Killer Whales

From: Pieter Arend Folkens (animalbytes@earthlink.net)
Date: Sun Nov 18 2001 - 03:00:29 EST


>1. Do they spend more time in cool or warm water?

There are several races of killer whales around the world. Just like
races of human beings, there is a preference for different
environments from warm to cold. The Inupiat people of the North Slope
and Laps from Finland would be uncomfortable on a tropical island or
in equatorial Africa. Likewise, Baka and Massai tribes from Africa
would not do well in Nunavut or Scandinavia. So it is also with with
killer whales. Some races of killer whales stay pretty much south of
the Antarctic Convergence and are often found at the edge of the pack
ice in cold water (<45F). Another group of killer whales is quite
satisfied living in the warm Sea of Cortez (Gulf of California)
(>65F). Just like in humans, the different races of orcas also have
differing physical appearances. It has been suggested that an
Antarctic race of orcas should be designated a separate species as
Orcinus glacialis.

>2. Are they prone to any diseases?

All mammals are prone to diseases. Since cetaceans (whales and
dolphins) evolved from a common ancestor with the artiodactyls
(even-toed ungulates like hippos, cattle, and sheep) they are prone
to some diseases similar to those animals. Dolphins in general are
susceptible to parasites, especially of the lungs, stomach, and ears.

>3. Are they becoming endangered?

Some populations are, others are not. The main threat to killer
whales is the declining quality of the habitat they live in (ocean
pollution) and over exploitation of fishing resources.

> 4.Is global warming affecting them or their habitat?

Global warming (climate change) has a distinct effect on whales. The
effect is more profound on the "lower" forms of animals, such as zoo
plankton, which are the basis of the food chain. For example, during
cyclic warm water periods in the North Pacific (known as El Nio
events), the water temperature drops several degrees. This warming
causes a decrease (actually a complete cessation) of upwelling. The
zooplankton die off, the fish that feed on them leave, and there is
no food for the whales (and other "higher" sea life including birds).
When a population is stressed in this manner (lack of food), one of
the first obvious effects is breeding failure. There are fewer calves
born, and of those that are born, few survive.

I will give you a little perspective on this climate change issue.
The first whales (called archaeocetes, 40-50 million years ago) lived
in a warm equitorial sea called the Tethys Sea that spanned west from
southern Asia to southeast North America. (The Mediterranean Sea is
the remnant of that ancient sea.) Near the Eocene/Oligocene boundary
(about 39 million years ago), Antarctica separated from South America
and opened up the circumpolar Antarctic Convergence. This had the
effect of changing currents and cooling the world's oceans. The
Archaeocetes could not handle this cooling. At least two and maybe
more forms of archaeocetes gradually modified their physiology and
anatomy through evolution to deal with these changes. During the
ensuing 40 million years they eventually became the modern whales.
There were many fluctuations in the world climate, ranging from cold
ice ages to long periods during which there was no ice anywhere on
earth. The diversity of whales fluctuated as some species survived,
others perished, and others evolved.

In the discussion of the present global warming trend, it is
important to note that during the recent past of human history
(roughly the previous 12,000 years, called the Holocene) the earth
has warmed and cooled several times. In fact, the average sea level
during that time was 1.5 meters higher than it is today. This means
the earth must warm sufficiently to melt enough polar ice to raise
the sea level world wide by 1.5 meters to reach the average during
the past 8,000 years. The maximum warm period during this time saw
the sea level about 3 meters higher than it is now. The most recent
maximum cold snap hit a low around 800 years ago. Our present warming
trend is not severe (but obvious), and was not caused by humans. It
is a natural climate change.

> 5. Why do their fins fall over in captivity?

The dorsal fin of adult male killer whales is tall. It maintains its
shape in healthy animals because the animal swims alot, often at a
good speed, and usually straight. In an inadequate captive
environment, the orca does not swim as much, almost never very fast,
and cannot go straight for very long. This causes the connective
tissue supporting the dorsal fin to atrophy. The weight of the tall
fin succumbs to gravity, and then gets stuck in the fallen-over
position.

> 6. Why do they need to migrate?

Killer whales do not really migrate. A migration is generally defined
as the seasonal movement of a group typically around breeding and
feeding. Killer whales "roam" over a defined area. Some orcas may
travel great distances as their home range, while others have smaller
ranges. Within those ranges, the movements can be associated with
seasonal increases in food. For example, a pod of orcas in Monterey
Bay shows up at the edge of the Monterey Sea Canyon each spring to
wait for gray whale calves. The rest of the year they can be almost
anywhere along the California coast.

> 7.Do they migrate to cooler or warmer waters?
> 8.Where do they migrate to?

A particular pod will typically remain in a comfortable water habitat
that does not fluctuate too greatly. However, a transient pod is
known to travel from the cool temperate Vancouver area to the warm
temperate waters off Baja. This was not a migration, per se, but
simply a movement of the group, perhaps to find new hunting grounds.

> 9.What is a killer whales average body temperature?

I don't know off the top of my head, but I may recall that it is
slightly higher than that of humans (98.6F).

Cheers,

Pieter Folkens
Alaska Whale Foundation

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