Posts Tagged ‘Silver Bluff Audobon Center’

When did the Fisher (Martes pennanti) Last Roam the Wilds of Georgia?

January 6, 2012

Another interesting mammal with northern affinities that used to range into what’s now Georgia is the fisher (Martes pennanti).

I found this photo of a fisher carrying a dead squirrel on google images but I think it’s from the cover of an issue of the Journal of Heredity.   They had an article about genetic bottlenecks of this species created from habitat fragmentation.  Fishers require complete forest cover and avoid open fields.

Fossil evidence of fishers in Georgia comes from Ladds stone quarry in Bartow County.  Ladds is a collapsed and eroded cave system that yields fossils of warm climate species such as giant tortoise, Florida muskrats, and rice rats; and c0ol climate species such as bog lemmings and meadow jumping mice, besides the fisher.  The warm and cool climate species may or may not have occurred during the same climate phase–the quarry operation may have mixed fossils of different ages together.  But asymmetric compositions of species are common in most other Pleistocene fossil sites, so no one is really sure.  The fossils found here are at least 10,000 years old.  I suspect they date to the Sangamonian Interglacial–more than 100,000 years ago for reasons I discuss in my blog entry, “The Giant Chipmunk (Tamias aristus).  Kicked up Version of the Eastern Chipmunk?” https://markgelbart.wordpress.com/2011/01/20/tamias-aristus-the-extinct-kicked-up-version-of-the-eastern-chipmunk/

The fossil material of the fisher found at Ladds consisted of a couple of fragments of cheekbone with teeth attached and a partial jawbone.  This proves that fishers occurred in Georgia thousands of years ago during the Pleistocene.  What is not known for sure is how recently they lived in state.  There is fossil evidence of both porcupine and fisher from the Law’s archaeological site ins northern Alabama which dates to about 1700 AD, and from the Etowah Indian Mound Site in Bartow County which dates to between 1100 and 1500 AD.  This doesn’t prove fishers lived in Georgia that recently.  Indians traded fisher pelts and porcupine quills, and they could have originated from their known historical range.  However, it’s quite possible fishers had a more southerly range within the last few hundred years and were trapped out by Indians selling pelts to newly available European fur markets. 

Historical range of the fisher.  They may have ranged further south but were uncommon and trapped out early after European contact.  During the Ice Age just about their entire modern range was under miles of glacial ice, so of course they once ranged further south in pre-historic times.

Ecological studies show fishers require continous tracts of mature forest, and they completely avoid open areas.  In New England now that fur trapping has gone out of style and forests are growing back, fishers are recolonizing states where they’ve been long absent.  They’ve got a long way to go before they reach Georgia though.

Fishers prey on squirrels, rabbits, mice, and birds.  Studies of their dietary habits have yet to find fish in their scat, so their name is misleading.  They’re one of the few carnivores that commonly prey upon porcupines, but they occasionally die from injuries suffered when they mishandle the spiny rodents.  They kill the porcupines by biting their faces off, not by flipping them over as is falsely believed.  Fishers will kill small house dogs and cats, but I don’t believe reports that they attack German Shepherds.  Fishers only weigh 10-15 pounds and would have a size advantage over smaller cats and dogs but a big dog could shake a fisher and break its back.  Scientists studying Canadian lynx report two cases of fishers feeding upon radio-collared cats.  I don’t believe a fisher can kill a full grown lynx.  In one instance there was no sign of a struggle in the snow which tells me the cat was already dead.  A fisher doesn’t have a powerful enough bite to kill a large animal instantly, precluding the possibility that it ambushed a sleeping cat.  I think the cat died of either sickness or starvation.  Likewise, a find of bobcat in fisher scat was probably from a kitten or an already deceased cat.  The following youtube video shows a fisher struggling to kill a gray fox.  Bobcats and lynx are much more powerful than gray foxes.  The former regularly preys on gray foxes.  (Note: The fox in the video is a gray fox, not a silver color phase of a red fox.)

http://www.youtube.com/watch?v=txdoUgli2FQ

When I visited the Silver Bluff Audubon Center a month ago, I heard a cry that sounded like the distress call of the gray fox from this video.  At the time I didn’t know what it was and thought I was hearing a bird I couldn’t identify.  Maybe I was hearing a gray fox being attacked by coyote or bobcat.