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Faculty Page - Sean K. Todd, Ph.D.


Current Research Activities
This page outlines Dr. Sean Todd's current research interests. Much of the work is performed either in cooperation with the students and staff of Allied Whale at College of the Atlantic, or as collaborations with members of the Whale Research Group at Memorial University of Newfoundland. Information on these pages is not public domain. Any quotes pertaining to information on this page require permission of Dr. Sean Todd at College of the Atlantic before public release.

Foraging Ecology and stable isotope analysis

Impacts of noise on marine mammals

EKGs of balaenopterids

Predicting distribution of cetaceans

Pinniped behavioral ecology

Marine mammal-net collisions and entrapments

 

 

Foraging Ecology and stable isotope analysis

Humpback, finback whales and minke whales are balaenopterid species, feeding on large schools of herring, capelin, sandlance or krill, depending on prey availability. Locally, balaenopterids may have a significant impact on the ecosystem; however, such impact is difficult to quantify in the absence of reliable diet data. Traditionally, studies of baleen whale diet are confined to examinations of gut contents post mortem. In the absence of large-scale whaling, researchers must design new investigatory tools to examine diet without killing the animal.

One such tool is stable isotope analysis (SIA). This technique, originally developed by geochemists, examines a consumer's storage tissues for chemical signatures unique to prey species. These signatures are created by the ratio of certain stable isotopes to their more abundant forms. In biological studies, the most common isotope ratios used are 13C/12C, and 15N/14N.

Allied Whale has recently embarked on a five-year study to examine balaenopterid diet using SIA. Skin samples are taken from photo-identified animals using a biopsy dart delivered by a crossbow, shown here.

Previous development of this technique in Newfoundland has revealed some interesting relationships previously unquantified. For example,

 

 

Further references on Stable Isotope Analysis:

Chisholm BS, Nelson DE, Schwarcz HP (1982) Stable-carbon isotope ratios as a measure of marine versus terrestrial protein in ancient diets. Science 216:1131-1132

Hobson KA, Sease JL, Merrick RL, Piatt JF (1997) Investigating trophic relationships of pinnipeds in Alaska and Washington using stable isotope ratios of nitrogen and carbon. Marine Mammal Science 13:114-132

Ostrom PH, Lien J, Macko SA (1993) Evaluation of the feeding of Sowerby's beaked whale, Mesoplodon bidens, based on isotopic comparisons among northwestern Atlantic cetaceans. Canadian Journal of Zoology 71:858-861

Peterson BJ, Fry B (1987) Stable isotopes in ecosystem studies. Annual Review of Ecology and Systematics 18:293-320

Schell DM, Saupe SM, Haubenstock N (1989) Bowhead whale (Balaena mysticetus) growth and feeding as estimated by d13C techniques. Marine Biology (Berlin) 103:433-443

Todd S, Ostrom P, Lien J, Abrajano J (1997) Use of biopsy samples of humpback whale (Megaptera novaeangliae) skin for stable isotope (d13C) determination. Journal of Northwest Atlantic Fishery Science 22:71-76

Todd SK (1998) Feeding ecology of humpback whales (Megaptera novaeangliae) in the Northwest Atlantic: Evidence from 13C and 15N stable isotopes. Ph.D. Thesis: Biopsychology Programme. Memorial University of Newfoundland, St. John's, Newfoundland

Wainwright SC, Fogarty MJ, Greenfield RC, Fry B (1993) Long-term changes in the Georges Bank food web trends in stable isotopic compositions of fish scales. Marine Biology (Berlin) 115:481-493

Walker JL, Macko SA (1999) Dietary studies of marine mammals using stable carbon and nitrogen isotopic ratios of teeth. Marine Mammal Science 15:314-334.

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Impacts of noise on marine mammals

 

Marine mammals have evolved over millions years in a relatively quiet ocean. However, the dawn of the Industrial Age irreversibly changed the nature of sound in the ocean. Today, the ocean is a complex acoustic environment, dominated by anthropogenic noise. In some cases, this noise may have no impact. In other cases, such noise may act to mask marine mammal communication and environmental interrogation (using echolocation). In the most extreme case, noise may physically harm an animal, causing deafness, or in cases of severe concussion, death. The picture to the left shows a research team extracting the earbones from a dead humpback whale for further examination.

Large vessels capable of across-ocean passage emit significant low frequency acoustic signatures. The impact of such signatures on marine mammals, and other marine life, is largely unsubstantiated.

In some cases, ship signatures may act to inform marine mammals of a vessel in the local vicinity. In such cases such emission may be preferable to minimize the risk of ship-marine mammal collisions (shipstrikes). Allied Whale recently completed a report centered on a mathematical model that examines the detectability of high-speed ferries, based on their acoustic signatures. While the model still requires further development, initial findings suggest that:

 

 

Further references on marine mammals and noise

Ketten DR (1995) Estimates of blast injury and acoustic trauma zones for marine mammals from underwater explosions. In: Kastelein RA, Thomas JA, Nachtigall PE (eds) Sensory Sytems of Aquatic Mammals. De Spil, Woerdwen, Netherlands, pp 391-407

Ketten DR, Lien J, Todd S (1993) Blast injury in humpback whale ears: Evidence and implications. (abstr. in) Journal of the Acoustical Society of America 94:1849-1850

Richardson WJ, Greene Jr. CR, Malme CI, Thomson DH (1995) Marine Mammals and Noise. Academic Press, San Diego

Todd S, Stevick P, Lien J, Marques F, Ketten D (1996) Behavioural effects of exposure to underwater explosions in humpback whales (Megaptera novaeangliae). Canadian Journal of Zoology 74:1661-1672

Todd SK, Damon J (1998) Modeling the effects of high-speed vessels operating in critical cetacean habitat. (abstr.) in the proceedings of the 13th Biennial Conference on the Biology of Marine Mammals, Maui, HW.

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EKGs of balaenopterids

Many physiological studies require a knowledge of an animal's cardiac output, stroke rate and EKG. EKGs of large baleen whales is logistically difficult, but has been successfully performed by a collaborative partnership between the Whale Research Group (Memorial University of Newfoundland), Dr. Fritz Meijler of the Cardiac Institute in Utrecht, Netherlands, and Medtronics Inc, Minnesota. By using a modified Holter monitor, EKGs were recorded from fishing gear-restrained individuals. Data were collected from humpback (shown here) and blue whales, belugas and harbor porpoise. Findings include that:

 

 

Further references on cetacean heart rate

Kanwisher J, Senft A (1960) Physiological measurements on a live whale. Science 121:1379-1380

Meijler FL, Wittkampf FHM, Brennen KR, Baker V, Wassenaar C, Bakken EE (1992) The electrocardiogram of the humpback whale (Megaptera novaeangliae) with specific reference to atrioventricular transmission and ventricular excitation. Journal of the American Colleges of Cardiology 20:475-479

Todd S, Meijler FL, Lien J, Brennen K (1993) A comparison of ECGs taken from selected cetaceans. (abstr. in) the Proceedings of the 10th Biennial Conference on the Biology of Marine Mammals, Galveston, Texas.

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Predicting distribution of cetaceans

 

Cetacean distribution during the summer is usually a function of prey availability, which in turn is a function of prevalent oceanographic conditions. For example, abundance of marine mammals on the Inner Schoodic Ridges, and around Mount Desert Rock, is thought to be a function of upwelling events.

Allied Whale, during its regular research season, is committed to locating groupings of marine mammals using GPS, and correlating such sightings with local oceanogarphic conditions, including sea surface temperature, temperature profiles, and bathymetry. This image shows an Allied Whale team collecting such data. The intent of this data collection is to create a GIS database that will allow is to better understand marine mammal distribution, and to be able to predict it.

 

 

Further readings in predicting cetacean distribution

Uz, O. and Todd, S. K. 1999. Correlations between cetaceans and biological oceanography in the northern Gulf of Maine. (abstr. in) the Proceedings of the 13th Biennial Conference on the Biology of Marine Mammals, Maui, HW Dec. 1999.

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Pinniped behavioral ecology

 

Mount Desert Rock is home to a colony of harbor and grey seals. At peak season, Mount Desert Rock is home to a colony in excess of 1000 seals. A majority of this colony consist of harbor seals (Phoca vitulina), with some grey seals (Halichoerus grypus). The grey seal is a substantially larger, and more aggressive animal, whose population sze appears to be growing. Coordinated by Steve Renner, a graduate student from University of Maine, Orono, researchers at Mount Desert Rock are examining the behavioral reactions between the two species, to examine if harbor seals are gradually being displaced. Other collaborations to investigate pinniped biology are currently being discussed, including an examination of contaminant loading in seal blubber, and a review of interactions between seals and the local lobster industry

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Marine mammal-net collisions and entrapments

 

Baleen whales, in particular humpback and northern right whales, can become entangled in fishing gear. Such collisions are potentially fatal to the animal, and can cost the fisherman significant time and money in repairs. This image shows a humpback whale entrapped around the flipper by a fishing gear line and a buoy.

Working in Newfoundland, the Whale Research Group at Memorial University discovered that certain nets are acoustically invisible, and are thus more prone to be hit by whales. Acting on this knowledge, a series of net 'alarms' were developed and tested on nets. These alarms appear to substantially reduce the risks of collision.

 

 

 

Further readings on whale-net entrapments

Lien J (1994) Entrapments of large cetaceans in passive inshore fishing gear in Newfoundland and Labrador (1979-1990). In: Donovan G, Perrin WF, Barlow J (eds) Gillnets and Cetaceans. International Whaling Commission Special Publication 15. International Whaling Commission, Cambridge, pp 149-157.

Lien J, Barney W, Todd S, Seton R, Guzzwell J (1992) Field tests of acoustic devices for codtraps designed to minimize collisions by large whales. Whale Research Group unpublished report.

Lien J, Todd S, Guigné JY (1991) Inferences about perception in large cetaceans, especially humpback whales, from incidental catches in fixed fishing gear, enhancement of nets by "alarm" devices, and the acoustics of fishing gear. In: Thomas J, Kastelein R (eds) Sensory Abilities in Cetaceans; Laboratory and Field Evidence. Plenum, New York, pp 347-362

Todd S, Lien J, Verhulst A (1992) Orientation of humpback (Megaptera novaeangliae) and minke (Balaenoptera acutorostrata) whales to acoustic alarm devices designed to reduce entrapment in fishing gear. In: Thomas JA, Kastelein RA, Supin AY (eds) Marine Mammal Sensory Systems. Plenum Press, New York, pp 727-739

Todd SK (1991) The acoustics of fishing gear; possible relationships to baleen whale entrapment. M.Sc. thesis: Memorial University of Newfoundland, St. John's, Newfoundland, 213pp.

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