Friday, October 24, 2008

Overgrazing leads to increased salamander populations?

That is what a recent study lead by Katherine Greenwald of Ohio State University seems to be suggesting. In her results, overgrazing by high populations of white tailed deer led to an increase in organisms like salamanders, snakes and other invertebrates. In the past, the increasing numbers in the deer population have led researchers to believe to have affected the bird inhabitants and the amount of flora present in that area.

With more forest areas become smaller over the past few decades predators like wolves and cougars are not around leading to dramatic increase in white-tailed deer in the eastern US and allowing them to graze freely at forest edges where they typically roam. Greenwald’s findings were definitely unexpected as stated by University of Turku’s Otso Suominen, who assumed that the high populations of deer would only be beneficial for organisms such as snails and slugs.

One theory explaining their findings is that the areas in which there are a high population of deer also means there will be more of their droppings present in the soil which then leads to higher soil quality. With the increased nutrients present in the soil more invertebrates become attracted to the area which also attracts salamanders because of the increased abundance of their food source inhabiting the area.

Because the study is only in its early stages Greenwald is hesitant to state that the high density of deer has any direct influence on the increased populations of salamanders, snakes and other invertebrates. With further research by Greenwald and others hopefully more information will shine a new light on their findings.

Posted by Debbie Theodat(6) 10/24

Updated 10/28:

According to the article, the white-tailed deer’s predators are not usually around to prevent the high populations of deer. Because they are fairly scarce in those areas whatever droppings that are there would not be efficient enough to dramatically affect the soil like white-tail deer have done. The high populations of white-tailed deer present means that there are also far more of their droppings in the soil than that of their predators.

The connection between the overgrazing and the increased populations in the salamanders, snakes and other invertebrates is that the areas where the white-tailed eat are also areas where they leave their dropping. The droppings that are present in the soil improve the quality of the soil by increasing its nutrients. The increased nutrients in the soil become ideal living conditions for insects and other invertebrates. The increased population of their food source present in one area attracts the salamanders who then attract snakes, who are also one of their predators.


At 4:47 PM, Blogger PWH said...

Nice topic, it's interesting that they would connect deer droppings to increased salamander populations. It makes sense somewhat, however, why would the population of salamanders only increase with more deer droppings, are wolf/cougar droppings non-beneficial to salamanders? I wonder if the wolves/cougars snacked on salamanders and other invertebrates while they were more common. That may be another possible explanation for the increase in population.

Ashley Maillet

At 6:03 PM, Anonymous Anonymous said...

That's interesting and shows another way that human development is changing ecosystems. What other work is being done on this subject to lead to more concrete conclusions?

Amy Kawazoe

At 12:37 AM, Anonymous Anonymous said...

The article mentioned that higher deer populations have a negative effect on mammal and bird populations. This seems to make sense if they are overgrazing certain areas. I wonder if the salamander and snake population is increasing because of the decrease of their predators, which could include certain birds and mammals. The deer dropping idea is interesting. It's one more example of how complex ecology can be. Nice Job.

Rachel Carboni

At 12:06 PM, Anonymous Anonymous said...

I never would have thought that these species were in any way connected. It really makes you wonder just how many situations there are like this one in the wild. Nice work!

Ericka Adey

At 2:38 PM, Anonymous Anonymous said...

Good topic. I wonder what more results would be discovered if they went further into this

Duy Nguyen

At 2:55 PM, Anonymous Anonymous said...

I usually associate salamanders with vernal pools not with following deer through the woods. Maybe this is how salamanders disperse to other territories? Be interesting to find out if there is some benefit/cost to one or both of these species resulting from this interaction.

Allan Eldridge

At 2:58 PM, Anonymous Anonymous said...

Very interesting article. Could you explain how smaller forests are decreasing the predator population? I'm a little confused on that part.
-Sasha Rogers

At 4:50 PM, Blogger PWH said...

I know that the deer population increasing may in fact lead to the increasing population of the salamanders, but I was just wondering about the details about why the deer population is increasing in the first place. You stated that with the decreasing size in forest areas over the past few decades was leading to the decrease of deer predators such as wolves and cougars, but why would the population of deer stay as healthy as it is and/or increase further more?

-Kiel Boutelle

At 5:20 PM, Anonymous Anonymous said...

Good article. These findings show how the changes in a ecosystem effects many different organism. I wonder if an increase of the predators would decrease in salamaders, snakes and invertebrates that flurished in the increase of grazing deer?

Alex Pavidapha

At 5:25 PM, Anonymous Anonymous said...

This is a very interesting article. It is nice to see that they are not immediately assuming correlation equals causation. What I don't understand the connection to overgrazing. Increased populations are mentioned but not overpopulation or overgrazing. What is the assumed connection to overgrazing?

Alex Jackson

At 5:31 PM, Blogger Dan said...

That's an interesting connection. Is the increase of the organisms listed going to affect the other inhabitants in any negative or positive way? It'd be unfortunate for a chain to start because of changing ecosystems.

~Dan Hong

At 6:06 PM, Blogger PWH said...

I can't imagine something as small as the deer's droppings would be the sole reason for the increase in these animals but I think it could play a part. I know that certian environments have "keystone" species that effect the populations size of many other species in the environment and I'm begining to think that deer may be the keystone species in the these particular environments. I'm sure a lot of work will be done on this topic and it should be pretty interesting to see how all these species are connected.

Patrick Salome

At 6:08 PM, Anonymous Anonymous said...

If what this study says is true, I wonder what the impact of a greater invertebrate population would be on the environment. Would they in turn use up other resources, or attract other animals to the region? This could end being an interesting study on the kind of domino effect removing the top member of the food chain (i.e. the cougars and wolves that used to feed on the deer) causes.

-Corinne Delisle

At 8:28 PM, Blogger PWH said...

This is an interesting finding and a good hypothesis by the researcher. I know that there are a few salamander species in the eastern U.S. that are moderately to severly endangered. Did the study mention which species populations in particular are increasing? Are the researchers seeing any increases in any threatened or endangered species populations? What methods were the researchers using to come to the conclusion that salamander numbers are in fact increasing?

Posted by: Lindsay Goodyear

At 8:37 PM, Anonymous Anonymous said...

Since there are high population of white tail deers, I'm wondering why there ain't more predators roaming smaller forest area to find these preys?

- David Huynh

At 9:52 PM, Anonymous Anonymous said...

Where was this study of white tailed deer observed? Is this seen among other habitats where white tailed deer are found? If it is, does it lead to an increase in the same type of species?

Why did the researcher believe in the past that the increasing numbers in the deer population affected the bird inhabitants and the amount of flora present in that area? How would the overgrazing by high populations of white tailed deer affect the areas in the future?


At 10:18 PM, Anonymous Anonymous said...

I thought that you summarized the article very nicely. I wonder if there are any radical consequences by having an increase in population of salamanders and invertebrates? Is the state more concerned with the decrease in the mammal population? I know that in my town they are very concerned with the over-population of deer.

Maura Mulvey 10/26/08

At 10:52 PM, Anonymous Anonymous said...

I really like the thing they measured in this experiment. The fluctuation of populations of "crawlies" is a very interesting variable of which to take note. How this factor can be the evidence used in an argument about deer populations is very interesting.

Jordan Grinstein

At 11:19 PM, Anonymous Anonymous said...

In your first paragragh third sentance, you are missing a few words. Anyway, I was wondering if any salamander species are more abundant than others thanks to the increase in the white-tailed deer population or if they are all growing equally?

Ada Marie Flores

At 1:11 AM, Blogger PWH said...

interesting, i thought more grazing means less shelter and that would expose the snakes and salamander to predators when they are roaming around in the fields, do you know what kidn of predators are present in their area?

Hessom Minaei


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