Archive for July, 2021

Vacation 2021–Dahlonega, Georgia

July 30, 2021

We chose a close destination for this year’s vacation–Dahlonega, Georgia located in the north central part of the state. My wife and I don’t like to travel and it was just a 3 hour drive. My daughter and I looked forward to nearby hiking trails, and I hoped to find some local wines to bring home with me.

Woody Gap Trail

Woody Gap Trail is part of the Appalachian Trail system. It hasn’t been logged for over a century and is in the process of becoming an old growth forest. Oaks were the most common kind of tree. I was surprised at how common black oaks were because I never thought of that species as a tree that occurs on mountains, but I was not surprised to see the rock chestnut, northern red, and white oaks. Tulip, maple, hickory, and elm were also abundant. Some of the tulip trees were quite large with diameters over 3 feet thick. In virgin forests they can get even get bigger, and I’m sure some of these will eventually grow to be enormous, unless a storm knocks them down. Ferns and tree saplings covered the forest floor. It wasn’t a good time of year to see wildlife. By midmorning, it was already so sultry, the animals were inactive and resting under cover. I saw a gray squirrel, a robin, and a crow, and I heard a bird call I didn’t recognize. It was from a species that doesn’t live in my neighborhood. I searched the internet for calls of bird species that live in deep forests such as wood thrush, white breasted nuthatch, and warblers, but none of their calls matched what I heard, so I suppose it will be a mystery bird. While we were walking on the trail, an 8 year old girl who was hiking with her family loudly imitated the sound of a monkey for 20 minutes non stop. We didn’t have to worry about stumbling upon a mother bear and her cubs. The air smelled good, except for a small area of the trail where a skunk must have passed earlier that morning.

The forest floor alongside Woody Gap Trail is covered in ferns and saplings.
Some of the tulip trees here get quite big–the trunks are over 3 feet in diameter.
Preacher’s Rock. Looks like it would make a good bear’s den, if it wasn’t next to the trail.

The Dahlonega Gold Belt

Dahlonega is located in an interesting geological region known as the Dahlonega gold belt. 500 million years ago, this area of the globe consisted of volcanic islands. Hot magma flowing into deep ocean dissolved gold from the sea water. The gold became concentrated in cracks of quartzite rock that resulted from faulting. Gold is a basic element that doesn’t erode and can be found among rocks that do erode. The discovery of gold here during 1829 caused a gold rush and further contributed to the desire among Europeans to remove Native Americans from the region. Crisson is an active gold mine in Dahlonega where people can pay to pan for gold. This sounded tedious to me, but I did find some interesting artifacts in their gift shop. They sell Jasper arrowheads. Native Americans made this type of arrowhead during the Archaic Age which lasted from about 6000 years BP to 1500 years BP. If I did pan for gold, I’d be more interested in fossils and human-made artifacts.

Jasper arrowheads. They are of Archaic Indian Age. They sell these for $1.50 at the Crisson Gold Mine.

Vineyards and Mead

There are 15 vineyards in the Dahlonega region. Grapes thrive here because of the climate and the sloping hilly land. Most of the vineyards have wineries where people can pay to taste wine, pretend they like it, and buy bottles. The wineries are only open for a few hours, a few days a week, and none were open at a convenient time for us. We did find a place that makes and sells its own mead. Mead is wine made by fermenting honey. My late great-grandfather was a beekeeper who made his living by turning his honey into mead. He would drive to bars in his horse and buggy and sell his mead. He was also a famous poet in Europe, and the Emperor Franz Josef of the Austro-Hungarian Empire invited him to recite his poetry. After the Nazis invaded Poland during World War II, they arrested him and his wife for being Jewish and he died in a concentration camp.

I bought mead at a meadery in Dahlonega. There are also 15 vineyards in the area, but their winerys are open just a few hours a day, just a few days a week.

The Sawnee Mountain Preserve in Forsythe County, Georgia

On the way home we stopped by the Sawnee Mountain Preserve, an area protected by Forsythe County, a suburb of Atlanta. We walked on the Fairy Tale Trail. Girl Scouts decorate the trail with little wooden houses where fairies can live. I was more impressed with the trees. White oak, swamp chestnut oak, southern red oak, hickory, and tulip were the most common trees I noticed. There were a few shortleaf pine but not many. This tract is also in the process of becoming an old growth forest. I heard cicadas and a tree frog, but again it is just not the right time of year for wildlife watching. They did have gold fish and red-eared sliders in a manmade pool.

Aerial photograph of the view from Sawnee Mountain in Forsythe County, Georgia in 1924 (top) and today. There was more agricultural land 100 years ago, but today there are more houses and trees.
3-pronged southern red oak at Sawnee Mountain Preserve.
Grapevines and saplings cover the forest floor alongside the Fairy Tale Trail in Sawnee Mountain Preserve.
There are a multitude of impressive white oaks in the Sawnee Mountain Preserve.
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Unique Fish of the Yucatan Peninsula

July 23, 2021

Underground rivers flow through the limestone bedrock underneath the Yucatan peninsula of Mexico. When a river enters a cavern it flows in a circular pattern, eroding the walls into a circular shape. The roofs of these caverns eventually collapse, creating a small bucket-shaped lake known locally as a cenote. There are almost 20,000 cenotes on the Yucatan peninsula, and they host many unique fish species found nowhere else on earth. A recent survey of 4 cenotes captured 1,350 fish including 11 species from 5 families. The cenotes studied were small and deep–less than 2 acres wide but over 30 feet deep.

The most common species found in this study were mosquito fish from the Poeciliid family. Cichilids were also common, most notably a beautiful fish, the yellow jacket cichlid. This fish is a popular game fish, reportedly with a good flavor. The yellow jacket cichlid has an interesting habit–it feigns death and preys on smaller fish that attempt to scavenge it. Colorful tetras, popular aquarium fish, live in cenotes, and they are preyed upon by the pale catfish, the top predatory fish in the studied cenotes. Scientists found blind swamp eels in these surveyed cenotes. Blind swamp eels are found throughout underground cave systems in the region and have no need for sight. Although some cenotes are connected to the ocean through underground passages, scientists found little marine influence on them. Instead, zooplankton and insect abundance along with phosphorus concentrations have a greater influence on fish populations.

View from inside a cenote. There are almost 20,000 of these geological features on the Yucatan Peninsula and they host fish species found nowhere else in the world. Photo from Thrillist.com.
Yellow Jacket Cichlid. A beautiful fish that is popular for catching and eating.
Blind swamp eel.
Pale catfish.

The Yucatan Peninsula was also home to an unique mammalian fauna during the late Pleistocene. Cenotes inundated by sea level rise preserved the remains of many species, including a species of giant ground sloth and a species of peccary found nowhere else. 4 complete human skeletons dating to the late Pleistocene were discovered in a cenote that is now below sea level. (See: yucatan peninsula | Search Results | GeorgiaBeforePeople (wordpress.com) )

Reference:

Camargen-Guerra, T; L.K. Escalera Vazquera, L. Zambrano

“Fish Community Structure Dynamics in Cenotes of the Biosphere Reserve of Sian Kaan, Yucatan Peninsula”

Revista Mexicana de Biodiversidae

Horn Size Comparison Between Bubalus arnee and Bison latifrons

July 16, 2021

Some species of extant megafauna demonstrate how impressive similar extinct species were. Asian water buffalo (Bubalus arnee) weigh up to 2600 pounds, and their horn span averages 3 feet long. The individual in the below photo has an horn span of about double the size of the average. The largest known horn span of an Asian water buffalo was from a specimen shot in 1955–it had an astounding horn span of 13 feet 10 inches. The extinct long-horned bison (Bison latfrons) had horn spans up to 7 feet long, but it seems likely the largest individuals had horn spans even longer than the record specimen of Asian water buffalo shot during 1955. Long-horned bison are estimated to have reached weights between 2700-4400 pounds–significantly heavier than Asian water buffalo–and if these estimates are accurate, some individuals probably had horn spans exceeding 14 feet long.

Asian water buffalo (Bubalus arnee). Their horn span averages 3 feet, but this animal has an horn span that is close to twice that long. I found this photo on Twitter. I don’t know who took it.
I took this photo of a Bison latifrons specimen at the Georgia College Museum in Milledgeville, Georgia. This specimen was found near Brunswick, Georgia and dates to 24,000 years ago. This species evolved into Bison antiquus during the Last Glacial Maximum. B. antiquus evolved into modern Bison (B. bison) after the end of the last Ice Age.

The Asian water buffalo has been classified as endangered since 1986. There are only 4000 left. They are found in small herds in 8 protected areas in India, 1 in Nepal, 1 in Bhutan, 1 in Thailand, and 1 in Cambodia. They are thought by many to be the ancestors of domesticated water buffalo, an animal used for pulling plows before the era of mechanization. Asian water buffalo prefer to live in swamps and marshes, and their hooves are wide and don’t sink in muddy ground, giving them superior performance in farm labor compared to a plain old ox. They also produce a richer milk than cows, and cheese-makers use their milk to make Mozzarella. Domesticated water buffalo have escaped from captivity in Australia, parts of Asia, Argentina, and Bolivia where they thrive on grass, sedges, fruit, bark, and twigs in wetlands. A species of European water buffalo became extinct about 10,000 years ago.

The ancestor of the long-horned bison crossed the Bering Land Bridge and colonized North America a little less than 300,000 years ago, marking the beginning of the Rancholabrean Land Mammal Age. They inhabited open woodland and prairie. Their long horns were a defense against big cats such as saber-tooths, giant lions, and jaguars (just like water buffalos use their horns to fend off tigers and lions). During the Last Glacial Maximum ((~21,000 years BP-~15,000 years BP) long-horned bison evolved into a smaller animal with shorter horns known as B. antiquus. This was likely in response to reduced quality of food and water sources. Following the arrival of man in North America, B. antiquus evolved into the even smaller but more mobile and migratory modern bison (B. bison). Instead of long horns and large bodies to battle big cats, bison needed longer legs, so they could run away from wolf packs and man.

Arthritic Glyptodonts

July 9, 2021

I am lucky so far. I am 59 years old and don’t feel arthritic yet, but my father was about my age when he first suffered from arthritis. The incurable disease forced him to give up playing tennis because his hand hurt too much when he tried to return a shot. About 50 million adults and 300,000 children suffer from arthritis. There are over 100 types of arthritis. The 4 most common include degenerative, infectious, inflammatory, and metabolic. Degenerative arthritis is caused by cartilage wearing away so that 2 different bones rub against each other at the joint. Bacteria cause infectious arthritis, and inflammatory arthritis is the result of the immune system turning against itself following an infection. Metabolic arthritis is caused by uric acid build up. This is the kind my dad had, and he also used to suffer terrible attacks of gout–a related condition.

Man isn’t the only animal that suffers from arthritis. Other primates, elephants, bears, and extinct ground sloths are known to be susceptible to the disease. Paleontologists examining bones of extinct glyptodonts found evidence of arthritic joints. Glyptodonts are related to armadillos. A recent genetic study found their closest living relative was the tiny pink fairy armadillo–an ironic discovery because fairy armadillos are so small, and glyptodonts weighed several tons. However, glyptodonts diverged from armadillos about 35 million years ago. The main difference between armadillos and glyptodonts is the shell. Armadillo shells in most species are flexible, and they can curl up in a ball when threatened. Glyptodonts had stiff turtle-like shells. The arthritic glyptodont bones were found in a limestone cave near Lajeda de Ecole, Brazil. Glyptodonts ranged throughout South America and into the southern parts of North America including coastal Georgia. The arthritic glyptodont specimen found in Brazil suffered from calcium pyrophosphate disease, a complication of spondyloarthropy. This disease is known as false gout because it is similar to gout, though the physiological cause differs. The specimen’s arthritis was in its arm and leg joints.

3 different species of glyptodonts compared to an average-sized man. I found this image on google. I don’t know who the original creator was.
Glyptodont joints with arthritis. Image from the below referenced paper.

Arthritic glyptodonts may have been more vulnerable to predators. When attacked, glyptodonts quickly turned around and swung their tails which in some species were clubbed. A glyptodont slowed by arthritis may have been too sluggish to swing their tail in time. Scientists found 1 specimen of arthritic glyptodont with gnaw marks from an extinct dog known as Protocyon trogylodytes. This predator may have killed the aged glyptodont or perhaps it scavenged an animal that died of old age.

References:

Aurauj-Junior, H. ; et. al.

“Overlapping Paleoinchnology, Paleoecology, and Taphonomy: Analysis of Tooth Traces in Late Pleistocene-Early Holocene Megafaunal Assemblage of Brazil and Description of New Ichnology in Hard Substrate”

Paleogeography, Paleoclimatology, and Paleoecology 468 2017

Barbosa, F. ; et. al.

“Arthritis in a Glyptodont (Mammalia, Xenartha, Cintulata)”

Plos One Feb 2014

Fossorial Spiders in Georgia

July 2, 2021

2 different groups of spiders live underground in Georgia soils: trapdoor spiders and wolf spiders. Trapdoor spiders belong to the Myglamorph order which also includes tarantulas, funnel web spiders, and purse web spiders. (The latter make tube shaped webs on tree trunks.) In Georgia there are 3 families of trapdoor spiders including the Ctenizidae (ravine trapdoor spiders), the Antrodiactidae (folding door spiders), and the Eucterizidae (wafer lid spiders). Spiders in the Ummidia genus belong to the Ctenizidae family, and as their name would suggest, their preferred habitat is moist ravines located next to rivers. However, most species of trapdoor spiders seem to prefer this type of environment. 1 recent study searched for trapdoor spiders in moist ravines along the Altamaha, Savannah, and Satilla Rivers in Georgia, and the spider hunters found 51 specimens including 3 species. Along with 1 species of ravine trapdoor spider, they also found wafer lid and folding door spiders.

All trapdoor spiders construct underground burrows where they wait for prey to cross across the door. When the spider senses an insect on its door, it will seize the unfortunate prey with fangs and pull it inside the burrow where the spider feeds upon it. The families differ in how their doors are constructed. Ummidia spiders use their abdomen covered in webbing as a door. Folding door spiders pull the rims of their burrows closed, unfolding it in time to catch an insect. Wafer lid spiders have a thinly-webbed door. Incredibly, the wafer lid spider, Myrmekiaphilia, constructs its burrows inside or alongside ant nests. Some species of wasps hunt trapdoor spiders. The arachnids have a defense–they desperately attempt to hold the door shut while the wasp tries to pull it open. Somehow, they are able to tell the difference between prey and a wasp.

There are at least 8-10 known species of trapdoor spiders in Georgia. Auburn University professor, Jason Bond, has discovered 37 species of trapdoor spiders in North America, and there likely are more than 10 species living in Georgia with many undiscovered. He’s named newly discovered spiders after celebrities including Barack Obama, Tobey Maguire, Angelina Jolie, and Stephen Colbert.

The moist mesophytic slopes where trapdoor spiders occur are particularly rich habitats for all wildlife. William Bartram described walking through a “magnificent” slope forest in his Travels. (See: https://markgelbart.wordpress.com/2011/04/11/william-bartrams-magnificent-forest/ ). A forest such as Bartram described no longer exists in Georgia, but even logged over 2nd growth forests are richer on these sites because they are wetter and cooler than the surrounding habitats. During Ice Ages when much of the surrounding environment was dry scrub, these sites likely provided refuge for hardwood forests and hence relic habitat for trapdoor spiders.

This photo angle is not good enough to identify what species of spider this is in my rain gauge, but I can tell it is not a trapdoor spider as I wrongly assumed at first. I made this false assumption because I thought a trapdoor spider was using an existing structure that imitated its burrow, but that is not the case.
Photo of a ravine trap door spider in the Ummidia genus. Photo from spiderid.com.
Wolf spider from the Tigerosa genus. This is the kind of spiders I see when I dig in my garden. Photo from spiderid.com.

I often come across spiders when I dig in my garden. Until I started researching information for this blog article, I wrongly assumed they were trapdoor spiders. Instead, I learned these are wolf spiders, probably belonging to the Tigrosa genus (named for the striped appearance). Wolf spiders are in the Lycosidae family, and they also construct burrows underground. Unlike trapdoor spiders, they are not sedentary predators. They hide from predatory birds in their burrows during the day, but they leave their burrows at night and actively hunt insects. They probably attack crickets, homing in on their noisy chirping. A wolf spider’s burrow can be as deep as 3 feet, keeping them safe from inclement weather and birds, but moles can find them. Female wolf spiders carry their eggs and young on their backs when they hunt at night. They are far more common than trapdoor spiders, and worldwide there might be as many as 2000 species.

Reference:

Stevenson, D.; and R. Godwin

“Notable Myglamorph Spiders (Aranae: Myglamorphae) Records for the Coastal Plain of Georgia”

Southeastern Naturalist 19 2020