|Dr. Kenneth Norris|
“These efforts have been wonderful adventures in field science,
complete with all the pleasures and trials of finding a place
and time where we could hope to see how a wild dolphin lives.
We found our window to their world along the shores of the Island
of Hawaii, and there were able to piece together our understanding,
bit by hard won bit…. We learned through our work that
a vital part of protecting an animal is knowing who it is.
The more we have learned about spinner dolphins, the more remarkable
they seem to us. Because we know them a little, we have
come to care for them a great deal. I feel it in
my bones that this will lead to their salvation out on the open
Deep Scattering Layer (DSL)
A grouping of fish squid and shrimp that hide down deep, in
the dark during the day and come up close to the surface at
night to feed. This layer is so dense that it looks
like a false bottom on a Fathometer.
Spinner Dolphin Circadian Cycle
Spinner dolphins feed offshore at night on the DSL.
In the morning they come in close to shore, locate a resting
area and go into a resting pattern. In the afternoon
they again become more active and head out to the feeding
grounds in the late afternoon. The amount of time a
school spends in deep rest varies with resting area.
dolphins are extremely acrobatic animals. They perform
a wide array of aerial behaviors.
Rotating around the longitudinal axis — the behavior they
are named for.
Head-over-tail and Tail-over-head flips where the animal is
rotating around its other major axis.
Spinning Flips: Probably the most acrobatic when a spin and a flip is combined in
Animals leaping high into the air.
Pict of Dolph THROUGH the Surface
water surface obscures what is going on underwater even on
an extremely calm day. A wave makes it appear that this
dolphin has a hump on its back.
A basic mammalian sound.
Clicks are used
for echolocation. They are of very short duration but contain a wide range of
pure-tone. They are of long duration but have a very narrow frequency range.
Yugoslavian News Report
A school of dolphins simultaneously produce whistles, clicks and burst-pulse
research on spinner dolphins (Stenella longirostris) began
in the late 1960’s when Dr. Ken Norris went to Kealakekua Bay, on
the Island of Hawai’i, to ascertain whether that would be a good
location to study dolphins. Since then the Island of Hawai‘i
has continued to be the center for spinner dolphin research.
There are many aspects of the research that merits mentioning.
The following are the areas that will be addressed here.
History of the Big Island Spinner Dolphin Research Program
research on spinner dolphins, off the Island of Hawai‘i (the Big
Island), represents the longest running study of spinner dolphins
in the world and one of the longest running studies of any dolphin
species, spanning over 30 years. The research has been carried
out in four separate studies, involving Ken Norris and several of
his colleagues, postdoctoral and graduate students.
- 1974 — The Initial Study
Dr. Ken Norris initiated the spinner dolphin research, when he found
them residing in Kealakekua Bay on the Big Island on a regular basis.
Ken’s early work focused on Kealakekua Bay and involved one of his
students, Tom Dohl. This initial work featured Ken’s extraordinary
skills as a naturalist, where he was able to describe the basic
framework of spinner dolphin biology. They observed the dolphins
from shore, and made aerial surveys around the Big Island and throughout
the Hawaiian Island chain. Several important discoveries came
from this work. They found that spinners rest near-shore during
the day and travel offshore in the afternoon to feed at night on
the deep scattering layer (see side bar), as it moves closer to
the surface, after dark. They discovered that, in Hawai‘i,
spinners tend to rest in bays with a sandy bottom and described
many details of the circadian (24-hour) activity cycle that spinners
go through, as well as, the various aerial behaviors that these
acrobatic dolphins perform. Ken developed the first underwater
viewing vessel, the “Semi-Submersible Seasick Machine” to study
dolphins underwater in the wild. This vessel was used to study
the spinners in Kealakekua Bay. Ken Norris describes this
pioneering research in “The Porpoise Watcher”.
- 1981 — The Hana Nai‘a Project
A group of Ken’s postdoctoral, graduate and undergraduate students
returned to the Big Island to continue the research. This
group included Bernd Würsig Randy Wells, Shannon Brownlee,
Christine Johnson and others, many of which that have made major
contributions in marine mammal science. This project focused
on quantifying many of the features of spinner dolphin biology that
had been described in the first study. The project was again
based in Kealakekua-bay. The dolphins were tracked from a
shore station with a theodolite, photographed from boats for individual
identification purposes, and radio-tracked at night to follow their
movement offshore to and in their feeding areas and along shore.
Their sounds were recorded and their behaviors were observed underwater
using the 2nd generation underwater viewing vessel, the
They also did aerial surveys and observed a captive colony of spinner
dolphins at Sealife Park,
on O‘ahu. Much of the information from this work can be found
in two books, a scientific book, “The Hawaiian Spinner Dolphin”,
and a popular book by Ken Norris, “The Life and Times of the Hawaiian
spinner dolphin”. The latter won the Burrough’s award for
best Natural History writing in 1992.
This study identified 224 individual spinner dolphins and estimated
between 1,000 and 2,000 dolphins around the island
of Hawai‘i. It described a fission-fusion society where schools
changed composition on a daily basis. However, some animals
were found to associate tightly. Some individuals were observed
to move from one side of the island to the other in a matter of
- Present — The Kula Nai‘a Project
After a brief project on the Island
of Lana‘i in 1988, we (then Ania Driscoll and Jan Östman) came to
the Island of Hawai‘i in 1989, to continue the research on the
spinner dolphin population. We were both graduate students
of Ken’s, and as such had a great base for our project from all
the excellent work that had already been done by the researchers
before us. We continued the emphasis on quantification and
focused our observations on the social organization, social behavior
and vocal communication of the spinner dolphins. We also made
underwater observations an important part of the research, using
the 3rd generation underwater viewing vessel, “Smygtittar’n”.
Working out of Honokohau harbor, our research was based North of
Kealakekua Bay, mainly from Noio Point to Mano Pt. However,
we also went farther South, to Kealakekua Bay and Kauhako Bay on
We identified 677 individual spinners and estimated a total
population size of 2,334 spinner dolphins around the Big
Island. The underwater viewing vessel made it possible to
sex 68 of the identified spinner dolphins, allowing us to compare
the association patterns of males and females. It also made it
possible to collect 50 hours of focal animal follows, where we videotaped
the social interactions between the focal animal and other spinners
for up to 45 minutes. Using DAT (Digital Audio Tape) recorders
we recorded their sounds, categorized their whistles and studied
the whistle choruses they make at certain times of the day.
social organization of Hawaiian spinner dolphins differ from that
of bottlenose dolphins, the most extensively studied dolphin species.
Spinner dolphins are found in much larger schools, often numbering
40 to 80 animals. Off the Kona Coast you can often see these
schools moving along the shore divided into subgroups of roughly
20-25 individuals each, spaced about 50 meters apart. Thus
a school with 2 subgroups often have around 40-50 individuals, while
a school with 3 subgroups may have about 60-75. To study these
groups further you need to be able to identify individual animals.
methods for identifying individuals
study the social structure of any species you need to identify individuals
and observe their patterns of association both in the short-term
and in the long-term. Biologists have learned to identify
individuals of many mammalian species by some variation in outward
appearance, such as the pattern of whiskers on lions, the shape
of a certain color patch on the necks of giraffes, or the coloration
and other markings on the tail flukes of humpback whales.
For most species of wild dolphins, the patterns of nicks and notches
on the leading and trailing edges of the dorsal fin is used, making
it possible to identify individuals by their dorsal fin silhouette.
(Trainers of captive dolphins learn to identify their animals by
their faces). Since many of these patterns are too subtle
for a definitive identification in the field you need to photograph
the dorsal fins of all individuals to get the complete school composition.
Unfortunately, however, many spinner dolphin fins are clean, i.e.
they do not have any identifying markings. This is especially
the case for younger animals and, we suspect, for females.
get a quantitative measure of the social affiliation patterns among
the spinners, we calculated a Coefficient of Association (CoA) for
each pair of the 677 individuals we have identified to date.
A CoA of ‘100’ means that the two individuals were ALWAYS seen together
in the same school, while a CoA of ‘0’ means that the two individuals
were NEVER seen in the same school
found that female-female associations among the spinners were similar
to those seen in bottlenose dolphins and lions, with an average
female-female pair spending about 40% of their time in the same
school. The male spinner dolphins, however, formed more extensive
networks of associations and often formed tight core groups of 6
or more males, spending 60% or more of their time together. Female-male
association were also very high, falling in between male-male and
female-female associations, and much higher than comparable associations
among studied bottlenose dolphins.
social interactions among spinner dolphins are very unusual for
a mammal. In most mammalian species, the females are very
important resources for the males, since they carry the offspring
in the womb for an extended period of time and then nurse the offspring
after it is born, thus putting a lot of energy into the offspring.
As a result male mammals tend to compete with each other for access
to females. They then engage in a consortship with the female
to convince her that he is the one that should be the father of
her offspring. Among mammals, then the emphasis is often on
male-male competition and female choice.
research indicates a very different pattern for spinner dolphins.
We need to collect more data to confirm these patterns statistically,
but the emerging pattern is consistent and intriguing. We
have seen females compete over access to males on several occasions,
while male competition over females appears to be muted. Females
have, furthermore been seen to solicit males, while males have not
been seen to overtly solicit females. Female spinners often
initiate social and sexual interactions with males by rubbing on
the males, and also solicited their attention in other ways.
Types of sounds spinner dolphins make
dolphins, like most other dolphins, make three types of sound, burst-pulse
sounds, clicks, and whistles. Burst-pulse sounds are
the basic types of sound you normally associate with mammals, like
barks, grunts, and moos. These sounds have not been much studied,
since they are hard to describe and to quantify. Clicks
are extremely short-duration sounds containing a very wide range
of frequencies. Individual clicks sounds like clapping you
hands or tapping concrete with a hard object. A series of
clicks may sound more like a rusty hinge when you slowly open a
door — think of your favorite scary movie. Whistles
are long duration sounds with a very narrow frequency range.
Dolphin whistles sounds just like human whistles, except that dolphins
are exceedingly better at changing the frequency (pitch) and have
a much wider frequency range.
Studying spinner dolphin whistles
study spinner dolphin whistles can be a very tedious endeavor.
When you put your hydrophone (underwater microphone) in the water
your may record a cacophony of sounds, where you may hear all three
types of sounds simultaneously. (Ken Norris called this the
Yugoslavian news report.) Then imagine trying to tease these
sounds apart, when you know that you have 60-80 animals around you.
At other times, however, you may only record one whistle at
the time from the same school.
We categorized whistle sequences in three categories, repeated
contours (the same contour is repeated several times, low chorus
(2-4 overlapping whistles) and high chorus (5 or more overlapping
contours). The low and high chorus became more frequent during
the afternoons, with the high chorus being especially prevalent
in the hour before sunset.
We also found that spinner dolphin whistles has both strong
individual identity and behavior state characteristics. We
suggest that whistle communication functions at three levels: to
exchange information between individuals, to coordinate subgroups,
and to signal or trace transitions of behavior states within an
Underwater viewing Vessels
underwater viewing vessel, Smygtittar’n, Swedish for “The Tip-Toeing
Looker”, or “The Peeping Tom” was a long time in the making.
It was the third generation underwater viewing vessel designed by
Ken Norris. It began with one of Ken’s crazy ideas.
He wanted to study dolphins underwater in the wild, something that
now seems to be an obvious, although difficult thing to try.
However, although Ken had grand ideas, he was limited financially
(a problem we are still struggling with), so he had to put together
something on the cheap. His first contraption, the “Semi-Submersible
Seasick Machine” (SSSM), was an airplane fuel tank, with a welded-on
inverted tower. This vessel could be towed by another vessel
or, later move under it’s own power. However, in field tests
during the initial study (1968-74) the usefulness of the SSSM was
found to be very limited, something that Ken describes in vivid
detail in his book “The Porpoise Watcher”.
he later came back to Kealakekua bay for the Hana Nai‘a project,
he brought the second generation underwater viewing vessel, the
“Maka Ala”, a vessel that Ken describes as a 17 foot skiff
with a coffin attached to its bottom. This was not a very seaworthy
platform and it ended up sinking in a rainstorm. It was also
of limited use, even though, just as its predecessor, it gave valuable
glimpses into the lives of the dolphins. For more descriptions
of the pros and cons of this vessel, see ”Dolphin Days”.
Smygtittar’n had it’s own history. It was initially donated
to the University of California Santa Cruz
and sat at the Long Marine Lab. for years, with weeds growing in
it. Initially it was a 19’ long by 6’ wide Coast Guard Crash
boat, with some big holes and rusty fasteners in it’s 1940’s fiberglass
cathedral hull. During it’s development into a research tool,
it grew to be 24’ by 8’. We had a 40” hole drilled through
its center and a well built up around it. An A-frame was built
to straddle the well and a three-foot-diameter, ten foot tall aluminum
observation chamber was hung in the A-frame via cable. This
allowed us to winch up the chamber while it was not in use and to
lower it down some six feet, with he help of 1.4 tons (3,000 lbs.)
of lead, and lock it in place with bolts into the observation position.
An observer could then climb down into the chamber and record the
dolphins’ interactions in front of the underwater viewing windows
with a still-photo or video camera. When it was time to go
back to the harbor, we could pull the chamber back up and turn the
bottom of the hull into a regular shape again, although the boat
again felt the weight of the ballast.
The total displacement of this 24-foot vessel, 4.5 tons (10,000
lbs.), gave it a tendency to go through the waves when the chamber
was up, rather than over them like a regular vessel. As a
result we only stayed within swimming distance from shore, less
than a mile out, at all times limiting our observation sessions
to the mornings when the dolphins were close to shore. When
the chamber was down, on the other hand, the vessel lost about half
of its weight, due to the buoyancy of the air in the observation
chamber. However, it gained a six-foot keel with a three-foot
diameter. It thus, turned into a slow but amazingly maneuverable
vessel. It could literary turn on a dime, since the chamber
when down served as a pivot point, allowing us to maneuver around
coral heads if necessary. (The development of Smygtittar’n
was made possible by funding and help from several sources, including
NSF, Waikoloa Marine Life Fund, and Hoogan Boatworks in Kailua-Kona.)