The western North Atlantic population of the northern right whale (Eubalaena
glacialis) was severely depleted by whaling over the last century. Despite over fifty
years of protection, fewer than four hundred individuals are believed to exist in the
North Atlantic. Relatively little is known about the diving behavior, respiratory
physiology, or diel activity of these whales, although such information could be useful
in predicting population abundance and distribution in relation to food or
environmental variables. Dive behavior data can be collected visually, but collection
is limited to daylight hours, calm weather, and fortuitous encounters with study
animals. Satellite-monitored radio tags offer the opportunity to collect data on
individual whales' diving behavior continuously, over long distances and periods of
time, and at relatively low cost.
Thirteen North Atlantic right whales were tagged and monitored in the Gulf of
Maine between 1989 and 1991. One male was tagged in 1989; two adult males, six
adult females (two with calves) and one juvenile were tagged in 1990; one adult
female (with a calf) and two juveniles were tagged in 1991. The duration of
monitoring for the whales varied from <1 day to 43 days. Characteristics of the
radio tags were different over each year in order to evaluate different attachment
mechanisms and methods of collecting and summarizing data for dive duration, dive
frequency, and time submerged. These data were then used to describe the dive
behavior and to predict aspects of the respiratory physiology for these whales.
The number of dives, their duration, and the time submerged varied
considerably among individual whales and between years. Over all, the whales spent
79% of their time underwater. However, most dives were short (i.e., 95% were
<14 min; the mean dive duration was 92.3 sec), although dives of 30-40 min
duration were observed for several individuals. In general, the number of dives a
right whale made was inversely related to the average duration of its dives within a
time interval. Furthermore, over a given time interval, the number of times a whale
dove was a better predictor of the percent time it was submerged than was the
average duration of its dives.
There was no evidence of diel variation in dive behavior (i.e., number of
dives, average dive duration, or percent time submerged) among these whales. Age,
sex, and reproductive status may have affected dive behavior, although these trends
were not statistically significant due to the small number of study animals and
individual behavioral variability. Males tended to dive more often and averaged
shorter dives than females. Females with calves dove more often and averaged
shorter dives than females without calves. Juvenile females dove less often but
averaged longer dives than adult males or females with calves.
It was predicted that the aerobic dive limit of an "average" right whale was
approximately 14 min. Ninety-five percent of the dives recorded for the 11
monitored right whales were < 14 min. Furthermore, there was no evidence of
recuperative periods (i.e., prolonged periods at the surface) after long dives. These
observations were consistent with the idea that the North Atlantic right whales dove
within their aerobic scope. They further suggest that physiological parameters alone
probably have little influence on dive characteristics, except to set an upper limit on
the duration of a dive.
Satellite telemetry provides an opportunity to monitor the movements and
behavior of free-ranging animals, and overcome many of the short-comings associated
with traditional, human-based visual techniques for tracking and studying such
animals. Although the tags used in this study were prototypes and varied in their
design from year to year, several right whales were monitored simultaneously and
were tracked over thousands of kilometers. Advances in tag miniaturization,
attachment, and software will likely extend the time tags stay attached and the detail
of the behavioral and environmental variables that can be monitored. As testimony to
the power of this technology, this application of satellite telemetry to monitor great
whales yielded one of the most extensive, long-term, continuously-monitored data sets
yet recorded on the diving behavior of a baleen whale. / Graduation date: 1993
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36164 |
| Date | 07 December 1992 |
| Creators | Nieukirk, Sharon L. |
| Contributors | Mate, Bruce R. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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