Archive for April, 2021

Pleistocene Ant Lions (Myrmeleontadae sp.)

April 29, 2021

Ant lion pits line the bare soil areas next to the back wall of my house. Ant lions, as the name suggests, prey on ants, though they will eat anything small enough to become trapped in their pits. The larval stage of most species is the monster hidden just below the sand of the bottom of the pit. When an ant lion larva senses an ant walking near the edge of the pit, it flicks sand at the ant, knocking the ant into the side of the pit. The action of flicking sand destabilizes the wall of the pit, forcing the ant to fall within the reach of the ant lion’s jaws. The ant lion then injects venom and devours the ant, or rather sucks the juices out of it. Ant lion larva can live for years without eating and during winter they dig deeper down to avoid frosts. But after they’ve had a meal, they go into a cocoon stage before emerging as adults. They survive on nectar for energy in their brief adult stage spent searching for mates. Fertilized females lay eggs in sand and the cycle begins again.

Some species of flies lay their eggs in abandoned ant lion pits, and their larva use the same strategy as ant lion larva. At least 1 species of parasitic wasp allows itself to be captured. It stings the ant lion larva and lays on egg on it, thus turning predator into prey.

Ant lion adult and larva. Image from below reference. The larva prey on ants and other small arthropods.
Ant lion pits next to the side of my house. Ant lions prefer sandy soil and are common in arid environments. They likely were abundant in the southeast during Ice Ages when the climate was dry and bare soil environments predominated.

There are about 2000 species of ant lions, and there are species on every continent except Antarctica. Their closest living relatives are owl flies and lace wings. They are most common in tropical dry climates, but they thrive anywhere they can find a sandy substrate. I hypothesize they were abundant in southeastern North America during Ice Ages when arid climates prevailed, resulting in vast landscapes with sparse vegetation. Pleistocene climate changes likely increased species diversification when populations became isolated from each other during wetter climate phases that turned sandy environments into isolated refuges.

Ant lions are rare in the fossil record. Ant Lions have been found in 99 million year old amber at a site located in Burma. Scientists think ant lions first evolved about 150 million years ago, so they lived under the feet of dinosaurs. There are no dinosaurs in my yard (unless one includes birds), but their contemporaries live right up next to my house.

Reference:

Badano, D.; M. Engel, P. Basso, B. Wang, P. Cerretti

“Diverse Cretaceous Larvae Reveal the Evolutionary and Behavioral History of Ant Lions and Lace Wings”

Nature Communications (9) 257 August 2018

The Former Abundance of Green Sea Turtles (Chelonia mydas)

April 22, 2021

Our ancestors didn’t appreciate wildlife. For them wild animals were considered either a pest or a resource to be ruthlessly exploited until that particular species was annihilated. I came across an article entitled “Turtling in Florida” written during 1890 and learned how abundant green sea turtles formerly were. According to the author, slaughtering turtles was great sport. So many turtles populated some lagoons that a man could theoretically walk from 1 side to the other by walking on their backs. Turtle stampedes endangered men’s lives. Sea turtles crawling on beaches to lay their eggs could become frightened by men hunting them and their eggs, and hundreds of 800 pound panicking turtles could crush men too slow to get out of their way.

Of course, man is much more dangerous to sea turtles than they are to us. In North America before man invaded the continent, adult sea turtles had few enemies–bears on beaches and tiger sharks in the sea. But man killed too many turtles and gathered too many eggs, and now green sea turtles are endangered. Several methods were formerly used to catch green sea turtles. Some men used nets, though in south Florida, they encountered problems with sharks and sawfish that often destroyed the nets. (Both sawfish and sharks are much more rare now than they were in 1890.) Other turtle-hunters used harpoons in a process called “pegging.” The harpoons were designed to just barely penetrate the shell, so the turtle could be reeled in and kept alive for as long as possible. Some Seminole Indians actually dove to the bottom of the sea, grabbed the turtles, wrestled them to the surface, lassoed them, and pulled them onto the boat. The most common method of hunting sea turtles was to simply sneak up on them while they were laying eggs on the beach, and turn them over. Sea turtles are helpless when on their backs. This method could be hazardous. The turtle-hunters could run into a bear in the dark (turtles lay their eggs at night). The article reports 1 expedition shooting and killing 5 bears on a night of turtle-hunting, and they could have killed more, if the sand flies hadn’t been driving them crazy. There was also the possibility of getting crushed in the aforementioned turtle stampedes.

Green sea turtles inhabit shallow coastal waters where they feed upon sea weed. They nest on tropical beaches.
Green sea turtle range map. They often stray far from where they nest.
Green sea turtles are considered a delicacy due to their vegetarian diet. They were formerly abundant, but overhunting by men has greatly reduced their numbers.
Aborigines can still get away with hunting sea turtles.

Green sea turtles were a popular delicacy over 100 years ago. Adult green sea turtles live on a diet of seaweed, giving their flesh a delicious flavor, according to old time accounts. People enjoyed eating turtle eggs too. No matter how long a turtle egg is cooked, the white part never solidifies. The eggs must have made cakes moist when they were used as an ingredient. The turtle shells were used to manufacture women’s jewelry as well. Now, green sea turtle populations are low and even raising them on farms for food is illegal. Nevertheless, various aboriginal groups around the world still hunt them and collect their eggs.

Reference:

Murphy, J.M.

“Turtling in Florida” from

Tales of Old Florida

Castle Books 1987

Pleistocene Whitefish (Coregonus clupeaformis)

April 17, 2021

Fish have an amazing ability to replenish and increase their populations. Lake whitefish, a species related to salmon and trout, can lay between 8,000-130,000 eggs. During Ice Ages 90% of their present day range was covered by glaciers, making it uninhabitable for them. Yet, in less than 12,000 years they recolonized this enormous territory. The reproductive ability of this species outpaced the population of predatory fish and birds that fed upon them. Scientists used a study of genetics to determine modern day whitefish descend from 2 different refugial populations that clung to survival during the Last Glacial Maximum. 1 population survived in Beringia–the area of Alaska and the Yukon that remained free of glacial ice. They may have survived in lakes now located near Nahanni National Park. The other population occurred in the Missouri/Mississippi River Drainage just south of the Laurentide Ice Sheet. Following the retreat of the Ice Sheet, lake whitefish populations exploded in the newly formed Great Lakes and managed to swim their way into lakes all over Canada. Whitefish are a cold water species and probably didn’t ever live far from Ice Age glaciers.

Map of present day range of lake whitfish. Most of this range was under glacial ice during Ice ages.
Lake whitfish.

Lake whitefish average 4 lbs. as adults, though the record for a rod and reel catch is 15.5 lbs. They spawn during fall, winter, and spring. Their diet consists of snails, clams, and insects. There are 2 ecotypes of whitefish that do not interbreed: the normal population that inhabits the bottom region of lakes and the dwarf population that swims in the upper layer of open water. Commercial fishermen net whitefish, and they are a popular food fish in cities and towns along the Great Lakes, but I can’t remember if I ever had the opportunity to try them when I lived in Ohio as a boy.

Reference:

Foote, C.; J. Clayton, C. Lyndsay, and R. Bodaly

“Evolution of Lake Whitefish (Coregonus clupeaformis) in North America during the Pleistocene: Evidence for a Nahanni Glacial Refuge in the northern Cordilleran Region”

Canadian Journal of Fisheries and Aquatic Services 49(4) April 2011

McDermid, J., J. Riest, R. Bodaly

“Phylogeography and Post Glacial Dispersal of Whitefish ( C. clupeaformis complex) in Northwest North America”

Advances in Limnology 60 Jan 2007

First Record of the Giant Short-Faced Bear (Arctodus simus) in South Carolina

April 8, 2021

Increased currents from the periodic release of water from an upstream reservoir on the Cooper River in South Carolina disturbs the sediment at the bottom of this river. Fossil hunters take advantage and scuba dive for fossils in the disturbed sediment. Recently, Eric Proulx discovered a fossil tooth while scuba diving in the river. He didn’t know what pre-historic animal it was from, and he showed it to Dave Cicimurri, curator of the Columbia Museum. The curator misidentified the tooth, mistaking it for a lion (Panthera atrox) canine. The photo of the tooth in a news article was shared on a Florida fossil hunters Facebook page where it became an object of some derision. Most of the amateur fossil hunters recognized the tooth as bear, not lion. (A lion’s canine is much longer.) Richard Hulbert of the University of the Florida Museum of Natural History looked at it and confirmed it belonged to a giant short-faced bear. This is the first record of this species in the state of South Carolina. Though fossil specimens of this species are more common in western states, they have been found in Fern Cave, Alabama, the Withlacoochee River in Florida, and at least 1 site in Virginia. This specimen shows this species ranged all the way to the eastern seaboard.

Eric Prouix found this tooth of a giant short-faced bear in the Cooper River in South Carolina while he was scuba diving. This is the first record of this extinct species in the state.

This map is from the below reference. I added the blue dot to indicate where the short-faced bear specimen was found in South Carolina.
Typical inaccurate image of a giant short-faced bear. Recent studies determined its legs were not as long as previously thought and its face not as short.

Much of what scientists thought about the giant short-faced bear has been revised. It was a very large bear, averaging as big as a Kodiak bear, the subspecies of brown bear that enjoys an high protein diet of salmon. This diet results in a bear able to reach weights of over 1000 pounds. But giant short-faced bears did not have unusually long legs, and their faces were not particularly short. So every illustration of this species on the web is wrong. Scientists also formerly thought giant short-faced bears were highly carnivorous, scavenging by driving other predators from their kills. Though I’m sure this happened on occasion, an isotopic study determined short-faced bears were omnivorous, just like most other species of bears.

The presence of giant short-faced bears in South Carolina shows 3 species of bears co-existed throughout southeastern North America during the Pleistocene. Florida spectacled bears and black bears shared the land with their larger cousins. In addition grizzly bears lived at least as far southeast as Kentucky, and polar bears may have occasionally roamed south along the Atlantic Coast when glaciers covered most of their present day habitat.

Reference:

Schubert, B.; R. Hulbert, B. MacFadden, and S. Sourle

“Giant Short-Faced Bears (Arctodus simus ) in Pleistocene Florida, U.S.A., a Substantial Range Extension”

Journal of Paleontology 84 (1) 2010

Tigers (Panthera tigris) Suppress Dhole (Cuon alpinus) Populations.

April 1, 2021

A new study determined tigers suppress dhole pack sizes in India. Dhole packs are smaller in areas with higher densities of tigers, even if there is an higher density of potential prey species. The scientists conducting the study used camera traps to estimate pack size and tiger numbers. In Tadoba-Andhari Tiger Reserve where tiger density is high, there were 7 dhole packs averaging 6.4 dholes per pack. In Navegaon-Naziri Tiger Reserve where tiger density is lower, there were 5 dhole packs averaging 16.8 dogs per pack. Pack sizes were 2.6 times greater in areas with lower tiger density. Both reserves are in a subtropical dry deciduous forest zone dominated by teak, argun, and giant crepe myrtle trees. The terrain is somewhat hilly. Leopards are another important large predator in the reserves, and the leopard population is also negatively impacted by tigers. Common prey species in the reserves include spotted deer, sambar deer, barking deer, nilgai antelope, wild boar, and gaur–a large species of cattle. Dhole pack sizes do increase in areas with greater prey density, but the abundance of tigers is a greater influence on pack size. Dholes tend to prey on smaller animals in areas with lots of tigers, so they can consume more of the animal before a tiger drives them away from the kill. Tigers depress dhole populations by directly hunting them and by chasing packs away from their kills.

Map of tiger reserves where the below referenced study took place. Map from the below referenced study.

Tigers totally dominate dholes. The authors of the study saw tigers kill dholes on 5 different occasions and drive packs away from their kills 23 times. They saw no instances of dholes killing tigers or driving them away from their kills.

Spotted deer are an important prey item for tigers and dholes.
Nilgai antelope, also known as blue buck are another important prey item for tigers and dholes. Hunters introduced nilgai antelope to Texas about 100 years ago, and now there is a feral population of 37,000 in that state.

India has the highest dhole population in the world. There are small packs in the northern montane forest, and larger packs in the dry deciduous forests of central and south India. Since tigers were eliminated from Laos, dhole populations have increased there. Dholes formerly ranged across most of Asia, and during the Pleistocene they ranged into North America, though fossil evidence there is limited to 1 site in Mexico.

Siberian tigers are known to depress wolf populations, and lions depress hyena and hunting dog populations in Africa. I wonder if big cats suppressed canid populations in Pleistocene North America. Saber-tooths were very powerful fanged cats, and American lions grew larger than any big cat species. Pleistocene jaguars grew as large or larger than modern tigers and are at least as common as dire wolves in the fossil record of Florida. There really is no way to know because abundance in the fossil record doesn’t necessarily reflect actual abundance in life.

Reference:

Bhanda, A.; P. Ghaskodbi, P. Nigram, and B. Habib

“Dhole Pack Size Variation: Assessing the Effect of Prey Availability and Apex Predator”

Ecology and Evolution March 29, 2021