Sunday, July 30, 2017

Gulf Coast Observations


As far as I can tell, there is no surefire way to escape the heat and humidity while remaining in my home state, Mississippi, during the dog days of summer.  However, even if we failed to avoid the mugginess, my family and I did manage to find distractions from it—and, really, isn’t that the best that can be expected in July?—by spending a few days in and around Ocean Springs, Mississippi.  We weren’t there for very long, but it turned out to be just what we needed for a refresher.  I saw a good variety of wildlife in the coastal woodlands, brackish marshes, beaches, and tide pools.
You can see Deer Island on the horizon.  It was originally part of the mainland, and isn't a barrier island.
Whether it’s because staring up at the sky or across the water when the sun is out eventually starts to hurt my eyes, or because there are no trees for me to scan for birds, walking on the beach tends to make me focus downward.  That was the case here, and I entertained myself much of the time by watching the vast variety of creatures on the seashore and in the tide pools.  I found a number of crabs, including the ones below:
Disclaimer: this particular crab was found at night, not during the daytime.  Even at night, though, it's a good idea -- for multiple reasons! -- to focus your attention on the ground while walking on the beach.
This is a fiddler crab, and the weirdly oversized claw marks it as a male.
There were also hermit crabs in the tide pools.  Unluckily for would-be photographers, these hermit crabs have an annoying tendency to scrunch themselves tightly down into their appropriated mollusk shells, making it difficult to capture decent pictures!

Occasionally, there will be something that really doesn’t belong on a beach.  No, I don't mean empty cans, fast food containers, or old firework tubes (although, unfortunately, all of those things turned up, too), but a squirrel treefrog.  For some reason, this small frog was shuffling through the salty sand only a few feet from the waves.  I suspected that it had come from the tree-lined area just off the beach, so I carefully relocated it. 
I later learned that squirrel treefrogs can apparently tolerate fairly saline environments (for example, Webb [1965] found that a squirrel treefrog breeding pool on a North Carolina barrier island contained 47% seawater http://amphibiaweb.org/cgi/amphib_query?where-genus=Hyla&where-species=squirella), so perhaps this individual had just been seeking out a rainwater puddle somewhere nearby.  Even so, I feel comfortable with my decision to move it away from the excessive foot traffic.

On most of the beaches of the Gulf Coast, you can expect to see (and hear!) Laughing Gulls, which, during our visit, seemed particularly laid-back—moseying around like tourists.  Occasionally, Royal Terns, sleeker and swifter than the gulls, flew by.  Brown Pelicans and Ospreys were also spotted from the beach during this trip.

Laughing Gulls
Great Blue Heron eying the fishing
Great Blue Herons hung out at the fishing pier, probably taking advantage of the atmosphere created by the people fishing: if they couldn't get handouts, or if they weren’t able to scavenge a few fish from the buckets, at least the bait that was continuously added to the water might attract more fish to the area.

Of course, beaches aren’t the only natural places worth visiting on the coast.  Gulf Islands National Seashore, preserved by the National Park Service, was also on our itinerary.  We walked some of the trails that wound through the coastal scrub forest, enjoying our looks at Spanish moss (actually a bromeliad, not a moss), huge live oaks, marshes, and more.  I heard Clapper Rails and saw Red-winged Blackbirds, Barn Swallows, herons, woodpeckers, and several other bird species.  Coastal wetlands, in particular, can play a major role in reducing storm surge from hurricanes and tropical storms, so conserving them is essential if we want the coastal cities that we enjoy visiting to exist years into the future.
Spanish moss -- an unusual plant for me -- growing on sweetgum, a species that I know extremely well.


Thursday, June 29, 2017

Summer Treefrogs and Cricket Frogs



This post serves as a follow-up to my earlier remarks about chorus frogs that breed in the late winter and early spring months.  By now, we are well into summer, which means that the spring peepers and upland and Cajun chorus frogs are silent, but other species of frogs are extremely vocal.  Mississippi is home to quite a few taxonomic families of frogs and toads, including Ranidae, or the true frogs (such as bullfrogs and leopard frogs), individuals of which are largely aquatic and can be found in ponds, lakes, and streams; Bufonidae, or the true toads; Microhylidae, or the narrow-mouthed toads; Pelobatidae, or the spadefoot toads; and Hylidae, or the treefrogs, a group that encompasses the chorus frogs (including the spring peeper and the upland and Cajun chorus frogs), as well as many other species that can be heard calling right now.  Let’s take a look at some of these hylids.

Treefrogs are distinguished by the sticky pads at the ends of their toes, which enable them to climb.  They are typically found in trees and shrubs near sources of water.  In the southeastern U.S., one of the most common species is the American green treefrog (Hyla cinerea).  As its name suggests, this frog is typically bright green.  However, like other treefrogs, it is capable of changing color to adapt to changes in temperature and environmental surroundings.  It usually, but not always, has pale stripes running along its sides, and its skin is very smooth.  The call is a nasally quank that carries for a good distance.  Large choruses of this frog can be heard in almost any wet, wooded area.

Another common species is the squirrel treefrog (Hyla squirella), a small frog with a raspy call that is reminiscent of a squirrel’s barking sound.  This extremely variable species may appear almost any color from bright green to dusky brown, depending on environmental conditions.  At first glance, a bright green specimen of the squirrel treefrog might be mistaken for a green treefrog.  However, the squirrel treefrog is smaller and always lacks the pale lateral stripes of the green treefrog.  Squirrel treefrogs were formerly restricted to the southern half of Mississippi, but have recently expanded their range northward. 

The next three species to be discussed, the common gray, Cope’s gray, and bird-voiced treefrogs, can be visually separated from the green and squirrel treefrogs by virtue of their bumpy skin.  Like all treefrogs, they are more likely to be heard than seen, so it is still a good idea to learn to recognize them by their calls.

As their name suggests, gray treefrogs are frequently mottled gray in color, although they may also be various shades of green or brown—again, depending on temperature and habitat.  The two species of gray treefrogs, common gray (Hyla versicolor) and Cope’s gray (Hyla chrysoscelis), look identical and are impossible to distinguish from each other in the hand.  This is due to the fact that one species, the common gray treefrog, is thought to have diverged from the other, the Cope’s gray treefrog.  Interestingly, common gray treefrogs are tetraploid, meaning that they have four pairs of chromosomes (i.e., genetic material)—twice the usual number.  Tetraploidy is fairly common in plants and invertebrate animals, but it is not as frequently observed in vertebrates.  While common gray and Cope’s gray treefrogs cannot be reliably distinguished from each other by sight, they can be easily identified by sound.  Both species have low-pitched trills, but the Cope’s gray treefrog’s call is faster and more snore-like than the drawn-out trilling of the common gray treefrog.  If you are a Mississippian, though, it's possible that you will not need to distinguish between the two, since the common gray treefrog may occur in only the northernmost sliver of the state: http://maps.iucnredlist.org/map.html?id=55687.  The Cope's gray occurs statewide: http://maps.iucnredlist.org/map.html?id=55448.

Bird-voiced treefrogs (Hyla avivoca) look like smaller versions of gray treefrogs.  One quick way to identify them in the field is to look at the ventral portions of their legs; unlike gray treefrogs, which have bright orange skin in this area, bird-voiced treefrogs have greenish-yellow.  You should have no trouble with identification if you hear the frogs, though; the whistling, bird-like call of the bird-voiced treefrog is drastically different from the sounds of gray treefrogs.  Also, while you could find gray treefrogs in almost any type of forest, bird-voiced treefrogs tend to be most common in swampy woods, especially those containing cypress and tupelo trees.  This is one of my favorite frog species in the state.  

The pine woods treefrog (Hyla femoralis) and the barking treefrog (Hyla gratiosa) are two species found in the deep southeastern portions of the U.S.  Unfortunately, I have had few encounters with either, and have heard pine woods treefrogs only in forests on the coast.  However, a friend and mentor of mine has heard that species as far north as Newton County, Mississippi, so it is certainly possible to find them fairly far inland.  They have strange calls—perhaps best described as sounding like hyperactive Morse code messaging.  The call of the barking treefrog, on the other hand, is throatier in sound than the green treefrog’s call.  Choruses of this species bring to mind—well, for me, anyway—hundreds of bouncing rubber balls.  The barking treefrog frequently has dark spots and is also noticeably bumpy-skinned, making it easy to distinguish from green treefrogs.  In the hand, pine woods treefrogs could be mistaken for squirrel treefrogs, but their inner thighs have rows of pale spots, unlike those of squirrel treefrogs.

The tiny, aptly-named cricket frogs are not technically treefrogs, as they belong to the genus Acris.  Nevertheless, they are hylids, and, like their relatives, they can commonly be found in vegetation near water.  Unlike treefrogs, cricket frogs tend to stay very low to the ground.  The southern cricket frog (Acris gryllus) and the northern cricket frog (Acris crepitans) are the two most common species in the state.  They are similar in appearance, and their insect-like calls are also a bit difficult to distinguish from each other.  However, the southern cricket frog has a raspier sound than the northern.  Both of these tiny frogs can be found in grasses and herbaceous vegetation near water.

So much for the adult hylids—but what about the earlier life stages: eggs and larvae?  Well, if you peer into small ponds, woodland pools, roadside ditches, or potholes on old dirt roads, you might be lucky enough to see these.  Frog eggs are in clusters, while toad eggs are in strings.  Tadpoles may take a month or more to fully metamorphose.  May the summer months be hopping!


Sources

The IUCN Red List of Threatened Species, http://www.iucnredlist.org/
Species Profile: Cope’s Gray Treefrog (Hyla chrysoscelis), Savannah River Ecology Laboratory, http://srelherp.uga.edu/anurans/hylchr.htm
Species Profile: Pine Woods Treefrog (Hyla femoralis), Savannah River Ecology Laboratory, http://srelherp.uga.edu/anurans/hylfem.htm