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Observations of small cetaceans in the Eastern
Caribbean
Oliver Boisseau, Russell Leaper, Anna Moscrop
Song of the Whale Research Team, International Fund for Animal Welfare Charitable Trust, 87-90
Albert Embankment, London SE1 7UD, UK. whalesong@ifaw.org
ABSTRACT
Research was conducted in the Eastern Caribbean by the International Fund for Animal Welfare during
the spring in 1995, 1996, 2000 and 2006, primarily to investigate the biology, distribution and
movements of sperm and humpback whales. During dedicated passive acoustic and visual surveys,
observations and acoustic detections of small cetaceans were also recorded. Thirteen different species
of small cetacean were encountered. The most commonly sighted and widely distributed species was
the pan-tropical spotted dolphin (Stenella attenuata). Other oceanic dolphin species such as long-
beaked spinner dolphins (Stenella longirostris) and deep diving odontocetes such as the short-finned
pilot whale (Globicephala macrorhynchus) and Cuvier’s beaked whale (Ziphius cavirostris) were also
encountered on several occasions. Mixed species groups, for example of melon-headed whales
(Peponocephala electra) and Fraser’s dolphins (Lagenodelphis hosei) were occasionally observed.
Little is known about the presence, distribution and abundance of small cetaceans within the region;
Given the long history of exploitation of some near-shore populations (and reported declining catches
in the 1970’s) and, in the absence of survey data for much of the region, there is much uncertainty
regarding population structure, abundance and status of small cetacean species.
KEYWORDS: SMALL CETACEAN; EASTERN CARIBBEAN; SURVEYS; OBSERVATIONS;
STATUS
INTRODUCTION
The distribution, abundance and population structure of cetaceans of the south-eastern Caribbean are
poorly known. Since the 1990’s some systematic efforts to describe the cetacean fauna have been
undertaken (for example, Romero and Hayford 2000 and Romero et al. 2002b for Grenada, and
Romero et al. 2002a for Trinidad and Tobago). Some insights into presence and distribution may also
be obtained from information on hunting of small cetaceans in the region (see for example, Caldwell
and Caldwell 1975; Price, 1985; Romero and Creswell 2005).
Here, data on sightings and acoustic detections of small cetaceans, collected during boat-based visual
and acoustic surveys conducted by the International Fund for Animal Welfare (IFAW) in the eastern
Caribbean are outlined. Information from research conducted in the spring of years 1995, 1996, 2000
and 2006, including dedicated surveys and opportunistic observations, are described. Visual and
passive acoustic surveys for cetaceans were conducted off the islands of Dominica, Martinique,
Guadeloupe, Grenada, Trinidad and Tobago. Opportunistic observations of small cetacean species
were recorded during research primarily aimed at investigating the biology, distribution and
movements of sperm and humpback whales. Data on large whales have been reported elsewhere (e.g.
see Gordon et al. 1998, Stevick et al. 1999, Boisseau et al. 2000).
METHODS
Surveys were conducted from three different vessels, Song of the Whale I, Silurian, and Song of the
Whale II (table 1). These are all small auxiliary-powered sailing research vessels ranging in length
from 14m (Song of the Whale I) to 22m (Song of the Whale II). All vessels had an elevated viewing
platform at a height of 12m on the mast and passive acoustic monitoring equipment including two-
element towed hydrophone arrays. Although all the hydrophone arrays were built to the same basic
design, there were differences in the technical specification of the pre-amplifiers and onboard data
processing systems.
In 1995, 1996 and 2000, track-lines were chosen with the aim of providing roughly even coverage of
the survey area and not based on prior knowledge of cetacean presence. In addition, some of the data
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reported is from passages e.g. off Martinique in 2000. Off Dominica, Grenada, Guadeloupe, research
was conducted off the western coasts in the lee of the islands, from just beyond the 100m depth contour
to 5-15 miles offshore. In 2000, surveys were conducted off the west coast of Tobago. In 2006, three
survey blocks to the east and west of Trinidad and to the north (encompassing the waters around
Tobago) were surveyed; survey tracks were laid out to provide even coverage of these pre-determined
survey boxes, although taking prevailing weather conditions into account. In addition, a survey of the
Saba Bank was conducted in 2006, to the west of the Dutch Antillean Island of Saba.
At all times, the computer programme ‘Logger’ was used for routine data collection (see
www.ifaw.org/sotw). This software automatically collects data from the GPS and other instruments and
also prompts for information on environmental conductions, weather, sightings effort and activity.
Dedicated observers were stationed either on the deck or observation platform in sea states of 4 or less.
The towed hydrophone was monitored for 1 or 2 minutes every 15 minutes and codes describing the
type and level category of cetacean vocalisations heard were recorded in the database. For the purposes
of this analysis, acoustic listening stations were divided into just two categories, odontocetes detected
(clicks or whistles but excluding sperm whales) or no odontocetes detected.
Each year, the research teams comprised a mixture of IFAW researchers and local participants
(including local scientists and student interns from the Wider Caribbean Region (WCR) and University
of the West Indies). Less experienced team members were provided with training in recognising
cetacean vocalisations and in estimating ranges and bearings to visual sightings.
RESULTS
Species sighted
The observation effort in terms of hours of survey for the waters off each island is listed in table 1.
Thirteen species of small cetacean were encountered from the surveys conducted off Dominica,
Martinique, Guadeloupe, Grenada and Trinidad and Tobago, (table 2). The islands of Dominica and
Grenada showed the highest diversity of species, (but this may also reflect level of survey effort).
Given the level of effort, Trinidad and Tobago seemed to have a relatively low diversity of species, but
this may be biased/affected by the poor visual survey conditions experienced during field work off
Trinidad and Tobago in both 2000 and 2006. Group sizes ranged from lone individuals to groups of up
to 200 individual dolphins and 50 pilot whales. Calves and juveniles were observed for the following
species; bottlenose dolphin (Tursiops truncatus), false killer whale (Pseudorca crassidens), Fraser’s
dolphin, killer whale (Orcinus orca), pilot whale, pygmy sperm whale (Kogia breviceps), spinner
dolphin and spotted dolphin.
Sightings rates
Sightings rates by hour of survey effort appeared to be highest off Martinique, followed by Dominica,
Grenada and Guadeloupe (table 3; figure 1). Pan-tropical spotted dolphins were the most commonly
encountered species in all areas except off Trinidad, where bottlenose dolphins were encountered more
frequently (table 2). The sighting rates in table 2 have not been adjusted to take into account weather
conditions.
Acoustic detections
Acoustic detection rates for small cetaceans were calculated for each island using the number of
listening posts at which clicks, whistles or burst-pulse sounds were heard (excluding sperm whales). To
minimise the biases presented by repeated detections of the same individuals (e.g. bowriding dolphins),
consecutive detections were excluded from analysis. A detection was only included if an odontocete
had not been heard for at least 45 minutes.
The distribution of acoustic detections of odontocetes (excluding sperm whales) off Dominica, Grenada
and Trinidad and Tobago are illustrated in figure 2. Dolphin vocalisations were heard at 8.4% of all
acoustic stations. As with visual encounters, the highest acoustic encounter rate was off Martinique,
followed by Dominica, Guadeloupe and Grenada. When comparing acoustic and visual detection rates,
acoustic detection rates are invariably higher (figure 1). However, visual and acoustic encounter rates
followed similar patterns for each different island. Trinidad and Saba had lower ratios of visual
sightings to acoustic detections, perhaps reflecting prevailing weather conditions less favourable to
visual sightings. The plots of acoustic detections and listening stations in figure 2 for the islands with
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pre-determined tracks (Guadeloupe, Dominica, Grenada and Trinidad and Tobago) showed a fairly
even distribution of small cetaceans with no obvious concentrations.
DISCUSSION
Annex II of the SPAW Protocol (the UNEP Specially Protected Areas and Wildlife (SPAW) Protocol
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,
born out of the Convention for the Protection and Development of the Marine Environment for the
Wider Caribbean Region (Cartagena Convention), which came into force in 2000, lists all species of
marine mammals of the WCR as threatened and endangered. Long-term objectives include to better
protect, and assist with the recovery of, marine mammal species and populations, and protect their
habitats (e.g., feeding, breeding, and calving grounds, movement corridors etc.) However, as noted in
the recently drafted UNEP Marine Mammal Action Plan for the WCR
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, better information is required
in order to assess the status of small cetaceans within the region and to develop effective regionally and
nationally specific conservation measures.
Reeves (2005) notes that ‘the subject of population structure of odontocetes within the WCR has hardly
begun to be addressed, but judging by findings elsewhere, considerable structure is likely present (e.g.,
island-associated near-shore populations and farther-ranging offshore populations). Given the long
history of exploitation of some near-shore species in some parts of the WCR (e.g. Caldwell and
Caldwell 1975; Price 1985; Reeves 2002), this could mean that a number of populations have already
been substantially depleted or even entirely eliminated. In the absence of even rudimentary survey data
for most of the region (except U.S. waters of the northern Gulf of Mexico), uncertainty concerning
population structure, abundance, and conservation status is the norm’.
The surveys described here can only provide a ‘snap shot’ view of the presence and distribution of
small cetaceans, during the months January-March, off certain islands in the eastern and southeastern
Caribbean. Due to their limited spatial and temporal scope, they are unable to provide insights into the
seasonal distributions/movements of species or changes or trends in abundance. However, the
observations presented here may complement and build upon the experiences of other research efforts
and local whale watching operators who are now starting to assemble a considerable body of
information about whales and dolphins in the Eastern Caribbean. This may in the future, form the basis
of a long-term year round database of sightings in certain areas, which could usefully inform
conservation measures. For many areas in this region visual surveys are limited by the prevailing wind
conditions, which make observation difficult. Thus, much of the research effort in this study was
limited to areas of relatively sheltered water. Acoustic surveys are potentially less affected by sea state
than visual observations. Gordon et al. (2000) used similar acoustic data to examine relative abundance
and distribution patterns of striped dolphins in the Ligurian Sea using a number of covariates to model
detection probability in relation to sea state, wind speed and time of day. However, further work in the
Caribbean region would be necessary to develop methods to discriminate small cetacean species
acoustically.
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Annex II of the SPAW Protocol lists all species of marine mammals of the Wider Caribbean as threatened and
endangered. In this context, governments have agreed on the need to develop a regional management plan for the
conservation of marine mammals, through Decisions IV (2) and 2 of the First and Second Meetings of the
Contracting Parties of the SPAW Protocol (Havana, Cuba, 27-29 September 2001 and Montego Bay, Jamaica, 6
May 2002, respectively); Articles 11 and 21 of the SPAW Protocol call for the development and implementation of
programmes for protected species, as well as guidelines and criteria for the management of protected species,
including migratory species
.
2
Draft Action Plan for Conservation of Marine Mammals in the Wider Caribbean Region. UNEP(DEC)/CAR
WG.27/2 Rev 3. 23 August 2005. Presented to Regional Workshop of Experts on the Development of the Marine
Mammal Action Plan for the Wider Caribbean Region, Bridgetown, Barbados, 18-21 July 2005 and Third Meeting
of the Scientific and Technical Advisory Committee (STAC) to the Protocol Concerning Specially Protected Areas
and Wildlife (SPAW) in the Wider Caribbean Region, Caracas, Venezuela, 4 - 8 October, 2005.
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ACKNOWLEDGEMENTS
Thanks to all the members of the SOTW team, IFAW staff, the staff of Silurian and the many interns
and participants who took part in field work in 1995, 1996, 2000 and 2006, including Carole Carlson,
and Jonathan Gordon, Richard McLanaghan and Kit Rogers (skippers of Song of the Whale and
Silurian), Irene Seipt, Simon Ingram, Kirsten Young, Luke Rendell, Jessie Lane, Steve Brown, Justin
Matthews, Tim Lewis, Claire Lacey, Bridget Jones, Magnus Danbolt and Paul Leeming. We greatly
appreciated support from local groups and individuals in the Caribbean, including the Dominica
Conservation Association, Springfield research station, Dominica Watersports Association, Dive
Dominca and the Anchorage Hotel, the Institute of Marine Affairs in Trinidad and Departments of
Education, Fisheries and Natural Resources and the Environment, in Tobago, Atherton Martin, Mona
George-Dill and Leslie Pierre. Thanks also to Koen van Waerebeek for advice in dolphin species
identification, and Marina Nimrod for information on bycatches in Trinidad.
'Song of the Whale', conducted work with the permission of the Dominican and Grenadian
Governments (Ministry of Agriculture, Fisheries Division, Ministries of Tourism and Education in
Dominica, and Ministry of Agriculture and Fisheries and the Ministries of Tourism and Education in
Grenada) in 1995 and 1996, and with permission of The Ministry of Foreign Affairs, the Government
of the Netherlands, for the survey of the Saba Bank, The Ministry of Foreign Affairs, Trinidad &
Tobago and Department of Fisheries, Tobago, and in collaboration with the Institute of Marine Affairs,
Trinidad in 2006.
'Silurian' undertook research with permission from the DIRENS in Guadeloupe and Martinique, the
Ministry of Agriculture, Dominica and the Ministry of Agriculture, Grenada and the Ministry of
Fisheries in Trinidad and Tobago in 2000.
REFERENCES
Boisseau, O., Carlson, C and Seipt, I. 2000. A report on cetacean research conducted by the
International Fund for Animal Welfare off Guadeloupe, Dominica, Martinique, Grenada and Tobago
from 12 January to 30 March 2000. Unpublished report, IFAW, 411 Main St Yarmouth Port, MA,
USA.
Caldwell, D.K. and Caldwell, M.C. 1975. Dolphin and small whale fisheries of the Caribbean and West
Indies: occurrence, history and catch statistics – with special reference to the Lesser Antillean island of
St Vincent. Journal of the Fisheries Research Board of Canada 32:1105-1110.
Gordon, J., Moscrop, A., Carlson, C., Ingram, S., Leaper, R., Matthews., J and Young, K. 1998.
Distribution, Movements and Residency of Sperm whales off the Commonwealth of Dominica, Eastern
Caribbean: Implications for the Development and Regulation of the Local Whalewatching Industry.
Rep. Int. Whal. Commn, 48:551-557.
Gordon, J.C.D., Matthews, J.N., Panigada, S., Gannier, A., Borsani, J.F. and Notarbartolo di Sciara, G.
2000. Distribution and relative abundance of striped dolphins, and distribution of sperm whales in the
Ligurian Sea cetacean sanctuary: results from a collaboration using acoustic monitoring techniques. J.
Cetacean Res. Manage. 2(1):27-36
Price, W.S. 1985. Whaling in the Caribbean: historical perspective and update. Reports of the
International Whaling Commission 25:413-420
Reeves, R.R, Swartz, S.L., Wetmore, S.E and Clapham, P.J. 2001. Historical occurrence and
distribution of humpback whales in the eastern and southern Caribbean Sea, based on data from
American whaling logbooks. J. Cet. Res. Manage. 2(3):117-129.
Reeves, R.R. 2005. Distribution and Status of Marine Mammals of the Wider Caribbean Region:
An Update of UNEP Documents. UNEP(DEC)/CAR WG.27/INF.3
Presented to Regional Workshop of
Experts on the Development of the Marine Mammal Action Plan for the Wider Caribbean Region, Bridgetown,
Barbados, 18-21 July 2005
by Randall R. Reeves, Okapi Wildlife Associates, 27 Chandler Lane, Hudson,
Quebec J0P 1H0, Canada.
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Romero, A., Agudo, A.I., Green, S.M., and Notarbartolo di Sciara, G. 2001. Cetaceans of Venezuela:
Their distribution and conservation status. NOAA Technical Reports, NMFS 151:1-60.
Romero, A., Baker, R., Creswell, J.E., McKie, A and Manna, M. 2002a. Environmental history of
marine mammal exploitation in Trinidad and Tobago, W.I. and its ecological impact. Environment and
History, 8:255-274.
Romero, A. Hayford, K.T., Romero, A. and Romero, J. 2002b. The marine mammals of Grenada, W.I.,
and their conservation status. Mammalia 66:479-494.
Romero, A. and Hayford, K.T. 2000. Past and present utlisation of marine mammals in Grenada, West
Indies. Journal of Cetacean Research and Management 2: 223-226.
Romero, A. and Creswell, J. 2005. In the Land of the Mermaid: How culture, not ecology, influenced
marine mammal exploitation in the southeastern Caribbean. Chapter 1 in: A Romero and S.E. West
(eds). Environmental Issues in Latin America and the Caribbean, 3-30. Springer, Netherlands.
Swartz, S.L., Cole, T., McDonald, M.A., Hildebrand, JA., Oleson, E.M., Martinez, A., Clapham, P.J.,
Barlow., J and Jones, M.L. 2003. Acoustic and Visual Survey of Humpback Whale (Megaptera
novaeangliae) Distribution in the Eastern and South-eastern Caribbean Sea. Caribbean Journal of
Science 39(2):195-208.
Stevick, P.T., Carlson, C.A., and Balcomb, K. 1999. A note on migratory destinations of humpback
whales from the eastern Caribbean. J. Cet. Res. Manage. 1(3):251-254.
Table 1. A summary of visual and acoustic effort for each study period and area .
Year Dates Study area Hours of Number of Vessel
visual effort listening posts
1995 01 Jan – 31 Mar Dominica 280 1836 SOTW
1996 09 Jan – 04 Feb Dominica 39 109 SOTW
1996 12 Feb – 29 Mar Grenada 106 509 SOTW
2000 12 – 29 Jan; 24 – 30 Mar Guadeloupe 112 333 Silurian
2000 17 Mar – 23 Mar Dominica 47 137 Silurian
2000 02 Feb & 16 Mar Martinique 23 55 Silurian
2000 04 – 08 Feb; 02 – 10 Mar Grenada 81 214 Silurian
2000 12 Feb – 29 Feb Tobago 65 266 Silurian
2006 24 Jan – 10 Mar Trinidad & Tobago 194 804 SOTW II
2006 20 Mar – 24 Mar Saba Bank 76 416 SOTW II
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Table 2. List of small cetacean species observed /reported within the study area. Values represent the
number of groups sighted; estimated minimum and maximum group sizes are expressed in parentheses.
* represents those species (by island) for which juvenile animals and/or calves were observed.
Species Saba Guadeloupe Dominica Martinique Grenada Tobago Trinidad Notes
Bottlenose dolphin 2* 1 1 5
Tursiops truncatus (10-10) (10-10) (1-1) (1-10)
Cuvier’s beaked whale 1*
Ziphius cavirostris
(2-2)
False killer whale 2* 1
3
Pseudorca crassidens
(10-25)
Fraser’s dolphin 8* 1
4
Lagenodelphis hosei
(2-200)
Killer whale 1*
Orcinus orca
(3-3)
Long-beaked common dolphin 1
5
Dephinus capensis
Melon-headed whale 1
6
Peponocephala electra
Pan-tropical spotted dolphin 11* 27* 2 11* 8* 1
Stenella attenuata (6-100) (5-100) (1-25) (10-100) (5-40) (2-3)
Pygmy sperm whale 1*
Kogia breviceps
(2-2)
Pygmy killer whale 4
Feresa attenuata
(1-12)
Rough-toothed dolphin 1
Steno bredanensis
(15-15)
Short-finned pilot whale 2* 10*
Globicephala macrorhynchus (20-20) (8-50)
Spinner dolphin 6 2 2*
Stenella longirostris (1-50) (1-20) (3-40)
Unidentified dolphin 1 4* 38 12* 2 2
species (1-1) (1-3) (1-55) (1-50) (1-20) (1-2)
Unknown 2 1
species
(1-9) (1-1)
Total no. species seen
1 5 6 2 4 2 3
(out of 13)
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P. crassidens also reported from St Lucia – observed 2 dead animals caught by fishermen in Castries, spring
1997.
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L. hosei were also observed opportunistically on passage to Grenada, off Carriacou
5
D. capensis identified from photographs of bycaught animal, off SE coast of Trinidad, April 2006
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P. electra were observed opportunistically on passage to Grenada, off Carriacou
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Table 3. Summary of visual encounter rates of all odontocete groups (excluding sperm whales) seen
between 1995 and 2006 when on dedicated survey effort. Overall mean visual and acoustic encounter
rates are derived for each island.
Species Saba Guadeloupe Dominica Martinique Grenada Tobago Trinidad Mean
Bottlenose dolphin - 0.006 0.003 - - 0.010 - 0.006
Fraser’s dolphin - - 0.013 - - - - 0.013
Pilot whale - 0.012 0.019 - - - - 0.016
Pygmy killer whale - 0.025 - - - - - 0.025
Pygmy sperm whale - - - - 0.006 - - 0.006
Rough-toothed dolphin - 0.006 - - - - - 0.006
Spinner dolphin - - 0.003 0.134 - - 0.013 0.050
Spotted dolphin - 0.055 0.040 0.067 0.038 0.070 - 0.054
Unidentified dolphin 0.013 0.006 0.059 - 0.070 0.020 0.006 0.029
Unknown species - - 0.003 - - - - 0.003
Overall visual rate 0.013 0.111 0.140 0.200 0.115 0.100 0.019 0.100
Overall acoustic rate 0.199 0.384 0.386 0.420 0.343 0.245 0.240 0.317
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
Saba
Guadeloupe
Dominica
Martinique
Grenada
Tobago
Trinidad
Encounter rate per hour
Sightings
Acoustic
Figure 1. Overall small cetacean encounter rate measured from all islands.
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a) b)
c) d)
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e) f)
g) h)
Figure 2. All sightings made off Guadeloupe (a), Dominica (c), Grenada (e) and Tobago (g). Listening posts are also shown for each island, with those at which small
cetaceans were heard displayed in black; all other listening posts represented in grey.
