Re: Another Goofy Alarishi Sovereignity

G'day,

OK I'll bite - I have this little voice telling me its all a drug
induced
joke though and I'm about to hear the line go twang and the rod whirl as
I
get wound in....

>So how many dolphins does it take to make a viable community,
>and how much room do they take up?

A few (potentially helpful) dolphin facts for you:

On average an adult dolphin will eat 4-9% of its body weight in fish
(either finfish or cephalopds) per day. 

The maximum age for bottlenose dolphins is between 40 and 50 years, but
this can average as little as 10 years in some regions (and for some
species... and whether or not they fish for tuna in the area) - many die
before the age of 2.

Female dolphins will give birth every 2-3 years and could have as many
as 8
pregnancies during their lifetime.

Dolphins travel in pods of up to 15. A pod typically consists of several
adult females, calves and adult males, but they seem to be in a periodic
state of flux (with individuals traveling with one group swimming miles
away with another the next day). A more stable subgroup of two to six
dolphins may remain together over long periods (probably the minimum New
LA
could get away with for social behaviour reasons). Mothers and their
calves
have been observed together for at least 3-6 years, and unrelated adults
often form long-term bonds (usually same sex and age group). Separation
of
groups along the lines of age and sex is common (i.e mothers and their
calves in one group, juveniles in another and mature males in a
different
pod again (which rarely mixes with either of the first 2)). During
feeding,
smaller pods may interact and join into larger groups. So although
solitary
individuals are sometimes seen in the wild dolphins usually live in pods
composed of two to twenty-five dolphins. Inshore, coastal, groups tend
to
be smaller, with an average size of ten, but groupings may exist as
large
as one thousand. The size of the group may depend partially on the need
for
surveillance against predators as well as the quantity and distribution
of
available food. So family interaction wise 5 is minimum, 10 is OK.
However,
dolphins are promiscuous so you'd want multiple mature males and females
if
they were to have a healthy reproductive behaviour. Genetics wise you'll
want 500+ for a sustainable, probably healthy population.

As for how much room they'll need, we are far from knowing the precise
ranges for populations of dolphins, especially those who live far from
shore. Most, seem to prefer a relatively small area within a protected
bay
or shallow lagoon where they establish a "home base". However, they
often
move within a larger range to find food, to mate, or to escape
predators.
Pods of bottlenose dolphins  in California seem to have a range of about
30
km along the coast line and in Florida they have a total max range of
about
85 km2. The actual distances traveled vary with sex and age: females
with
calves have the largest home range (average 40 km2); juvenile males
usually
have a significantly smaller range; and groups of adult male, adult
females
without calves, and juvenile females have the smallest ranges (about
15-20
km2). With each subrange of the larger pods was centered in different
areas, so it looks like social units of like sex and age tend to define
the
home ranges of various pods.

Hope that helps the hardy citizens of la Nueva Ciudad de Nuestra Senora
de
Los Angeles - though it does bring up the question of import/export
bans... ;)

Cheers

Beth

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Elizabeth Fulton
c/o CSIRO Division of Marine Research
GPO Box 1538
HOBART 
TASMANIA 7001
AUSTRALIA
Phone (03) 6232 5018 International +61 3 6232 5018
Fax 03 6232 5053 International +61 3 6232 5053

email: beth.fulton@marine.csiro.au