Subject: EIS;whale twinning; oil spills; male/female whales

Dagmar Fertl (
Wed, 22 Sep 1999 11:11:30 PDT


Thank you in advance for answering my fifth graders whale questions.


George and Tim: Do whales ever have twins?

Sue Shirley
Dedham Country Day School
Dedham, MA
Maggie and Stephanie,

I actually studied the association of the dolphins with shrimp boats. There 
should be a link via the WhaleNet A.S.K. page to an article that I published 
with my major professor in graduate school about this topic.  In short, it 
wasn't the shrimp I was interested in, but the dolphins following the shrimp 
boats. Bottlenose dolphins follow shrimp boats for fish. Shrimp trawls (the 
nets used to collect shrimp) drag the sediment for shrimp which hide there 
during the day. There are also fish that live on the bottom of the ocean; 
they become disturbed when the nets are dragging and try to get out of the 
way of the nets (sometimes getting hit) or are actually caught in the shrimp 
trawl as bycatch. In the southeastern United States, 5-8 pounds of fish 
(that the shrimpers don't want and then discard when sorting their catch) 
are caught with each pound of shrimp. It is the fish that are stunned and 
disoriented by the nets, or actually caught by their gills in the net, that 
interest the dolphins. This is part of what I studied for my graduate 
degree.  It appeared this feeding behavior was especially important to 
mother dolphins with young calves, since the moms have to eat so much more 
food (double their food intake) while nursing their babies with a high-fat 

An EIS is an Environmental Impact Statement. More information on EIS' is 
available via the MMS webpage, which has a link from WhaleNet via the A.S.K. 
section. Basically, before some human activities may take place (like 
drilling for oil or putting sound in the ocean to measure global warming - 
ATOC -) scientists review what the natural environment in the area is, and 
how it might be affected by those activities. For example, for dolphins and 
whales in the Gulf of Mexico, I consider the effects of oil spills, noise 
from oil platforms, noise from boats and helicopters taking things and 
people to and from the platforms, discharges from the platform, marine 
debris, and seismic surveys. I take what information is available from the 
Gulf of Mexico, as well as from other locations world-wide, as well as 
looking at where and how whales and dolphins are distributed in the Gulf to 
decide how much of an impact there might be on the animals, especially 
compared to other human activities like commercial fishing and shipping, to 
the proposed activity. All of this is required by law (National 
Environmental Policy Act).  In the case of the Gulf of Mexico, we have a 
coral reef - Flower Gardens - which is a National Marine Sanctuary and there 
are special laws that protect this area and oil companies can only drill XX 
distance away from the coral reef, so that they will not hurt it. This is 
just a really basic answer to the question of EIS, but I hope it helps.
George and Tim,

It is possible that whales could be born sometimes as twins, but only one 
calf most probably survives, since there is a lot of care involved and not 
enough of mom to go around for two babies.
Lindy and Sarah,

I am not directly involved with oil spills, if you mean with going and 
helping birds or mammals caught in oil. I do know people who do this.
I did participate though in an oil spill response class before I came to MMS 
to work.
Maddie and Michael,

I'm not sure what exactly you are looking for with how males and females are 
different. Are you asking how to tell them apart in the wild? If you want to 
write back to me with a question that is more specific, I'd be happy to try 
to answer it.

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