Robin W. Baird

Deep–diving behaviour of the northern bottlenose whale, Hyperoodon ampullatus (Cetacea: Ziphiidae)

Using suction–cup attached time–depth recorder/VHF radio tags, we have obtained the first diving data on northern bottlenose whales (Hyperoodon ampullatus), the first such data on any species within the family Ziphiidae. Two deployments in 1997 on northern bottlenose whales in a submarine canyon off Nova Scotia demonstrated their exceptional diving ability, with dives approximately every 80 min to over 800 m (maximum 1453 m), and up to 70 min in duration. Sonar traces of non–tagged, diving bottlenose whales in 1996 and 1997 suggest that such deep dives are not unusual. This combined evidence leads us to hypothesize that these whales may make greater use of deep portions of the water column than any other mammal so far studied. Many of the recorded dives of the tagged animals were to, or close to, the sea floor, consistent with benthic or bathypelagic foraging. A lack of correlation between dive times and surface intervals suggests that the dives were predominately aerobic.

Low worldwide genetic diversity in the killer whale (Orcinus orca): implications for demographic history.

A low level of genetic variation in mammalian populations where the census population size is relatively large has been attributed to various factors, such as a naturally small effective population size, historical bottlenecks and social behaviour. The killer whale (Orcinus orca) is an abundant, highly social species with reduced genetic variation. We find no consistent geographical pattern of global diversity and no mtDNA variation within some regional populations. The regional lack of variation is likely to be due to the strict matrilineal expansion of local populations. The worldwide pattern and paucity of diversity may indicate a historical bottleneck as an additional factor.

Possible indirect interactions between transient and resident killer whales: implications for the evolution of foraging specializations in the genus Orcinus

SummaryTwo distinct forms of killer whale (Orcinus orca) occur off the coast of British Columbia, Alaska and Washington State. These have different diets, and may be reproductively isolated. Because the primary food of transient whales (pinnipeds) is a potential competitor for the primary food of resident whales (salmon), or for the smaller fishes on which salmon feed, there should be an indirect interaction between the two forms of killer whale. We use simple mathematical models to show that this interaction will be either of a “plus-minus” type, or a “plus-plus” type (indirect mutualism), depending on whether or not pinnipeds and residents are on the same trophic level. In the case of the “plus-minus” interaction, increasing the population density or improving the environmental conditions of transients will increase the population density of residents, while increasing resident populations will reduce the equilibrium population size of transients. In the case of the “plus-plus” interaction, increasing the population density or improving the environmental conditions of transients will increase the population density of residents, while increasing resident populations will reduce the equilibrium population size of transients. In the case of the “plus-plus” interaction, increasing the population density or improving the environmental conditions of transients will increase the population density of residents, and vice versa. Such effects may not be currently manifest due to reduced populations at most levels in the food web. Regardless, considering such indirect interactions may be important for the management of many of the species involved, and can also provide a valuable framework for examining the evolution of the two forms of killer whales. Frequency-dependent indirect interactions, acting in concert with density-dependence within populations and disruptive selection on prey-type specific foraging characteristics, may have favoured reproductive isolation of the two forms of killer whales. We suggest that these two forms of whale are in the process of speciating, i.e., the two forms are incipient species.

Levels of organochlorine compounds, including PCDDS and PCDFS, in the blubber of cetaceans from the west coast of North America

Abstract Levels of organochlorine compounds (PCDD, PCDF, PCB and organochlorine pesticides) were determined in cetaceans collected from the west coast of North America between 1986 and 1989. The samples included gray whale (Eschrichtius robustus), killer whale (Orcinus orca), false killer whale (Pseudorca crassidens), Rissos dolphin (Grampus griseus) and Dalls porpoise (Phocoenoides dalli) collected in British Columbia, and harbour porpoises (Phocoena phocoena) collected in British Columbia and central California. TCDD and TCDF levels ranged from 1 to 8 ng kg−1 and 2.0 to 109 ng kg−1, respectively. The highest levels of PCDDs were found in the harbour porpoises; the levels of 1,2,3,6,7,8-HxCDD in the samples from Victoria, Campbell River and Qualicum River were 128, 128 and 62 ng kg−1, respectively. Five other 2,3,7,8-substituted dioxins and dibenzofurans were detected in the cetaceans at levels ranging from 1 to 10 ng kg−1. In addition to the 2,3,7,8-substituted congeners, several non 2,3,7,8-substituted congeners were detected. The patterns of the PCDDs and PCDFs in the British Columbia porpoises were consistent with implication of chlorophenols as the source of the PCDDs and PCDFs, which were either present in wood chips used in bleached kraft paper mills, or came from direct contamination by chlorophenols. No PCDDs or PCDFs were detected in the California samples. One false killer whale sample had exceptionally high levels of DDT compounds (1700 mg kg−1 DDE, 120 mg kg−1 DDT and 40 mg kg−1 o,p′-DDT) and Toxaphene (89 mg kg−1). PCB levels in the cetaceans were highest in the false and killer whales (22 to 46 mg kg−1 GM), and lowest in the Rissos dolphin (1.7 mg kg−1). Levels of DDE in the British Columbia harbour porpoises were 6.0 mg kg−1, and probably reflect the accumulation of global background levels of DDE.

Ingestion of Plastic and Unusual Prey by a Juvenile Harbour Porpoise

Considerable quantities of plastic debris are found throughout the world’s oceans (e.g., Dufault and Whitehead, 1994), and may impact a diversity of species, including marine turtles, birds and mammals (Laist, 1997). Since many species of whales and dolphins live in waters far from shore, and may sink upon death, opportunities to record instances of ingestion of marine debris by cetaceans are infrequent. Despite this, there are several cases where ingestion of plastic or other marine debris has been documented for cetaceans, with published reports existing for 21 species of odontocetes (Laist, 1997). We know of an additional five species of odontocetes for which marine debris ingestion has been documented: the killer whale (Orcinus orca; K. Evans, pers. comm.), northern bottlenose whale (Hyperoodon ampullatus; R. Michaud, pers. comm..), finless porpoise (Neophocoena phocoenoides; C. Parsons, pers. comm.), white-beaked dolphin (Lagenorhynchus albirostris; R. Kastelein, pers. comm.), and pantropical spotted dolphin (Stenella attenuata; K. Robertson, pers. comm.). For most species of odontocetes, only one or a few records have been reported. Here we document the third reported case of plastic ingestion by a harbour porpoise (Phocoena phocoena), and discuss factors that might have contributed to its ingestion.

Organochlorine concentrations in resident bottlenose dolphins (Tursiops truncatus) in the Shannon estuary, Ireland

S.D. Berrow *, B. Mchugh , D. Glynn , E. Mcgovern , K.M. Parsons , R.W. Baird , S.K. Hooker e a Shannon Dolphin and Wildlife Foundation, Merchants Quay, Co. Clare, Kilrush, Ireland b Marine Institute, Abbotstown, Castleknock, Dublin 15, Ireland c Department of Zoology, University of Aberdeen, Tillydrone Avenue, Aberdeen AB9 2TN, UK d Department of Biology, Dalhousie University, Halifax, NS, Canada B3M 4J1 e British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK