Download English

UNITED
NATIONS
EP
Distr.
LIMITED
United Nations
Environment
Programme
UNEP(DEC)/CAR WG.27/INF.3
18 July 2005
Original: ENGLISH
Regional Workshop of Experts on the
Development of the Marine Mammal Action
Plan for the Wider Caribbean Region
Bridgetown, Barbados, 18-21 July 2005
DISTRIBUTION AND STATUS OF MARINE MAMMALS OF THE WIDER
CARIBBEAN REGION: AN UPDATE OF UNEP DOCUMENTS
1
Distribution and Status of Marine Mammals of the Wider Caribbean
Region:
An Update of UNEP Documents
Randall R. Reeves, Okapi Wildlife Associates, 27 Chandler Lane, Hudson, Quebec
J0P 1H0, Canada
Abstract
The purpose of this paper is to “update” two documents – Marine Mammals of the Wider Caribbean
Region: A Review of their Conservation Status (by Ward and Moscrop, 1999) and Elements for the
Development of a Marine Mammal Action Plan for the Wider Caribbean: A Review of Marine Mammal
Distribution (by Ward, Moscrop, and Carlson, 2001). Although it is frequently stated that “little is known”
about marine mammals in the WCR (a familiar refrain in many other regions and contexts as well), enough
is known to make some broad generalizations and to generate working hypotheses to inform the
conservation planning process. It is proposed here that the region’s marine mammal populations should be
ranked in some way to reflect their significance to global biodiversity conservation. The basis for such
ranking could involve such things as: endemism, resident vs. migratory population(s), continuous vs.
fragmented distribution, current relative to historic abundance, and global status of the species (e.g., with
reference to the IUCN Red List, the CMS appendices). These factors would, of course, need to be balanced
against other concerns, such as economic valuation (e.g., whalewatching), cultural traditions (e.g., hunting),
and immediacy or severity of threats. As a working hypothesis, it is suggested that manatees (Antillean
subspecies in particular) rank highest (assuming that the West Indian monk seal is extinct), but determining
which species or populations should fall “next in line” is bound to be a challenge.
Introduction
The two main background documents for the WCR action plan initiative – Ward and
Moscrop (1999) and Ward et al. (2001) – summarize much of the relevant literature,
specify the marine mammal species known from the region, describe their distribution,
ecology, and conservation status, and identify threats, socio-economic opportunities, and
research needs. In this paper, I attempt mainly to do two things. First, I review some
information that has become available since those documents were prepared and that I
consider relevant to the workshop’s needs. Second, I propose an approach for ranking
species and populations for attention under the draft plan. I have made no attempt to
update information on manatees, on the understanding that other presenters would be
covering that species.
New Information of Relevance
Pinnipeds
Ward and Moscrop (1999) and Ward et al. (2001) correctly (in my judgment) considered
the West Indian monk seal (Monachus tropicalis) to be extinct, despite the fact that Boyd
and Stanfield (1998) offered “circumstantial evidence” for its possible continued
existence. Definite evidence is now available that hooded seals (Cystophora cristata)
occasionally wander from their Subarctic and Arctic range to occur as vagrants in the
WCR, e.g. in Puerto Rico and Guadeloupe. Unlike California sea lions (Zalophus
californianus), which are truly exotic in the region, having arrived through human
2
agency, the occasional occurrence of hooded seals represents natural dispersal by a North
Atlantic endemic. The occasional appearance of stray harp and harbor seals (Pagophilus
groenlandicus and Phoca vitulina, respectively) from the northern North Atlantic might
also be expected.
Baleen Whales
It appears, on present evidence, that only one species of baleen whale depends on the
WCR for food resources, namely the common Bryde’s whale, Balaenoptera cf. brydei.
Whether it migrates seasonally into and out of the region remains to be discovered. Two
other species that are regular non-residents, the humpback whale (Megaptera
novaeangliae) and the common minke whale (B. acutorostrata), are considered seasonal
migrants at the winter (breeding) end of their annual cycle – definitely in the case of the
humpback, probably in the case of the minke. The other balaenopterids that have been
recorded – blue, fin, and sei (B. musculus, B. physalus, and B. borealis) – are probably
“just visiting,” but the possibility cannot be ruled out that their visitation is more regular
and frequent in unstudied or poorly studied parts of the region, or that the WCR is a
significant portion of the normal range of one or more populations of these species.
Similarly, the rare reports of North Atlantic right whales seem to suggest that they are, in
some sense, “extralimital.” However, in view of recent occurrences of right whales in the
region, this conclusion deserves careful reconsideration.
At the 2004 Workshop on Shortcomings of Cetacean Taxonomy (Reeves et al. 2004:9),
participants concluded that one of three high-priority subjects in relation to baleen whales
was the need to obtain “immediate clarification” of the borealis-edeni-brydei-omurai
complex. The present IUCN Red List classification of the Bryde’s whale as “data
deficient” is owing mainly to the problem of taxonomic uncertainty. According to R.G.
LeDuc of the Southwest Fisheries Science Center in La Jolla, California (pers. comm.,
June 2005), he and the cetacean genetics group there are especially interested in obtaining
more tissue samples of Bryde’s whales from the WCR for DNA analyses. Their
preliminary findings based on a small number of samples suggest that further
comparisons of Caribbean animals with those from the western North Pacific and
elsewhere will be highly informative to the overall phylogeography of Bryde’s whales,
and indeed of the borealis-edeni-brydei-omurai complex. Two activities would seem
timely in this regard. First, an updated review and synthesis of records of finner whales
(Balaenoptera spp.) in the WCR is needed (cf. Mead 1977). Second, a concerted effort
should be made to obtain tissue samples, whether from strandings, sightings (biopsy
darting), or animals killed opportunistically by Caribbean whalers.
With regard to humpback whales, the recent findings of Swartz et al. (2003) deserve
critical evaluation. Having acknowledged that their study was not designed to obtain
abundance estimates, those authors nevertheless reached conclusions implying that they
had adequate quantitative information to make comparisons between current (2000) and
pre-exploitation abundance of humpbacks in different parts of the WCR. The statement in
their abstract that “the species continues to occupy its historical range” is inconsistent
with the statement in their main text (p. 205), that “apparent low abundance of whales in
3
the formerly important breeding habitats of the eastern and southeastern Caribbean
suggests failure to reoccupy their former range despite … protection….” Moreover, their
suggestion that the “abundance of humpbacks using the eastern and southeastern
Caribbean … remains low” would seem to require a better understanding not only of
actual abundance, but also of how individual whales may circulate during the 4- or 5month winter season (January-May) – between the “primary breeding aggregations” in
the northern Greater Antilles and the extreme southern limits of the population’s
distribution along the northern coast of South America. Perhaps the most important result
of their study was the failure to find any evidence of present-day use by humpbacks of
the Gulf of Paria and waters along the southern coast of Trinidad, which they attributed to
“the effects of disturbance and noise associated with the development of extensive oil and
gas production facilities … and to heavy commercial shipping traffic since the turn of the
20th century” (p. 205). If this finding is borne out in the light of all other evidence, it
would represent one of the few empirical examples available of the outright loss of
cetacean “breeding” habitat from ocean urbanization.
Toothed Cetaceans
In terms of science and conservation, research on two species or species groups of
cetaceans in the WCR has particular prominence globally: the sperm whale (Physeter
macrocephalus) and the beaked whales (Ziphiidae). Ongoing studies of sperm whales
around Dominica by Hal Whitehead and his students from Dalhousie University promise
to add important insights on the species’ social structure and behavior, particularly when
used in comparative analyses with their results from the eastern Pacific. Of more
immediate applied importance is the diverse program of research on sperm whales in the
northern Gulf of Mexico that includes satellite telemetry, photo-identification, monitoring
of dive behavior and physiology, and controlled-exposure experimentation to assess the
effects of underwater sound (e.g., Miller et al. 2004a, 2004b; Thode et al. 2002). This
work’s significance derives from global concern about the effects of acoustic disturbance
on sperm (and other) whales, especially that from offshore oil and gas development.
Long-term studies of beaked whales have been undertaken in just two areas of the world
– The Gully off Nova Scotia, Canada (northern bottlenose whale, Hyperoodon
ampullatus), and the Bahamas (Blainville’s beaked whale, Mesoplodon densirostris). In
the latter area, the work of Claridge and Balcomb (2001) was key in documenting the
vulnerability of beaked whales exposed to military sonar under particular circumstances.
Given the general rarity of opportunities for observational studies of beaked whales, and
the high profile of the controversy surrounding the effects of high-intensity underwater
sound on this group of whales, it is important that research effort in the Bahamas be
maintained and, if possible, expanded.
Another point worth highlighting, although already noted by Ward et al. (2001:23),
concerns the habitat requirements of beaked whales. Contrary to the usual descriptions of
various species’ distributions as “cosmopolitan” or “worldwide” in deep offshore waters,
it appears that their distributions are considerably more specialized and thus limited. The
Bahamas studies provided the first good evidence of this for the mesoplodonts, as
4
summarized by Ward et al. There, Blainville’s beaked whales generally occur only in
depths between 200-1000 m and near areas with particular bottom topography. It should
be noted in this context that similarly analyses of habitat preferences of other odontocetes
have been conducted in the northern Gulf of Mexico (e.g., Baumgartner et al. 2001).
Thus, the WCR has become a focal region of research on several species, including the
beaked whales, the sperm whale, and several tropical to warm temperate delphinids.
The aforementioned 2004 workshop (Reeves et al. 2004) ranked taxonomic uncertainty
as high for killer whales (Orcinus sp.) and called for a global inventory of specimen
material for that genus. It seems clear from the records summarized by Ward et al. (2001)
that at least some of the killer whales in the WCR are mammal and sea turtle predators,
but in the absence of rigorous analysis of morphological, dietary, and other types of data
from the region, it remains impossible to judge whether more than one ecotype (and thus
possibly eventually subspecies or species) is present. A regional inventory of sighting,
stranding, and take records, perhaps followed by a directed effort to obtain and analyze
biological materials from killer whales in specific parts of the WCR (via biopsy), could
be a significant contribution to ongoing global analyses. The same can be said of
Blainville’s beaked whales and Cuvier’s beaked whales (Ziphius cavirostris), both of
which the workshop described as “warranting special attention to resolve taxonomic
uncertainty” (p. 10). Their vulnerability to underwater noise as well as entanglement in
drift gillnets was noted, as was the fact that Dalebout (2002) found strong evidence of
population structure in Cuvier’s beaked whale, suggesting that there could be isolated
regional populations. Its apparently widespread and regular occurrence in the WCR
makes Cuvier’s beaked whale a candidate for focused effort along the same lines as
mentioned above for killer whales.
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 (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.
Ranking
How should the various marine mammal species and populations in the WCR be ranked
as conservation priorities? One possibility is to develop a matrix that allows multiple
criteria to be taken into account. Such an approach could be pursued at two levels or in
two separate contexts – one of global biodiversity and the other at a regional scale. For
the first of these, the criteria could include:

Endemism, i.e., to what extent do a species’ or a population’s range and number
of individuals fall within the WCR?
5



Residency, i.e., does the population remain year-round in WCR waters? If not,
how critical is the WCR, as a migratory destination, to the population’s
persistence?
What is the officially recognized status of the species or population according to
global listing schemes, e.g., IUCN Red List, appendices or annexes of
conservation conventions? Such listings may provide useful guidance but should
not necessarily be accepted uncritically.
Potential for contributing to scientific understanding relevant to conservation (this
can refer to either a global or a regional level).
Another set of criteria could be developed at the regional level, to include:




Socio-economic importance, e.g., is the population subject to human use of any
kind (e.g., revenue from tourism or live-capture, as a food source)?
National biodiversity conservation policy, i.e., does a legal framework exist that
obligates authorities to take management action?
Known or suspected threats, e.g., deliberate exploitation (killing or live-capture),
offshore military or industrial activity, fisheries operating in the area (especially
gillnets or trawls). Such threats can be in the past, ongoing, or anticipated for the
near-term future.
Historical evidence suggests that the species is present in the region, but little or
no recent information exists on its status, i.e., there is high uncertainty.
It would be appropriate for the Action Plan workshop to consider these and other criteria,
and attempt to integrate them in setting priorities for proposed actions. The presumably
extinct monk seal is the only endemic marine mammal in the region. Populations
(subspecies?) of manatees probably would rank high on the basis of a scheme such as the
one proposed here. It seems likely that the humpback whale, possibly the Bryde’s whale,
the sperm whale, the common bottlenose dolphin, the short-finned pilot whale, and the
sperm whale would also rank relatively high based on current understanding. Several
others, such as some beaked whales, the killer whale, the clymene dolphin (Stenella
clymene), and the marine tucuxi (Sotalia fluviatilis guianensis), would likely rank high
according to at least some of the criteria.
References
Balcomb, K.C. and Claridge, D.E. 2001. Mass stranding of cetaceans caused by naval
sonar in the Bahamas. Bahamas Journal of Science 4:2-12.
Baumngartner, M.F., Mullin, K.D., May, L.N. and Leming, T.D. 2001. Cetacean habitats
in the northern Gulf of Mexico. Fishery Bulletin 99:219-239.
Boyd, I.L. and Stanfield, M.P. 1998. Circumstantial evidence for the presence of monk
seals in the West Indies. Oryx 32:310-316.
6
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.
Dalebout, M.L. 2002. Species identity, genetic diversity and molecular systematic
relationships among the Ziphiidae (beaked whales). Ph.D. thesis, School of Biological
Sciences, University of Auckland, New Zealand.
Mead, J.G. 1977. Records of sei and Bryde’s whales from the Atlantic coast of the United
States, the Gulf of Mexico, and the Caribbean. Report of the International Whaling
Commission (Special Issue) 1:113-116.
Miller, P.O. Miller, P.J.O., Johnson, M.P. and Tyack, P.L. 2004a. Sperm whale behaviour
indicates the use of echolocation click buzzes 'creaks' in prey capture. Proceedings of the
Royal Society of London B 271:2239-2247.
Miller, P.J.O., Johnson, M.P., Tyack, P.L. and Terray, E.A. 2004b. Swimming gaits,
passive drag and buoyancy of diving sperm whales Physeter macrocephalus. Journal of
Experimental Biology 207:1953-1967.
Price, W.S. 1985. Whaling in the Caribbean: historical perspective and update. Report fo
the International Whaling Commission 35:413-420.
Reeves, R.R. 2002. The origins and character of ‘aboriginal subsistence’ whaling: a
global review. Mammal Review 32:71-106.
Reeves, R.R., Perrin, W.F., Taylor, B.L., Baker, C.S. and Mesnick, S.L. (eds.). 2004.
Report of the Workshop on Shortcomings of Cetacean Taxonomy in Relation to Needs of
Conservation and Management, April 30 – May 2, 2004, La Jolla, California. NOAA
Technical Memorandum NMFS-SWFSC-363.
Swartz, S.L., Cole, T., McDonald, M.A., Hildebrand, J.A., Oleson, E.M., Martinez, A.,
Clapham, P.J., Barlow, J. and Jones, M.L. 2003. Acoustic and visual survey of humpback
whales (Megaptera novaeangliae) distribution in the eastern and southeastern Caribbean
Sea. Caribbean Journal of Science 39:195-208.
Thode, A., Mellinger, D.K., Stienessen, S., Martinez, A., and Mullin, K. 2002. Depthdependent acoustic features of diving sperm whales (Physeter macrocephalus) in the
Gulf of Mexico. Journal of the Acoustical Society of America 112:308-321.
Ward, N. and Moscrop, A. 1999. Marine mammals of the Wider Caribbean Region: a
preliminary review of their conservation status.
Ward, N., Moscrop, A. and Carlson, C. 2001. Elements for the development of a marine
mammal action plan for the Wider Caribbean: a review of marine mammal distribution.
7
8