Posts Tagged ‘jaguars’

Panthera atrox! What Kind of Cat was it?

July 28, 2010

One of the biggest cats to ever stalk the world roamed across North America during the Pleistocene.  Panthera atrox, weighing up to 500 pounds and possibly more, was a giant in the genus that includes lions, tigers, jaguars, and leopards.  It fed upon the bison and horses and camels that grazed the Ice Age grasslands and woodlands.  Atrox is a Latin word, meaning cruel, though it’s an error for humans to attach our emotions to an animal that merely did what it needed to do to survive.  Nevertheless, I pity any poor animal caught in the clutches of this powerful predator.

The first fossil specimen of this species was discovered in Mississippi in 1850, and its discovery immediately caused scientific controversy.  Some thought the skull resembled that of a tiger; others thought it was a lion’s skull.  By 1930 scientists had learned how to determine the difference between lion and tiger skulls.  It seems the sutures on the foreheads of the two species are quite different.  Moreover, tigers have noticeably longer nasals.  And from a view of the top of the skull, lion nostrils are visible because their skulls are more elongated, whereas those of the tiger can’t be seen from that angle.  Because Panthera atrox‘s skull closely resembled that of the lion, scientists determined that’s what it was.  Now, a new study using statistics based on data from detailed measurements of lion, tiger, jaguar, and atrox skulls and jaws, has upended the line of reasoning that assumed Panthera atrox was a lion.

The jaw bone of Panthera atrox most closely matches that of the jaguar, though it’s not an exact match, just like the skull of atrox most closely resembles that of the lion but is larger and more elongate in shape, and so is not an exact match of that species either.  So what was it?  The authors of the study referenced below measured every part of the skulls and jaws from 23 atrox fossils, 78 tigers, 126 lions, and 57 jaguars.  They then did a statistical analysis of the results and found that despite deviations between individual specimens of each species, all the measurements clustered into 4 groups, corresponding to each of the 4 species–strong evidence that Panthera atrox was indeed a distinct species.

Though this study surprises me, it makes sense because fossils of Panthera atrox are on average consistently 25% larger than anatomical specimens from extant lions.

Fossils of Panthera atrox are relatively common in western fossil sites, but they’ve also been found in Florida, and South Carolina in addition to the original type specimen discovered in Mississippi.  Undoubtedly, it occurred in Georgia.  True lions did live north of the ice sheet in what today is Alaska, but jaguars and Panthera atrox never advanced above the Cordilleran and Laurentide glaciers that covered what is now Canada.

The scientists who authored this recent study conclude that both Panthera atrox and jaguars descended from a Pliocene-age cat known as Panthera gombaszoengis which is sometimes referred to as a Eurasian jaguar.  This species colonized North America at the beginning of the Pliocene and different populations split into different species: some inhabiting forests evolved into jaguars, same living in open prairies evolved into Panthera atrox, which heretofore on this blog, I’ll refer to as the giant panther.

I believe genetic studies will eventually support this study.

The giant panther had a larger brain than lions and probably was more intelligent, making them a successful large predator, able to kill large game without the help of others of their species.

Because the giant panther is not as closely related to lions as formerly thought, it’s unlikely to have lived in prides.  Instead, like the vast majority of cat species, it survived as a solitary predator and competed with dire wolves and saber-tooths over the many large ungulate species then extant.  Throw in the mighty scavenging short-faced bear (Arctodus simus) and battles galore must have been the norm during Pleistocene dinnertimes.

Reference:

Christiansen, Per; and John Harris

“Craniomandibular morphology and phylogenetic affinities of Panthera atrox: Implications for evolution and paliobiology of the lion lineage.”

Journal of Vertebrate Zoology 29 (3) 934-945 September 2009

Note: Perhaps the giant panther looked like these jaguar/lion hybrids, though I guess they had a tawny coat, possibly lightly spotted.

www.bearcreeksanctuary.com/jaglions.htm

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