Posts Tagged ‘lynx rufus’

What was the Pleistocene Range of the Canadian Lynx (Lynx canadensis)?

July 15, 2013

William Brewster was an ornithologist who went on an expedition to the North Carolina mountains in 1885 before much of it was logged.  He was interested in finding boreal species of birds in the higher elevations where spruce forests replaced deciduous forests.  On Whiteside Mountain he found a remarkable forest of 70 foot tall hemlock trees with a thick understory of 25 foot tall rhododendrons.  The highlight of his expedition though was his journey to the summit of Black Mountain.  Below 4050 feet, a forest of oak, hickory, chestnut, tulip, beech, and sugar maple covered the mountain.  Brewster declared it the finest forest he had ever seen–many of the trees were 6-7 feet in diameter, 125 feet tall, and neatly spaced 100 feet apart.  At 4050 feet, Brewster encountered the first red spruce tree.  A mixed forest of red spruce and deciduous trees stood between 4050 and 5050 feet.  At this elevation he encountered red squirrels–an animal that prefers boreal forests, but he had begun seeing boreal species of birds at 3600 feet..  Above 5050 feet, the forest consisted of red spruce, balsam fir, and a few yellow birches.  Stunted black spruce trees grew at the summit.  Brewster camped near the summit and heard a wolf howl and saw sign of bear and deer.  Evidentally, large mammals hadn’t been extirpated from this region yet.  He also mentioned in his journal that locals believed Canadian lynx lived at higher elevations, replacing bobcats which roamed the lower elevations.  Other than this passage, I can find no evidence in the scientific literature of Canadian lynx in North Carolina.

Historical range map of the Canadian lynx.  There’s no concrete evidence they lived farther south than this within historical times. However, 90% of their historical range was under glacial ice during the height of the last Ice Age.  They must have occurred farther south then.

Canadian lynx.  Note the big paws and long legs that help them run through snow.  This gives them a competitive advantage over their close relative–the bobcat–in regions with heavy snowfall.  Bobcats outcompete lynx everywhere else.

The Canadian lynx is well adapted to living in deep snow.  They have wider paws and longer legs than those of bobcats, and this gives them an advantage over their close relatives when running through soft snow.  Historical records show Canadian lynx were plentiful in mountainous regions of New York and Pennsylvania, and a few even lived in West Virginia.    There are no records of Canadian lynx in Virginia, North Carolina, or Tennessee where potential habitat at higher elevations existed.  It’s likely deep snows didn’t occur often enough to give Canadian lynx a competitive advantage over bobcats here.  Overall, bobcats (Lynx rufus) are a more adaptable cat species.  I believe the locals Brewster mentioned were mistaken.  However, it is probable that Canadian lynx ranged farther south during the height of the Ice Age when over 90% of their current range was covered by glacial ice, making all of Canada unsuitable for most organisms.

Canadian lynx prefer habitat favorable to the main item in their diet–snowshoe hares (Lepus americanus).  Snowshoe hares make up 75% of the Canadian lynx’s diet.  Snowshoe hares are most abundant in disturbed spruce/fir or spruce/northern hardwood forests.  They thrive in the brushy second growth that covers clear cut tracts in the decade following logging.  This kind of habitat also occurs naturally when blizzards blow down large stretches of spruce/fir forests.  Like Canadian lynx, snowshoe hares are well adapted to living in regions with deep snow, but lose their competitive edge to similar species in areas with a more moderate climate.  Cottontails breed faster and are more adaptable than snowshoe hares.  Historically, snowshoe hares did live farther south than Canadian lynx, occupying the higher elevations in the mountains of Virginia, North Carolina, and Tennessee.  They still live in West Virginia.  But I think bobcats, not Canadian lynx, were their main feline enemies in the more southerly parts of their range.

The snowshoe hare turns brown during summer to blend in with the forest floor and white during winter to blend in with the snow.  They are part brown and part white in fall and spring.  They are also known as varying hares because their coat color varies with the seasons.

Historical range map of the snowshoe hare.  I believe it has been extirpated from North Carolina, Tennessee, and Virginia.

When Canada was underneath the Laurentide Glacier some 20,000 years ago, the Canadian lynx must have ranged farther south than it does today.  Paleobotanical evidence does show that boreal forests, their required habitat, predominated as far south as the north Georgia mountains when cooler climates and lower atmospheric CO2 levels allowed spruce trees to grow at lower elevations.  Deeper snows likely occurred more often in these southerly latitudes then.  Unfortunately, Pleistocene-aged fossils of Canadian lynx are scarce throughout the whole continent and completely absent in the south, unlike bobcat fossils which are among the most common mammals found in fossil sites all over North America.  Some of the fossils of Canadian lynx that have been found date to the Sangamonian Interglacial over 118,000 years ago, indicating it is not a recently evolved species, so it must have been present somewhere south of the ice sheet.  It may be possible to predict the Ice Age distribution of Canadian lynx by using snowshoe hare fossils as a proxy.  Snowshoe hare fossils have been found in Arkansas and Missouri–well south of their present day range.  The presence of snowshoe hares makes it likely Canadian lynx were in the environment preying upon them this far south as well. Fossils of carnivores are usually less common than fossils of herbivores because they are less abundant than their food source.  This explains the absence of Canadian lynx fossils  in areas where they may have lived in the past.  Although fossil evidence in Georgia is lacking, Arkansas is close in latitude to north Georgia.  I assume Canadian lynx and snowshoe hares occupied the higher elevations of north Georgia during snowy climate phases of the Last Glacial Maximum.

On the fringes of their ranges, Canadian lynx and bobcats occasionally interbreed.  In all recorded cases of interbreeding, it was a male bobcat that mated with a female Canadian lynx.  Bobcats are much fiercer than their northern cousins, and a male tom bobcat will always drive off male lynx.  From what I’ve read, it’s not clear whether bobcat/Canadian lynx offspring are fertile.  Attempts by fur farmers to backcross bobcat/lynx hybrids have failed.

The Bobcat (Lynx rufus)–Another Pleistocene Survivor

September 20, 2012

On New Year’s Day 2005 I saw a live wild bobcat.  This is the only time I’ve ever seen one.  I was looking out the window and noticed the brown rump of what I thought was a medium-sized dog.  It had a bob-tail and was sniffing around my neighbor’s mailbox.  I realized it was a bobcat, not a dog, and I rushed outside to take a closer look.  By this time it had wandered into the vacant lot across the street from my house.  I tried whistling to see if I could get it to approach me.  Instead, it stared at me, and its eyes widened in fear, as if it had never seen a human before.  The cat retreated in zig-zag pattern into the brush that then covered the lot.  This bobcat was much longer and larger than an ordinary housecat.  Though the rump was brown with black spots, most of its body was tawny-colored, so that it could blend with winter shades of grass.  Perhaps not coincidentally, a few months earlier a bobcat killed a 120 pound pit bull terrier on Beech Island, South Carolina about 20 miles from my house.

2004 article from The Augusta Chronicle detailing the fatal attack of a bobcat on a 120 pound pit bull terrier in Beech Island, South Carolina. Click on the image to make the article large enough to read.

According to the dog-owner, she heard her dogs making a commotion.  She went outside and tried to drive the cat off with a stick, but the cat chased her back inside her trailer.  I believe it may not have been coincidence that I saw one within the same year because bobcat populations are cyclical. The local bobcat population may have been high following a cyclical increase in the rabbit population, though they’re not supposed to be as tied to cottontails as their cousins, the Canadian lynx, are to snowshoe hares.

I think bobcats are rather uncommon most of the time in the region where I live.  Road-killed deer and coyotes are common, but I’ve never seen a road-killed bobcat.  I may be wrong, however; bobcats may simply avoid roads whereas coyotes hang around roads to scavenge the automobile carnage, explaining why they’re more often hit by cars.  Radio telemetry studies do show that bobcats avoid roads.  A healthy population of 26-35 bobcats living on Kiawah Island, South Carolina (near Charleston) has been intensively studied.  Scientists have come across a few road-killed bobcats there.  Kiawah Island bobcats help keep the deer population in check, and they are welcomed by nature-loving residents.  One study mentions a well-meaning but misguided tourist who chased away a bobcat that was about to kill a deer fawn on a golf course.  Do-gooders like that just get on my nerves.

This robust looking bobcat killed this mule deer.

Rabbits and rodents make up the majority of a bobcat’s diet.

This bobcat conquered a snake.

Bobcats were introduced to Cumberland Island, Georgia in 1989 in the hopes they would help control the feral hog population by abducting the piglets.  Bobcats were extirpated from the island circa 1910.  They adapted well to this roadless environment which consists of beach, interdune myrtle thickets, maritime live oak and pine forests, palmetto scrub, and fresh and saltwater marshes.  Wilderness areas on the southeastern coastal plain may host up to about 3 bobcats per 5 square miles.  Developed areas support a smaller density of bobcats because they are forced to roam wider areas in order to avoid people.  Their diet includes approximately 20% deer, 65% rabbits and rodents (especially cotton rats), and the balance consists of birds, reptiles, and insects.

Adult bobcats weigh between 20-50 pounds.  It’s surprising that a 20 pound cat can kill a 200 pound deer.  This curiosity of nature is almost like something from Ripley’s Believe it or Not.  But this predation has been recorded many times–I found half a dozen photos on google images of bobcats successfully killing adult deer, though they more often kill fawns.

Bobcats are one of the most common species of carnivores in the Pleistocene fossil record, evidence they outnumbered all other species of cats in North America.  In Georgia bobcat fossils have been excavated from Ladds, Yarbrough Cave, and the Isle of Hope site.  Bobcats evolved from a holarctic species of lynx during the Pliocene.  Early and middle Pleistocene bobcats were larger than late Pleistocene and modern bobcats.  I hypothesize that evolving to a reduced size helped them avoid competition with dire wolves, saber-tooths, and jaguars over larger prey items.  As I’ve noted before on this blog, the biomass of smaller animals such as rabbits and rodents far outweighed the biomass of large herbivores during the Pleistocene, even though it’s more famous for megafauna.  Bobcats survived the extinction of the megafauna because their smaller size enabled them to thrive on the smaller creatures that were still abundant.  During the Pleistocene megafauna populations fluctuated greatly but smaller prey items were always available.  I also hypothesize the bobcat’s ferocity, as evident when they attack much larger deer (and dogs as the above newspaper article relates), comes from an inherited mind-set.  The bobcat may have evolved into a smaller feline, but it still thinks of itself as a 75 pound cat rather than a 40 pounder.

Reference:

Griffin, John

“Bobcat Ecology on Developed and Less Developed Portions of Kiawah Island”

UGA Thesis 2001

 

Pleistocene Fossil Felid Ratios from the University of Florida Database

January 16, 2012

I followed the same procedure from last week’s study but counted the number of cat fossils in the University of Florida’s Natural History Museum database instead of dog fossils.  I only counted fossils dating from the Rancholabrean Land Mammal Age 300,000 BP-11,000 BP.  The results may be off a little because I was scrolling down while looking at a computer screen.  The results may also be misleading because many specimens may come from just 1 individual.   Nevertheless, I think the data reveals a good estimate of the ratio of species composition during the Pleistocene.

Listed on the University of Florida Museum of Natural History database, I counted 46 jaguar (Panthera onca) specimens, 21 giant panther (Panthera atrox) specimens, 42 saber-tooth (Smilodon fatalis) specimens, 6 scimitar-tooth (Dinobastis serum) specimens, 41 cougar (Puma concolor) specimens, 46 bobcat (Lynx rufus) specimens, 12 river cat (Leopardus amnicola or weidii) specimens and 1 ocelot (Leopardus pardalis) specimen.

The results are similar to those reported by the amateur fossil collectors who post on the fossil forum.  The most significant difference between their reports and database information is abundance of jaguar to saber-tooth abundance.  Amateur fossil collectors claim jaguar fossils are much more common in Florida than saber-tooth, though they do collect the latter and some have found scimitar-tooth specimens as well which are rare in the database.  It may be that the UF database includes a skeleton of a saber-tooth accounting for multiple specimens from 1 individual.

Dire wolves accounted for 64 specimens in my previous study, making them 33% more common, at least in the fossil record than any single species of big cat.  Overall, big cats combined outnumbered dire wolves 156 to 64, making large felines more than twice as common as dire wolves.  Perhaps there was less competition among species of canids, but more among felids.

Pleistocene habitats favorable to various species of big and small cats varied widely.  Mesic oak forests and cypress swamps, which expanded during warm interglacials and interstadials, favored jaguars, river cats, and ocelots.  Jaguars are adabtable enough to live in desertlike brush conditions which were common during cold arid stadials.  Cougars and bobcats thrive in many different types of environments.  The exact environments favored by giant panthers, saber-tooths, and scimitar-tooths is unknown, but it’s likely they were capable of adapting to many different ecotones.

Saber-tooths were evidently one of the most common large carnivores south of the ice sheets in North America.  They were actually no larger than a modern day jaguar.  Saber-tooths never colonized Eurasia, but a distant cousin, the scimitar-tooth had close relatives that did live from the southern tip of Africa to Alaska.  Scimitar-tooths also had longer front legs but these were more slender than those of the saber-tooth.  Their fangs were also smaller and more curved.  In Africa, Asia, and Europe scimitar-tooths became extinct much earlier than saber-tooths did in America.  I suspect they never learned to fear man, explaining their earlier extinction.  I suggest fanged cats didn’t often back down from anything.  Scimitar-tooths probably colonized southeastern North America during stadials when grasslands expanded due to dry climate which in turn caused an increase in the populations of ungulates. 

Giant panthers probably resembled large maneless lions.  True lions did live in Alaska and across Eurasia.  But south of the ice sheets in North America, the common ancestor split into 2 different species–Panthera atrox and Panthera onca.

8 cat 10 Biggest Cats in the History

This image comparing Pleistocene jaguars with modern jaguars may be a slight exaggeration, but jaguars did grow bigger during the Pleistocene because they preyed on larger mammals and had more competition among carnivores.

I’ll write more about the presence of margays and ocelots in Pleistocene Florida in my next blog entry.

Here are some related articles about big cats from my archives.

“Panthera atrox! What Kind of Cat was it?”– https://markgelbart.wordpress.com/2010/07/28/panthera-atrox-what-kind-of-cat-was-it/

“Why did fanged cathttps://markgelbart.wordpress.com/tag/saber-tooth/s have sloping backs and large forelimbs?”–

“Two new studies of saber-tooths.”– https://markgelbart.wordpress.com/2011/07/08/two-new-studies-of-sabertooth-smilodon-fatalis-anatomy/

“Cougars vs. jaguars”–https://markgelbart.wordpress.com/2010/07/08/cougars-vs-jaguars/