ACS Research Committee Report

MALE BOTTLENOSE DOLPHIN ASSOCIATION IN SARASOTA, FL
Source: Owen, E.C.G., Wells, R.S., and S. Hofmann. 2002. Ranging and association patterns of paired and unpaired adult male Atlantic bottlenose dolphins, Tursiops truncatus, in Sarasota, Florida, provide no evidence for alternative male strategies. Canadian Journal of Zoology. 80: 2072-2089.

This study examines patterns of ranging and association among paired and unpaired adult male bottlenose dolphins near Sarasota, FL. Previous studies have documented general patterns of association for adult males, but a more detailed examination of interactions of adult males with both females and other adult males required a larger long-term dataset. The 8-year study found that 57% of the males at least 7 years old were paired and the remainder unpaired. They found a strong correlation between age and proportion of males paired, concluding that the majority of unpaired males are either too young to form a pair bond or their partner has died and they haven't formed a new bond. They suggest that unpaired males may be an intermediate stage, rather than an alternative strategy. This study also found that males do not generally associate with males other than their partners. This is in contrast to male alliances found in Shark Bay (see below). Male alliances such as these pairs are hypothesized to increase mating opportunities. For example, in pairs they may be able to range farther and may then encounter more females. They may also be better able to separate or herd females away from groups. Females may prefer a male that is in a synchronized pair. Finally, males in pairs may be able to out-compete other males (paired or unpaired) and "guard" their mates. This study found that paired males had a significantly larger overall ranging areas and core areas than unpaired males, which supports the hypothesis that pairs may range farther. The researchers feel that additional demographic analyses is needed to conclude whether or not paired males are the "norm" and if unpaired males are another strategy or an intermediate stage.    

MALE BOTTLENOSE DOLPHIN ASSOCIATION IN AUSTRALIA
Source: Krutzen, M., Sherwin, W.B., Connor, R.C., Barre, L.M., Van de Casteele, T., Mann, J., and R. Brooks. 2002. Contrasting relatedness patterns in bottlenose dolphins (Tursiops truncatus) with different alliance strategies. The Royal Society. (Published online).

Long-term studies on bottlenose dolphins in Shark Bay, Australia have found that the males have one of the most complex societies outside humans. Studies have revealed two broad mating strategies. The first involves stable, "first order", pairs and trios that herd individual females that are ready to mate. The second, "second order", consists of teams of "first order" alliances (5-6 individuals) joining together against rivals in competition for the females. Another potential strategy, or "super alliance", involves roughly 14 individuals in varying pairs and trios, but these groupings lack the stable associations of either the first or second order alliances. This study examined the relatedness of the dolphins found in each type of social grouping. They found that males in stable first and second order alliances are often strongly related, and therefore may gain inclusive fitness benefits from alliance membership. However, individuals found in a super-alliance were no more closely related than expected by chance. The researchers feel that within this one population and one sex, there is more than one evolutionarily stable strategy.    

AGE DETERMINATION OF MYSTICETE WHALES USING DISEQUILIBRIA OF LEAD AND RADIUM
Source: Kastelle, C.R., Shelden K.E.W., and D.K. Kimura. 2003. Age determination of mysticete whales using 210Pb/226Ra disequilibria. Can. J. Zool./Rev. Can. Zool. 81(1); 21-32

Radium (226Ra) and its progeny Lead (210Pb) are found and retained in the tympanic bullae of some mysticete whales. The disequilibrium of the two components may be used as a chronometer in radiometric aging. Accurate age determination if fundamental to the study of population structure and individual growth rates of mysticetes. This study examined samples from 5 gray whales and two bowhead whales. They found that the ratio of lead and radium can possibly be used to estimate ages in gray whales, but successful application to bowhead whales is doubtful.    

INCIDENTAL GRAY WHALE MORTALITIES CAUSED BY FISHING OPERATIONS
Source: Baird, R.W., Stacey, P.J., Duffus, D.A., and K.M. Langelier. 2002. An evaluation of gray whale (Eschrichtius robustus) mortality incidental to fishing operations in British Columbia, Canada. J. Cetacean. Res. Manage. 4(3): 289-296.

This paper evaluates gray whale mortality incidental to fishing operations in British Columbia. The researchers mailed a questionnaire survey to all commercial fishing license holders in the province and also reviewed records of incidental catches, strandings, and dead floating animals. Only 15.8% of the questionnaires (848 of 5375) were returned which causes some bias in their results. Based on other published and non-published reports, they extrapolated that 27% of the dead gray whales reported in BC die incidentally in fisheries. Collisions with fishing gear are estimated to occur approximately 20 times per year. They also estimate an annual mortality of 2 animals per year. Taking the biases of their information into account, they feel that the estimated mortality levels are small relative to the population size.    

USING PHOTO-IDENTIFICATION TO MONITOR ENTANGLEMENTS IN THE GULF OF MAINE
Source: Robbins, J. and D.K. Mattlia. 2001. Monitoring entanglements of humpback whales (Megaptera novaengliae) in the Gulf of Maine on the basis of caudal peduncle scarring. Unpublished report to the Scientific Committee of the International Whaling Commission. SC/53/NAH25. 14pp.

Entanglements in fishing gear are a source of injury and mortality of humpbacks in the Gulf of Maine. The caudal peduncle, or tailstock, is commonly implicated in these entanglements. Since this body part is consistently presented during terminal dives, photographs of this area can be used to examine evidence of entanglement-related scarring. This two-year study examined photographs of 261 humpbacks and the images were blind coded to reflect the presence or absence of wrapping scars, notches and other injuries that were believed to be entanglement related. Scars along the caudal peduncle were found to be fairly permanent, generally remaining diagnostic for more than a year, even when caused by short-term or minor entanglements. Results found that males were more likely than females to exhibit entanglement-related scars. This may reflect different foraging strategies between the genders. Yearlings were at highest risk, although whales continued to become entangled when mature. Younger animals generally spend more time in higher latitudes than adults, which increases the chances of entanglement. Calves were at a significantly lower risk than all other classes. Because calves nurse, this indicates that animals may be at greatest risk of entanglement when they are foraging or feeding. However, it may also be that mothers limit their calves' interactions with gear by either avoiding areas or remaining resident in fewer areas. On the whole, females with evidence of prior entanglement produced significantly fewer calves during the time of study compared to females with no evidence of prior entanglement. Thirty one percent of the animals re-sampled acquired new scars during the study period, which indicates a fairly high level of annual entanglements, major and minor. Evidence shows that 1-2% of the population becomes severely entangled each year. Based on known entanglements, the study also proposes that only 3% of these entanglements are reported each year, and concludes that preventative measures need to be focused on rather than human intervention.