Apple Snails-Pomacea species-in Texas
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Today is 9/28/2021. I hadn't known anything about
Apple Snails before July of this year. Since then, I've
read a lot about them, found them, filmed them, and tried to
help
control them. I quickly gathered a lot of imagery and
information about them, so...here it is. For now, the newest
material is at THE BOTTOM of the page. This shows
how my knowledge of these snails has changed over time.
07/08/2021
-
07/10/2021 A
friend of mine told me about seeing Apple Snail egg clusters along the
Live Oak Trail at BBSP. He also mentioned that Limpkins had
appeared in the area--
since they are known to eat adult apple snails. I'd only recently
learned that the egg masses of Apple Snails look like wads of pink
bubble gum stuck on surfaces near water, because I'd
seen one mass on a tree in Houston, at Fiorenza park. Just *one*
mass, and at the time I didn't know what it was. I haven't seen any
there since. But, about a week ago, I noticed a few egg
masses at Scobee field, but hadn't thought much about how they got there
and what they meant. But then I started reading about them. And I
went back to Scobee for another look, and took
the pictures here. At some time recently, most of that park must have
been flooded. This makes sense because that entire area is *inside* the
Barker Reservoir-a flood-control structure
which is designed to capture water. Anyway, I went there between
bouts of rain, so didn't have a lot of time this trip. The
pictures are all of the same area. Note where the eggs are.
The
masses on the "bridges" over the ditch aren't a big surprise (there's
water in the ditch) but then there are masses on the tree, and on the
picnic table. Water must have been higher. I didn't
see any snails this trip. Also, I dealt with all the egg clusters
I took pictures of (and more that I didn't get pictures of).
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Egg Aftermath
Then I did more research. The source I liked best--which seemed
relevant to Texas was this one: Identity, reproductive potential,
distribution, ecology and management of invasive Pomacea
maculata in the southern United States (by Romi L. Burks et.al.
2017). This book was also very informative:
Biology and Management of Invasive Apple Snails ed. Ravindra C.
Joshi, Robert H. Cowie, Leocadio S. Sebastian 2017. It also
contains the prevous study. I found the book in many places
online. Here's one link: https://enaca.org/?id=931
This is what I've learned. The term "Apple Snail" is too
general. Over time, it has led to some confusion while discussing
these animals. In the Southern U.S., the species Pomacea maculata
is
the most widespread. P. maculata were probably
introduced here through mishandling of the snail by aquarium owners. The
snails can keep enough air in their shell to allow them to float.
Then,
if the body of water they are living in became flooded (like in a
hurricane. Harvey, for instance.) the water can carry them everywhere
and anywhere. Perhaps that's how they got to Scobee field.
P. maculata lay eggs on surfaces above the water line, usually
during dawn and dusk. A normal clutch of eggs is about 1500-2100
and takes about 30 minutes to deposit. The eggs hatch in
about 2 weeks, and can yield hundreds of hatchlings. The best
hatching results if the eggs remain dry for 6 - 9 days. Any submergence
during this time can affect the stability of the eggs. The
eggs are also toxic, possibly a by-product of the same chemistry
that allows them to incubate in open air. Their bright pink color may
also serve as a warning against being eaten.
P. maculata apparently eats almost everything. Like many snails, P.
maculata eats periphyton (algae, detritus, etc. that cling to surfaces);
but they also eat macrophytes (larger plants that are
visible all the time...duckweed, rice, lotus). In Louisiana,
they are of major concern for rice farmers, as the snails will eat young
plants. The snails will also eat crawfish eggs. Although the
eggs
are toxic, the newly-hatched snails are fair game. It's
possible the young snails could be eaten while they're growing by the
predators that are usually around--crustaceans, insects, fish,
turtles,
wading birds and some mammals. Some crawfish species seem to
prefer P. maculata hatchlings to those of native snails. The birds
called Limpkins don't normally live in Texas, but some have
recently been observed here eating Apple Snails!!
One more thing--P. maculata-like many snails-are inhabited by many
parasites. Some of these are dangerous to humans. One worm in
particular--Angiostrongylus cantonensis (aka Rat
Lungworm) is pretty nasty. It is generally spread to humans when
they eat improperly-cooked snails. The book I mentioned above
gives a very good view of how many countries are trying to
control the damage being done by the various species of "Apple
Snails". The studies are good examples of what major incursions of
the snails look like. They look BAD. A common method of
early control is to destroy egg masses whenever they are found, and
capturing and disposing of adult snails. In both cases, care should be
taken to avoid being contaminated by contact. Also, I
haven't found very much descripton in what do do with snails after
they're collected. It is illegal to transport the snails in many
places--to prevent further contamination. I suppose crushing them in
place is an option (but not very humane...which might be why
it isn't suggested often). I've also seen references to
freezing them....for a few days to be sure they're dead. It appears
that
P. maculata can also survive short exposures to freezing
temperatures.
Now, when I look at my pictures, it seems that there
isn't really much at that park there for adult snails to eat. The
hatchlings might be able to live off periphyton for a while, but there
isn't much else.
And, once the rain stops, those ditches are normally dry over the
summer. Between the wading birds coming in to clean out the wet
ditches, and lack of water, perhaps the snails who have ended
up at Scobee will mostly die anyway. To be sure, I did
make sure to smush all the egg masses I took pictures off--plus more
that I didn't.
On
07/10/21, I returned to Scobee Field. I went early,
hoping that I could catch a snail laying eggs. And, I did! I
shot some pictures of the snail at work, and some video clips as well.
If you
examine the pictures below, you'll see how much more water there
is. It rained a lot Saturday. The model airplane group that
runs Scobee Field were having an activity there, so I didn't stay in
their way (They were perfectly friendly. I just didn't want to be
in the way.) There was one snail at work, so I filmed that one.
The video
is here. I was amazed when I saw how the eggs were
carried out of the snail, and up to the wall. There was a
sort-sort of trench in the snail's flesh. But, it wasn't a defined
structure. It changed shape, and other dimples formed to carry
separate
clumps of eggs. Pictures in the bottom row below show
this....trench. The video shows it working.
The final picture shows an empty shell that was there. Something had
eaten most of the snail out of it. There were lots of wading birds
around that morning. One of the folks walking around
suggested that raccoons might eat the snails. That's encouraging, but I
have a question (at least one, anyway). Since the eggs are toxic-which
prevents most animals from eating them (the bright
pink color might act as a warning (aposematic coloration)); then what
happens to animals that eat a snail that has eggs inside? Also,
the egg masses I saw, and the snails I found--were
removed carefully. They're gone. Since I always carry hand
disninfectant, I used it after this.
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Egg
channels
The shell is not smooth everywhere.
Something ate most of this one.
07/25/2021 and 08/01/21-
I've been doing more research on our
apple snail invaders since July. When I saw the inside of an adult
Pomacea, I noticed orange masses or organs. I figured that
those were eggs. Since the deposited egg masses are toxic, I wondered if
the eggs inside the snail were also toxic. And, if the eggs are
toxic--how can any animals --such as Limpkins--eat the
adult snails? After a lot of searching, I couldn't find any
detailed description of how this situation is dealt with. The
first picture below was taken on 7/24/21, but I'd seen inside other
snails before
then. The other two pictures were taken 7/10/21, and show a snail
that something had eaten. At the time, I hadn't realized that the toxic
egg masses had been left inside the shell.
I found a number of references saying that animals that eat the snails
discard the albumen glands. But the only predator I saw named
doing this was Snail Kites. But no clear descriptions.
I started searching for proof that Limpkins
might discard these organs. I found a video on youtube that shows a
Limpkin doing this! After that, I started looking around BBSP for
signs
of this behavior.
But let's pause a bit. Limpkins? Limpkins (Aramus guarauna)
are long-necked wading birds with long, pointed beaks. They're about the
size of Night Herons (maybe a bit larger).
According to Avibase, the World Bird Database, it is the only extant species
in the genus Aramus and the family Aramidae. The "home range" of 4
subspecies of Limpkins is: Florida, Cuba,
Jamaica ; southern Mexico south to western Panama;
Hispaniola and Puerto Rico; central and eastern Panama; South America,
south west of the Andes to western Ecuador, and east of the
Andes south to northern Argentina. Like many wading birds, Limpkins can
be generalist predators but according to many sources, the greatest
component of their diet is: Apple Snails. If we
examine the list of regions in their "home range", we can see
something missing-- TEXAS.
That's right. In fact, their home range is far
from Texas.
Texas is now being invaded by Apple Snails. If only Limpkins were
in Texas! Well...they ARE in Texas. In fact, they have been
hanging around in the lake next door to BBSP for some months
now.
That lake is infested with snails. Unfortunately, the snails have made
their way to the BBSP side of the fence, along Live Oak Trail. But the
Limpkins have been picking them off there, also.
Discarded snail shells litter the trail. I went down Live Oak Trail on
7/18, and I saw something interesting among some discarded shells. I
took a few pictures. Next to one
of the shells is a pink mass. I think that mass is one of the "albumen
glands" that was discarded by the Limpkin that ate that snail. The trail
was really wet, so I didn't go further.
First 3 images below show shells on the trail, and a pink mass neer
them. The last image was taken there on 8/1/21, and shows pink material
in the discarded shell.
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I returned to Live Oak Trail the next week (7/25).
I'd been around the other trails, and entered Live Oak from the East end
and walked West. I was doing snail egg removal. It was Noon,
and it was hot, so I didn't expect to see anything. A Limpkin
appeared on the South side of the trail, near the fence, and hunted the
area near the fence. I stayed back, and hardly moved.
It came to the trail, walked on it a bit, then went back under the fence
and eventually up the levee and across. I got pictures and a bit
of video! This is all edited into this video.
Next weekend (8/01). I'd been out on the
other trails first. I met a couple park visitors I'd sent to Live Oak
trail and they told me they'd hadn't seen any Limpkins, but had seen
snail egg masses,
and even a few live snails. So I was on Live Oak Trail again, at
about 12:30pm. I'd gotten almost to one of the "bridges" when I
saw a Limpkin up in a tree between the trail and the
road--that is, North of the trail. I watched it for about 20 minutes,
until thunder from approaching rain clouds convinced me to start back to
my car. I got a brief look at another Limpkin
in a tree near the one I'd been watching. They both moved, and
seemed to start hunting, but I didn't want to get caught in rain that
seemed to be approaching. I got photos and video
clips. Again, this has all been edited
into
this video. More information about Limpkins is on my limpkins page.
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And, I found another snail shell that seemed to have remnants of a
discarded "albumen gland" in it. I also found another paper that
seems to have been inspired by the habit of snail predators
discarding the "albumen gland": "Apple
Snail Perivitellin Precursor Properties Help Explain Predators’
Feeding Behavior" 2016 by Cadierno, Dreon, Heras. While it
discusses Pomacea
canaliculata and not our problem (P. maculata), I think it's still
related. This study is where I got the term "albumen gland" for the
organ which produces the snail eggs. Perivitellin
serves as a
nutrition source for snail embryos (similar function to egg yolk
). While the paper is a bit technical for me to fully understand, for me
it verified: a) that the organs are
toxic, and therefore
consumption of the entire snail could be dangerous; b) that
experienced predators do
discard toxic parts of the snail, rendering it safe to eat. From the
paper: " Therefore, as the noxious
perivitellin precursors are exclusively confined
within
the AG, this explains why it is the only usually discarded organ, even
when this behavior implies a large loss of the total energy and
nutrients available from the soft-body biomass (Estoy
et
al. 2002). Finally, we propose that the reddish-pink gland color may
contribute to this behavior, helping the visual-hunting predators of
adult snails to associate the bright AG color with the noxious
compounds it carries."(page 466 "AG"=albumen gland)
This could be trouble for our local predators (such as alligators) that
might consume entire snails. Raccoons might be able to identify
and remove the glands, but they'd have to learn about the
danger first (that might be what ate the snail in the picture above).
It's potentially good news that Limpkins are eating snails here. It will
be better news if they establish a breeding population in
Texas. They can help control the spread of the Pomacea. But, regardless
of predation, and it seems to me that the snails will remain. I
think the most we can hope for is that the predators that
have followed the snails (and other local predators) and the snails will
reach a "balance" where the snails will not overpower the environment.
There must be reasons why Limpkins haven't made
the journey here before. If lack of snails was a
factor...where they're here now. But, if there are other environmental
reasons (such as temperature) the Limpkins may not stay. I
hope they do.
My Big Apple Snail Followup, written
09/28/2021-------------------------------------------------------------------------------------------------
Update 09/28/21-
I made repeat "snail expeditions" to
Scobee afterwards. I scraped off egg masses, and on one visit
removed 52 snails--and those were moving around in the drying ditches
and trenches. One might
think that we could just leave them alone and the snails would
eventually dry up and die. After all, they're only snails, right? But
these are *really tough* snails. LOL
They have been observed feeding in
water at 2deg C . In hot dry weather they can aestivate and can
survive easily in 15 - 35 C ( 59 - 95 F) (from:
"Identity, reproductive potential, distribution,
ecology and management of invasive
Pomacea maculata in the southern United States" by Burks et. al. Page
305)
Oh...and
this species has a gill and a LUNG. An actual, vascularized
lung--which allows them to breathe while out of the water.
From:
"Comparing
apples with apples: clarifying the identities of two highly invasive
Neotropical Ampullariidae (Caenogastropoda))" by KENNETH
A. HAYES, ROBERT H. COWIE, SILVANA C.
THIENGO
and ELLEN E. STRONG: "The results of the anatomical
investigation confirm previous findings regarding anatomical
organization of ampullariids generally, and Pomacea specifically.
Ampullariids
are large to very large basal caenogastropods, and the only gastropods
with both a monopectinate gill and a lung. Nuchal lobes are elaborated
on both sides of the neck; the lobe
on
the
left elongated to a greater (e.g. Pomacea spp.) or lesser (e.g.
Felipponea spp. and Lanistes spp.) extent to form a snorkel (referred
to as a ‘siphon’ by many authors) that can be used to direct
air
to the lung opening when the animal is submerged." p.745
From: "Physiology of the Apple Snail
Pomacea maculata: Aestivation and Overland Dispersal" by
KRISTY MUECK, LEWIS E. DEATON, ANDREA LEE, AND TREY
GUILBEAUX
Biological Bulletin 235(Aug
2018):43-51":
1)In
one experiment 80 snails were started to aestivate by putting them
in air at 20C at 60% humidity. P44.
2)Experiment
was stopped after half the snails died. That was 308 days. Half
the snails survived 10 months out of water!!! P.46
3)Snails
traveled
2 to 358 cm in 30minutes call it 180cm in .5 hours or 5'10"
in 30minutes or 10' per hour (or about the width of the Live Oak
Trail)--OVER LAND. P.47
4)Based on the present study, P.
maculata can sustain travel over dry land for more than 3.5 h at an
average of 2 meters per hr, sometimes covering up to 3.5 meters in
less than an hour. p.49
5)This
study has shown that the Louisiana invasive apple snail P.
maculata is well adapted for survival in the absence of water.
It can remain fully active under conditions of high RH, or it
can
aestivate for long periods
if the humidity is low. The ability of P. maculata to sustain
travel over damp substrates and endure aerial exposure suggests
that the reduction of water levels is less
likely to be as effective as has been reported for P. canaliculata. also p.49
Adult Apple Snails are very
strong, and make a lot of toxic eggs. It seems like a grim
situation, but there are allies already here in our environment
that may be able to keep the snails from
overrunning everything.
I've gathered images and video that I believe
illustrate some of the descriptions I've read, and they're
below. I have also put together an 8-minute long
video that shows
some of the activities
I describe here. Here's the video link. If anyone is
curious about adult snails I've filmed--all of the adult snails
that I filme were removed from wherever they were found and
were rendered unable to
metabolize.
I had revisited Scobee Field on 7/17/2021--between
the two visits described above. Although I shot the images shown
below then (and some video) I decided to read more to try
to put some perspective on to
what I had recorded. These are examples of the snails moving on
land. Other snail species can do this, but this species-Pomacea
maculata-is the destructive
invasive of concern. I found two
separate examples showing how snails could push through thick
vegetation and even leave a trail! The first two images below
show one of these trails,
and also how long it was. The
rake is 15 inches wide. Next is the snail, with scale to show
size. The last image shows the shallow "ditch" and the
remaining water in it.
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Snail track in the grass.
Rake =15 inches wide
There's the snail.
Snail is about 2.5 in (6cm)
Water in shallow ditch.
The
pictures
below show other views of the same ditch. A snail was able to
deposit eggs on a single twig (that must have been interesting).
Then in that shallow puddle, I found 5 adult snails.
Two of them are shown in the 3rd
picture below, with a closeup of one snail in the fourth
picture. These pictures can be compared with others taken
before and after this time (in sections above).
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More of the ditch.
Lone egg mass on a twig.
Two snails in the shallow
puddle.
Snail moving in shallow water.
The
first
picture below shows egg masses on a tree surrounded by mud--many
feet from the water. The last three pictures show a
different track and the snail that made it.
There is water visible through
the plants, but the snail is not submerged.
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Egg masses on a tree, no
water nearby.
Snail track through the plants.
The snail making the track.
Snail moving over very shallow water.
At
Scobee Field on 7/24/2021--The
ditches
dried, though the dirt was still damp. I noticed a snail shell
in a hole in the mud. Since I'd read about these snails can
aestivate, I took pictures of the
shell before I moved anything. I had already seen many snail
shells lying out of the water in other locations, and they'd all
been empty(dead). But just in case, I took many pictures
of this one.
The depression, or hole, or whatever, was intriguing.
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Snail in the dried ditch
Shells of dead small snails litter the area
Snail in the hole shot with flash
Snail
in the hole shot without flash
Then
I
turned the shell over. The snail was alive! I could
tell by the sealed operculum. I took pictures of the snail
and the depression. The hole wasn't elaborate, but it seems like
the snail made
it. As of this date (9/29/2021) I haven't found any
description of how Pomacea aestivate naturally. Do they dig
burrows, or dig anything? I've read of one experiment shows that
it's possible for
these snails to survive TEN
MONTHS without water, as long as they can maintain a
seal to conserve internal moisture. The snail had "backed into"
the hole, so perhaps it could dig by
manipulation of its foot.
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Snail flipped over. It's alive!
Flipped snail next to the hole
Closer view of the hole
Snail near the hole, view
shifted a bit.
At Scobee Field on 8/17/2021--The
ditches
had some water again. I found an adult snail moving around in
the water at one of the culverts. In this case, there were
strings of amphibian
eggs in the water, too. I think they belonged to a species
of toad. I've read that Pomacea will consume amphibian eggs as
well as the various types of plants. So, I watched (and filmed)
the
snail as it moved around the ditch and over the eggs many times.
I didn't see any sign that this adult snail paid any attention
to the eggs at all. The snail didn't pause, the eggs remained
intact.
The video clips I captured are included in the edited video.
Here's
the video link.
Snail in the ditch with
amphibian eggs. 1
Snail
in the ditch with amphibian eggs. 2
Snail
in the ditch with amphibian eggs. 3
At Scobee Field on 9/18/2021--A
small bit of water appeared in the ditches. The pictures below
show that the water hadn't been there long. But when I looked
into that shallow puddle,
I
found 5 adult snails. Where did they come from? How did
they get there? I started filming, and this time I captured more
interesting behavior.
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Very shallow puddle
in the same ditch.
Live snails moving in
the water!
The water hasn't
been there long.
Two
snails moving around mower tracks.
Apple
Snails (and some other species of snails) have gills and
a lung. This explains why the snails can go over land, or climb
trees--etc. While I watched the snails moving around
the
shallow puddle I noticed them probing with their "siphon".
But the probe went straight up until it broke the surface
of the water, where it opened. The siphon had become a snorkel!
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Pinched-closed
siphon reached up.
Pinched-closed
siphon breached the surface.
Siphon begins to open.
Siphon opening expands.
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Siphon is now a snorkel.
Siphon is now a snorkel.
Breathing through the snorkel.
Close
the opening and submerge.
I noticed something else while
the snorkel was being used. With the snorkel deployed, the head
of the snail moved in and out; as if acting like a pump.
The series of images below are frame
grabs from the video. They show how the head moved in and out.
This is also shown in the same edited video clip. Here's the video link.
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Snail's eyes,
antennae, and face.
"Air Pump" cycle, snorkel up, head is
out. "Air Pump" cycle, snorkel up,
head is in.
"Air Pump" cycle, snorkel up,
head is out.
Although
these
snails are pretty tough, there are already natural allies here
that may help control them--that is, help stop them from taking
over the environment. After all, they do have a natural
habitat (continent of South America), and are part of the
ecosystem there. So, here are some of the animals on the Home
Team:
1) Raccoons have been observed eating the adult snails--and they
discard the toxic albumin glands. Here's a link to the article "Observations of
Raccoon (Procyon lotor) Predation on the
Invasive Maculata Apple Snail (Pomacea maculata) in
Southern Louisiana". And, here's a link to connected video
showing raccoons with snails. The links were good
when I used them.
Can't guarantee they still are.
2) Remains of Apple Snails have been found in stomach contents
of alligators harvested in Louisiana. In article "ALLIGATOR
MISSISSIPPIENSIS (American Alligator). NOVEL NON-NATIVE PREY".
Link to the article (in
Herpetological Review, pages 627-628).
3) At least one native species of ant will attack snail egg
masses. Surprise!! Not fire ants (although they might consider
it). Article: "Observations of Acrobat Ants (Crematogaster sp.)
Preying
on the Eggs of the Invasive Giant Applesnail (Pomacea
maculata)" Link to the article is here. Link to a related video is here.
4) A native sunfish--Redear Sunfish (Lepomis microlophus) AKA "shellcracker"
is known to eat small snails of many kinds, including young
Pomacea. TPWD link here.
5) Limpkins! These birds are not native here, but have
moved in to Texas, at least for the summer, and they are
specialists in eating Apple Snails. As far as I know, Limpkins
have not been
seen nesting here yet, so they might not have established a
population here--so far.
6) Crawfish. Some crawfish are voracious. Native Red
Swamp Crawfish (Procambarus clarkii) are for sure, and I've read
that they will also eat young Pomacea. Which is good, since I've
also
read that adult Pomacea snails can ravage crawfish habitat and
also eat their young. So that's a few of the animals that can
help control the growth of Apple Snail populations. Along with
these...
are people. Scientists around the world have been trying
create some kind of control but have not yet found one. In the
meantime, collecting and destroying adult snails, and scraping
snail eggs off
and into the water can help. I have done a bit of
this at Scobee (removed about...70 snails total and maybe a
hundred or so egg masses I think). And also at Brazos Bend
State Park (only found
about 20 snails, but have removed about 400 egg masses off the
trees along Live Oak Trail there.) This is not much
compared to the efforts of some other groups of people at some
other ponds
and lakes. The images below are from Brazos Bend State Park on
09/05/2021.
They will give some idea of the number of masses possible on the
trail. I've found 180 masses along a 100-yard stretch in two
hours. A short video demonstration of scraping technique
is
in the same edited video.
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7 egg masses, with old
smears others.
4
egg masses, with old smears others.
4
egg masses, maybe different species
9
egg masses, with old smears from others
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5 egg masses, from the picture of
9
13 egg masses, with old smears
from others
12
egg masses, with old smears from others
Scraping with paint roller handle step 1
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Scraping with paint roller handle
step 2
Scraping with paint roller handle
step 3
Scraping with paint roller handle
step 4
Rinsing toxic egg goo off of
scraper.
04/24/2022. Springtime has brought new life
and activity to the park. Over the last few weeks, people
have starting seeing bright pink decorations on
some of the trees at BBSP. NO--I don't mean the Spoonbills
(although they're here, too). I mean the egg masses of Apple
Snails have appeared along the Live Oak Trail--mostly.
Unfortunately, the eggs are also appearing at other places now.
I took a quick trip around the 40-Acre Lake trail to check
on(the alligator mom--she and her pod seem to have moved away
from the den site where they wintered. I heard a
couple alligator bellowing choruses, and some were close enough,
or out of cover enough, for me to see them bellow. I went back
to my car,
retrieved my "snail-egg removal tool" and went to Live Oak trail
to look for Limpkins and pink eggs. At first Limpkins were
around, but not very busy on our side of the fence.
Snail eggs were there, but most
of them were on plants far away from the trail. I went to
the second footbridge (going West to East), then turned around
to scrape eggs on the way back. It
looked like area nearest the trail was too dry (or too shallow)
for the snails to get close too the trees at shoreline. But,
tree trunks that were
accessible to snails were very "popular."
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Snaileggs Image 04 (above) and
05(below) show a single trunk that had about 20 egg masses (some
hidden by the tree) before and after the egg mashing. It wasn't
the only one.
Snaileggs 06 (below) show an in-between Little Blue Heron being
with some egg masses. When I was at the water's edge, I realized
that there
were hundreds of snail shells littering the mud!
Most of these were not full-sized shells, but mostly maybe 1.5 -
2.0 inch diameter shells, with some larger and some smaller
mixed in. From what I've read of these snails, no
weather-or other
natural event-happened at BBSP over the winter that would have
killed that many--so were these all remnants of
predator activity? WOW! While working back
East-to-West I removed
113 egg masses. But there were many, many more eggs
on plants out in the water where I couldn't reach them.
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I
think Egg masses stopped appearing near the trail a little West
of the first footbridge (but I'm not sure exactly where). A
single Limpkin foraged even further West, in an area that looked
drier to me. But, I'm
not the snail-hunting expert. Some time later, I returned to 40
Acre Lake.
Update 05/19/2022 - From BBSP on 05/15/2022 Springtime at BBSP has been
quite pink lately. Some of the pink is good news but,
unfortunately, some of the pink is bad news. Bad pink
first: The apple snails are still at work on the Live Oak
Trail. I walked down to the second footbridge, then turned
around to scrap eggs off the nearer plants. As the first photo
shows,
the snails use whatever they can use to lay their eggs out of
the water. The water level in the swamp is low, and most
of the plants near the trail have been knocked down. This limits
the climbing points available to the snails. But, as the
pictures show, the remaining exposed climbing points are VERY popular--and they are
covered by egg masses.
I removed about 140 egg masses (and my scraper broke); but they
were concentrated along a relatively short stretch of the trail.
The last three pictures below show the same tree with eggs
from two angles (the arrow points to a "3-lobed"
clump that changes perspective). I count about 40
egg masses on that single tree! The last image
shows the tree after scraping.
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The
Limpkins are still over there, I took a few pictures of
them--just because I can. Limpkins...in Texas.
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That was the "unwelcome" pink.
The "good" pink was Spoonbills, on
another page.
05/27/2023 I
went to Scobee Field to see what the rain a few weeks before
might have affected. The area was mostly dry, although there was a
little bit of water in the
ditches near the road. I examined the dried ditches to see what sort
of burrows were left, and I found another example of an Apple Snail
in a burrow! Although they live in
water, Apple Snails can aestivate in mud during dry periods for 10
months! There were a few egg masses on the culvert near the
restrooms even though the ditch was
dry. So I knew that adult snails had been around. Then I saw this
hole that contained 2 snail shells.
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I
used a metal rod I'd found in the area to measure the depth to the
top of the snail shell--about 5 centimeters. When worked the snail
out of the hole (it was a tight fit), I
found that the snail was alive. The operculum was sealed across the
shell opening and was being held tightly closed. I was taking
pictures with my phone, and in the
bright sunlight it was hard to focus into the hole. But I got a few,
that show the bottom was rounded across the width, and pretty
smooth. How does an Apple Snail dig,
anyway? Of course, the hole was dug while the bottom was still soft,
as the water was evaporating. The snail was about 5cm...long?
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The
hole was about 5-1/2 cm across (of course, "snail-sized"). I used
the same rod to measure the depth of the hole--about 9cm! I still
can't find any images of Apple Snail
burrows anywhere online (although I can find mention that they do
burrow to aestivate). This is my second direct observation of an
Apple Snail in a burrow. The first one
was also at Scobee Field, and is shown on this page , as well as
one of my ichnology
(animal traces) pages here.
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01/05/2025
At BBSP, just as I got to the West edge of
40 Acre Lake and Pilant Lake (both on either side of the 40 Acre Lake
Trail) I found this empty
Apple Snail shell. The first image below is facing the "hill" and the
far end of my walking stick marks the snail shell. By itself, it may
seem like just an empty shell. But, this
was obviously a fresh kill. There were 3 major components left in a
tight arrangement that shows some interesting features.
In
the dim morning light, the pink object was prominent. That is
the "albumen gland", the organ where eggs are produced by a female
Apple Snail. The organ, like the eggs,
is toxic. Therefore, it was discarded by whatever had eaten the snail.
Next to that was a dark, oval, flat object-which reminds me of a giant
guitar pick. That was the snail's
operculum-a structure that the snail used like a door to seal off the
open end of its shell. And finally, there was the large snail
shell--which was intact, and without holes
pierced in it. Whatever had eaten the snail had left these objects
(plus another pink part shown in the second image above) in the neat
arrangement. Raccoons, and
birds
called Limpkins, have both been documented
eating Apple Snails and discarding these parts. I couldn't find any
footprints or other signs in the area that helped me
guess what had eaten the snail. Both Raccoons and Limpkins live in the
park.
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