SPECIES MANAGEMENT PLAN
For this project, we created management plans to rid the Durango Nature Studies Property of invasive bullfrogs. To do this, we conducted field work at DNS and analyzed the data, including sorting macroinvertebrates, conducting a Shannon-weiner index (a method of determining biodiversity), and assessing water quality. We then used this information and data to create a species management plan, and conducted a formal presentation to a panel of professional biologists trying to sell our plan to them.
In the article “Time to stop worrying about invasive
species”, Karen Hopkin says that native species shouldn’t be given priority in
an ecosystem simply because they are native, but rather that each species
should be considered on an individual level regarding their impact on the
environment. An example the author gives is that the mountain pine beetle,
which is believed to kill the most amount of trees in America, is not invasive.
This article suggests that invasive species should be defined not by their
place of origin but by their effect on the immediate ecosystem.
Personally, I think that this article has a fair point; it should
be based on a case by case basis. There is no need to punish a species for no
other reason besides the fact that they are invasive, especially if they are
contributing to their habitat. However, I think that many invasive species do
threaten biodiversity or their populations can become uncontrolled, which is
why I have come to the conclusion that yes, species should be considered on a
case by case basis. However, the size and habits of such invasive species
should be kept in mind to ensure that no smaller, less significant population
decimates. In this specific case regarding bullfrogs in Colorado, I think that
it is so large of an issue that it requires immediate action, however bullfrogs
are very common in both native and invasive habitats, and often do threaten the
stability of an ecosystem. Because of this I do believe that our management
plans are justified.
In this project I learned a few different things. Firstly, I
struggled with writing objectively at the beginning of the project, and I believe
that I made quite a bit of progress in that area. Also, I am the first to admit
that my public speaking skills aren’t exactly beautiful. I often get really
nervous before presentations like this, especially because my partner and I
presented in front of a panel of professional biologists as a challenge option.
I few days before the presentation I was very stressed out and felt unprepared.
However, I had learned from past presentations and POL’s that practice does
help. My partner and I worked really hard practicing with our slideshow, and I
think that our work paid off. Besides a few minor slip-ups, our presentation
was very much a success, and I definitely learned that, although maybe not the
most exciting thing to do, practice really does help when it comes to public
speaking!
Here's our Final Management Plan:
Species
Management Plan for
Rana
pipiens & Rana catesbeiana on the Durango
Nature
Studies Nature Center Property
Hanna
Martens and Martina Pansze
Durango,
CO
2011
Field
Condition Form: Hanna Martens
Land
manager Durango Nature Studies, wants to promote native leopard frog amphibians
on their 140 acre property and control the bullfrog (Rana catesbeiana) population. Bullfrogs started appearing on the
DNS property a little over three years ago, and because they are an aggressive
generalist predator, they have been effecting the population of other
amphibians that are native to the area. According to the Bullfrog Literature
Review, Rana catesbeiana (bullfrog)
is on the list of 100 most invasive species (Smith, 2007).
Animas
High School students preformed a visual encounter survey of the amphibians in
the area in order to estimate the population size of bullfrogs and leopard
frogs. Water quality tests were conducted for data and research purposes to
examine biodiversity. A wildlife
inventory was also completed to get an idea of the ecosystem as a whole.
The
DNS property is used for many activities. During the summer months youth summer
camps, adult workshops are hosted on the property. Fort Lewis, Colorado State University, Southwest
Conservation Corp. and other organizations conduct ongoing research on the
property. Many schools K-12 from around the area go to the property to do
research and learn more about animals and habitat. It is under a conservation
easement, which protects the land and all its inhabitants from
development. All of the activities
provided on the property effect our research because there are human influences
we have to take into account for when creating a successful management plan.
Durango
Nature Studies has a maximum budget of 2,000 dollars that will go to managing
and monitoring how to keep the bull frog population to a minimum in the Durango
Nature Studies area.
Plan
Development: Hanna
Martens
Rana Catesbeiana: This species of frog is adaptable and
versatile when it comes to habitat types. It is an invasive species and is
capable of coming into a new environment and negatively impacting ecosystems. They
are mostly found in lowland permanent water bodies including wetlands, ponds,
lakes, sloughs, creeks and rivers (Hallock, 2009). Similar to its native
range, bullfrogs likely overwinter in permanent water bodies near sources of
well-oxygenated water. The frog is mainly aquatic, but it can spend a
considerable amount of time on land. Eggs and larvae develop in permanent slow
or non-flowing water bodies (Spitzen, 2010).
Well-developed vegetation is a requirement for the bullfrog to have a
stable habitat.
Rana Pipiens:
The leopard frog lives in a wide variety of
habitats. There are three main habitat types, winter, summer (adult), and
tadpole developing. All of these must be
in close proximity to each other in order for the frog to migrate as needed. The tadpole habitat is also the breeding
area, in which tadpoles spend approximately three months of their life. These
areas must be in shallow quiet ponds that are usually not connected to other
bodies of water. Ideally the ponds do
not support fish populations, however some do.
In the fall, the frogs migrate to what scientists call an overwintering
site. In these specific sites, the frog usually will use the bottoms of flowing
streams and rivers that are large enough so they do not freeze over during
winter. Oxygen saturation must be relatively high for the leopard frog to
maintain health and preventing low energy levels for the frog. After reproduction, adult northern leopard
frogs move into upland habitat where they can feed for the summer (Smith,
2007). Generally these areas are in
close proximity to water, and are in grassy meadows. In all of these habitat
types, the pH level must be between 6.0 and 9.5 alkalinity, for an ideal living
condition of Rana pipiens.
Durango
Nature Studies acquired 140 acres of land bordering the Florida River in 1998.
This land is under a conservation easement in which it is kept free of
development. Throughout the property is
a wide variety of habitats- riparian, meadows, oak woodlands, piñon-juniper
forests, and desert arroyos. The upper 35 acres of the site is comprised of
public access and parking area, prairie dog colonies, bird boxes, a children's
habitat play space, an ancient ponderosa pine cross-section with marked rings,
xeriscaped landscaping, and a sage-rabbit brush habitat. All of the studies Animas High conducted were
located on the northern pond, and on the Florida River (Figure 1).
On the Durango Nature
Studies property, Animas High School conducted studies and tests to acquire
knowledge of the property as a whole.
The Florida River tested positive for coliform bacteria which suggests
the presence of harmful protozoa and viruses. The pond and river showed small
traces of nitrogen (1 ppm- pond, 2 ppm- river) which is considered unpolluted
on the nitrogen scale (under 4 ppm is not polluted). The pH level in the pond
and river were between 8 and 9 which suggest that it consists of mostly
alkalinity. The pond was 2ppm and river was 1 ppm for the phosphate levels
which shows the levels are relatively high and can be assumed to increase plant
growth. The dissolved oxygen level in the pond was 6.5 mg/L and the river was 8.5
mg/L which is indicating that the area is capable of supporting many kinds of
aquatic organisms, and is a healthy ecosystem.
Research was also conducted to get a sense of the biodiversity in the
area, by studying the macro-invertebrates collected while out in the
field. After compiling all the data,
Animas High School concluded the water quality was good. The Diversity Index in the DNS pond was 0.98,
and the Florida River was 1.02. These numbers indicated that the biodiversity
in the river was on the lower side of normal, and the pond indicated that the
biodiversity was somewhat unstable.
Pollution indices were also tested through the macro-invertebrates, in
which our data showed that because there were mayflies present in the pond, it
indicated that the water quality was high. The Florida River lacked stoneflies,
which meant that the water quality was healthy but indicated some pollution elements.
Plan
Implementation : Martina
Pansze
Animas
High School would like to promote Rana
pipiens (Leopard Frog) populations on Durango Nature Studies property in
order to maintain native biodiversity. In the interest of promoting leopard
frogs, Animas High School will conduct a yearly visual encounter survey of
leopard frogs. If the population has dropped from the previous year, the DNS
pond will be opened to the public for the fishing of bluegill, a predator of Rana pipiens. Animas High School will
also monitor the field surrounding the the pond as well as the edges of the
Durango Nature Studies pond to ensure that the muddy banks of the pond stay
generally clear of debris and litter, and that human activity is limited in the
meadow.
Animas
High School will not act on maintaining the Bluegill until the leopard frog
population decreases because children’s bluegill fishing programs occur in the
summer. However, the bluegill fish is a predator of the leopard frog, and therefore
the leopard frog populations must be closely monitored by Animas High School
every October (fall is the most suitable time for the monitoring because the
frogs are not in hibernation or in mating season, as not to disturb eggs) (World, 2008) to
determine if action is needed to be taken on the bluegills. As a rule, if the
number of leopard frogs becomes lesser than ten in the pond (Animas High School
previously did a visual encounter survey, and estimated 10 leopard frogs), the
pond may be opened for lethal bluegill fishing until the leopard frog
population is again sufficient (above ten). To avoid complications in counting,
the bluegill population will not be counted, but instead necessary actions will
be taken according to leopard frog count data. Every October the banks of the
Durango Nature Studies pond will be cleared of debris including wood, litter,
and any weeds that appear to be invading the bank area. This is a necessary
measure because Rana pipiens use the
pond banks as a habitat, a hibernation spot, and an area to lay their eggs in
the spring, and the mud needs to be accessible. The human activity in the
meadow must be monitored (to determine if buildings or new trails will
significantly impact leopard Frogs) because that is the Rana pipiens habitat (Sutton,2003), and continuous
human activities could have negative consequences and destroy resources. This
plan would cost nothing to Durango Nature Studies except to advertise fishing
of the bluegill on the property. A probable estimate for this amount would be
$50. Animas High School’s budget for the project is $2,000.
To
promote the leopard frog, have concluded that the best way to achieve this is
to eliminate the frogs by means of direct removal via pitfall traps and
humanely killed by means of a CO2 tank.
The Direct removal is the most appropriate way to confiscate the
bullfrogs because it is inexpensive and will not significantly affect the
ecosystem as electrocution or altering water quality would.
Every
fall during the leopard frog visual encounter survey, Animas High School will
search the pond and immediate bank area for bullfrogs in the pitfall traps as
well. Four traps will be set up in total, and will be checked every day in case
a species besides Rana catesbieana
has fallen into a trap. If any bullfrogs are caught, they will be taken to
Animas High School and killed with a CO2 tank to be used for dissection. In
addition, approximately one inch of water will be added to the bottom of the
pitfall buckets to avoid killing any animals stuck in them, and to prevent
bullfrogs from escaping. The cost of this plan would be approximately $440 for
buckets (for the pitfall traps), a CO2 tank, cooler, and additional supplies (Smith and
Keinath, 2007).
Plan Evaluation:
Hanna Martens
The plan suggested will
impact some of the species, habitat, and activities that take place on the property.
Although the Bluegills will for the most part, remain untouched,
removal/control of bluegills could cause impacts to non-target species.
Bluegills feed on crustacean and insects, so because the ecosystem have
somewhat adapted to the introduced species, population of insects and
crustaceans will flourish, therefore throwing off the balance of other species
that depend on similar resources (Bluegill, 2011). Pitfall traps will be used
for the direct removal of bullfrogs, however will trap other non-target
species. To best prevent from impacting other species, the traps will be
checked at least once a day. While the
management is active, activities around the pond should be halted.
Monitoring
populations of the designated species will be conducted by Animas High School
Sophomore Biology students. Every
October, Animas High will do a visual survey for leopard frog counts as well as
clear the Florida River and DNS pond banks of excess debris and matter. Direct
removal of the bull frogs (Rana
catesbeiana) will also take place. With this, all the bull frogs caught
will be taken back to the Biology classroom and given away or used for
educational purposes. Each year, as the
new sophomores come into Biology class they will participate in a unit similar
to the 2011-2012 class, but instead maintain the population and take population
counts.
It can take a maximum of 4 years for the bullfrog to
fully develop (Spitzen, 2007). If no bullfrogs are seen on the property and the
leopard frog sightings are showing an increase over a 5 year time period, the
management will be considered successful.
If things change during the process and there is either progress or decline,
then the amount of time might vary. After
5 years of the plan showing its success, Animas High School will return to the
property and take another visual encounter survey to make sure the plan in
maintaining stability. Every 5 years, the property will be checked, and if the
plan is unsuccessful over a long period of time it will be reinstated or
reassessed.
(I am not able to post of the pictures because of size, however you can find a map of the DNS property here)
Invertebrate
|
Pond
|
River
|
Caddisflies
|
2
|
120
|
Mayflies
|
41
|
125
|
Midges
|
5
|
15
|
Blackflies
|
0
|
5
|
Coleoptera
|
0
|
5
|
Stoneflies
|
0
|
0
|
Damselflies
|
53
|
0
|
Dragonflies
|
1
|
0
|
Sum
|
102
|
270
|
S/W Index
|
0.99
|
1.02
|
Vendor
|
Item Description
|
Cost per unit
|
Quantity
|
Total Cost
|
Durango Herald
|
Advertisement
|
(1 Week) $15
|
2+
|
$30+
|
Horticulture Source
|
C02 Tank
|
$140
|
1
|
$140
|
Kegworks
|
Cooler & Accessories
|
$270
|
1
|
$270
|
Wal-Mart
|
Bucket
|
$10
|
4
|
$40
|
Total
|
$480+
|
$480+
|
Reference List:
Hallock, A., and McAllister. "American
Bullfrog." Washington Herp Atlas. N.p., May 2009. Web. 1 Nov. 2011.
<http://www1.dnr.wa.gov/nhp/refdesk/herp/html/4racat.html>
"Leopard Frog." Frog World. N.p., 2008. Web. 14 Oct. 2011. <http://frogworld.net/leopard-frog/>
Smith, Brian E., and Douglas A. Keinath.
"Northern Leopard Frog (Rana pipiens): A Technical Conservation
Assessment." N.p., 16 Jan. 2007. Web. 14 Oct. 2011. <http://www.fs.fed.us/r2/projects/scp/assessments/northernleopardfrog.pdf>.
Sutton, Bill. "Northern Leopard Frog: Rana Pipiens." Marshall Herpetology. Ed. Adam Mann. N.p., Dec. 2003. Web. 14 Oct. 2011. <http://marshall.edu/herp/Toads_Frogs/Leopard_Frog.htm>
Zollinger, R., and A. M. Spitzen-
van der Sluijs. Literature review on the American bullfrog Rana catesbeiana.
Nijmegen: Ravon, 2009. 5-25. Print.
