Sunday, October 19, 2008


What do Sea otters share with Bald Eagles?


According to Robert Anthony and the Oregon Cooperative Fish & Wildlife Research Unit of the U.S. Geological Survey and Oregon State University they have a lot in common. Since the 1970's scientists have understood that kelp, urchins and otters all play an important role in each other's life cycle. Ur chines are the main predator of sea kelp. They attach themselves to the prey and can defoliate entire kelp forests if their number is great enough. Luckily for the kelp, sea otters enjoy eating these pesky urchins. These otters actually keep the sea urchins in check disabling them from eating all the kelp around. Unfortunately for Alaskan kelp, their savior otters are being driven away by yet another predator, the killer whale. Over the last few decades killer whale populations have increased which effects the otter population in two ways. The first of which the population will decrease because the chance of being preyed on by a killer whale increases. Secondly, the sea otters are forced to move their colonies elsewhere. Both of these effects allow sea urchins populations to grow enabling kelp forests to become defoliated.
This is where the Bald eagle comes into play. Alaskan bald Eagles set up nests on cliffs right on the shore. 90% of their diet comes from the ocean (usually relatively small fish). kelp forests usually provide a shelter and food source for these fish. When the otters are forced away and the urchins are given the power, these fish suddenly find themselves migrating to the next closest kelp forests. These bald eagles now have to find alternative sources of food which usually turns out to be other marine inhabiting birds. This shift in their diet not only effects the way eagles are forced to prey but also effects related populations of species.
The sea otter has long been known to be a keystone species in the ocean. Because of its detrimental protection of the kelp forests it plays a large role in determining the behaviors of other species. This study however, is the first time that the presence of the sea otter has been shown to have an effect on a terrestrial species.

Patrick Salome

11 Comments:

At 5:30 PM, Anonymous Anonymous said...

This is very interesting that both of these animals, I believe both of which are endangered, are connected in the food chain, it just shows how much all of nature is connected and how this has been going on forever. For the first time, its not human interference that seems to be making things worse but I bet we are somehow involved...

-Alicia Stein

 
At 7:05 PM, Anonymous Allison Cornell said...

This is a very good example of a food web and how easily it can be disrupted, and therefore changed. What caused the increase in the killer whale population that led to the change? How is this new dynamic affecting the other bird species?

~Allison Cornell (5)

 
At 7:39 PM, Anonymous Anonymous said...

If bald eagle's are currently shifting their diet to other bird species, how have their attack strategies changed? Are humans doing anything to keep sea urchan levels down to make up for the lack of sea otters?

Ada Mare Flores

 
At 9:23 PM, Anonymous Anonymous said...

This topic is really interesting! i remember learning about the otter and kelp relationship in Biology 101 with Professor Houlihan last year, and I was amazed at how one thing can set everything else in the area of! I do wonder though, why are there so many killer whales now? Is there anything we can do to help this problem, or just let nature run its course?

-Alyson Paige

 
At 9:26 PM, Anonymous Anonymous said...

Did the article mention if the otter movement to safer foraging areas is a permanent move or just for a certain time of the year? If that was a permanent move than that could cause many of those affected species to suffer long term consequences.

Allan Eldridge

 
At 10:05 PM, Anonymous Anonymous said...

I am really interested in how animals are migrating. You said "sea otters are forced to move their colonies elsewhere". I wonder whether this kind of things are related to disappearance of some honey bees.

-Yi, Jeongsang

 
At 10:25 PM, Blogger PWH said...

It is so interesting how Ecology works. All these organisms need each other to survive and one change in an increased population of a predator completely changes the life style and habits of several organisms. It is just a vicious cycle. I was curious to know why such an increase in the population of killer whales? Will the eagle be able to survive just on other birds? Wouldn’t this dramatic change in diet effect the eagles overall behavior and health? Great article, I have a particular interest in this type of research. I am going to read more about it.

-Carlos A. Varela

 
At 10:43 PM, Anonymous Anonymous said...

Interesting post. I've read and heard of a lot of similar examples of how factors of one population affect the other. I've heard of examples where changing environmental factors have caused habitat change therefore, affecting the ecology of the animal populations of that area. It does have a huge impact especially when it affects keystone predators. Is it the change in water temperature due to global warming that are moving the killer whale populations?

Maura Mulvey

 
At 10:06 AM, Anonymous Anonymous said...

I don't really understand the title. It makes sense that otters are a keystone species and their leaving affects many other species but they don't seem to have anything in common with Eagles based on this.

-Alex Jackson

 
At 2:17 PM, Anonymous Anonymous said...

I wish you had provided a link to the original article.
As the symbol of the United States of America, the bald eagle is an incredible bird of prey. Comedy Central's The Daily Show and Cobert Report did a linked special report on bald eagles. They investigated a small fishing town of Alaska where the bald eagle population has steadily grown over the past years to a point where the eagles are pests for the inhabitants of the town. An overabundance of available food, excellent nesting conditions in and around the town, and lack of natural predators are the reasons for the overpopulation of the bald eagle in some areas. With literally thousands of bald eagles living on this coastline, I wonder what effect so many birds of prey have on the neighboring aquatic ecosystem.

Jordan Grinstein

 
At 8:50 PM, Blogger PWH said...

As far as I can tell humans are not doing anything to interfere with this strange circumstance. I think that since this cycle is so delicate the possibility of introducing another species or human manipulation would be out of the question. Scientist would be much to concerned about the effects of doing this so they are seemingly let nature run its course. As for the link to the original article I tried to post it apparently failed resulting in a box underneath the picture you can see. Here is The link to the actual website.
http://www.sciencedaily.com/releases/2008/10/081003081635.htm
Patrick Salome

 

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