Archive for the ‘Pleistocene Mammals’ Category

Spotted Lions

August 20, 2020

Vast areas of Africa remained sparsely inhabited until well into the 20th century, and I think this is why more megafauna survives on that continent than any other.  Some quite large African animals were unknown to Western science until the 1900’s, including mountain gorillas, bonobos, and okapis. A rare big cat, probably extinct now, could be added to that list. Last week, I wrote about post speciation hybridization events in big cats, and following the completion of that article, I recalled reading about reports of spotted lions in Africa.  I wondered if a population of leopard/lion hybrids might recently have existed on the dark continent.  I researched everything I could find about spotted lions on the internet, and the verdict is inconclusive.

Spotted lion, illustration

Photoshopped image of a spotted lion.  

A pelt of a spotted lion killed by a Kenyan farmer in 1931.  This is the only proof they ever existed.

During 1931 a Kenyan farmer shot and killed a pair of spotted lions that were stalking an herd of buffalo.  A few other locals had also seen spotted lions, and the natives knew this animal as the marozi and distinguished it from a leopard.  Later, Kenneth Dower led an unsuccessful expedition to find spotted lions.  Lion cubs often have spots that they retain through sub-adulthood, but reports of spotted lions hunting suggested these were adults.  Spotted lions were reportedly intermediate in size between lions and leopards.  There are 3 possibilities.  The marozi may have been a distinct species or subspecies of lion adapted to living in a forested montane habitat.  (All of them were seen at high elevations in the mountains.)  They may have been a population of lion/leopard hybrids.  Or they may have been a population of lions with a mutation for a spotted coat.  Scientists could answer this question with a DNA analysis of the pelt from the specimens shot by the Kenyan farmer, but so far no one has attempted to do this.

Lions share a close evolutionary relationship with leopards, but presently the physical appearance and behavior patterns of the 2 species are much different.  Lions live in prides and hunt in open habitats, while leopards are solitary and prefer environments with more trees and bushes.  The common ancestor of both likely had a spotted coat.  Lions lost their spots when they began occupying tawny-colored savannahs and deserts where a plain coat offered better camouflage.  It’s a curious possibility that a population of spotted lions, closely related to the ancestor of all lions and leopards, may have continued to exist until the 20th century.  I’m convinced they are extinct now.  They may have been a relict population killed off by farmers.

Post Speciation Admixture in Big Cats

August 13, 2020

12 million years of evolution separate the domestic housecat from the African lion.  A recent study used the genome of the housecat as an outgroup in their examination of the evolutionary relationships between big cats in the Panthera genus which includes the lion (Panthera leo), jaguar (P. onca), leopard (P. pardus), snow leopard (P. uncia), and tiger (P. tigris).  The ancestor of all species in the Panthera genus diverged from its now extinct relatives 4.58 million years ago.  The common ancestor of lions, leopards, and jaguars diverged from this early lineage 3.65 million years ago.  The common ancestor of tigers and snow leopards diverged from the rest of the Panthera lineage 3.47 million years ago.  Leopards and lions diverged from each other 2.57 million years ago.  (The chart below simplifies this history.)  However, genetic evidence suggests after these species diverged from each other and became separate species they occasionally interbred with each other.   Lions interbred the most because they had the widest geographical range and overlapped with more species.  Lions formerly lived from the southern tip of Africa across Eurasia and to the east coast of North America, and they came into contact with more species.  Jaguars originally evolved in Eurasia and were common there during the late Pliocene/early Pleistocene.  After jaguars crossed the Bering Land Bridge and colonized the Americas they became extinct in Eurasia.  Jaguars periodically interbred with lions during the early Pleistocene.  Snow leopards and tigers also interbred with each other during the early Pleistocene.

Chart showing speciation divergence within the Panthera genus and later hybridization events resulting in admixtures of certain genes that were positively selected for survival of the species. From the below reference.

Leopon (male leopard & female lion hybrid) - Apparently a leopard ...

Lion/leopard hybrid.  Lions and leopards diverged over 2 million years ago, but rarely did hybridize in the wild following this divergence.  Lions interbreed with tigers, jaguars, and leopards in captivity, but currently are not known to do so in the wild.  

Genetic evidence indicates some of the hybridization events benefitted the descendants and were a positive force in naturally selecting characteristics that helped the species survive.  The trait that gives jaguars a large skull and powerful bite originated from when a jaguar mated with a lion.  This characteristic later helped jaguars survive the megafauna extinction event because they could prey on heavily armored caimans and turtles as a substitute.  Interbreeding between snow leopards and tigers was also important.  The characteristic that helps snow leopards thrive at high altitudes originated from the pairing of a snow leopard and a tiger.  Populations of cats in the Panthera genus fluctuated during the Pleistocene and the authors of the below study believe hybridization events facilitated the survival of these species.

Reference:

Figueiro, H. etl al.

“Genome-wide Signatures of Complex Introgression and Adaptive Evolution in the Big Cats”

Science Advances July 2017

https://advances.sciencemag.org/content/3/7/e1700299

The Clarendonian Land Mammal Age

July 13, 2020

Many science writers often describe the Pleistocene of North America as resembling the modern day African Serengeti.  I debunked that notion 7 years ago in an article I wrote for this blog (See: https://markgelbart.wordpress.com/2013/12/09/the-faunal-diversity-of-pleistocene-north-america-was-less-than-that-of-modern-day-africa/ ) In terms of biomass Pleistocene North American might have been as impressive but not when it comes to biodiversity.  Africa has almost twice as many species of mammals as Pleistocene North America. However, there was a time period during North America’s natural history when it was biologically more diverse than modern day Africa.  The Clarendonian Land Mammal Age during the middle Miocene lasted from ~13 million years ago to ~9 million years ago.  The age is named after the Clarendon local fauna based on fossils found from 24 sites in Donley County, Texas.  Scientists are aware of 34 mammal families that lived in North America during this age.  This includes 8 genera of artiodactyls such as camels and llamas, peccaries, deer, and pronghorns.  There were 15 genera of horses plus tapirs and 2 species of rhinoceros.  1 species of primitive oreodont still clung on, though they were formerly more diverse.  Bear-dogs (Amphycyon sp.) also still survived but were headed for extinction.  4-tusked gompotheres, kin to elephants, entered North America by crossing the Bering Land Bridge and colonized the continent.  Predators included 8 genera of canids and 11 genera of weasels, and there were 9 genera of rodents.  River dolphins and dugongs swam in the waters.  The bone-eating dogs (Borophagine), ancestors of saber-tooth cats (Nimravides), and false saber-toothed cats (Barbourofelis) were the dominant large predators.  Fanged cats and cat-like animals came in all sizes.

Among the amazing diversity of mammals were some remarkable morphological convergences with modern day species of African fauna.  There were giraffe-like camels that evolved long necks to feed on the tops of trees, aquatic hippo-like rhinos, and fast running gazelle-like horses.

Teleoceras | Animal of the world Wiki | Fandom

The hippo-like rhino Teleoceras.

Aepycamelus | Extinct animals, Ancient animals, Prehistoric animals

The giraffe-like camel Aegypcamelus.

Nannippus sp. by Dinogod.deviantart.com on @DeviantArt

The gazelle-like nannihippus.

Climate over most of North America during the middle Miocene was warm and mostly non-seasonal.  Before the Clarendonian Land Mammal Age tropical and sub-tropical forest covered most of North America, but the uplift of the Sierra Nevada and Cascade Mountain Ranges caused increased aridity.  Warm savanna grassland and open woodland replaced the thick forest, and this resulted in a greater diversity of mammals, taking advantage of this more productive habitat.  Grazing herds of ungulates and burrowing populations of rodents in deep grassland soils thrived in this environment.  Climate change brought an end to the Clarendonian Land Mammal Age.  Conditions became even more arid and seasons became more pronounced.  Warm savannahs and open woodlands were replaced with steppe grasslands where  winters started to trend toward sub-freezing temperatures.  Many species of mammals could not adapt to harsher winters and simply went extinct. By the end of the Miocene and beginning of the Pliocene large mammal diversity was much reduced, but new cold-adapted species from Eurasia (crossing the Bering Land Bridge) and new immigrants from South America (crossing the newly emerged Isthmus of Panama) helped replenish biodiversity in North America. Though large mammal diversity never again approached that of the Clarendonian, it was an healthy cavalcade until the end of the Pleistocene when man wiped most of them out.

New Study of the Seda-DNA in Hall’s Cave, Texas

June 29, 2020

A new study of seda-DNA and bone DNA from Hall’s Cave documents the changes over time in the plant and animal communities on the Edward’s Plateau in Texas.  Previously, scientists had collected and identified thousands of bones in Hall’s Cave from 56 species of mammals, 30 species of birds, 9 species of amphibians, 3 species of reptiles, and 2 species of fish.  The bones date from the Last Glacial Maximum (~20,000 years BP) to the early Holocene (~9,000 years BP).  The new study extracted DNA from the bones but in addition took samples of DNA from the sediment. (Scientists call DNA from sediment samples, “seda-DNA.”)  Sampling DNA from the sediment has the added advantage of detecting the presence of plant remains that were otherwise unidentifiable, and the presence of animals that perchance left no skeletal remains at all in the cave.  For example 2/36 bone samples were from cat but 7/10 sediment samples detected cat.  Jaguars and bobcats urinated, defecated, and shed hair in the cave but left no skeletal remains.  The seda-DNA samples detected 36 of the 56 species of mammals known to have  occurred in the cave from fossil evidence but they found an additional 7 species of mammals as well as additional species of birds not collected as fossils here, including ducks and geese.  They also determined which species of woodrat lived in the cave, an identification not really possible by just looking at the bones.

Deer mouse, cottontail rabbit, and eastern woodrat were the most common species of small mammals found in the cave since the Last Glacial Maximum, and these species occurred throughout all climate phases.  White-tailed deer and bison were the most common large mammals found in the cave and they too were found throughout all climate phases, though they became less abundant over time.  Hackberry and oak were the most common plant species found in the cave, and they were found throughout all climate phases.  Hackberry still grows near the entrance of the cave.  According to local pollen studies, pine was the most common tree growing on the Edward’s Plateau during the Ice Age, but it is absent from the cave.  Pine simply didn’t grow near the cave.

Hall’s Cave.

Edwards Plateau Savannas map.svg

Location of Edward’s Plateau.

Dendrogram of species found via DNA sampling in Hall’s Cave.  From the below referenced study.

The study sheds light on the changes that occurred on the Edward’s Plateau since the Last Glacial Maximum.  During the height of the last Ice Age weather patterns differed from those of today–more precipitation fell on southwestern North America whereas southeastern North America was more arid.  As a result, the Edward’s Plateau hosted a prairie environment with trees found at scattered locations.  Soils were much thicker because dense grass regularly decayed.  Deeper soils were good environments for prairie dogs, 13-lined ground squirrels, pocket gophers, and marmots.  Common large mammals included camel, pronghorn, and flat-headed peccary that were preyed upon by saber-tooths, dire wolves, and giant short-faced bears.  Birds that preferred treeless plains–prairie chickens, upland sandpipers, horned larks–abounded here then.

The environment changed here about 15,000 years ago during the Boling/Alerod Interstadial when temperatures and precipitation increased.  The prairie converted to open woodland and forest with widely spaced oak, ash, juniper, walnut, mulberry, and hackberry trees.  Plenty of grass still grew between the trees…enough to support a population of horses.  Many of the open plains animals disappeared from the record here including the pronghorn, camel, and flat-headed peccary.  Black-tailed jackrabbits, northern grasshopper mice, and prairie chickens all left the area as well.  However, turkey, bobwhite quail, and barking tree frogs moved onto the Plateau because they liked the newly expanded tree and thicket habitats.

12,900 years ago, during the Younger Dryas cold phase, the climate suddenly became much colder and dryer.  Vegetation decreased and the region became desert-like.  Small and large mammal and plant diversity decreased.  Following the end of this cold phase, temperatures and precipitation increased, though rainfall didn’t increase to the levels of the LGM and Boling/Alerod Interstadial.  Soils of the Edward’s Plateau were still thinner than they were during the LGM and today the region is dominated by a plant community of live oak, juniper, and hackberry.  Plant and small animal diversity rebounded but large mammal diversity did not.  The authors of this paper suggest man is likely responsible.  Plant and small mammal ranges adjusted to climate change, and they disappear and re-appear in the seda-DNA samples over time.  If not for overhunting by man, the same should hold true for large mammals.  14 species of large mammals that lived on the Edward’s Plateau during the late Pleistocene are either extinct or extirpated from the region.

Plant and animal composition does not stay constant, and the study found some non-analogue components living side by side.  Today, white-tailed jack rabbits and barking tree frogs have ranges that do not come close to overlapping, but both species lived on the Edward’s Plateau during the Boling/Alerod Interstadial.    Bog lemmings and least weasels ranged much farther south then and co-occurred with species of more southerly affinities.  Animal and plant communities are dynamic and always changing.

Species Profile: Barking Treefrog (Hyla gratiosa) | SREL Herpetology

Range of barking tree frog.

White-tailed jackrabbit - Wikipedia

Range of white-tailed jack rabbit.  White tailed jack rabbits and barking tree frogs both lived on the Edward’s Plateau during a warm interstadial of the last Ice Age, indicating the existence of non-analogue environments dissimilar to any that occur today.

Reference:

Seersholm, F.; et al

“Rapid Range Shifts and Megafaunal Extinctions Associated with Late Pleistocene Climate Changes”

Nature Communications 2020

https://www.nature.com/articles/s41467-020-16502-3#:~:text=Large%2Dscale%20changes%20in%20global,impacted%20ecosystems%20across%20North%20America.&text=Instead%2C%20five%20extant%20and%20nine,the%20end%20of%20the%20Pleistocene.

The Lujanian Land Mammal Age, the South American Equivalent of the Rancho La Brean Land Mammal Age

May 19, 2020

(Note: I accidentally published this article earlier today before I added the text.  I deleted that mistake. Here is the text.)

The Rancho La Brea Fossil site in California produced so many spectacular fossils that it gives the name to the Rancho La Brean Land Mammal Age, a period of time including the last 300,000 years of the Pleistocene.  All the fauna from this age in North America is referred to as Rancho La Brean.   In South America this age is known as the Lujanian Land Mammal Age and is named after a former site in Lujan, Argentina where fossil hunters found in quality and quantity specimens that are at the very least the equal of those found at Rancho La Brea.   People began collecting fossils here as early as the late 18th century and continued to do so well into the 20th century until the site was swallowed up by urban development.  The Lujanian Land Mammal Age was originally considered to have begun when horses of the equus genus first entered South America, however, paleontologists have since determined equus horses colonized South America much earlier, perhaps over 1 million years ago.  (Horses from the hippidion genus lived in North America even earlier.)  In any case land mammal ages are an artificial construct invented by men to define the composition of fauna that lived during certain periods of time.

Luján | Argentina | Britannica

Location of Lujan, Argentina highlighted in white.

At least 31 species of mammals weighing over 40 pounds lived in and around what is now known as Lujan during the late Pleistocene.  This list includes an astonishing 14 species of xenarthans: 2 large species of armadillos, 7 species of glyptodont, and 5 species of giant ground sloth.  By comparison Rancho La Brea was home to just 3 species of xenarthans.  Ecologists puzzle over how the environment could support such a wide variety of closely related species.  The different species of animals likely ate different species of plants.  The ground sloths Glossotherium and Lestodon were bulk feeders of grass, Mylodon and Scelidotherium were mixed selective feeders, and the huge Megatherium was the most selective feeder of all the sloths.  Similar niche partitioning likely occurred among the large armadillos and glyptodonts.

Doedicurus clavicaudatus

The glyptodont, Doedicurus clavicaudatus.

3 species of primitive ungulates occurred during the Lujanian Age–2 species of toxodon and the bizarre ancient litoptern.  Toxodons were hippo-like in build and may have been semi-aquatic.  Litopterns (Macruachenia patachonica) diverged from the ancestors of horse, tapir, and rhino before the dinosaurs became extinct, yet those odd-toed ungulates are their closest living relatives.

The Toxodon was so weird - Business Insider

Toxodon platensis.

Darwin's dilemma: Bizarre ancient animal identified through DNA

The extinct litoptern, Macrauchenia patachonica.

More modern ungulates ranging near Lujan during the late Pleistocene were 4 species of llamas (3 now extinct), collared peccaries, an extinct species of horse, and a large extinct species of deer (Morenelephus lujanensis.  A mastodon-like gompothere (Stegomastodon platensis) roamed the land with them.

5 large species of carnivores preyed upon the plant-eating beasts.  Smilodon populator, a 750 pound saber-toothed cat, took on and took down some of the megaherbivores.  Jaguars and cougars attacked smaller prey than Smilodon’s victims.  The little known small wolf (Dusicyon avus) may or may not have hunted in packs but was probably more a scavenger, like a coyote.  An extinct bear (Arctotherium tarijensis) opportunistically ate meat whenever it had a chance.

Reference:

Farina, Richard; Sergio Vizcaino and Gerry De Juliis

Megafauna: Giant Beasts of Pleistocene South America

Indiana University Press 2013

 

Learning about Mammals of Costa Rica (part 2)

May 7, 2020

I was most interested in learning about squirrels of Costa Rica because they are active during the day and would be the mammal I’d most likely see.  5 species of squirrels occur in Costa Rica, and the 2 most common–the red tailed (Sciurus granatensis) and the variegated (S. variegatoides)–co-exist throughout the country.  On ranges where they co-occur red-tailed squirrels tend to eat harder nuts such as palm nuts and Brazil nuts, while variegated prefer softer food including mangoes, avocadoes, and young coconuts.  Both eat acorns.  Mountain forests in Costa Rica are dominated by oaks, beech, and bamboo; but they are rich environments with many species of tropical trees and vines including palm, coffee, avocado, and figs.

ADW: Sciurus variegatoides: INFORMATION

Variagated squirrels have many different coat patterns.

Squeamish people might cringe at the numerous species of large rodents living in Costa Rica.  Yellow-spined porcupines (Coendou mexicanus) live in the trees, but the large gray Watson’s climbing rat (Tylomys watsoni) occasionally invades homes.  Spiny rats, 7 lb agoutis (Dasyprocta punctata), and 30 lb pacas (Agouti paca) forage on the forest floor.  Pacas are rare because they reportedly taste good and are a frequent target of hunters.

Lowland paca - Wikipedia

Many large rodents, such as this 30 lb paca, live in the jungles of Costa Rica.

3 species of skunks and 4 species of weasels live in Costa Rica.  The 5 lb grison (Calicotis vittosa) and the 10 lb tayra (Eira barbara) tackle large snakes as well as rodents.  7 species from the raccoon family (Procyonidae) occur in Costa Rica.  White-nosed coatis (Nasua nativa) are among the most common, foraging on the forest floor in groups of up to 30.  This family also includes the adorable arboreal kinkajou (Potos flavus) and olingos (Bassarieyon sp.).

Coati Mundi Stock Photos - Download 35 Royalty Free Photos

White-throated coatimundis patrol jungle floors.

Just 2 species of canids occur in Costa Rica (coyote and gray fox), but an astonishing 6 species of cats live there including oncilla (Leopardus tigrina), margay (L. wiedii), ocelot (L. pardalis), jaguarundi (Herpailurus yagaourundi), cougar (Puma concolor), and jaguar (Panthera onca).  I was unaware of the existence of the oncilla until I read this book.  It is arboreal and closely related to the margay.  Jaguarundis are the most common wild cat here because they prefer disturbed habitats and don’t sport a colorful coat coveted by humans.  Jaguars hunt sea turtles on Costa Rican beaches, dragging the 440 lb chelonians into the jungle.  Jaguars have a powerful bite and eat smaller turtles, shell and all.  They eat the exposed head and neck of sea turtles and scoop out the rest with their paws.

Oncilla-Leopardus tigrinus | Animals, Small wild cats, Wild cats

An oncilla.

5 species of ungulates occur in Costa Rica–Baird’s tapir (Tapirus bairdii), white lipped (Tayassu pecari) and collared (Pecari tajacu) peccaries, and red brocket (Mazama americana) and white tailed (Odocoilus virginianus) deer.  White lipped peccaries and Baird’s tapirs are confined to protected areas.

Central American Red Brocket Deer - Encyclopedia of Life

This red brocket deer is particularly red-coated.

The freshwater dolphin (Sotalia fluviatalis), a small species, swims in rivers as far inland as 50 miles in Costa Rica and even further in Brazil.

Reference:

Wainwright, Mark

Mammals of Costa Rica

University of Cornell Press 2006

Learning about Mammals of Costa Rica (part 1)

April 30, 2020

A few years ago, I fantasized the U.S. exiled me.  I chose Costa Rica over Canada as my new country of residence because of the more pleasant climate.  I even went so far as to search for a Costa Rican house online, and I found a nice 1 for $90,000–the equivalent value of my actual house (property values in Richmond County, Georgia are much lower compared to those of most of the rest of the country).  The ad for the house mentioned monkeys and coatis in the back yard.  For my birthday this year, I purchased a copy of The Mammals of Costa Rica to learn about what animals I might see, if the U.S. ever exiles me.  There are many species I never even heard of or only knew about vaguely.

8 species of opossums live in Costa Rica.  The Virginia opossum (Didelphis virginiana) reaches the southern limits of its range in Costa Rica, but a similar species (D. marsupialis) takes its place further south.  The woolly opossum (Caluromys derbianus) lives in trees and are monkey-like with large brains, forward setting eyes, and prehensile tails.  There are 2 species each of 4-eyed opossums and mouse opossums.  Perhaps the most interesting opossum species is the yapok (Chironectes minimus), an aquatic mammal that feeds upon crustaceans, frogs, fish, and insects.  It has a water-tight pouch to protect its young when it swims, and the young have a low metabolism, so they can survive without much oxygen for a long time.

Mystery Animal Contest: Who Is This Creepy-Handed Yelper ...

A water opossum.

7 species of edentates or xenarthans occur in Costa Rica.  The brown three-toed sloth (Bradypus variagatus) and Hoffman’s two-toed sloth (Choelupus hoffmani) evolved their arboreal lifestyles from 2 completely different ancestral families of extinct ground sloths.  (See: https://markgelbart.wordpress.com/2015/01/08/choloepus-tree-sloths-are-closely-related-to-the-largest-extinct-ground-sloths/ ) Biologists believe tree sloths make up the most abundant biomass of any mammals in the region.  This is impressive considering their slow rate of reproduction.  2 species of tree anteaters occupy different niches.  The northern tamandua (Tamandua mexicana) feeds upon ants and termites on the main trunks and larger branches.  They use their large claws to quickly break opens nests and consume insects before too many fiercely armed soldiers show up in defense.  The much lighter silky anteaster (Cyclopes didactylus) feeds upon ants and termites on the outer branches by using a claw to deftly slice open plant stems.  There is little overlap in the species of insects each anteater feeds upon.

Northern tamandua - Wikipedia

A northern tamandua.

Silky anteater - Wikipedia

Silky anteater.  

At least 109 species of bats fly around Costa Rica–almost double the number found in the U.S. and Canada combined.  Included among the sac-winged bats is the ghost bat (Diclidurius albus), a strikingly white creature.  There are also mustached bats, nectar-feeding bats, fruit bats, tiny disk-winged bats, and tent-making bats.  The latter actively make tents from large leaves to keep them dry and sheltered when they rest.  Free-tailed bats don’t occur in colonies as large as those found north of the border. Costa Rica is home to bats familiar to us in the U.S. including myotis and red bats, though they are different species.  But many species are unique.  False vampire bats (Vampyrum spectrum) are predators that kill rodents, birds, lizards, and other bats.  The related frog-eating bat (Trachops cirrhosus) specializes in preying upon frogs and locates them by pinpointing their calls.  True vampire bats (Desmodontinae) do feed on blood.  The fishing bats (Noctilio sp.) really catch minnow-sized fish and will carry them in their cheek pouches.

This Halloween, meet a fishing bat that hunts at sea | Oceana

Greater fishing bat.

4 species of monkeys range across Costa Rica.  Noisy howler monkeys (Alouata paliuru) are the most common.  They evolved to subsist on a diet of mostly leaves, though they eat some fruit.  The largest monkey in Costa Rica, the spider monkey (Atelis geoffoyi), mostly eats fruit but eats some leaves.  It weighs up to 15 lbs.  Squirrel monkeys (Scimmiri ocrstedis) are ominivores that are currently less common because of the pet trade.  The most intelligent monkey is the white-throated capuchin (Cebus capuceaus).  They use tools and have been observed using wooden sticks to kill venomous snakes.  They hunt birds and rodents and will knock squirrels to the ground and tear them apart.  Fruit and other plant foods make up a larger part of their diet, however.  They also use medicinal plants, often rubbing them all over their bodies.

White-throated capuchin | monkey | Britannica

White throated capuchin monkey.

Reference:

Wainright, Mark

The Mammals of Costa Rica

University of Cornell Press 2007

1 Thing I Knew and 2 I Didn’t

March 19, 2020

I’ve learned a couple things this past week in my search for blog fodder.  A new study presented evidence saber-toothed cats fought each other.  This is not at all surprising–I always just assumed this was true.  All extant large mammals battle each other in intraspecific conflict over mates or territory.  Of course, saber-toothed tigers were no different.  However, scientists found actual evidence–2 Smilodon populator skulls found in Argentina (1 by an amateur and 1 by a professional paleontologist) have punctures in them that exactly match the canine of another saber-tooth cat.  Smilodon populator was a huge species of saber-tooth, reaching 750 pounds in weight, that lived in eastern South America until about 11,000 years ago.  It was closely related to the more widespread Smilodon fatalis which ranged throughout most of North America and western South America until the end of the Pleistocene.  Previous studies have suggested Smilodon biting pressure was weak compared to most other species of cats, but apparently it wasn’t that weak…they were capable of puncturing bone.  The same kinds of injuries occur in extant species of cats.  Undoubtedly, most of these wounds are fatal, and the canine of a Smilodon was so long it definitely caused a fatal bite because it penetrated well into the brain.

saber-toothed cat skulls

Saber-toothed cats sometimes died during intraspecific fights.

I was watching a nature show on National Geographic wild entitled Wild Portugal and learned there were wolves still living in Portugal.  This, I did not know.  There is a population of 2000 wolves living in northeastern Spain and northern Portugal, and they are protected, though farmers try to kill them when they can get away with it.  The wolves take an heavy toll on the local sheep.  Some consider them beneficial because they control populations of wild boar.  They also hunt feral horses and deer.  Genetic evidence suggests the Iberian wolf has been isolated from other European wolves since before the Last Glacial Maximum when the populations were separated by a glacier.

Iberian wolf.

I also didn’t know there was a feral population of cats in Madagascar that already evolved to twice the size of a regular house cat.  Arab traders brought cats to Madagascar about 1000 years ago, and they went wild.  The evolution in size is an adaptation for hunting lemurs–a regular part of their diet along with rodents, snakes, and birds.  They outcompete a native predator, the fossa–a distant relative of the mongoose.

Image result for feral cats in madagascar

Feral cat in Madagascar.  They are twice the size of a regular house cat.

Reference:

Chimento, N; et. al.

“Evidence of Intraspecific Agonistic Interaction in Smilodon populator (Carnivora, Felidae)”

Comptes Rendus Palenal 18 (4) June 2019

At Least 1 Species of Giant Ground Sloth (Eremotherium laurillardi) Lived in Groups

February 28, 2020

Some scientists have long suspected at least 1 species of giant ground sloth lived in groups.  The bones of Eremotherium laurillardi are often found in intergenerational assemblages, and there is a large degree of sexual dimorphism within the species.  Animals with large males and small females or vice-versa tend to live in social groups.  Lions are an example of this.  However, most of the sites where mixed-age assemblages of E. laurillardi occur were difficult to interpret–scientists were unable to determine whether the collection of bones came from a simultaneous die-off or accumulated over a long period of time.  But a site in southwestern Ecuador known as Tanque Loma does contain bones of E. laurillardi that clearly resulted from a simultaneous die-off.

Image result for tanque loma

Photo of the Tanque Loma excavation from the below reference.

Scientists excavated 575 specimens of E. laurillardi from at least 22 individuals at the Tanque Loma site.  They found less than 100 bones of other species including  gompothere (a type of mastodon), glossotherium (a smaller species of ground sloth), pampathere (a very large armadillo), horse, and deer in the same genus as white tail deer.  The bones of E. laurillardi come from individuals of different ages and sexes, suggesting it was a social group. Sloth coprolites and stomach contents were found as well, but the plant remains have not been identified or if they have the results have not been published yet.  Tanque Loma was a temporary marshy pond that apparently dried up during dry seasons, then periodically refilled during rainy season.  This region of Ecuador was a tropical grassland during the Last Glacial Maximum, similar to modern day East Africa.  The remains are estimated to be between 18,000-23,000 years old, but the conditions of this site make radiocarbon dating less reliable.  Humidity and the presence of tar interfere with accurate radio-carbon dating.  It was not a tar pit trap because the tar seeped into the deposit after the animals had been dead for a long time.  The bones were preserved when they were quickly buried in a low oxygen environment.

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Replica skeleton of Eremotherium laurillardi mounted at a museum on Skidaway Island.  They were common along the Georgia coast during interglacials.  They reached 20 feet in length and weighed over 4 tons.  They may have been hairless like elephants and unlike other ground sloths.

The authors of this study believe this group of sloths died when the marsh shrank and the sloths fouled the water with a concentration of their own fecal matter.  The high nitrogen input may have caused a toxic algal bloom that poisoned the group, the members of which died within a few weeks.  Large mammal die-offs like this occur in East Africa today, especially among hippos when they are congregated around shrinking water holes.

E. laurillardi ranged into Florida and coastal Georgia during warm interglacials, but they disappeared from the region at least 30,000 years ago.  They were not as well adapted to temperate climates as Harlan’s ground sloth and Jefferson’s ground sloth (which occurred in Alaska).  These latter 2 species had furry coats and dug deep burrows.  Eremotherium may have been hairless and may not have dug deep burrows.  The temperate species of ground sloths didn’t become extinct in North America until men wiped them out.

Reference:

Lindsay, Emily; et. al.

“A Monodominant Late-Pleistocene Megafauna Locality from Santo-Elena, Ecuador: Insight on the Biology and Behavior of Giant Ground Sloths”

Paleogeography, Paleoclimatology, Paleoecology 544 April 2020

Nutria (Myocastor coypus) have Invaded Richmond County, Georgia

January 10, 2020

I think I’m the first person to document the presence of nutria in Richmond County, Georgia.  I was driving down Mike Padgett Highway last week and spotted a large road-killed rodent in the suicide lane, and I assumed it was a small beaver.  On the return trip I got a look at the posterior and noticed it did not have the broad naked tail of a beaver, but it was much too large to be a muskrat.  This specimen was at least 24 inches long, not counting the 12 inch tail, while muskrats grow to just 7-12 inches long.  I pondered over what it could be, and it dawned on me that it was a nutria.  I reviewed the description and photos of nutria in Mammals of Georgia by Stan Tekiela and confirmed my identification. His book was published in 2011 and shows the known range of nutria in Georgia then was along the Atlantic coast and the most southern boundary of the state, but apparently they have expanded their range since.

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I have no doubt that I saw a road-killed nutria in Richmond County, Georgia.

I considered taking a photo of the specimen as proof, but it seemed ridiculous to go back and risk getting run over by a car in order to photograph a dead rodent.  Though the traffic is not normally bad at this location, the carcass was in the middle of the suicide lane around a curve in the road.  The specimen was located about half a mile from the nearest water source (Spirit Creek, a tributary of the Savannah River).  Perhaps it was traveling across land to a different stream in search of an unrelated mate.

This species has been expanding its range north through the Savannah and probably other River drainages in Georgia.  They are well adapted for aquatic life and breed fast.  A nutria can produce 4 litters a year of up to 11 kits.  A nutria’s tits are angled to its side, so the kits can nurse with their noses above water while the mother swims.  Their population can explode.

Nutrias are native to South America.  Fur farmers have introduced nutria around the world–the U.K., France, Italy, Russia, and most notably Louisiana.  Fur farmers invariably go bankrupt, and the nutria escape to the wild.  Nutria feed upon the bulbous stem of aquatic plants, often killing them.  This causes erosion when the plant dies and the roots rot away.  To prevent damaged wetlands, some people advocate eating nutria meat, and 1 company even makes dog food from the meat.  Reportedly, it tastes like a cross between turkey and pork.  Cold winters may also contribute to a range reduction, but in Richmond County, we haven’t experienced a severe winter since 2012/2013.

Nutria fossils have been found at 6 sites in South America, dating from the early-late Pleistocene.  Their closest living relative is the painted tree rat ( Callistomys pictus ), an endangered species found in the disappearing Atlantic rain forests of Brazil.

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Endangered painted tree rat, the nutria’s closest living relative.  They must have diverged from a common ancestor many millions of years ago–1 is arboreal and the other is aquatic.

As far as I know, I am also the only person to document the presence of star-nosed mole in Richmond County.  See: https://markgelbart.wordpress.com/2016/12/02/the-strange-little-star-nosed-mole-condylura-cristata/