Friday, April 8, 2011
Today we estimated the White Tailed Deer population in the forest. To do this, we did not trap the deer; instead we used field signs to calculate the population. Field signs are any signs that the animal was in the area. These signs can range from evidence of feeding (chewed off buds from trees, bones and carcasses) to animal dens and burrows. In this case, we used scat to determine the animal. Scat is, yes, feces and poop! See the video below to get a good description of deer scat.
We know that white tailed deer produce approximately 20 piles of poop in 1 hectare per day, and it takes 40 days for the poop to decompose before you cannot see it. That means that 1 white tailed deer produces 800 piles of scat (poop) in 1 hectare over time.
Now that we know this, we can estimate the population.
If we look at a 10 by 10 meter area (1/100th a hectare), a deer should poop 8 times in that 10 by 10 meter area (800 poops/100= 8 poops in a 10 by 10 meter square).
IN a 10 by 10 square, we found 1 pile.
Questions (answer in the comment section of the blog. show your work!)
1. How many deer should be in the 1 10 by 10 square (it can be a fraction of a deer...)
2. By our estimates, how many deer should be in a 137 hectare park (the size of the area)?
3. Why do you think we look at scat, and not trap the deer, like we did with the voles?
4. What do you think would happen with the deer population in the summer? Why do you think this?
Posted by Stanley Richards at 7:03 PM
Thursday, April 7, 2011
Good question, you might think...
The Principal Investigators (Chris and Christina) are recording vole populations over time to see the population growth and decrease over time. In the summer, after breeding season, vole population is at the highest. As more and more animals eat the voles, and breeding ends, the population decreases over time, until winter, where the population is at the lowest. Once spring hits, the population begins growing again.
Nova Scotia winters have been getting warmer over the past years, and the researchers are using vole populations to make a connection between increased populations in the winter and warmer temperatures.
Before we can make that connection, we first need to estimate the population in the area. To do this, we use a method called CAPTURE-MARK-RECAPTURE. This is the reason Dr. Bueshling was cutting fur on the back of the mice... to mark them so we know if they were caught before.
For an explanation of CAPTURE-MARK-RECAPTURE, see the video below. This is our second investigator, Dr. Newman. Forgive the shaky camerawork.
The equation we use to get the population of the area is:
Population of the area= (N1 x N2)/R
N1= captured population of day 1
N2= captured population of day 2
R= number of recaptured population on day 2 (the ones that were marked)
So let's try this with the population that we captured for the past couple of days.
On day 1, we caught 6 total; 4 voles and 2 mice
On day 2, we caught 7 total, 2 mice and 5 voles.
On day 2, 4 of those caught were marked from the first day.
Answer the questions below in the comments section of the blog.
1. From the data, how many rodents (voles and mice) are in the total area? Show your work in your comment.
2. What assumptions do we make about the population? How could our numbers be off? (THINK ABOUT WHAT MIGHT HAPPEN TO THE POPULATION BETWEEN DAYS...)
3. How might this be helpful to estimating population?
4. What other ways do you think we can estimate population of larger animals that we cannot capture?
Posted by Stanley Richards at 10:19 AM
Tuesday, April 5, 2011
After setting our traps, we waited the night to see whether we actually caught anything. Though we keep the traps stocked with bedding and food, voles easily can get hypothermic over a short period of time, so we check them twice a day; once in the morning and once at night. The reason why there is the styrofoam covering the bedding chamber is to make sure that there is insulation over the night.
On day 1, we caught 2 mice and 4 voles over 24 hours. In the video below, you will see my first attempt at catching the mouse that was trapped overnight. It was a male vole, and survived through the harsh winter to help repopulate the area with voles. Because of the fact that it survived so long, Dr. Bueshing (one of the main researchers) puts each mouse or vole caught through a maze before being released, to test intelligence. The vole to the right is about to go through the maze.
Check out the video! Note: Don't shake the trap, otherwise you might scare the vole, as I did...
Questions to respond to. (Yes, Liam, you do respond by commenting on the post.... and I do read them...)
1. Since the voles survived over the winter, would you consider them more or less intelligent? Would you expect for the times of the vole going through the maze to be longer or shorter? How do you think the times would compare to a mouse or vole that was born during the summer?
2. Why do you think Dr. Bueshing clips the hair of the vole (as seen at the end of the video)? Why would this be helpful?
3. In the video, notice that I checked the first part of the trap, then the rest of the trap. Why do you think this is?
4. What data do you think that Dr. Bueshing keeps on each mouse or vole caught? How would those numbers help with showing the health of the animal, and the environment?
Posted by Stanley Richards at 8:11 PM
Sunday, April 3, 2011
Well, not so sunny. It has been hovering around freezing for the past week, but in the past couple of days, the temperature has increased to a balmy 45 degrees. I have beenworking in the field, capturing voles (a small rodent) over a half hectare (about the same size as a football field).
To capture the vole, we use what
are called longworth traps
(seen to the left) that have a small opening that the vole goes through, attracted to the food and bedding in the larger chamber. When they go through, the door shuts behind them. The styrofoam covering the traps make sure that the animal is warm during the night, and the bedding and food make it comfortable for the vole.
I am in charge of 20 traps, and have been laying them
throughout the forest, trying not to get lost! Below is a picture of where I have left traps.
The investigators we are working with, Chris and Christina, have been studying small mammal populations for 5 years, looking at populations and how they are affected by climate change. Since it is the end of winter, the population is low, because they have not hit spring mating season yet, and
many do not survive the cold winters.
In your response to this blog, please answer the following questions from what you read, or what you hypothesize about what might be happening in the population.
PLEASE WRITE YOUR NAME IN YOUR RESPONSE SO I KNOW WHO IS RESPONDING! ANSWER IN COMPLETE SENTENCES!
1. How do you think we are estimating the population of voles with such a small area that we are studying (Nova Scotia is 21000 square miles)?
2. Do you think that the place where I laid my trap would be good to catch voles (think about the fact that voles are eaten by many predators, and because of that, need to hide from animals from above)? What other places should I lay traps?
3. The past Nova Scotia winter was mild in comparison to past winters. Do you think that this would affect the population of voles now? Why? How might this be connected to global warming?
4. If there was an increase in vole populations, how might that affect the food web (think about the fact that the vole is at the bottom of the web)?
Posted by Stanley Richards at 6:46 PM