Posts Tagged ‘evolution of size reduction’

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