
