For upper elementary school students: Controling invasive plants using goat browsing

Hi!  My name is Katie, and I’m an ecologist.  Ecologists are scientists who study interactions between living things and their environments.  I’ve worked on a variety of projects, but today I want to tell you about the research project I’m working on right now.  I’m currently studying using goat browsing to control invasive plants.


The understory of this forest is choked with an invasive bush or small tree called common buckthorn.  These goats are reaching high to go after as many leaves as they can reach.

You may have seen invasive plants or other species in your community.  They grow quickly and crowd out other species.  Some are considered “noxious” by state governments, meaning that they have negative impacts on humans or the environment so we should try to control their growth when we can.  The main plant that we are studying is called common buckthorn, which is a bush or small tree that is considered to be a noxious weed where I live in Minnesota.  This plant doesn’t just crowd out other plants, it also has more direct effects on humans through agriculture.  Buckthorns can become infected with an important germ that infects oats (oat crown rust), and support pest insects over the winter that damage soybeans.


These goats are out in the woods at a local park near St. Paul, Minnesota to eat buckthorn and garlic mustard in the early spring.  Not all goats like to eat garlic mustard, but these goats don’t mind its spicy taste.

People have started trying to use goats to control buckthorn for a few reasons.  It is hard work for humans to cut down, pull, or use herbicide to kill buckthorns.  It can also be dangerous when people try to remove buckthorns on steep slopes.  Some people like the idea of using a method that doesn’t require herbicides.  Goats have a primarily browsing feeding habit, meaning that they prefer eating woody plants like buckthorns.  They are also extremely sure-footed on slopes, which makes them much safer than a human with a chain saw in the same environment.

These goats are eating buckthorn leaves at one of my field sites.

Many people believe that goats work to control invasive plants like buckthorn by making casual observations and listening to stories about it.  Those are fine reasons to believe something, but they only get you so far.  Our job is to scientifically measure the amount of difference that the goats make, and test the hypothesis that goat browsing has a negative effect on invasive plants.  There are a lot of benefits to looking at the issue from a scientific perspective and collecting data.


This is one of the plots where we are monitoring what the plants look like and how many there are both before and after the goats arrive. (This is a before shot). Most of the plants in this picture are invasive buckthorn and garlic mustard.

  • People who manage land might want to know how many times the goats would need to return to an area to adequately control a certain invasive plant.
  • People might want to compare the effectiveness of using goats to other types of control, such as cutting or using herbicides.
  • People might want to know whether the goats would impact their favorite wildflower, either positively or negatively.
  • We’ve had members of the public wonder if the goats could be spreading buckthorn seeds when they eat the fruits and poop out the seeds.  We designed an experiment to test whether it true and found that goats destroy most of the buckthorn seeds they eat.


My friend who has goats helped me answer the question I had about whether goats could be spreading buckthorn seeds around when they eat the fruits.  We put diapers on them, and collected their poop for three days.  After that we looked through the poop for seeds.  We didn’t find many seeds.  Most were destroyed as the goats digested their food. (Something to consider if you ever have a sewing class at school: I needed to sew two of the diapers myself by copying an example I received.  Sometimes scientists need weird skills.)

We use an idea called the scientific method to help us understand how goat browsing impacts invasive plants.  It involves these steps:

  1. Make an observation or have a question. (We see goats eating invasive buckthorns.  They could be having a negative effect on them.)
  2. Do background research. (Other people have also made this observation.  However, there haven’t been any scientific studies so if we really want to answer our question we need to do the studies ourselves.)
  3. Construct a hypothesis. (Our hypothesis is that goat browsing has a negative effect on the growth and survival of buckthorn plants.)
  4. Design and perform an experiment to test the hypothesis. (We individually mark differently sized buckthorns in areas where goats have or have not browsed and compare how those plants are doing over time.)
  5. Analyze data and draw conclusions. (We are still working on this one.)
  6. Often answering one question just gives you more questions. (Example: Who has the world record for longest fingernails? What does that person look like? How did those fingernails get so long? How does the person keep them clean? Does the person keep them clean? Why would someone grow their fingernails so long? What do their friends and family think about it? Etc.)

We are also studying the effects that goat browsing has on the rest of the plants, and trying out a method to keep the goats from getting a potentially deadly parasite from white-tailed deer.


We see some really beautiful things during our work, like this showy orchid.  I love seeing the early spring wildflowers bloom.

I really love my job.  I get to spend a lot of time out in the woods, interact with the goats, and meet the baby goat kids.  I also have awesome people who work with me who have different things that they are good at, like identifying many species of plants.  There are some days when I work alone, but in general scientists today often work in teams with members who have complementary skills.  A lot of ideas we have about scientists are either no longer true or were never true.


Does your idea of what a scientist does include overalls, mud, and muckboots?  How about cute baby goats?

If you think you might want to be a scientist when you grow up, I have some secret knowledge for you.  Being able to write well and communicate your ideas to others are extremely important for all scientists, even theoretical physicists.  Also, even when I went to college I had no idea how important math is for ecologists and biologists.  It’s worth getting good at even if you don’t like doing it right now.

I have some questions for you to consider:

  • Why is science important to society?  Why is science important to you personally?
  • What environmental problems do you see locally? Do you have any questions about how to deal with them? How could you answer some of those questions?
  • How might reading this have changed your ideas about what scientists do?
Photo by Efdal Yildiz from Pexels.

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