by Rick O'Connor | Aug 7, 2015
First let me explain that Seahorse Key is not in the Florida Panhandle but the story is interesting and a similar phenomena could occur here. Seahorse Key is an isolated island 3.6 miles southwest of Cedar Key in Florida’s Big Bend. There is a science lab owned and maintained by the University of Florida and Captain Kenny McCain on the island but can only reached by boat. Many forms of wildlife, particularly birds, seek out these isolate islands for nesting due to the lack of predators; and Seahorse Key is no exception. Another interesting point about this island is that it may have the highest density of cottonmouths in the state. Dr. Coleman Sheehy has been studying this population and estimates that there may be about 600 cottonmouths on the island. So what is the mystery?
Seahorse Key. An isolated island near Cedar Key
Photo: FMSEA
Well we will first look back to last year and the nesting habits of the island’s birds. In 2014 Vic Doig of the U.S. Fish and Wildlife Service had logged seven different species of egrets, herons, cormorants, pelicans, and ibis nesting on the island. The number of nest per species varied from 100 to 5,000 with the white ibis producing the highest number. Dr. Sheehy surveys the cottonmouths by walking the shoreline and counting the number of snakes he encounters; which is typically around 30. The snakes and nesting birds are concentrated near Gardiners Point. Though the cottonmouths feed on rats they seem to rely on the fish that fall from the nests above.
As 2015 began the biologists noticed something different right off the bat. Though the birds were returning they were not returning in typical numbers, particularly the white ibis. These birds normally are the most abundant nesters on the island, but not this year. Dr. Peter Frederick, University of Florida’s Department of Wildlife Ecology and Conservation, did not seemed to alarmed by this knowing that white ibis are nomadic and do not stick with the same nesting locations for more than a few years. They tend to go where the food is most abundant. No mystery here… Then it happened…
A cottonmouth consuming a fish from a birds nest.
Photo: University of Florida
Within a very short period of time, during the second week of April, all of the other birds began to leave. Researchers found the nests falling apart, no eggs or chicks within them, and hundreds of eggs on the ground. They also found the remains of 26 dead birds in the area. Where had they gone? What had happen?
Autopsied birds found no consistent cause of death. Most of the eggs on the ground had small holes indicating they were preyed upon by birds, most probably fish crows. However these birds are more opportunistic scavengers and would have fed on the eggs only after they had fallen from the nests. Researchers then discovered that many of the birds had relocated to nearby Snake Key. Though they had begun nesting there, fewer than half had done so. All seven species were found there but the number of nests had dropped from 100 – 5,000 to 50 – 600. Many of the birds were still missing. Where did they go? Better yet, why was Snake Key selected and Seahorse abandoned? And did the exodus of birds from Seahorse impact the snakes? The answer is… Yes. Dr. Sheehy’s survey found that the number of snakes encountered along the forest edge had dropped from 30 to 10. He noticed these snakes were thinner and he observed one cottonmouth consuming another, something he had not noticed before. The snakes had been impacted by the decline in nesting birds. What had happened on Seahorse Key?
One idea was put forth by Dr. Sheehy. He had noticed an increase in the number of raccoons on the island. Again, these isolated islands are selected for by nesting birds because of the lack of such predators and Dr. Harvey Lillywhite indicated that the typical number of raccoons on the island is zero. But Dr. Sheehy and Captain McCain had trapped and relocated seven raccoons earlier this summer. This suggests that a large group (large for this island) had found their way to Seahorse Key. Dr. Sheehy suggests that the cause of the movement of birds were the raccoons. There is no evidence of them attacking the birds but they believe the shear presence of the animals was enough for the birds to relocate. However Dr. Fredrick points out that (a) there was little evidence of the raccoons preying on the fallen eggs and (b) he could not find track or scat evidence of more than one or two raccoons on the island during his initial survey after the birds left. He is not so sure the raccoons were the cause.
Nesting birds on Seahorse Key
Photo: courtesy of flickr
Then there is the question… Where did the seven raccoons trapped come from? One suggestion was that they were released by locals. This was based on the fact that raccoons captured were well fed and had a mild temperament, not what you typically encounter with trapped raccoons from the wild. Later there was a confirmed report of a local who does take in orphaned raccoons, raises them, and releases them; they could have released some on Seahorse Key – but this has not been confirmed.
So right now this mystery remains unsolved. But the story does indicate the types of problems that can occur when humans relocate animals to habitats they do not typically live in. It takes years for Mother Nature to develop a balance only to have it quickly fall apart by the human release of animals we wish to move or that we think will do better in another location.
You can read more on this story at:
http://fieldguide.blogs.gainesville.com/427/amysteryatseahorsekey/
http://fieldguide.blogs.gainesville.com/450/a-mystery-at-seahorse-key-part-2/
by Rick O'Connor | Aug 7, 2015
The elongated body of the Golden Orb Weaver. Photo: Molly O’Connor
TELL ME NO! Please tell me these huge spiders are not a part of our summer. People are afraid snakes… that’s a given – but there are just as many afraid of spiders. Honestly, after years of leading field hikes into the north Florida environment, when we encounter a spider web on the trail I have heard more screams from the boys than from the girls. But most are afraid and there nothing is more terrorizing than the huge, almost hand-size, Golden Orb Weaver (or banana spider).
The Golden Orb Weaver is one of 180 species of orb weavers from around the world; one from Australia is large enough to feed on small birds. The local species is Nephila clavipes and is found throughout the southeastern United States; in the warmer months it may reach as far north as New England. Female Orb Weavers are the really big ones you find on the webs. Their body lengths can reach 2” (not including the extended legs) and the males are much smaller at 0.02”. They have long inward pointing legs with hair-like tuffs at the joints. These are very useful in web building. They have the typical “red/yellow/black” coloration of a venomous animal and their mimics; but N. clavipes is no mimic… though mild, they do have venom. There is another orb weaver spider that is large a constructs large webs. This is the Black and Yellow Argiope (Agriope aurantia). One way to distinguish this spider from the Golden Orb is the “zig-zag” pattern it adds to its’ web near the center (where the spider spends a lot of its time).
The zig-zag pattern of the Black and Yellow Argiope spider helps to distinguish from the Golden Orb. Photo: Molly O’Connor
The name “Golden Orb” does not come from their body coloration but from the color of the silk produced for their webs. It is believed that the yellow/golden color of this silk makes it difficult for others to see in open sunny areas. Many hikers can attest to this… they are hard to see, until you become entangled… then become aware the large spider is very close and heading your way… then the scream. N. clavipes can actually adjust the hue of yellow in the silk to match the sunlight conditions where it is building its web. It is amazing to see how quickly they replace their large webs, over 3 feet in diameter, after they have been removed by people. Actually they mend and move their webs regularly. They tend to build them off ground, at eye level to the tree tops, in open areas near a line of trees. I have actually seen one build the web across a dirt road between two stands of pines as if it were going to try and capture a truck! Though species of Orb Weavers feed on small birds and snakes, N. clavipes prefers flying insects. They do not wrap their prey in silk for later feeding, as many spiders do, but rather consume them almost immediately. This may be because of a small slivery spider called Argyrodes. This spider feeds on the captured food of other spiders. N. clavipes feeding may be an adaptation to combat this kleptoparasitic spider. Another interesting behavior I have noticed is when the heavy rains come. I have noticed the web remains but the spiders leave. I am not sure where they go, most likely a hiding spot nearby, but they do leave.
The fear of spiders is most likely similar to the fear of snakes… they are venomous. Venom is used to kill prey and many times is not strong enough to kill humans, but the fact that some species can kill makes folks a bit nervous. Despite local tales that say otherwise, the venom of N. clavipes is mild. It is a neurotoxin, which can be potent, but the bite from this spider is not lethal. The typical response is pain and redness at the site of the bite, blisters may form, but it is actually less potent than a bee sting.
Like many other species of spiders, the Golden Orb Weaver is a beneficial backyard creature consuming hundreds of biting (in some cases disease carrying) insects. The large webs can be a nuisance around backyard patios and swimming pools but they can easily be moved to other locations with a rake or broom. We have many of them in our yard, one out of my office window, and enjoy watching them work. They are good panhandle neighbors.
For more information on these beneficial creatures visit:
http://okeechobee.ifas.ufl.edu/News%20columns/Orbweaver.spiders.htm
http://edis.ifas.ufl.edu/in017
http://edis.ifas.ufl.edu/in467
by Rick O'Connor | Jul 31, 2015
For locals along the coast ghost crabs are as common as mockingbirds and mourning doves. Before Ivan, when the dunes were larger and closer to the road, viewing the white crabs scouring across the road at night in your headlights forced all into defensive driving maneuvers. And for those who have ever tried to catch one, all would agree it is one of the fastest animals on the beach.
The common ghost crab. Photo: Virginia Institute of Marine Sciences
Ghost crabs (Ocypode quadrata) are members of the fiddler crab family. Like their fiddler crab cousins, they are more terrestrial than aquatic and dig burrows to protect themselves from predators and the intense heat of the midday sun. Though ghost crabs can be found in a variety of locations on the island, they are most frequently found between the mean high tide line and the upper portions of the primary dune line; typically on the Gulf side. Their “J” shaped burrows reach the water level below the sand and can run as deep as four feet. Larger individuals can dig deeper burrows and are often found further away from the water’s edge. These are crabs and thus still possess gills. Gills must be in contact with water in order to obtain needed oxygen. To do this ghost crabs have a gill chamber that will hold water for periods of time. The crabs can obtain water either at the bottom of their burrow or by running to the edge of the Gulf. And running is a good term for what they do. Once they have left the burrow they will lift five of their 10 legs above their head running on the remaining five. Running sideways they will have three in contact with ground in the direction they are going and two on the opposite side; if you look closely you can actually the remaining legs raised high in the air. When they tire, they will stop, make a 180° turn, and begin running again; resting their legs. They have reached speeds of 1.6 meters/second, which is 3.5 mph!
Ghost crabs are most active at night, though they are found at dawn and dusk and occasionally at midday. They feed on invertebrates at the surface zone such as mole crabs (sand fleas) and coquinas (bean clams). Dead fish and other animals found along the shoreline are also part of their diet, often dragging them back to their burrow. Unfortunately they are one of the predators of sea turtle hatchlings heading to the Gulf at night. Ghost crabs breed in late spring and early fall. The females will carry her developed eggs to the surf zone to release them. The developing young will return the following spring to mate and release their own eggs. Females may produce eggs in their second year but rarely live to do the same the third year. They are quite social with other crabs communicating, like their fiddler crab cousins, with body postures and claw movements. They are most active from March to December, plugging the entrance of their burrows and going dormant during the colder months of the year.
There has been concern about the impact of the oil spill on their numbers and the numbers of their prey, mole crabs and coquina. Our beaches did have small and large patches of oil that seeped down into the sand and then there were the methods used to remove the oil from the beach. At this point we do not know how hard their populations were impacted but scientists have collected data before and after the spill and are analyzing this now. However low their population dropped I am sure these resilient creatures will rebound and we will once again dodge them during our evening drives.
by Rick O'Connor | Jul 24, 2015
I was sitting on my back porch late in the afternoon this past week enjoying the breeze and the sunset when the familiar sound of the bugs some call “locust” began their buzzing songs. Not all would agree with me but I really enjoy the sound of these animals. They remind me of camping and warm summer evenings, they remind me of living in Florida. They have been with me all of my life and I quite enjoy hearing them – would actually miss them if there were not here.
The adult body of a local cicada.
These bugs are not locust but a type of insect called cicadas, which is different from the “katydid” which is a different insect all together. Many who have grown up in Northwest Florida are quite familiar with their songs but not with the insect itself. Cicadas begin their lives in the trees – this is where the females lay their eggs. Most of them will find a split or tear in the twig tissue but others will actually make such a tear and here deposit their eggs. When they hatch they fall to the ground as an ant-sized larva. These larva burrow under the ground and move via burrows feeding on the sap and tissue of plant roots. Some species spend 2 years here, others as many as 17 years before they emerge. Like all members of Arthropoda these insects have external skeletons and must molt, or shed them, as they grow. Cicadas molt three times while living beneath the soil before emerging as a nymph. The nymph will climb a tree where they will molt once more becoming the winged adult some of us have seen. Many have found the empty cast of these molting nymphs clinging to the side of the tree. The males do most of the “singing” using drum-like structures called TIMBALS along their abdomen. These timbals are controlled by muscles and vary from species to species. The songs are species specific and are used to communicate with others but particularly the females, with whom he wishes to breed with before their lives come to an end in a few weeks. Landscapers and contractors have claimed that the sounds of their lawn equipment and power tools will sometimes attract cicadas and there is some evidence that it in fact it does… particularly females.
The empty molt of a cicada nymph.
There are many species of cicadas in the United States. One group will lay their eggs, the larva will drop and remain subterranean for 17 years emerging all at once! There are 19 species found in Florida and the mass emergence does not occur here. Our adults emerge every season, singing their songs, and relaxing our souls. I am glad they are here. Enjoy the summer.
by Rick O'Connor | Jul 17, 2015
The air temperatures are in the high ‘90’s and the heat indices are reaching over 100°F; heck the inland water temperatures are in the high ‘80’s – it’s just hot out there! But our barrier island wildlife friends are doing okay, they have had to deal with this many times before. Deep burrows and nocturnal movement lead the list of behavior adaptations to cope but some still scurry around during daylight hours.
People visiting the Gulf coast during the summer.
I typically begin my monthly hikes along the Gulf shore to see what is out and about; this month there were humans… and lots of them. This is the time of year that vacationers visit our islands. Traffic is bad, nowhere to park, long lines, etc. But it is part of living on the Gulf coast. We are glad to have visitors to our part of the state. We do ask that each evening they take their chairs, tents, and trash with them. Have fun.
This plant, Redroot, grows in the wetter areas of the secondary dune.
Seaside Rosemary
During these hot days of summer this flower was blooming all throughout the freshwater bogs of the secondary dunes. The plant is called REDROOT and it is really pretty. I did not see any insects near it but it was in the warm part of the day that I made my hike this month. The round shaped SEASIDE ROSEMARY is one of my favorite plants on the island. The odor it gives off reminds me of camping out there when I was a kid and of the natural beach in general. I have been told that Native Americans did use it when cooking, but can’t verify that. This is a neat plant either way. I believe there are male and female plants in this species and they have a low tolerance of fire and vehicle traffic.
The new, young seeds of the common sea oat.
Though it appears small, this is the same species of pine that grows tall inland.
The most famous plant on our barrier islands is the SEA OAT. However most think of them in the primary dune fields only. They actually grow all across the island as long as their seeds fall in a place where the wind is good, usually at the tops of dunes. As many know the roots and rhizomes of this plant are important in stabilizing the dunes, hence the reason why in most states it is illegal to remove any part of the plant. This PINE is the same type found growing 40 feet up in your yard but here on the beach salt spray and wind stunt their growth. Also the moving sand covers much of the trunk, making the tree appear much smaller than it really is. Pines are quite common on the island.
The tall trees are covered by quartz sand forming the tertiary dune system.
The expanse of marshes that make up Big Sabine on Santa Rosa Island.
The large trees of the barrier island system are typically found in the TERTIARY DUNE field. Here we see pine, oak, and magnolia all growing forming dunes that can reach 50 feet high in some places. Behind large tertiary dunes are the marshes of BIG SABINE. These marsh systems are some of the most biologically productive systems on the planet. 95% of our commercially valuable seafood species spend most, if not all, of their lives here. We will focus on this ecosystem in another edition of this series Discovering the Panhandle.
The red cones of the Sweet bay identify this as a relative of the magnolia.
The “mystery tracks” we have been seeing since January now show the small tracks of a mammal; probably armadillo.
This SWEET BAY is a member of the magnolia family and the small red cones show why. I had not seen the cones until now, so guess they like the heat and rain. WE HAVE SOLVED THE MYSTERY TRACK… knew we would. If you have read the other additions in this series you may recall we have found a track that appeared to be a “slide” coming out of the marsh and into a man-made pond from the old hatchery. Never could determine what was causing this but saw it each month of the year. However this month you could see the individual tracks of a mammal; I am guessing armadillo but could be opossum or raccoon as well. Cool… got that one behind us. On to other discoveries.
Acres and acres of Black Needlerush indicate this is a salt marsh.
Bulrush and other plants indicate that this is not salt water, but a freshwater marsh.
Marshes differ from swamps in that they are predominantly grasses, not trees. Salt marshes, as you would expect, have salt water. Fresh water the opposite… yep. The photo on the left is the salt marsh. The grass species are different and help determine if the water is fresh or brackish. Next year we will do a whole series in this ecosystem – it is pretty cool.
Until next month… enjoy our barrier islands.
by Rick O'Connor | Jul 10, 2015
What is the Gulf of Mexico Dead Zone you ask? Well…it’s a layer of hypoxic water (low in dissolved oxygen) on the bottom of the Gulf of Mexico. It was first detected in the 1970’s but reached its peak in size in the 1990’s. The low levels of dissolved oxygen decrease the amount of marine life on the bottom of the Gulf within this zone, including many commercially valuable species supporting the Gulf seafood industry.
The red area indicates where dissolved oxygen levels are low.
What Causes this Dead Zone?
Drops in concentrations of dissolved oxygen within the water column can occur for a variety of reasons but is usually caused by one of two reasons. (1) Increasing water temperatures—as water temperature increases, its ability to hold dissolved oxygen decreases. (2) A process called eutrophication.
What is eutrophication?
Eutrophication is a process where an increase of nutrients in an aquatic system triggers an algal bloom of microscopic phytoplankton. These phytoplankton produce oxygen during the daylight hours but consume it in the evening. Once the bloom dies, decomposing bacteria begin to break them down and consume larger amounts of dissolved oxygen in doing so. When the dissolved oxygen concentrations drop below 2.0 mg/L we say the water is hypoxic and many marine organisms either begin to move out or die. The nutrients that trigger such blooms are primarily nitrates and phosphates. These can be introduced to the water column with plant and animal waste and with synthetically produced fertilizers we use on our fields and lawns. There is natural eutrophication, but when the process is triggered or accelerated by human activity we use the term cultural eutrophication.
So which is it; warming waters or eutrophication?
The Gulf of Mexico Dead Zone usually forms in spring and lasts through September. These are certainly the warmer months of the year, but the warmer waters are near the surface and much of the water column is not warm enough to cause this. Another point is that the Dead Zone is near Louisiana and there are warm locations in other parts of the Gulf where dead zones do not occur. However the Mississippi River does discharge near Louisiana. This river drains 41% of the continental United States, which contains 52% of the nation’s farms. The agricultural waste (plant, animal, and synthetic fertilizers) discharged into the Mississippi River contains nitrogen and phosphorus, the two key nutrients that trigger algal blooms. Based on this, most scientists agree that cultural eutrophication is the primary cause of the Gulf Dead Zone.
When they say it will be a “typical year”, what does that mean – what is a “typical year”?
Scientists from NOAA, the U.S. Geological Survey, and six partnering universities have released their annual forecast of the Dead Zone. The 2015 prediction has the area of the dead zone about equal to the size of Connecticut, which has been the average size for the past several years. This is what they mean by typical.
Can these dead zones occur in our area waters?
Yes, and they do. We do not typically call them “dead zones” but the same process occurs all over the world, including the bays of the Florida panhandle.
What can we do to reduce cultural eutrophication locally?
If you can do without fertilizing your lawn (or field), then do. If this is not an option then only put the amount of fertilizer required for your land/lawn. Most people over fertilize, which not only reduces water quality but is expensive for the property owners. If you can compost your plant waste, do so. With animal waste, please dispose of properly, in a manner where it not reach local waterways.
For more information on hypoxia, eutrophication, and solutions to reduce this problem, contact your county Extension office.
http://www.tulane.edu/~bfleury/envirobio/enviroweb/DeadZone.htm
http://www.iseca.eu/en/science-for-all/what-is-eutrophication
http://earthobservatory.nasa.gov/Features/Phytoplankton/
