NANFA-- September 21 sampling

Denkhaus, Robert (
Sun, 22 Sep 2002 11:25:02 -0500

Yesterday, I took 21 members of the 2002 class of the Cross Timbers Chapter of
the Texas Master Naturalists out on the wetland/aquatic systems field trip.
As usual, we visited a number of sites around the Fort Worth Nature Center &
Refuge, which contains a long stretch of the West Fork of the Trinity River,
and a number of backwaters, marshes, and sloughs.

The Texas Master Naturalist program is designed to train a diverse group of
amateur naturalists in the intricacies of the local ecology so that they can
participate in resource management and educational programs in the state.
Participants range from professionals who would like to learn more about local
ecology to housewives, bartenders, and retired folks who want to be involved
in local environmental efforts.

The local training program, 9 weeks in length, focuses on our local
environmental systems including forest, prairie and urban systems along with
the wetland/aquatics habitats. The training for each system includes 2
classroom sessions and one 6-hour field experience. The Fort Worth Nature
Center & Refuge sponsors the local (Fort Worth, AKA Cross Timbers) chapter and
participates in both the North Texas (Dallas) and Elm Fork (Denton) chapters'

For more information on this exceptional program, which has become a model for
a number of other states, check out

Yesterday was a perfect day, weather-wise. Highs were in the mid-80s with
clear blue skies. Everyone was excited about the upcoming adventure. I had
tried to set the stage during the classroom sessions so that no one would be
surprised that this field trip required immersion in the habitat. I had also
given sufficient warning regarding the various hazards of the trip including
but not limited to venomous snakes, poison ivy and alligators.

We started by examining a currently dry vernal pond site to look at wetland
soil types and dominant wetland vegetation. We then moved to the Lotus Marsh
where we checked out emergent and submergent vegetation and discussed the
avian and mammalian residents of aquatic systems. This led to a discussion
regarding feral hogs since the Lotus Marsh is a hotbed of hog activity and our
impending control plan just hit the local media last week.

After a short 4WD adventure, we reached the area that we intended to examine
in detail. This area, one that I have described a number of times before, is
immediately downstream from the Eagle Mountain Dam spillway. In the past, I
have found quite a diverse array of species in this area. Yesterday though,
the water level was down considerably (we are at the mercy of what Eagle
Mountain Lake will give us ("dam" them!) and the collecting was not as good as
usual. I did have the opportunity to introduce the fish neophytes to the

Longear Sunfish
Redear Sunfish
Largemouth Bass
Creek Chub
Black-striped Topminnows
Black-spotted Topminnows
Gizzard Shad
Longnose Gar (3 feet)

The fish catch was rather disappointing but we did add some invertebrates to
the total including:

Glass shrimp
Dragonfly nymphs (numerous species)
Damselfly nymphs (numerous species)
Predacious diving beetles (numerous species)
Water Scorpion
Freshwater mussels (4 species)

We also saw a number of banded watersnakes, cricket frogs, green tree frogs,
and southern leopard frogs.

The highlight (or lowlight, depending on your point of view) of the day came
at the very end. On Wednesday, 18 September, I had released a 5 feet long
male alligator that had been given to me by a local zoo/aquarium because it
had outgrown its relatively small exhibit. Yesterday, a 5' gator was found
floating just below the surface and somewhat entangled in some submerged
snags. Both of the right legs had been torn off cleanly. It appeared that
the limbs had been twisted off at the joint. Closer inspection showed tooth
puncture marks across the skull and another set of punctures across the
shoulder area of the back. It appears that the released gator met up with a
resident male of considerably greater size (ballpark - 8' based upon the
distance between the punctures). No one has seen an 8 footer on the Refuge in
at least a decade but who knows?

Anyway, none of the group wanted to go back in the water after the dead gator
was found so we packed it up and headed back. I'll be doing a necropsy on the
gator in the next week or so.

Rob Denkhaus
Fort Worth Nature Center & Refuge
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