2011-2012, Collier, Field Experience I (Collier Seminole State Park): Manatee Middle School
Revised: 11/28/11
Invasive Exotic Animals - Cuban Tree Frog vs. Green Tree Frog
Summary: This activity teaches students the concept of native versus exotic animals, and explains the ways in which
exotic animals can become invasive exotic and take over an ecosystem.
Vocabulary: Invasive, Non-invasive, Exotic, Native, Competition, Resource
Equipment: 4 Cones, flagging tape, 20 Vests, 20 yellow poker chips, 20 red poker chips (other colors may be chosen if
they are more visible on the playing field, whiteboard and marker
Procedure: In this activity, students will learn how invasive exotic species out-compete native species for resources.
Beginning with a group of 25 students, choose 5 students to represent the newly introduced Cuban tree frogs. Cuban
tree frogs will head to the “Cuban tree frogs” side of the playing area, and the remaining students will head to “green
tree frogs” side of the playing area. At the blow of a whistle, students from both sides will need to race into the playing
area to retrieve one shelter token (yellow) and one food token (red) then the green tree frogs try to return to the safe
area. The only difference between Cuban tree frogs and green tree frogs is that green tree frogs will have to pick up 2
tokens, while Cuban tree frogs have to pick up a shelter token, but have the choice as to whether they want to pick up a
red token for food, or eat a green tree frog for food. Because the green tree frogs know that the Cuban tree frogs are a
predator, the green tree frogs need to retrieve their tokens as quickly as possible and make it back to the starting line.
The Cuban tree frogs can linger in the playing area in order to try and tag a green tree frog. After the first rounds, any
green tree frogs that were tagged by Cuban tree frogs will move to the Cuban tree frogs side and become a Cuban tree
frog. Play for several more rounds, and during the final round, tell students that Cuban tree frogs are cannibals, and that
in addition to eating green tree frogs, they can also eat each other! At this point, mayhem should break loose and you
can end the game shortly after.
If time allows, start the whole game again. When you get to a point where there are only a few green tree frogs
remaining you can add a new unexpected twist to the game. Occasionally, we get cold winters that can kill Cuban tree
frogs because they aren’t adapted to the cold while green tree frogs’ range extends into the Carolinas so they may be
survive a good cold snap, even freezing temperatures. At the point of the game when you are ready to tell the Cubans
that they can be cannibalistic, instead, quietly tell the few remaining green tree frogs that they have already won the
round because the Cuban tree frogs are going to freeze. Let them know that when you say start, that they can slowly
walk around the playing field and pick up as many of the tokens as they want because the Cubans won’t be able to get
them. Before you start this round go over to the Cuban tree frog side and make sure they are excited and ready to start
the round. Ready! Set! Wait, wait, wait… a cold front just came through and froze all of the Cuban tree frogs. At this
point the green tree frogs can come out and collect all of the tokens.
Review how the game worked and make sure the students understand that sometimes the Cuban tree frogs have an
advantage because they are larger than the natives, can eat the natives, and often aren’t eaten themselves because of
their caustic slime. However, in the last game, the green tree frogs had an advantage because they are native to the
area they are better adapted to deal with extreme temperature drops – which the Cuban tree frogs, being from Cuba,
are not. So, sometimes one species has an advantage, sometimes the other species does.
NOTE: During all rounds, use a whiteboard to draw a graph and keep track of the Cuban tree frog population vs. green
tree frog population. This will demonstrate to students how an introduced non-native species can quickly become
invasive. If you have time for the second game then make sure you talk about how sometimes native animals might
have an advantage over introduced ones.
A Learning in Florida’s Environment (LIFE) Field Lab
Office of Environmental Education - Florida Department of Environmental Protection
Page 1
2011-2012, Collier, Field Experience I (Collier Seminole State Park): Manatee Middle School
Revised: 11/28/11
Diagram: note the random distribution of food and shelter
Cuban tree frogs
green tree frogs
A Learning in Florida’s Environment (LIFE) Field Lab
Office of Environmental Education - Florida Department of Environmental Protection
Page 2