Rana sphenocephala

Rana sphenocephala
Leopard Frog, Rana pipiens sphenocephala

Thursday, September 18, 2014

Lotta Big Birds

My first job out of college was to maintain a lab for a university prof. One of the projects he (Sam) had his graduate student Allen and me construct was a floating aquatic sampling machine – basically a boat containing sampling and power machines plus collection containers. Upon completion of assembly, Sam told us to take it out on Newnans Lake the following morning and test all the equipment to see if the sampling system worked.

Allen had an early class so we met at the boat ramp at dark-thirty. Stars were still out and it was bitter cold, as a polar front had come through earlier that night. We gamely did our do on the foggy waters, circling the lake and sampling here and there. As the dawn slowly lightened, before sunup even, we gradually became aware that the perimeter ring of mature cypress trees held a bunch of big black birds. We couldn’t make out what they were for the longest time, so we assumed they were vultures as vultures are wont to mass up at night. But as the sun did rise up over the horizon and we got a good look at the birds, we could see that each and every one of them had a white head and a white tail. Using the best principles of wildlife management that I could muster, I counted all the eagles within a pie-shaped slice of the lake and multiplied out the number for the entire lake. My conservative estimate was in excess of 400. They had evidently migrated south before the cold front.

This was during the winter of 1971-72, during the middle of the multi-decadal DDT Winter, when there were estimated to be only about 1000 bald eagles in the entire coterminous United States. Is it possible that Allen and I were looking at nearly the entire population of the Atlantic Seaboard’s Bald Eagles that morning?

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.