Red Fox as Weapons of Mouse Destruction

If you use the slightest bit of common sense, the chance of getting rabies from a raccoon, fox, possum, skunk or groundhog is very low, even if you work your terriers to such quarry year-round.

The chance of getting Lyme disease is a little bit higher, but it too is a very rare problem -- far rarer than most people think.

Lyme disease was first identified in Old Lyme, Connecticut in the 1970s. This zoonotic disease is passed to humans by blacklegged deer ticks which are infected with the spiral-shaped Borrelia burgdorferi microbe.

The illness was probably around a long time before being discovered, but prior to the 1970's it was rare enough that no one bothered to name the illness, much less study it.

Then, beginning in the early 1970s, the deer population in the Middle Atlantic and Northeastern United States began to grow rapidly. At the same time, more and more people began moving into the country, generally onto small farms located next to small woods.

Small woods in the Eastern U.S. are often dominated by young oak trees, and these same small woods serve as daytime shelter for fairly dense deer populations of 50-200 animals per square mile (as compared to 25 per square mile in pre-Columbian times).

Very dense deer populations are possible in the eastern U.S. because the deer are able to feed at night in nearby hay, corn and soy fields.

The proximity of houses to shelter-belt forests means deer jungled up in these woods are safe from hunters who cannot legally fire weapons in such close proximity to occupied buildings.

Most people assume deer are the primary reservoir for Lyme disease, but scientists now believe the primary reservoir for is not deer, but something quite a bit smaller -- the whitefooted mouse.

Ticks are not born with Lyme disease. The Borrelia microbe is not passed from female tick to egg, but from Borrelia-infected mammal host to blacklegged deer tick, and from the tick to humans as part of the multiple-host lifestyle of all ticks (for more on that, see >> here).

Almost all whitefooted deer mice have Borrelia coursing through their veins. In addition, almost every tick that bites a whitefooted mouse ends up carrying Borreleia. For reasons not yet understood, other Borrelia-infected animals do not pass Borrelia on quite so easily. While possums, raccoons, fox, coyotes and most birds can carry Borrelia, and often host deer ticks as well, the ticks that feed on these animals become infected with Borrelia only 10% of the time as compared with a 90% infection rate for whitefooted mice.

Clearly, a key component to controlling Lyme disease is reducing the number of whitefooted mice in an area.

Mice populations, it turns out, tend to explode with acorn production which tends to be cyclical. In high-mast years when the ground is littered with vast numbers of acorns, the whitefooted mouse population in small oak woods will explode, and with it the incidence of Lyme disease in an area. Deer coming into these woods pick up the ticks and ensure their dispersal while supplying the tick with a large blood meal (absent a human host).

Obviously, ending acorn production in the Eastern woods is not in the cards. So what else can be done?

One thing that seems to reduce mice populations is to increase the degree of ecological diversity in an area. As the variety of plant sources increase, the popualtions of meso-predators such as possums, raccoons, fox and coyote tends to increase, and with it a decline in mice populations.

Predators, such as fox, are impotant to keeping whitefooted mice populations -- and to some extent Lyme disease -- in check. Fox are highly mobile predators that continuously suppress mice populations all year long. In the absence of mice, fox easily switch to berries, crickets and grasshoppers, young rabbits, voles, and even roadkill and garbage. When mice populations do rise, however, a few red fox can go a long way towards knocking their numbers back down again.

How many mice can a fox eat in a year? If it eats little else, a fox can knock off about 5,000 mice a year. That's not enought to eliminate Lyme disease in an area, but it can have a significant impact, and every little bit helps.

What else can be done? In many areas more deer culling needs to be done, especially of does. With a reduction in deer densities, forest understory has a chance of growing back in, and with it will come an increase in bird populations and other non-mouse fauna.

Such simple precautions such as spraying your pants with bug spray before going out walking in forest and field can help reduce the chance of tick-borne infection quite a lot, as can mowing walking paths short. Move brush piles and firewood stacks away from the house as they are havens for mice populations. After returning from a day in the field, check yourself over for ticks, paying especially close attention to areas you do not normally look at, such as the back of your legs and your back and neck.

If you find a tick, do not worry -- a tick has to feast on you for three days or so before it is able to transmit Borrelia. If a tick bite, or a bite from an unknown bug, develops a large red ring around it, see a doctor immediatly or (if you have doxycline in your vet kit) take a 3-day regime of doxycline. Lyme disease generally very easy to treat in its early stages with a simple one or two-week regime of antibiotics.

And, of course, practice agressive flea- and tick-prevention on your dogs. I hunt most weekends and generally wash the dogs with a low-cost flea shampoo after they return. A few days later I look them over pretty carefully to see if they have any ticks on them that I might have missed while washing them (it helps to have smooth coated dogs!). Other folks use Frontline. Whatever works for you is fine.

The most important element of flea and tick control is vigilance -- paying close attention, on a daily basis, to your dogs. Simply running a hand over their coats once a day will tell you a lot, and not just about ticks, but about weight gain and muscle tone as well.

The Red Fox: the ultimate weapon of mouse destruction.
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Bird Species Decline in the U.S

In large parts of the U.S., over half of our songbird species are in decline. Scientists say habitat destruction is largely to blame.

Across the United States, more than 250 species of neotropical migratory birds fly south for the winter.

Beginning in the early 1970s, scientists began to notice that many species seemed to be in decline

What was going on?

Scientists have concluded that the decline of neotropical migratory song birds in the United States is closely linked to four issues closely linked to human population growth and habitat destruction:

• Tropical Forest Destruction
  The population of Latin America and the Caribbean has doubled in the last 35 years, and with it has come unprecedented destruction of tropical rainforests. As populations have exploded, more landless peasants have colonized forest areas and cleared vegetation, with slash-and-burn cycles becoming progressively shorter. At the same time, logging over wide areas and the rapid expansion of commercial farming has accelerated the disappearance of forests and fueled the rapid destruction of once-lush bird habitat. In the Peten region of Guatemala, for example, 77 percent of the land was covered in dense forest in 1960. By 1990, that number had fallen to just 29 percent.
  
  
• Pesticide Use Overseas
  Neotropical migratory birds are being killed by the heavy use of insecticides, herbicides and fungicides, which are used to boost crop productivity to feed increasing numbers of people in the developing world. In some cases, birds are poisoned outright by chemical application, or by consuming grain and insects that have been sprayed. In other cases, the pesticides accumulate and concentrate within the birds, resulting in deformed chicks or eggshells that are so thin they break before hatching.
  
  
• Suburban Sprawl and Forest Fragmentation
  As the population of the United States has grown from 76 million in 1900 to over 280 million today, cities and suburbs have sprawled outward. Fairfax, Virginia, for example, a suburb of Washington, D.C., saw 69 percent of its forest converted to homes and businesses between 1980 and 1995. As human populations have risen, and forests have fallen, primary predators such as wolves, bobcats, and cougars have been wiped out, while the ecological niche of meso-predators such as feral cats, raccoons, possums and foxes has expanded. The result has been massive predation of Neotropical songbirds, which tend to nest in the open and near the ground rather than in tree cavities or higher up in the forest canopy.
  
  With forest fragmentation has come an invasion of native and non-native birds that compete with deep-forest species for food and nesting sites. One example is the brown-headed cowbird. Cowbirds were once confined to the forest edges of mid-western prairies where they fed in grasslands grazed by roaming bison. Today, however, because of widespread forest fragmentation, parasitic cowbirds can be found all across the United States. A single cowbird may lay as many as 20 eggs in a breeding season - one or two eggs per songbird nest. Because Neotropical migrants tend to build open cup-shaped nests, and raise only a single brood a year, they are particularly susceptible to cowbird parasitism.
  
  
• Intensive U.S. Farming Practices
  As American farmers make increasingly intensive use of their lands, bird populations suffer. Post-to-post cultivation has wiped out edge-row thickets where many songbirds used to nest, while many farmers now cut hay three times a year where they used to cut just once. The result is that hedgerow and ground-nesting birds like the northern bobwhite, the eastern meadowlark, the vesper sparrow, and the grasshopper sparrow are in rapid decline.
  
  

Cowbirds, Mesopredators, & Grass Nesting Birds

The National Audubon Society's Christmas bird count is a pretty good organizing tool, but a little weak on science, since it is mostly counting bird-feeder birds that are not in too much danger of loss.

So what birds are in decline in the U.S.? Mostly neo-tropical migrants and grassland-nesting birds. More on neo-tropical migrants tomorrow. For now, let's look at grassland birds.

U.S. populations of Henslow's Sparrow, Cassin's Sparrow, Grasshopper Sparrow, Field Sparrow, Savannah Sparrow, and Vesper Sparrow exist in numbers only a fraction of what they did in the 1850s when the tall grass prairies had yet to fall under the plow.

Over the course of the last 20 years alone, the Breeding Bird survey has enumerated a very rapid decline in these birds that seems unrelated to loss of land across the U.S. Other grassland birds also seem to be in decline, especially such sparrow-like birds such as the Bobolink, the Dicksissel, and the Western Meadowlark (the state bird of Kansas, Montana, Nebraska, North Dakota, Oregon and Wyoming).

What is going on? The short answer is industrial agriculture.

As human population numbers have increased in the U.S. and across the world, more and more pressure has been put on America's farm land -- the source of 15% of the world's cereal production.

The good news is that record crops are being produced despite the fact that less and less land is being put under the plow.

The bad news is that this increased production has required more automation, less fence-row cover, and more intensive management of farm habitat than ever before.

A good example of what is going on can be seen by taking a look at America's hayfields. While 40 years ago a hay field might have been harvested once a year, most hayfields are cut three times a year now, thanks to automation. The second and third hay harvests typically occur just as grassland birds are breeding.

The good news is that while we are farming our most productive lands more intensively, we are putting a lot of marginal farm land into a Conservation Reserve Program (CRP) started in 1982.

The CRP has worked to take more than 32 million acres of farmland out of production in order to slow top soil loss and exhaustion, and to provide habitat for native plants and animals. CRP lands now total more than 50,000 square miles across the United States, and make up vast stretches of some prairie states.

Unfortunately, despite the extensive acreage put into the CRP program, it has not been enough to reverse the decline of some grassland bird species.

One problem is that much of the land in the CRP program is in relatively small blocks, often bordered by working farms. This "edge" habitat is perfect for deer, fox, raccoon, raptors, pheasant, grouse and turkey, but it is not always conducive to the successful breeding of grassland birds, many of which only do well in very large blocks of prairie devoid of trees.

In fact, because the population of medium-size predators such as fox, raccoon, possum and hawks is high in edge habitat, grassland nest mortality of small grass-nesting birds is often unnaturally high in small-acreage CRP locations.

In addition, the tree cover provided by old farm windbreaks and shelterbelts provides a near-perfect habitat for the brown-headed cowbird.

The brown-headed cowbirds is a brood parasite species which lays its eggs in nests of other birds and leaves them for the host bird to raise.

Because cowbird eggs hatch a few days before those of their hosts, the larger cowbird chick is able to push out the eggs and chicks of the host bird, thereby winning all the food resources for itself.

The destructive capacity of the brown-headed cowbird is hard to overestimate: a single female can destroy the clutches of 20 or more song birds in a single season.

Would I advocate shooting a cowbird? In a minute.

In fact, in some areas the only way to get native bird species back up to acceptable levels is with Larsen Traps designed to catch cowbirds. To learn how to build a cowbird trap (a good project for a boy scout !) click here.
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Making Hay and Losing Birds

As human population numbers have increased in the U.S. and across the world, more and more pressure has been put on America's farm land -- the source of 15% of the world's cereal production.

The good news is that record crops are being produced despite the fact that less and less land is being put under the plow.

The bad news is that this increased production has required more automation, less fence-row cover, and more intensive management of farm habitat than ever before.

A good example of what is going on can be seen by taking a look at America's hayfields. While 40 years ago a hay field might have been harvested once a year, most hayfields are cut three times a year now, thanks to automation. The second and third hay harvests typically occur just as grassland birds are breeding. The result -- a tremendous decline in grassland breeding birds across the U.S. (PDF at link)

The number of hayfields in the U.S. is also in decline -- a direct consequence of fewer horses and fewer grass-fed beef cattle, and also a decline in grass-fed dairy production.

Today most cattle are fed and fattened on grain, which produces both greater milk yields and more rapid beef production. While consumers benefit, grassland bird populations are in general and rapid decline.
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Possums and Horses

A possum around the barn could be detrimental to a horse's health because possums are carriers of equine protozoal myeloencephalitis (EPM), a neurological disease they acquire from eating dead birds. The disease itself is caused by a single-celled protozoa by the name of Sarcocystis neurona.

As part of its life cycle, this parasite may travel through a opossum and infects the cells in the animal's gut. It is then passed out of the possum in its feces, which, in turn, can be ingested by horses grazing in the pasture or in hay kept in a loft.

The bad news is that more than 50 percent of all horses are exposed to the parasite.

The good news is that only a few actually become affected by disease, which may require an immunity deficiency in the horse for the disease to actually become fatal.

EPM is hard to diagnose because it mimics other diseases, such as Wobbler's syndrome, equine herpes and West Nile virus.

The disease effects the horse by inflaming tissue around the parasite within the spinal cord.

Eliminating possums around a barn or horse pasture reduces the chances of horses contracting EPM.

The disease is not transmitted between infected horses -- only between possums (and possum scat) and horses.

Bottom line: If your farmer has horses, offer to toss the terriers up into the hayloft a couple if times in the Fall and Winter when possums are most likley to be looking for winter shelter. A warning, however: Be able and ready to move those large round bales should your dog find deep in the stack.

The Cow and the Derrick

I hunt several farms where corn and soy are grown and beef cattle are raised. One farm is entirely organic, and the cattle there are grass-fed Angus. Another farm has a mixed herd of cross-bred beef cattle, and they too are grass fed. A third farm has few cattle, but they raise over 1,500 acres of soy and roast it for cattle feed. All three farms also grow corn.

I mention this because in many ways these farms are oddities. When I was a young boy, almost all beef cattle were grass-fed, but today most beef comes to the table not from the farm, but the feed lot. You can drive a long way in parts of America today and see mile after mile of corn without ever seeing a cow.

A corn field is a lovely thing, but if you know what you are looking at it's easy to have mixed emotions. If you walk through a modern American cornfield today, you will find no weeds; almost all corn is now "Roundup Ready," which means it has been genetically engineered to be immune to the powerful herbicide "Roundup". Most soy is now Roundup Ready as well.

It has been said that the rise of modern feed lots has transformed cows from natural solar-powered ruminants into artificial fossil-fuel-guzzling hamburgers on the hoof. Because corn depends on fertilizers, pesticides, and herbicides -- and machines to harvest, plant, and transport it -- it has a high "oil price." It takes about 1.2 gallons of oil to grow a bushel of corn which is then converted into a few ounces of beef.

Corn, and to a lesser extent soy, are the main live stock feeds used today because they are so cheap and plentiful. This is due, in part, to federal crop subsidies (in the form of cheap water, low-cost loans, and price support programs), genetic engineering, and petrochemical fertilizers. It is also due to the tremendous natural potential of America's lands, and the expertise of American farmers.

As a result of our tremendous corn-and-soybean glut, the USDA encourages farmers to find a new markets for corn and soy, and -- absent a new market to dispose of it -- that means turning as much of it as possible into animal feed.

Compared with grass or hay, corn is a compact and portable, making it possible to feed tens of thousands of animals on small plots of land -- the modern American feedlot.

We are not going back to grass-fed beef, for the simple reason that there are too many people in the U.S. and they are too demanding. Grass-fed beef tends to be harvested in late Fall, after fattening up all summer, and before the grass grows dormant in winter, while corn-fed beef can be harvested all year round. People want to eat McDonalds, and they do not want to eat beef "in season" like sweet corn and tangerines.

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