Posts Tagged ‘bears’

My Pleistocene Mammal Checklist of East Central Georgia 36,000 Years BP Revised

August 13, 2021

8 years ago, I wrote a blog entry listing the exact species of mammals I thought probably lived in east central Georgia 36,000 years ago. I chose this time because it was the most recent period when climate was similar to today’s climate, coinciding with the last time when man was probably absent. I wondered what mammals would live in an environment untouched by man but with a similar climate. My list was an educated guess because there is only 1 Pleistocene-aged fossil site in this region, though there are some to the immediate north, south, and east. This time period was an interstadial–a warm wet period between colder drier Ice Ages. Pollen evidence suggests oak tree populations expanded. So I assumed the ecosystem was a mix of open oak woodlands, some grasslands, wetlands, and relict arid scrub environments persisting from the previous stadial. Since I wrote this blog, new information has come to light, and my list needs to be revised. Before I started to write this, I didn’t realize I had already edited some of the changes into my original article. (See: https://markgelbart.wordpress.com/2013/12/27/if-i-could-live-during-the-pleistocene-part-xii-my-mammal-checklist/ )

The 9-banded armadillo is an addition to my list. 9-banded armadillos have recently recolonized the region, but until a few years back scientists didn’t realize this species had also lived in southeastern North America during the Pleistocene. Their fossils had been confused with those of the beautiful armadillo, a different extinct species that was about twice as big. But analysis of genetic material shows that both co-existed over the same range.

On my original list I put question marks next to species that I was unsure lived in the region during this time period. Fox squirrels are 1 that should have a question mark next to it. There is no evidence in the Florida fossil record of fox squirrels until very late during the Pleistocene ~12,000 years BP. However, fox squirrel remains have been found in a Georgia cave that date to the LGM ~21,000 years ago. They may be a late invader of southeastern North America, but on the other hand they could just have been local in distribution and perchance never left remains in fossil sites. By contrast gray squirrels are commonly found in regional fossil sites. Perhaps east central Georgia was an area where fox squirrels occurred 36,000 years ago and from where they expanded into the rest of the south, but the dearth of fossil sites explains why this is unknown.

On my original checklist I included 2 species of horses, but it seems likely there was only 1–Equus caballus. Fossils of the pseudo-asses that date to the late Pleistocene are restricted to the west. The pseudo-asses did occur in southeastern North America during the Pliocene and early Pleistocene, but by 36,000 years ago they were not living in the region.

I included elk on my original checklist, but genetic evidence suggests this species did not colonize North America until about 15,000 years ago. No radiometrically dated remains of elk on the continent prior to that date have ever been found. Unless there was an extinct lineage of elk ranging here, I don’t think they lived in the region. White-tailed deer were likely the most common species of deer in the region then, just like today. However, I do believe woodland caribou and the extinct stag-moose did occasionally range into the region. Fossil remains of both species have been found at this latitude. They were probably more common in the region during Ice Ages, but I think it seems likely a few stragglers did wander into the region during interstadials. After all, this was unchecked wilderness. Some caribou herds likely migrated haphazardly, and sometimes they wandered into the region.

I think herds of caribou wandered into east central Georgia even during interstadials.

Scientists identify the remains of a medium-sized canid as coyote from fossil sites that are known to date throughout the late Pleistocene. However, genetic evidence suggests coyotes diverged from the population of gray wolves that crossed the Bering Land Bridge into North America just 20,000 years ago. So what were these coyote-like canids? I think they are an unnamed extinct species anatomically difficult to discern from modern day coyotes. This species likely played a similar ecological role. On my list Canis latrans should be changed to unnamed extinct canid.

Dire wolves and jaguars were likely the most common large predators in the region. Giant lions and saber-tooths may have existed in low numbers here. The former were more common in the more open grasslands to the south of the region. But I think bears were by far the most common carnivores. If a person could travel back in time and take a walk in the woods of this region, it would be impossible not to run into a bear. Bears are omnivores and can breed and reproduce even when there are low populations of other large mammals. Grizzly-sized black bears, Florida spectacled bears, and giant short-faced bears all roamed the region then.

I still think most of the other famous Pleistocene megafauna occurred in the region, but some may have been transitory. I think Jefferson’s ground sloth and Harlan’s ground sloth were year round residents as were stout-legged llamas and long-nosed peccaries. Herds of long-horned bison roamed around looking for fresh pasture. Mammoths possibly passed through during annual migrations. And mastodons moved up and down the river valley bottoms.

Cougars vs. Jaguars

July 8, 2010

Cougars and jaguars co-existed for at least 500,000 years throughout North America, and today still co-exist in many areas of South America and Mexico.  Both species are adaptable enough to occupy a wide variety of environments, including deserts, lightly wooded savannah, flooded swamps, and tropical rain forests.  They also feed upon many of the same prey species.  This spawns two questions: what ecological differentiation allows two big cat species to co-occur on the same range, and what factors allowed cougars to remain in much of North America where jaguars were extirpated?  A number of scientific studies help solve these ecological mysteries.

Comparison of cougar and jaguar diets

Studies of jaguar and cougar diets consistently show significant differentiation.  Although cougars and jaguars tackle many of the same species, the latter selects for larger sized individuals.  One study of co-occurring jaguar and cougar populations in Venezuala–a region consisting of woodland, savannah, and swamp–found the following differences in prey size selection between the two species.

…………………………………….Cougars……………………………Jaguars………………

Small size prey…………………17%……………………………………1%……………….

Medium size prey……………..31%……………………………………14%……………..

Large prey……………………….52%……………………………………85%…………….

For example in this region collared peccaries are an important diet item for both species, but cougars exclusively take small juveniles, while jaguars take mostly adults and sub-adults.  Both big cats took a wide range of prey species with cougars taking 12 different kinds of animals and jaguars taking 10.  Jaguars preyed more heavily upon capybaras here than cougars did.  Jaguars also preyed upon white-lipped peccaries–an aggressive species that cougars completely avoided.  White-lipped peccaries live in large groups and frequently come to the aid of their comrades and attack predators.  They’ve been known to kill jaguars and even humans.

Illustration by John James Audubon

Another study of jaguar diet, this one in southern Brazil where flooded plains are the predominant habitat, found that the jaguar diet there included 31% cattle, 24% caiman, 21% peccary, 4% feral hog, 3.0% marsh deer, 3.2% giant anteater, 2% capybara, 1.6% brocket deer, and about 10% other.  438 prey items were recorded, showing that jaguars will take what’s generally available.  Incidentally, both jaguars and cougars are capable of killing the alligator-like caiman, but take them less than would be expected based on their abundance.

Illustration by John James Audubon

A third study, this one in Mexico where both jaguars and cougars mostly prey on deer, peccary, and armadillo, also found that jaguars select for larger prey items.  This study concludes that the “cougar’s ability to exploit smaller prey gives them an advantage over jaguars when faced with human-induced habitat changes.”  This conclusion brings to obvious light one of the reasons why cougars survived throughout much of North America where jaguars didn’t.  After Indians overhunted much of North America’s megafauna, jaguars had difficulty finding the larger prey they preferred.  The extinction of two Pleistocene species of peccary in North America was probably devastating.  Indians even overhunted white tail deer into scarcity as John Lawson, an early European explorer (circa 1704) noted when he pointed out that deer were rare around large Indian settlements in South Carolina.  But cougars could survive in these areas on rabbits, possums, raccoons, and turkeys.

I agree that the preference for larger game that no longer exists is one factor that’s limited the jaguar’s range in North America, but I think there are other factors.

Evolution of size, coat color, adaptability to cold, and personality traits

The fossil record suggest jaguars, along with dire wolves, were the most common large carnivores (excluding omnivorous bears) in southeastern North America during the Pleistocene.  Yet, cougars found their niche here too.  During the Pleistocene both species were somewhat larger than the present day versions of these species.  Rancho La Brean specimens of cougars show that on average they were 5% larger than those of today, while Pleistocene jaguars approached modern day tigers in size.  I think this is due to the larger size and quality of prey available, particularly horses and the larger sized species of peccaries, and it’s clear these two big cats not only had a better diet, but further impetus to evolve to a greater size, so they could successfully exploit this larger prey.  One study reported that modern jaguars living in areas where cattle were introduced tend to approach the size of the larger Pleistocene jaguars, and it’s believed that jaguar populations increased following the introduction of European livestock to South America.

I theorize the spotted coat of the jaguar is another factor in its range reduction.  Indians valued the beauty of its fur and hunted them unmercifully.  There’s a possibility that Pleistocene cougars had spotted coats.  Scientists believe that cougars evolved from a kind of spotted cheetah.  Cougar kittens retain these cheetah-like spots–evidence of this evolution.  But I think many adult cougars may have been spotted until very late in the Pleistocene when man colonized the continent and hunted the spotted cougars for their coats, leaving only the dull tawny and gray coated individuals to breed, which in turn genetically swamped the spotted ones.

It has been suggested that spotted cats are more vulnerable to cold climate–another factor which may limit the jaguar’s range, but I disagree with this hypothesis.  The snow leopard of the Himalayas is an example of a spotted cat that lives in a cold region.  Moreover, jaguar fossils have been excavated from as far north as Oregon and Pennsylvania when even during the warmest interglacials, subfreezing temperatures occurred during winter. 

Jaguar fossils in Georgia have been excavated from Ladds Quarry and Kingston Saltpeter Cave.  A nearly complete skull was recovered from the former location along with giant tortoise and armadillo bones that have jaguar gnaw marks on them.  Fossils from this period probably date to a warm climate phase, but the jaguar remains from KSC are associated with the kinds of animals that live in cold and temperate climates, indicating jaguars survived colder conditions than any endured by extant populations.  Cougar fossils also were found at Ladds and in Yarbrough Cave which dates to the last glacial maximum.

One more factor in the cougar’s survival where jaguars didn’t may be evolutionary selection towards more timid individuals.  Those members of the cougar population that learned to avoid man were more likely to survive.  Timidity possibly occurred less frequently in prehistoric jaguar populations.

Cougars vs. Jaguars, wolves, and bears

So which would win in a battle between a jaguar and a cougar?  According to scientific studies, cougar and jaguar ranges frequently overlap, but they tend to avoid each other.  Certainly, a jaguar wouldn’t think it worth the effort to battle a raging mother cougar defending her kittens.  Conversely, a cougar would be out of its mind to engage in a battle with a larger, more powerful cat that bites harder than any other kind of cat in the world.  However, in one paper, international big cat expert, Howard Quigley, did cite a case of a jaguar attacking and killing a cougar.

Packs of wolves also dominate cougars in the Rocky Mountains.  Wolves occasionally kill cougar kittens, sub-adults, and even adults.  The average biomass of wolves in packs that attack a cougar outweighs the cat by a 13:1 ratio.  Rarely, cougars have been reported to kill wolves (sub-adults and adults, but not pups), but in these cases it was one-on-one and the biomass was a 1:1 ratio.  A certain percentage of cougar kills are lost to wolves and bears in areas where their ranges overlap.

References

Carvolcanti, Sandra; and Eric Gese

“Kill rates and predation patterns of jaguars (Panthera onca) in the southern pantanal of Brazil”

Journal of Mammalogy 91 (3) 722-736 2010

Hoogesteyn, Rafael; and Edgardo Mondolfi

“Body mass and skull measurements in four jaguar populations and observations on their prey base”

Bulletin of the Florida Museum of Natural History V. 39 (6) pg. 195-219 1996

Hornocker, Maurice; Sharon Negri, and Alan Rabinowitz

Cougar: Ecology and Conservation

University of Chicago Press 2002

Nunez, Rodrigo; Brian Miller, and Fred Ludjey

“Food habits of jaguars and cougars in Jalisco, Mexico”

Journal of Zoology 252 (3) 373-379

Scognamillo, Daniel; et. al.

“Co-existence of jaguar (Panthera onca) and puma (Puma concolor) in a mosaic landscape in the Venezualan llanos”

J. Zoological Society of London 259 269-277 2003