by Rick O'Connor | Jun 18, 2021
In our continuing series on the biogeographic distribution of island vertebrates, this week we look at a creature that, for some, is as scary as sharks – the rays. The term stingray conjures up stinging barbs and painful encounters, and these have happened, but rays are easily scared away by our activity. Occasionally people will step on one and the venomous spine is used to make you move your foot. You can avoid this by shuffling your feet when moving across the sand. Rays detect the pressure and move before you reach them. Again, negative encounters with rays are not common.
The Atlantic Stingray is one of the common members of the ray group who does possess a venomous spine.
Photo: Florida Museum of Natural History
There are 18 species of rays (from 9 families) found in our area. An interesting note, only eight of those possess a barb for stinging, and five are from the family Dasyatidae (the stingrays). Others that have barbs include the butterfly ray, cownose ray, and the eagle ray.
Rays are related to sharks but differ in that (a) the pectoral fin begins before the gills slits, and (b) the gill slits are on the underneath of the body – not on the side as found in sharks. Shark distribution seems to be controlled by water temperature. We see this with ray distribution as well, but interestingly the skates seem to be restricted to the Gulf of Mexico. Some are found almost exclusively in the east or west side of the Gulf.
Skates resemble stingrays but lack the venomous barb. They will usually have small thorns on their bodies and lay their developing embryos in a leathery egg case folks call “mermaid’s purse” when they wash ashore. There are four species found in the Gulf, but the spreadfin skate is ONLY found in the Gulf of Mexico and is not found along the Florida peninsula. The clearnose skate, which can be found all along Florida and the eastern seaboard of the U.S., is absent from western Gulf. It is interesting to try and understand why. What barrier keeps these two skates from colonizing the entire Gulf?
There is a large plume of muddy freshwater that expands from the Mississippi River into the Gulf off Louisiana. This plume could be a barrier for coastal species trying to expand their range. However, the spreadfin skate is reported to be an outer continental shelf species and may not be influenced by this lower salinity water. So, what is their story?
And why are these not found in the Caribbean? In the Caribbean you do enter tropical waters where coral reefs become more common. There is certainly a species shift when you reach this zone and it could be the food needed by these skates is not found here – a biological barrier. Many find these biogeographic situations interesting.
There are 12 species that have the typical “Carolina marine fish” distribution, which means they are found throughout the Gulf up the eastern seaboard to Massachusetts and south to Brazil. Two, the Atlantic torpedo ray and the roughtail stingray, expand their range farther into Canada. As a matter of fact, the roughtail stingray prefers colder waters.
Torpedo rays are an interesting group. This family of fish includes two species here in the Gulf, the Atlantic torpedo ray and the lesser electric ray. Yep… these two have special muscle cells that can deliver an electric shock. It is believed this electric current can detect and stun prey as well as repel predators. The voltage is not dangerous but will get your attention.
Three of those “Carolina marine species,” the guitarfish, the lesser electric ray, and the yellow stingray, do not reach Massachusetts. Their distribution ends at North Carolina. You would have to guess water temperature as a barrier here. The warm Gulf stream begins heading east across the Atlantic Ocean off Cape Hatteras towards Europe. They could follow this current to Bermuda, but they have not been reported there. This could be due to depth (pressure), being benthic fish, or food barriers.
There is one family that is tropical, the sawfish. These bizarre dinosaur looking creatures were once common in the estuaries of the Gulf region. They are now rare and protected.
One species of stingray, the Atlantic stingray has been found in the lower reaches of Louisiana rivers. Like bull sharks, salinity may not be a barrier for them.
And then we have our “world travelers”. The manta and eagle rays are found across the globe in tropical waters, and eagle rays are common in temperate parts of the world.
The distribution of our rays is not as universal as sharks. The skates in particular have an interesting distribution pattern. Pensacola lies right at the boundary of the eastern and western Gulf of Mexico, so we find both geographic groups here. Though they may scare many people, rays are fascinating creatures and cool to see.
by Rick O'Connor | Jun 3, 2021
With this article we are going to begin a short series on the biogeography of panhandle vertebrates. Biogeography is the study of distribution of life and why species are found where they are. Many are interested in what species are found in a specific location, such as which sharks are found in our area, but understanding why others are not is as interesting.
The Bull Shark is considered one of the more dangerous sharks in the Gulf. This fish can enter freshwater but rarely swims far upstream. Photo: Florida Sea Grant
All species have a point of origin and from there they disperse across the landscape, or ocean, until they reach a barrier that stops that dispersal. These barriers can be something physical, like a mountain range, something climatic, like the average temperature, or something biological, like to abundance of a specific food or predator. There are a lot of barriers that impede dispersal and explain why some species are not present in some locations.
Sharks are marine fish. In general, there is little to impede the dispersal of marine fish. All oceans are connected and there is no reason why a shark found in the Gulf of Mexico could not swim to Australia, and some have. But there are barriers that keep some species of south Florida fish from reaching north Florida – mean water temperature being one.
There are 24 species of sharks from nine different families found in the Gulf of Mexico. Most have a wide distribution range, and some are found worldwide. Nurse sharks are more tropical, common in the Keys, but are found in our area of the northern Gulf of Mexico. They are fans of structure and are often found near our artificial reefs.
Whale sharks and hammerheads are circumtropical, meaning they are restricted by water temperature but found worldwide in warmer waters. Whale sharks are the largest of all fish, reaching a mean length of 45 feet, and are not common near shore. They are plankton feeders and, though large, are harmless to humans. There are five species of hammerheads found in the Gulf of Mexico. They are easily identified by their “hammer” shaped head and are known for their large dorsal fin that, at times, will extend above the surface while they are swimming. Finding species of hammerhead inside the bay is not uncommon.
Several of our local sharks are not as restricted by water temperature and are found as far north as Canada. Sand tigers, threshers, and dogfish seem to prefer the cooler waters and, though found in the Gulf, are not common. There are two members of the mackerel shark family found here. Great whites, of movie fame, prefer cooler waters and are found worldwide – except for polar waters. There are records in the Gulf, but most are offshore in cooler waters. As you know, these are large predatory sharks, reaching up to 25 feet in length, and are known to feed on large prey such as seals. Their cousin the shortfin mako, prefers warmer waters and is more common here. Nearshore encounters with makos is rare but has happened.
The largest family, and best known, are the requiem sharks. There are 13 species in the Gulf, and many are common in our area. Many are not as restricted by water temperature and can be found as far north as New York. Bull sharks are not restricted by salinity and have been found up rivers in Alabama, and Louisiana. Silky sharks are more tropical, and the tiger and spinner sharks are more circumtropical.
The geographic distribution of sharks seems centered on water temperature. Most can easily swim the oceans to locations across the globe but congregate in areas of preferred temperatures and food. Though feared because of attacks on humans, a rare thing actually, they are fascinating animals and world travelers.
by Rick O'Connor | May 21, 2021
Six Rivers “Dirty Dozen” Invasive Species
Torpedograss (Panicum repens)
Torpedograss
Photo: University of Florida
Define Invasive Species: must have all of the following –
- Is non-native to the area, in our case northwest Florida
- Introduced by humans, whether intentional or accidental
- Causing either an environmental or economic problem, possibly both
Define “Dirty Dozen” Species:
These are species that are well established within the CISMA and are considered, by members of the CISMA, to be one of the top 12 worst problems in our area.
Native Range:
Africa and Asia.
Introduction:
Torpedograss was initially introduced prior to 1876 in seed for forage. In the early 1900s the USDA introduced the plant as a forage crop for pastures.
EDDMapS currently list 13,900 records of this plant. They range throughout the coastal states of the southeastern U.S. but most (96%) are in Florida and those records spread across the entire state from Pensacola to the Florida Keys.
Within our CISMA there are 2262 records, most are in Okaloosa County. The extent is probably underreported.
Description:
It is a tall grass reaching a height of 3-4 feet and grows along the shorelines, though it has on occasion been found more inland. The leaves are thin, stiff, flat, and “hairy” on the top and around the sheath. It has a waxy coating that appears “whiteish” and the leaves may fold. It has an extensive rhizome system that can grow deep into the ground and ends in a sharp point, where it gets its common name “torpedograss”. The flowers are a panicle-type inflorescence extending from the top of the plant.
Issues and Impacts:
This is an aggressively growing plant dispersing primarily from fragmentation and expansion of the sharp-pointed rhizome system. It quickly forms dense mats and out competes native grasses, many times forming monocultures along the shoreline where native plants have been removed. By 1992 it was reported in 70% of Florida’s public waterways, restricting waterflow, recreational use, and has become particularly problematic on golf courses.
Management:
Torpedograss spreads primarily by extended their rhizomes, or fragments of these rhizomes. When removing from the shoreline it is important to remove ALL of the rhizomes or the plant will return. It is also important not to spread fragments of these rhizomes while mowing or weed-eating the plant.
It is most aggressive in open disturbed areas. After mowing or burning land is when dense patches emerge. Maintaining a diversity of native shoreline grasses will help impede dispersal and growth.
Mowing and disking have not been very effective. In fact, disking may cut and spread the rhizomes.
When choosing chemical treatment, glyphosate has been every effective. However, this chemical is non-selective and overspray can kill native plants you wish to keep. Also, the plant is often in the water and an aquatic version of glyphosate should be used. When using near water read all instructions carefully to avoid killing other aquatic plants. Since the rhizomes can grow deep, and are at times submerged, re-treatment may be needed.
There are no biological agents currently approved for torpedograss management but cattle and goats both will eat the plant. Though it does not always remove the rhizomes, grazing can be a method of control.
For more information on this Dirty Dozen species, contact your local extension office.
References
Torpedograss, University of Florida IFAS Center for Aquatic and Invasive Plants
https://plants.ifas.ufl.edu/plant-directory/panicum-repens/.
Early Detection and Distribution Mapping System (EDDMapS)
https://www.eddmaps.org/
Six Rivers CISMA
https://www.floridainvasives.org/sixrivers/
by Rick O'Connor | May 20, 2021
I was recently gathering information together for a presentation on Florida snakes, highlighting those in the Florida panhandle. This particular reference listed 44 species found in the state. Of those, 29 were found throughout the state – north, central, and south Florida. Granted, there were subspecies for many which made for some distinction, but most of our snakes (66%) have few barriers and seem to have adapted to the different habitats and climates. And let’s face it, north and south Florida are two different worlds. That says a lot for the adaptability of these animals, they are pretty amazing.
Snakes do make many nervous but most of our 44 species are nonvenomous.
Photo: Nick Baldwin
Another trend was obvious. As you looked at those species which were only found in north Florida (here defined as the panhandle across to Jacksonville and south to Gainesville) and compared that to species only found south of Gainesville, we have a rich diversity of snakes in our part of the state. There were 12 species found in Florida that were only found in north Florida. South and central Florida only had 3 species that were unique to their part of the state. I saw this same trend with turtles. Of the 25 species of turtles found in Florida, 9 are unique to north Florida, 2 to central and south.
It has been known that the biodiversity of the panhandle is pretty amazing, and that the Apalachicola River basin in particular is a biodiversity hot spot. In the panhandle, several “worlds” collide and species, many using these river systems we find here, can easily reach this area. Some produce hybrid versions of two species. Some produce new species only found here. There may be more reptiles / acre in central and south Florida (I did not look at that) but the variety of these creatures in the north Florida is pretty amazing.
The Escambia River. One of the alluvial rivers of the Florida panhandle. Is a natural highway for many reptiles to disperse into our state.
Photo: Molly O’Connor
But what about those 12 species unique to our part of the state?
Four of them are small terrestrial snakes, rarely getting over a foot in length. These are easy prey and nonvenomous so are most often found beneath the leaf litter of the forest, or beneath the ground, coming out at night to feed on small creatures. We generally find them living in our flower beds and gardens. Most are ovoviviparous (producing an egg but instead of laying it in a nest, the female keeps it internally giving live birth), with only the Southeastern Crowned Snake laying eggs (oviparous).
- Smooth Earth Snake (Virginia valeria) This snake has records from Pensacola Bay area and areas south of the Georgia line.
- Rough Earth Snake (Virginia striatula) This snake has most records west of the Apalachicola River, but there are records from the Suwannee basin in north Florida.
- Red-bellied Snake (Storeia occipitomaculata) Common across north Florida.
- Southeastern Crowned Snake (Tantilla coronate) Found only in the panhandle.
Six of the unique panhandle 12 are nonvenomous water snakes. This would make sense in that we are host to several long alluvial rivers that reach deep into the southeast. The Escambia, Choctawhatchee, and Apalachicola Rivers are highways for all sorts of riverine species, and those closely associated with rivers, to cover hundreds of miles of territory with few barriers (except for the occasional dam). Though these water snakes are nonvenomous, they are known for the “bad attitudes” and high tendency to bite. They feed on a variety of prey and are often seen basking along the riverbank or in a tree branch hanging over the water where they can escape quickly if trouble comes, and they do escape quickly. Some are quite large (over 4 feet) and most are ovoviviparous. The northern watersnake is known to have a placenta-like structure to nourish its young (viviparous) and the rainbow snake lays eggs (oviparous).
The banded watersnake is one found throughout the state and resembles the cottonmouth.
Photo: UF IFAS
- Queen Snake (Regina septemvittata) is only found in the western panhandle (west of the Apalachicola River). This snake likes cold, clear streams with rocky or sandy bottoms and plenty of crayfish.
- Northern Watersnake (Nerodia sipedon) also is only found in the western panhandle. It can be found in almost any body of water and has been reported on barrier islands.
- Plain-bellied Snake (Nerodia erythrogaster) This snake also can be found in just about any water system.
- Diamondback Watersnake (Neroida rhombifer) has only been found in the Pensacola Bay area (Escambia and Santa Rosa counties). They can be found at times in large numbers around almost any body of water.
- Western Green Watersnake (Neroida cyclopion) only as records in one Florida county – Escambia. There they have been found in a variety of water habitats including man-made ones.
- Rainbow Snake (Farancia erytogramma) This snake likes to feed on American eels and is usually found in aquatic systems where this prey inhabits.
Another interesting trend with these unique panhandle watersnakes is the number only found in the western panhandle. Four of the six are only found there and two are only found in the Pensacola area. Some say, “Pensacola is not really Florida”, the snakes might agree.
The last two of the unique 12 are venomous snakes. Florida has six species of venomous snakes, but two are only found in the north Florida.
This copperhead was found JUST across the state line in Alabama. The more copper color and “hour-glass” pattern of their bands lets you know it is not it’s cousin the cottonmouth.
Photo: Molly O’Connor
- Copperhead (Agkistrodon contortrix). Though quite common in Alabama and Georgia, most records in our state are from the Apalachicola River basin area. Many local panhandlers will tell you they see this snake everywhere, but they use this name for the cottonmouth also (a close cousin). The true copperhead is not common here. It seems to like rocky areas further north and is usually found with limestone rock areas that have been formed over time from river erosion.
- Timber Rattlesnake (Crotalus horridus). As with the copperhead, this is a common snake in Alabama and Georgia associated with rocky terrain and is not common in our state. Many ole timers will speak of the “canebrake”, which was found in the common cane of north Florida. There was discussion at one point of this being a separate species from the timber rattler, but the specialist now believe they are one in the same. So, the name canebrake is no longer used by herpetologists. Records of this snake in Florida are mostly east of the Apalachicola River and not common.
This timber rattlesnake has chevrons (stripes) instead of the diamond pattern on its back.
Photo provided by Mickey Quigley
I think the diversity of wildlife in our part of the state is pretty special. Even if you do not like snakes, it is pretty neat that we have so many kinds not found south of the Suwannee River. Snake watching is not as popular as bird watching, for obvious reasons, but it is still neat that we have these guys here.
by Rick O'Connor | May 5, 2021
EDRR Invasive Species
Land Snail (Bulimulus sporadicus)
Bulimulus sporadicus
Photo: University of Florida
Define Invasive Species: must have ALL of the following –
- Is non-native to the area, in our case northwest Florida
- Introduced by humans, whether intentional or accidental
- Causing either an environmental or economic problem, possibly both
Define EDRR Species: Early Detection Rapid Response. These are species that are either –
- Not currently in the area, in our case the Six Rivers CISMA, but a potential threat
- In the area but in small numbers and could be eradicated
Native Range:
Bulimulus sporadicus is native to the West Indies.
Introduction:
There appears to have been multiple points of entry into Florida. It was first identified in Florida by Dr. Harry G. Lee, who discovered the snail in Duval County in 2009. Additional surveys found four different populations all associated with the CSX railways. It is believed the snail was introduced via the railway cars coming from Mexico. Populations began to appear both north and south of the original location, all near the CSX railways. The animal has been reported from central and south Florida, as well Georgia, Alabama, Mississippi, and Northwest Florida.
EDDMapS currently list only 2 records of Bulimulus sporadicus. One in central and another in south Florida. There are no EDDMapS records of the snail in the Florida panhandle, but it has been reported in Pensacola and Panama City. There are no records within the Six Rivers CISMA but it is believed to be here. Records of this animal is certainly under reported.
Description:
This is a small (3/4 – 1”) land snail. It has a conical shell that is light brown to tan in color. They are often found near gardening areas and seem to like the high humidity and moist conditions here.
Issues and Impacts:
A 2018 publication from the Center for Invasive Species and Ecosystem Health noted that it was not designated as invasive in any state, nor the federal level. However, with the relatively new introduction and wide spread of this species it warrants observation.
Management:
There are no management plans for this snail at this time. Chemical treatment of plants to reply the snail are not recommended. It appears the snail prefers the leaf litter within the mulch rather than the live plants. Snail baits, and other pesticides, can be harmful to pets and native wildlife and are not recommended. They do like mulched areas within gardens and if the home owner is having a serious problem, management of this type of habitat may be needed.
For more information on this EDRR species, contact your local extension office.
References
Stauderman, K. 2020. A Snail That Rode the Rails. UF/IFAS Extensions Volusia County Blog. http://blogs.ifas.ufl.edu/volusiaco/2020/04/07/a-snail-that-rode-the-rails/.
Snail (Bulimulus sporadicus, O’Brigny 1835). 2018. Center for Invasive Species and Ecosystem Health. https://www.invasive.org/browse/subinfo.cfm?sub=78908.
Early Detection and Distribution Mapping System (EDDMapS)
https://www.eddmaps.org/
Six Rivers CISMA
https://www.floridainvasives.org/sixrivers/
