Rana sphenocephala

Rana sphenocephala
Leopard Frog, Rana pipiens sphenocephala

Thursday, July 3, 2014

Deer, Ticks, and Lyme Disease

Connecticut scientists have published the results of a 13-year monitoring study of what happens to tick numbers and the incidence of Lyme disease when deer populations are reduced in number: tinyurl.com/oaqf65s.

They found that when an area’s deer population was reduced in number by 87%+, as in their case by hunting, the numbers of ticks found on people and cases of Lyme disease dropped 76 and 80%, respectively.

Computer modeling studies indicate that populations of some species can be eliminated over time by reducing the number of fertile individuals below some threshold. In the case of feral cat colonies that are not artificially augmented (e.g., immigration, abandonment), TNR must sterilize ≥ 82% for colony die-out over 11 years. I suspect that similar rates might be appropriate for some other mammals. However, 87% is evidently not too high for deer in Connecticut (and likely not for feral hogs, either).

Nonetheless, these two sets of observations lead to two notions, that (1) we might be able to reduce the incidence of Lyme disease by reducing deer populations through intense hunting pressure and predator restoration, and (2) extirpated large predators and a pre-Columbian contiguous Eastern forest together may have limited deer numbers and consequently kept Lyme disease case numbers down.

Eat mo’ venison!

Saturday, September 28, 2013

Emerald Trappers

As if two blogs weren't enough, I have started a third blog called Emerald Trappers:

The Intro tab (which is also the blog's first post) of the Emerald Trappers blog explains the blog, which is to be the mouthpiece of a new non-profit company called Emerald Trappers, Inc. In a nutshell, the mission of Emerald Trappers is to own and use remote-controlled feral hog control equipment on private properties within a 12,000-acre project area inhabited by feral hogs. The project area includes San Felasco Hammock Preserve State Park, Millhopper Geological Preserve State Park, Turkey Creek Hammock Preserve County Park, an Alachua County Trust natural area, and a City of Gainesville natural habitat tract, plus residential, commercial, and agricultural zones.

Check out the Emerald Trappers blog if you are having feral hog problems. There is new, game-changing technology that promises to be able eradicate feral hogs if followed correctly. Hopefully, federal, state, and local governments will adopt it and restore our public natural areas. Of course, support for the new approach is up to you. Please let your local natural-area managers know which side of the feral hog equation that you are on.

Wednesday, September 11, 2013

My Intro to Game Cameras

I bought a game camera and have been practicing with it in my yard in prep for field work this winter on the Emerald Pendant Feral Hog Removal Project. So far, the raccoon, opossum, common crow, gray squirrel, and whitetail deer have been snapped as they foraged around my kitchen scrap “compost” pile. Here’s five whitetail deer (Odocoileus virginianus) that couldn’t have posed any better than they so graciously did:

That’s the best photo the Moultrie D-444 game camera has taken for me. Most of the small animals in the photos are blurry, as they are quick and the camera evidently has a long shutter speed (but I cannot find that spec). It also has a long wake-up time and long interval between shots, 15 sec in each case, reducing the number of second and third chances at photo-ops. Nonetheless, it captured several shots of the slowly grazing deer, enough to think that there probably are five in that group, and even smaller, faster-moving animals are identifiable to species based on who is known to occur around here. These facts suggest that this camera will be sufficient to characterize feral hog sounders. We shall see. Below are the best pics of other animals it collected, in color by day and B/W at night. They illustrate both what is blurry and what is clear.

Opossum (Didelphis marsupialis):

Raccoon (Procyon lotor):

Gray squirrel (Sciurus carolinensis) and Common American Crow (Corvus brachyrhynchos):

The camera has been set on its simplest settings to obtain all the photos above, so today I set it in 3-shot mode. I’ll move up through the more-and-more and faster-and-faster modes, and get into its video capabilities in a week or two. I want to become familiar with each capability of the camera by the time I return to Florida in early October so that I can start tracking feral pigs just as soon as my RV’s umbilicals are hooked up.

Friday, September 6, 2013

The Bat and Viral Disease Conundrum

I read a News & Analysis article in the journal Science (30 August 2013, vol. 341, pp. 948-949) entitled Link to MERS virus underscores bats’ puzzling threat. It seems that bats carry more viral diseases than they are supposed to, and more than their share of the dangerous ones like Nipah, Hendra, SARS and its predecessor, Ebola, Marbourg, Australian bat lyssavirus, rabies, KasokeroDuvenhage, and Menangle.

Scientists have put the blame on a variety of causes like hibernation, bat immune systems, and even echolocation! Others think the reasons are simply their high numbers and lifestyle.

One reason often cited is the high number of species of bats – more than 1300 species, or a fifth of all mammal species. More bat species means more parasitic species means more virus species means more diseases – simple biology. Angela Luis published an enumeration of rodent and bat viral diseases, finding that bats harbor 61 and rodents 68, yet there are roughly twice as many species of rodents as bats, so perhaps there’s more to the matter.

Bats are on all continents except Antarctica, are abundant, can fly, some species migrate up to hundreds of miles, maternity colonies contain huge numbers of densely-packed bats and susceptible young, and species intermingle when roosting and hibernating. These factors force them to be exposed frequently to viruses, often at high levels of contamination.

I like another factor that was not mentioned in the Science article, and that is the microhabitat conditions within ceiling pockets, or bell-holes, occupied by bats during warm-month daytimes. Bell-holes are upside-down, bowl-shaped pockets in the ceilings of caves, and can vary widely in size up to a few meters with depths of up to a half-meter or so. A typical bell-hole is about a third-meter wide and half that deep. Bats often occupy bell-holes, and I suspect that bats are responsible for their creation via the same actions responsible for making bell-holes favorable for transmitting viruses.

A bat flying up into a bell-hole to roost grabs the ceiling with its claws and holds on, thus creating an opportunity for mechanical erosion of the rock. The bat breathes out warm, humid air that is slightly acid due to carbon dioxide from respiration, and contains water vapor, aerosolized water droplets, and viruses. This relatively warm mixture of gases and particulates rises up into the bell-hole and its acidity eats away at the rock, enlarging it beyond what claws and hydrology also erode. I don’t know how long viruses can survive outside the bodies of bats within bell-holes, but I suspect that the bell-hole micro-environment might sustain viruses at least a little longer than cold cave air would.

A much more complex process is proposed by Linfa Wang that invokes bat immune systems. Wang’s group sequenced the genomes of a small insectivorous bat and a large fruit-eating bat, and found that both were missing a hunk of DNA that senses microbial DNA and initiates an inflammation response. This might make bats more susceptible to disease.  Wang thinks that the high energy demands of flight caused the release of metabolites that damaged DNA so much that bats evolved special DNA repair mechanisms, but bats suffer less damage from them because their immune systems use some of the same molecules that are also involved in DNA repair. In other words, a genetic coincidence results in bats being more vulnerable to infection but less vulnerable to serious disease and death. Wang’s hypothesis is rather complex compared to simpler environmental explanations, and Occam’s razor shaves me, but it will be an interesting story to follow.

Monday, July 8, 2013

Torreya Seedling Status – Summer 2013

Only one of ten Torreya seeds from the 2010 crop given to me ever sprouted. It was a disappointing result, and other Torreya Guardians had a similar lack of success. Nonetheless, my single seedling grew vigorously, growing six inches that spring (2012) in Florida. It grew another two or three inches in the first three weeks in the pot at my North Carolina home, was planted in the ground in May, and at this writing is 21 inches tall. I think it likes it here in the Southern Appalachians:

My 2011 seeds started off rather slowly. None germinated the following spring in Florida, and only three sprouted in July 2012, in North Carolina. Other Guardians reported similar results, and it looked like a repeat of the 2010 track record. But after only a month following their return to north Florida, in December 2012 another four seeds sprouted, in January 2013 another germinated, and the ninth seed germinated in February 2013. That yields a 90% success rate for the 2011 seeds, and again other Torreya Guardians enjoyed a similar pattern of delayed but successful germination. I gave two of my 2011 seedlings to my gardening friend Brack in Williston, FL, and planted another three (height range 9-10 in) at my NC place during the last three weeks:

In case you are wondering about the deer exclusion cages, they are constructed of 2x4 inch mesh, 4 ft tall, 1.5 – 2.0 ft diameter galvanized steel fencing, and set a couple of inches into the ground so that roots will grow over the bottom wires to hold them down:

My four 2011 seedlings (height range 6 - 13 in) remaining to be transplanted are in pots protected by rodent exclusion cages:

Those cages also contain fifteen seedlings from the 2012 crop of twenty seeds given to me. The 2012 seeds were small, pale floaters, quite unlike the larger, darker, denser 2010 and 2011 seeds. I planted four to a 1-gal pot (previous years had two per pot) in Florida, and by late April four of them had sprouted and were growing vigorously. Shortly after moving from Florida to North Carolina, a flush of eight sprouted during early June 2013 and another three have sprouted since then. That totals fifteen sprouted seedlings from the 2012 seeds, or 75%.

My Torrrya seeds tend to sprout in flushes of three or more at a time, and they tend to do so shortly after I move from Florida to North Carolina in the spring and then again to Florida in autumn. It will be interesting to see if any of the five as-yet unsprouted 2012 seeds will germinate when I return to Florida in November.