A Northwoods Almanac for Nov. 1 – 14, 2019
Acorns and Lyme Disease
Our northern oaks have had a boom year for acorns. Walking a woods trail lined with northern red oaks is like walking on a path littered with large ball bearings – there’s tens of thousands of acorns on the ground. In some areas, there may be more than 100 acorns per square meter. Like most trees, oaks ascribe to a ‘boom and bust’ cycle, producing a pittance of acorns in a lean year and raining them down in a boom, or “mast,” year.
While chipmunks, squirrels, deer, blue jays, and a host of other acorn eaters are in seventh heaven during a boom year, unfortunately mice also gorge on acorns. They’ll store them for the winter, helping them to go into next year’s breeding season very well-fed. Acorn boom years thus typically cause a population boom for white-footed mice the following spring.
White-footed mice are fine fellows, but there’s a proven link between white-footed mice populations and an increased risk of Lyme disease. Field studies over 20 years have confirmed the relationship between boom acorn mast years, resultant mouse outbreaks, and the prevalence of infected ticks.
It’s essential to note that ticks are born free of the pathogens that cause Lyme disease – they catch it from other animals like white-footed mice and chipmunks. Thus, the concern for a mouse boom.
Here’s how the complicated life cycle of deer ticks (also known as blacklegged ticks) works: Deer tick eggs typically hatch as larvae in late spring and spend their summer looking for a blood meal, which most often is a bird or a small mammal. Once a tick larva has found and fed on a host, it drops off and molts into a tiny nymph about the size of a poppy seed. It then seeks a host again, but this time ranging from small mammals to larger prey like deer, humans, or a dog.
Once they attach to a new host, the nymph will feed for several days, drop off, and then molt into an adult tick, now about the size of a sesame seed. However, the larval and nymphal stages are the ones to be most concerned about because ticks typically pick up and transmit Lyme pathogens from a host during these stages. They’re so tiny that they’re hard to detect and, therefore, are less likely to be removed. I had ehrlichiosis, a form of Lyme disease a few years ago, and never knew I’d been bitten. Our daughter Callie just got over a bout with Lyme, and she also never knew she’d been bitten. And we’re pretty vigilant!
As adults, male ticks seldom feed again, but adult females will seek a final blood meal from a large mammal, most often a deer (high deer populations thus also contribute to a higher incidence of Lyme disease). The male tick then seeks an engorged female to mate with on the host, the female is mated, falls off the host, lays her eggs, and dies. And the lifecycle goes around again.
A tick’s lifecycle can last two to three years, which means that for two years following a boomer acorn crop, there’s likely to be a high abundance of white-footed mice, and therefore of infected ticks.
So, we’ll see if the tick-mouse-Lyme relationship holds true next summer. It will certainly pay to check ourselves for ticks even more carefully than usual.
Deer, Hemlocks, and Tannic Acid
I led a hike in September on the Raven Trail for UW Madison students from the “Biohouse,” a residential learning community created in a partnership between WISCIENCE and University Housing. BioHouse residents live on the same floor of a campus dormitory, and they work, play, study, and explore opportunities in biology together. Dr. William Karasov, the faculty director of Biohouse and a professor of forest and wildlife ecology, chaperoned the group.
I stopped at an eastern hemlock tree seedling to talk about how hemlock reproduction is complicated, and, in particular, how deer heavily browse hemlocks in the winter. I went on then to talk about how hemlock bark contains 10% tannic acid and was used extensively in leather tanneries throughout Wisconsin.
At this point, Dr. Karasov interjected about how foods that contain high amounts of tannic acid are very difficult to digest for most animals. Tannins typically reduce palatability, limit digestibility, and increase toxic load. But not for deer. After his detailed explanation of how deer manage this, I asked him to send me the information so I could pass it on, and here’s what he wrote translated into simpler terms (if you want the pure science, read “Do Salivary Proline-Rich Proteins Counteract Dietary Hydrolyzable Tannin Laboratory Rats?” in Journal of Chemical Ecology, 9/2004): Deer saliva contains substances that basically neutralize the damage that tannins could do within the intestines. The tannins aren’t digested, but rather attached, or bound, to proteins that are expelled in the deer’s droppings. The deer lose a nutrient – nitrogen – in the process, but still gain some nutrition from the hemlock needles.
Mulching Leaves
I just finished grinding up the leaves in our yard with our mulching lawn mower, as I’ve done every fall for decades. Rather than rake, I mulch because I’ve always thought of leaves as free fertilizer given that they contain nitrogen. Leaves also insulate the soil, cover up root systems, preserve soil moisture (not an issue this year!), and suppress weeds.
It’s also one heck of a lot less work, and costs less.
Do I end up with a perfect thick, green lawn? No. I have an okay lawn, which is all I should have on the poor sandy soils in our area. This is the Northwoods after all. Our specialties here are trees, shrubs and wildflowers native to our area, not Kentucky bluegrass.
Potato River Hike
I, along with 25 others, hiked to the Potato River in northern Iron County on 10/25 as part of an ICORE (Iron County Outdoor Recreation Enthusiasts) sponsored event. We were led by Jim and Joy Perry, retired botanists, who clearly love the Potato River, and well they should – this little river hosts an array of rapids and waterfalls.
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| an unnamed waterfall on the Potato River |
The Potato is the eastern-most tributary to the Bad River which eventually flows through the Kakagon Sloughs and into Lake Superior. It originates in western Iron County, and along its course, it’s joined by Norman, Turntable, Apple, Alder, and Vaughn Creeks. The water runs rusty-colored due to the tannins and the iron in the watershed, but it runs fast.
Like all the rivers in our area flowing north from the Sub-Continental Divide, it has a whole lot of elevation to lose before it reaches Lake Superior. The Divide wanders across central Iron County and then along the northern edge of Vilas County, averaging somewhere around 1,700 feet in height. Rivers flowing into Lake Superior, which is around 600 feet, thus have 1,100 feet to drop in often as little as 50 miles. Add to this elevation loss, the rocky geologic formation of the Gogebic Range, and it can feel like you’re in a different world from the sandier and flatter landscapes south of the Divide.
Along the Divide, headwaters of separate rivers often begin in close proximity to one another. Sometimes two rivers rise from opposite ends of the same marsh. The Brule and St. Croix Rivers may be the best-known example of the "one marsh-two rivers" phenomenon in northern Wisconsin. Both rivers originate in a large marsh off of Highway P near Solon Springs, the Brule flowing north, the St. Croix south.
In Iron County, the north-flowing West Fork of the Montreal and the south-flowing East Fork of the Chippewa originate within two miles of one another.
The Indians and Voyageurs knew about these watershed divides, and their knowledge turned this area into a sort of river-traveler’s switchyard. A relatively short portage permitted them to pick up a river that would eventually connect them to a network of other rivers flowing to nearly anywhere in the Eastern U.S.
Sightings: Snow Buntings, Northern Shrike, Cardinal, More Robins, Saw-whet Owl
The North Lakeland Discovery Center Bird Club hiked Powell Marsh on 10/24, their last bird hike of the year, and had first-of-the-year sightings of snow buntings and a northern shrike.
In Manitowish, we have had a male cardinal visiting our feeders in the last week of October,
and it’s now been joined by a red-bellied woodpecker. Rusty blackbirds and robins continue to visit our property in large numbers, the robins now eating all of our crabapples which we like to provide for winter visitors like bohemian waxwings and pine grosbeaks. Oh well, we planted them for birds, and the robins have equal rights. I just wish they’d be less gluttinous.
Sarah Krembs in Manitowish Waters emailed this on 10/15: “I was coming home last night at about 10 p.m. and I was just north of Bakken Rd on Hwy 51 [when] something ran into the side of my car! I thought it might be a rabbit, a fox, I couldn’t tell. I turned around and went back to see a little creature standing on the white shoulder line, and it was flapping its wings. It must’ve been flying just above the ground because it seemed to hit so low I’d thought it was a creature running on the ground . . . I shone the headlights on it and realized it was an owl. A teeny tiny saw-whet. He let me come right up to him with a sheet and pick him up . . . I went home (cuz it’s only a couple miles) to try to decide if I should call NWLC or what. He only had one eye open. But I had seen him flapping both his wings, so I figured that was a good sign.
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| photo by Sarah Krembs |
“In the end, I decided to ask Mum to drive me back to Bakken while I held him because he was starting to move around a bit. We got there, I gently unwrapped him and he hopped up and stood on my hand. He was soo tiny! He turned his head all the way around making it look like his eyes were migrating around his head. It was incredible. I’ve never seen that in real life. I figured his neck muscles must be okay. Both his eyes were open and bright. And then after a few moments he flew away. Biggest sigh of relief ever.
“I have never seen a saw-whet in the wild, but this was definitely NOT how I wanted to see one. But it ended in just about the best way possible. It’s amazing how resilient some birds can be.”
September Temperatures
NOAA reported that this September was tied with September 2015 as the warmest September on record in data going back to 1880. Other agencies agreed that last month was near the top, although their placements varied slightly. Minor differences in rankings can arise because of how the various agencies handle data-sparse regions such as the Arctic, where few surface weather stations exist. NASA, for instance, ranked last month as the second warmest September on record, just behind 2016 and ahead of 2015.
The bottom line is that last month was among the three warmest Septembers globally in 140 years of recordkeeping. As NOAA pointed out in a news release, “The 10 warmest Septembers have all occurred since 2005, with the last five years (2015-2019) being the five warmest Septembers on record.”
Thought for the Week
“A river is the report card for its watershed.” – Alan Levere
Please share your outdoor sightings and thoughts: call 715-476-2828, e-mail at manitowish@centurytel.net, snail-mail at 4245N State Highway 47, Mercer, WI, or see my blog at www.manitowishriver.blogspot.com
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