ACS Research Committee Report

HABITAT OF BOTOS AND TUCUXIS
Source: Martin, A.R., da Silva, V.M.F., and Salmon, D.L. 2004. Riverine habitat preferences of botos (Inia geoffrensis) and tucuxis (Sotalia fluviatilis) in the central Amazon. Mar. Mamm. Sci. 20 (2): 189-200.

Botos and tucuxi dolphins are native to the Amazon river in South America. Surveys for these dolphins conducted in two large rivers in western Brazil found that 99% of boto groups contained one to four dolphins, whereas 98% of tucuxi groups contained one to six individuals. The dolphins displayed some small habitat preferences, but similar trends were seen between the two species. Botos were found in relatively high densities along river margins, primarily in four habitats: beach, floating vegetation, confluence (the mouth of a channel joining a big river), and bay (shallow and dry at low water). Tucuxi were at lower densities in river margins than botos. Tucuxi had the highest density in waterway junctions and an intermediate density in bay and floating vegetation habitats. In general, both species preferred "low current" habitats, including bay, floating vegetation, and confluence, over the higher flow of the central river areas. Presumably, this preference is because the dolphins do not have to expend as much energy to maintain their position and these areas are preferred habitat for fish prey. Confluences are used by fish migrating along rivers because these areas are highly productive and provide underwater structure for refuge. Floating vegetation also provides refuge for fish and these areas are used by the dolphins for foraging. The preference for low current areas is more pronounced for botos, which are smaller dolphins and would be more affected by high current.    

GEOGRAPHIC GENETIC VARIATION OF FRANCISCANA DOLPHINS IN SOUTH AMERICA
Source: Lazaro, M., Lessa, E.P., and Hamilton, H. 2004. Geographic genetic structure in the franciscana dolphin (Pontoporia blainvillei). Mar. Mamm. Sci. 20 (2): 201-214.

Franciscana are small dolphins that live in the near shore waters of the southwest Atlantic coast of Brazil, Uruguay, and Argentina. Previous research indicated that there may be two different populations of franciscana separated geographically north and south of Santa Catarina Island in Brazil. Samples for this study were collected from dead animals found along the South American coast. Genetic analysis yielded evidence of two distinct groups, one in northern Brazil and one in southern Brazil, Uruguay, and Argentina. There were no shared haplotypes between the northern and southern population, but haplotypes were shared amongst all southern locations. The genetic differences indicated a recent isolation of the northern and southern groups. The isolation appeared to be due to distance, because gene flow was higher in adjacent sample locations and decreased as distance increased.   

DETERMINING BLUBBER FATTY ACID COMPOSITION
Source: Thiemann, G.W., Budge, S.M., and Iverson, S.J. 2004. Determining blubber fatty acid composition: a comparison of in situ direct and traditional methods. Mar. Mamm. Sci. 20 (2): 284-295.

Fatty acids in marine mammal blubber can demonstrate their diet and foraging ecology; the fatty acid patterns in the prey influence lipid (fat) stores. In this study, full-depth blubber biopsies were collected from gray seals and beluga whale carcasses. The blubber was not homogenous over its depth. The inner layer of seal blubber more reflects the animal's recent diet, but there is significant turnover and addition of fatty acids throughout the blubber layer. In cetaceans (whales, dolphins, and porpoises), the inner blubber layer is the most metabolically active and is where most of the fatty acids are stored. Cetacean blubber overall is more stratified, or layered, than seal blubber. The blubber samples were sub-sampled in different locations, including just below the skin. The sample just below the skin, or any other single sample, did not reflect the fatty acid makeup of the entire blubber layer, indicating that biopsy samples collected from living animals may not be completely accurate for fatty acid analysis. In seals, the inner blubber layer shows diet changes more quickly, but even the outer layers will show diet change within ten days of ingestion of prey. In cetaceans, only the inner half of the blubber may truly be reflective of diet.    

SIGHTINGS OF BOTTLENOSE DOLPHINS AND HARBOR PORPOISE IN THE MORAY FIRTH, SCOTLAND
Source: Thompson, P., White, S., and Dickson, E. 2004. Co-variation in the probabilities of sighting harbor porpoises and bottlenose dolphins. Mar. Mamm. Sci. 20 (2): 322-328.

Violent interactions have been witnessed from bottlenose dolphins to harbor porpoise in the Moray Firth, Scotland. The function of this aggression is unknown. Surveys were conducted from dolphin watching trips. In 21.4% of surveys, only bottlenose dolphins were sighted; in 25.8%, only harbor porpoise were sighted; and in only 2.7% of surveys both species were sighted. In general, the harbor porpoise were more often seen offshore, whereas the bottlenose dolphins were more coastal. There was a fine-scale segregation, both geographic and temporal, of the two species. The probability of sighting harbor porpoise was lower in the presence of bottlenose dolphins. This segregation could be for several reasons: the two species may use different habitats or prey, they may separate to avoid competition for resources, or they may avoid each other for a reason related to the aggressive interactions.    

GRAY WHALES WITHOUT TAIL FLUKES
Source: Urban, J.R., de Sahagun, V.F., Jones, M.L., Swartz, S.L., Mate, B., Gomez-Gallardo, A., and Guerrero-Ruiz, M. 2004. Gray whales with loss of flukes adapt and survive. Mar. Mamm. Sci. 20 (2): 335-338.

In 1982, a gray whale without tail flukes was sighted with a dependent calf in Laguna San Ignacio, Mexico. The whale dove by sloping its head down and rolling almost 90° to one side and swing the broad side of the tail stock laterally. In 1997, a fluke-less gray whale was sighted in the Laguna, but it was unknown if this was the same whale. This whale could swim up to 4-5 km/hr; when it surfaced, it brought its head above the surface and to dive it lifted the end of the tail stock above the water. There were also reports of sightings of fluke-less gray whales from 1976, 1989, and 1992. The scarring on some of these whales suggests a gradual loss of the fluke, perhaps from an entanglement in fishing gear.    

HUMPBACK WHALE SINGING RECORDED ON A NORTH ATLANTIC FEEDING GROUND
Source: Clark, C.W. and Clapham, P.J. 2004. Acoustic monitorinig on a humpback whale (Megaptera novaeangliae) feeding ground shows continual singing into late spring. Proc. R. Soc. Lond. B 271: 1051-1057.

Six bottom acoustic recorders, called "pop-ups," were placed in western Georges Bank in the Gulf of Maine, a feeding ground for North Atlantic humpback whales. These pop-ups were primarily used for the purpose of detecting North Atlantic right whales, but they also recorded sounds from humpback whales. From 14 May to 7 June, 2000, humpback whale song was recorded on every day. During the period 14 to 30 May, song was detected during every hour of the day. The percentage of hours of song decreased to 58% by 7 June. The 21 May had the highest number of singers, with 12 hours of recordings with one singer, 11 hours with two singers, and one hour with three singers. The number of singers also decreased by 7 June. Aerial survey data verified the presence of humpback whales during this period. Humpback whale song appears to be more common in the feeding grounds than originally thought. A commonly accepted hypothesis is that song is produced by males to attract females for mating purposes. Perhaps the use of song during the feeding season indicates mating continuing past the end of the breeding season in the Caribbean. Whaling data shows that there are some outliers in fetal length, suggesting mating outside of the breeding season may occur on a low level. On the other hand, singing is affected by testosterone levels, so it is possible that fall and spring singing is simply resulting from residual hormone levels.