General Sea Life Facts
Learn about whales, dolphins, porpoises, and otters from marine mammal experts!
- Grades: 3–5, 6–8
The following questions were answered by whale biologist Sally Mizroch, research biologist Dan Odell, zoo nutritionist Ellen Dierenfeld, and zoo biologist Will Waddell.
How would humans measure intelligence in a marine mammal?
Intelligence is a hard thing to measure, even in people. I don't think anyone really knows just how smart the whales and dolphins are. Their environment is so different from ours that I think it would be hard to measure them by our standards. We know they have large brains and appear to use them well. They are very aware of their environment and of all the things around them. I think that's smart.
Are many mammals being taken from our oceans to zoos or water parks?
Marine animals are collected for zoos, aquariums, and home aquariums. Most of these animals are fish and invertebrates (like snails and clams). Very few mammals are collected. In some cases — harbor seals, California sea lions, bottlenose dolphins, killer whales — captive-breeding programs are so good that there is no need to collect wild animals at the present time. Penguins also reproduce very well in zoos and aquariums.
Are we doing more harm than good to sea mammals by keeping them in captivity?
Very few of the many species of marine mammals have been kept in captivity. The most common are California sea lions, harbor seals, and bottlenose dolphins. While life in an aquarium cannot be identical to that in the wild, it seems to be satisfactory for most marine mammals, though some people do not believe that marine mammals or any other kind of animal should be held in captivity under any circumstances. One measure of the success of life in captivity is successful reproduction. California sea lions and harbor seals reproduce so well that it has not been necessary to collect any from the wild for many years. To the best of our knowledge, seals, sea lions, and bottlenose dolphins live as long in captivity as they do in the wild. There is a lot of disagreement about killer whales in captivity, but there is very little information about their lives in the wild from which to make comparisons. I do not believe that we are doing any harm to wild marine mammals by keeping a few in captivity. The things that we learn from them may help us to save some of the dolphins and seals that are truly endangered in the wild.
Have there been any new mammals discovered in the past ten years?
Yes, a new species of beaked whale was discovered in Peruvian waters a few years ago. It is the Peruvian beaked whale, Mesoplodon peruviensis. There are probably other undiscovered whales and dolphins in the ocean.
What happens to whales when people catch them in their nets?
Mostly bad things. Dolphins, porpoises, seals, and sea lions can get totally entangled in nets and drown. Large whales, like humpbacks, can get netting wrapped around them and either drown or end up carrying a big, uncomfortable load of netting or crab pots.
Most fisherfolk do not want to have marine mammals stuck in their nets. A marine mammal stuck in a net can ruin it, and the process of freeing the animal slows down the collection of the fish. There is a scientist named Jon Lien in eastern Canada that has developed some really good techniques to free whales that have been trapped in nets. Jon's work is dangerous, and not always successful, but he has saved a lot of whales. Also, Jon has done a lot of work with the local fishing community to help them learn techniques to avoid problem interactions with whales.
What do you feed sea otters?
In the aquarium, sea otters are fed clams along with fish.
What is the impact of heavy storms on sea life?
Because marine mammals are almost always in the water — except for seals, sea lions, and polar bears when they haul out on shore or on ice — they probably are not bothered by rain directly. Strong winds cause the seas to turn choppy and can make it harder for these animals to catch their breath. Weak or very young marine mammals might drown in bad storms. Rain storms may also affect marine mammals indirectly by tearing out kelp beds, like those used by sea otters. Siltation from erosion can muddy ocean waters for miles down-current from rivers. This may damage animals that marine mammals feed on, such as plankton, clams, mussels, and small fish.
Why are there so many marine mammals on the endangered species list?
Marine mammals, for the most part, are difficult to count. We see them when they come to the surface for air, but we cannot tell how many of them are still underwater at that time. This makes it hard to tell how many animals are in the population, so we don't know how well or poorly a species is doing. When all the research shows there are very few animals, this species will be listed on the endangered species list to help protect them. Many marine mammal species are on the list, but some are doing so well, like the California gray whale, that they are no longer considered endangered and have been removed from the list.
Is it true that in prehistoric days whales and dolphins walked on land?
It is true that in prehistoric days, animals that eventually became whales and dolphins did walk on land. About 60 million years ago, animals kind of like sea lions began to spend more and more time in the water, and about 10 million years after that, scientists found fossils of long, streamlined animals that spent all of their time in the water.