Archive for September, 2021

Pleistocene Toads

September 24, 2021

During the first months of 1976 I was the new kid at Patty Hilsman Middle School in Athens, Georgia where a group of cruel, little jerks decided to give me the nickname–toad. The nickname stuck immediately. Jocks, nerds, “cool” kids, and pretty girls all referred to me as toad instead of my given name of Mark. I was 13 years old, and the experience didn’t enhance my self-esteem. It also gave me a dim view of southern hospitality (our family had moved from Ohio), and after living in the South for over 45 years, I can confirm it is a myth. I saw a southern toad (Bufo terrestris) hopping in my yard the other day, and it brought back the unpleasant memory of being likened to an ugly amphibian. Nevertheless, it also reminded me that I’ve never written about this amazing Pleistocene survivor. Toads may seem insignificant, but they have outlasted many of the beautiful more dynamic animals that lived during the Pleistocene.

Southern toad. This species is common in my yard. Photo from Alamy.

Georgia is home to 2 species of true toads, 1 species of spadefoot toad, and 1 species of narrow-headed frog that is given the common name of toad. Southern toads are the most common species. They live in areas with sandy soils where they can burrow during the heat of the day. They hunt insects at night. After heavy rains, they breed and lay eggs in temporary pools where, if the pool doesn’t dry out, their tadpoles can metamorphize into adults. Fossil evidence of southern toads dating to the Pleistocene has been found at 6 sites in Florida and 1 site in Alabama. They were likely just as widespread then as now.

Oak toad. My neighborhood is close to the northern range limit for this species. I’ve seen small toads in my yard but they may be juvenile southern toads. Photo from pininterest.

Oak toads (Bufo quercicus) also prefer sandy soils and are common on coastal plain pine savannahs. This species is small, growing to just an inch in length. Fossil evidence of this species dating to the Pleistocene has been found at just 1 site in Florida (Reddick).

Eastern spade foot toad. They live in spiral burrows underground but emerge above ground to breed.

Eastern spade foot toads (Scaphiophus holbrooki) belong to the Pelobotidae family and are not closely related to true toads. They are named for a protuberance found on both feet that helps them dig deep spiral burrows where they spend most of their life, and for this reason they are rarely seen. Their burrows are much deeper than those of the true toads. After heavy rains, they emerge to breed and lay their eggs in temporary pools. This species is so well evolved to live in pine savannahs they can survive the light ground fires that occur in their environment. Fossil evidence of this species dating to the Pleistocene has been found at 10 sites in Florida.

The narrow-mouthed toad is not a true toad but belongs to the narrow-headed frog family. Photo from wild herps.

Narrow-mouthed toads (Gastrophyne carolinensis) are not true toads but instead belong to the narrow-headed frog family (Microhylidae). This species burrows near wetlands and spends much of its time in emergent wetland vegetation. They mostly eat ants. Fossil evidence of this species has been found at Ladds in northwest Georgia.

Woodhouse toads (Anaxyros woodhouseii) no longer occur on the southeastern coastal plain of North America, but their fossil remains have been found at sites in Florida and Alabama. The reason for their regional disappearance is a mystery. Perhaps, unlike other species of toads here, they are not well adapted to human set fires.

Toads secrete poisons that make them unpalatable to mammalian predators. However, toads do make up the majority of the hog-nosed snake’s diet. Toads do have a defense mechanism against the snakes too. They swell their bodies, making them hard for the snake to swallow. Sometimes this defense mechanism works and sometimes it does not.

Golden Silk Orb Weavers (Trichonophila clavipes) in My Yard

September 17, 2021

Golden silk orb weavers made my backyard their home this summer since about the middle of June. Last week, I counted 5 different webs in my yard. Their webs are huge, measuring 10 feet across and 6 feet from top to bottom. These deadly traps catch all kinds of insects from mosquitoes to wasps. This species is not reported to prey upon vertebrates, but I would not be surprised, if they do catch tree frogs, hummingbirds, and bats on occasion. They are a large spider over 1 inch long from abdomen to head, and their leg span is even wider. Golden silk orb weavers are also known as banana spiders because most are yellow. (They are also some times found in boxes of bananas.) The specimens in my yard seem to be brown with yellow spots, likely a local variation. This species ranges from North Carolina to Argentina, and they are expanding their range due to global warming.

There are currently at least 5 golden silk orb weaver webs in my backyard. The webs measure about 10 feet across and about 6 feet from top to bottom. They angle their bodies according to the time of day to reduce direct exposure to the sun. The webs survived a recent rain storm from the latest hurricane. I took this photo.

Golden silk orb weavers belong to the Nephilidae family and were formerly given the scientific name Nephila clavipes. However a recent genetic study determined they should be classified in the Trichonophela genus within the Nephilidae family. Females are 6 times larger than males, so if a smaller spider is seen in their web, it is probably a male. Females eat males when they are done mating with them. A genetic study suggests the characteristic of female gigantism in the Nephilidae family originated over 100 million years ago. There is another species of spider–the silver-colored, fat-bodied Argyrodes nephilae–that some times lives on the outside of golden silk orb weaver webs. This species steals captured prey from the golden silk orb weaver by cutting the webbing attached to the web-wrapped insect and lowering it to the outside of the golden orb weaver’s web where it is safe for the Argyrode spider to consume. A golden silk orb weaver web is an ecological community in itself with female and male golden orb weavers, web-wrapped insects, and a smaller species of spider that lives life as a thief.

Reference:

Kuntner, M. et. al.

“Golden Orb Weavers Ignore Biological Rules: Phylogenomic and Comparative Analysis Unravel a Complex Evolution of Sexual Size Dimorphism”

Systematic Biology 68 (4) July 2019

Monster Centipedes

September 10, 2021

The top predator on Philip Island is a 12 inch long centipede with armored plating and a venomous bite. This monstrous creature preys upon sea bird nestlings, lizards (skinks and geckos), and crickets. It also eats the vomited fish and squid parent birds regurgitated to feed their chicks. About half of its diet consists of vertebrates, an unusual ratio for a terrestrial invertebrate. Scientists estimate 11%-19% of black-winged petrel chicks are lost to centipede predation every year. However, centipedes don’t prey upon white winged petrel nestlings because they are larger and can defend themselves against the centipedes.

Phillip Island Centipede with a black-winged petrel. This species of centipede regularly feeds upon black-winged petrel chicks. 13 species of sea birds nest on Philip Island. Photo from the below referenced study.
Photo and location of Philip Island. Note how denuded the island is of vegetation. This is from feral pigs, goats, and rabbits all of which have been eradicated. Image also from the below referenced study.

Scientists think centipedes may be able to help restore the ecology of Philip Island. Originally, the island was covered with white oaks, Norfolk pines, and red legged grass; but sailors introduced goats, pigs, and rabbits as a food source, and the feral animals denuded much of the island of vegetation. People eradicated the animals about 40 years ago to save the island ecosystem. Centipedes eat the sea birds and transfer marine nutrients to the rest of the island in their feces. This added nutrition may help the trees and grass grow back faster.

This is the largest species of centipede that lives in Georgia. Scolocryptis sexspinosus. It grows to 3 inches long. I’ve seen this species in my yard. Photo from insectidentification.org.

The largest species of centipede in Georgia grows to about 3 inches long–1/4th the size of the Philip Island centipede. This species is known as the red bark centipede (Scolocryptis sexspinosus), and I have seen this species in my yard. They have a venomous bite that is painful to humans but not fatal. It can live up to 5 years and will molt its exoskeleton as it grows. They are predatory but not often seen because they are usually nocturnal and fossorial. Worldwide, there are 8000 species of centipedes. Though their name means 100-legged, their number of legs can vary from 54-354, depending upon the species. Centipedes don’t mate. Instead, the male drops off its sperm, and the female later comes along and engulfs it. Females defend their eggs, and some species even defend their young.

Reference:

Halpin, L; et. al.

“Arthropod Predation of Vertebrate Structures Trophic Dynamics in an Island Ecosystem”

The American Naturalist 198 (3) September 2021

Cougars (Puma concolor) Control Feral Horse (Equus caballus) Populations in Some Environments

September 3, 2021
Photo of Cougar feeding on a horse from The Wildlife Society

President Teddy Roosevelt called the cougar that “horse-killing cowardly cat.” Though Teddy Roosevelt was a progressive President for his time, I think some of his opinions and attitudes were highly distasteful. He was a war monger and a sadist. He went on a safari to Africa and slaughtered thousands of animals, using the excuse that he was sending specimens back to an American museum. Cougars kill for food, but Roosevelt was slaughtering thousands of animals from a distance with an high-powered rifle under the false guise of obtaining scientific information. I think he did it because he enjoyed being a bloodthirsty killer. I respect the bravery of a cougar far more than anything Roosevelt ever did as an outdoorsman. Cougars are 1 of the few solitary carnivores that regularly attack prey larger than themselves.

There is no doubt cougars kill horses, but Steve Rinella, a Trumpanzee with an hunting and fishing show on the Outdoor Network, disputed a New York Times column written by Dave Phillipps, suggesting cougars could control feral horse populations. Phillips refused to appear on Rinella’s podcast, and Rinella seemed to relish how another expert had proven the author of the column wrong. He’s not wrong. A recent study determined cougars could control feral horse populations in sagebrush environments. Scientists studied 21 radio-collared cougars–13 in the Great Basin region of Nevada and 8 on the Sierra Nevada range. They counted 820 predation events and learned that in the Great Basin region horses made up 60% of the cougars’ diet while mule deer just made up 29% of their diet. On the Sierra Nevada range, mule deer made up 91% of their diet. Cougars hunted horses in sagebrush environments quite often, but rarely in mountain environments. In the Great Basin individual cougars killed an horse about once every 2.5 weeks. Another study looked at cougar prey on the Pryor Mountains. Here, cougars killed no horses and their primary prey was mule deer, though bighorn sheep made up 9% of their prey. 1 individual female cougar specialized in preying upon bighorn sheep, but most cougars preferred deer. I think horses are not an important part of the cougar diet in the Pryor Mountains because there are less than 200 of them there, and they are located in an area with no cougars.

Of course, cougars hunt horses. During the Pleistocene cougars co-existed with horses over the span of 2 continents for hundreds of thousands of years. I’m sure there were certain ancient environments where horses were the most available prey species. Horses are well adapted to arid grasslands, and during the Pleistocene were more common than deer in this type of environment. Cougars would have been competing with dire wolves, giant lions, and saber-tooths in open areas, and they likely were more common in woodlands or forest edges. But they may have held their own in some locations where horses and competing carnivores were abundant, depending upon ecological conditions. Incidentally, the Pleistocene cougars that lived in North America were not directly ancestral to cougars that live on this continent now. They were an extinct ecomorph that grew slightly larger than modern cougars and may have had spotted fur. According to genetic evidence, all modern North American cougars descend from a population originating in eastern South America about 10,000 years ago. Strange as it may seem, this population completely replaced the Pleistocene ecomorph.

Horses originated in North America and lived here for millions of years, until man wiped them out. People who claim feral horses harm the environment are full of shit. Horses make trails, defecate all over the place, and graze down vegetation…just like they did for millions of years. Horses recolonized North America, and this recolonization is no different from when wildlife managers re-introduce endangered species to lands where they had previously disappeared. There are only about 83,000 feral horses in North America today compared to tens of millions of cattle, yet cattle ranchers and do-gooder environmentalists would dishonestly lead people to believe horses are the problem, not the cattle. I call bullshit.

References:

Blake, L.

“Foraging Ecology of Cougars on the Pryor Mountains of Wyoming and Montana”

Utah State Graduate Thesis 2014

Andreason, A.; K. Stewart, W. Longled, J. Berkman

“Prey Specialization in Cougars on Feral Horses in a Desert Environment”

Journal of Wildlife Management July 2021