Literature Review: Pleistocene and Holocene

by Carl Strang

Today’s notes are from last year’s literature on the recent ice ages and subsequent prehistoric times. Some are biological in focus, others relevant to past and present climate change.

Coyotes once were bigger and more carnivorous than they are today, according to the following study.

Coyotes once were bigger and more carnivorous than they are today, according to the following study.

Meachen, J.A., A.C. Janowicz, J.E. Avery, and R.W. Sadleir. 2014. Ecological changes in coyotes (Canis latrans) in response to the ice age megafaunal extinctions. PLoS ONE 9(12): e116041. doi:10.1371/journal.pone.0116041 They measured coyote skulls from 29,000 years ago (La Brea tar pits) to present day, and found a transition from features associated with predation specialization to the present-day omnivory. Another study had found in addition a decrease in body size. They interpret this as a change in predator interactions. When the much larger dire wolf was the other dominant canid, and megafauna were abundant, coyotes could make a good living as specialist predators. Megafauna loss, and associated dire wolf extinction, opened the door for gray wolf immigration from Europe. This new, smaller predator was similar ecologically, but at the same time larger than the coyote, forcing a coyote niche shift to a more generalized diet.

Maher, K., and C.P. Chamberlain. 2014. Hydrologic regulation of chemical weathering and the geologic carbon cycle. Science 343:1502-1504. Kerr, Richard A. 2014. How Earth can cool without plunging into a deep freeze. Science 343:1189. The Kerr news article was based on the Maher and Chamberlain paper. The study looked at the mechanism that limits ice age cooling, preventing it from running away to a pole-to-pole glaciation. Volcanoes add carbon dioxide to the atmosphere, warming climate but also dissolving in rainwater, the resultant carbonic acid dissolving rock. The products flow to the sea, are taken up by plankton for skeleton building, and ultimately are buried. This removal process limits carbon dioxide buildup. Most of the dissolved rock is in mountains, and mountain uplift as in the Andes and Himalayas thus is tied to a global thermostat turndown. However, cooling slows the weathering reactions, allowing carbon dioxide to build back up.

Pena, Leopoldo D., and Steven L. Goldstein. 2014. Thermohaline circulation crisis and impacts during the mid-Pleistocene transition. Science 345:318-322. They found evidence for a profound change in oceanic circulation patterns corresponding to the change in glacial cycling from 41-thousand-year to 100-thousand-year durations. They conclude that “North Atlantic ice sheets reached a milestone in size and/or stability” that led to the ocean circulation change, resulting in a greater carbon dioxide drawdown, increased polar glaciation, and setting the pattern for the following 100,00-year cycles.

Guil-Guerrero, J.L., et al. 2014. The fat from frozen mammals reveals sources of essential fatty acids suitable for Paleolithic and Neolithic humans. PLoS ONE 9(1): e84480. doi:10.1371/journal.pone.0084480 They analyzed the fat chemistry of frozen woolly mammoths, horses and bison from Siberia. The fats were judged to be nutritionally good for human hunters of the time (41,000-4400 years ago). Furthermore, the fats of mammoths and horses were like those of hibernating mammals. The authors suggest that the mammoths and horses hibernated in similar fashion to present-day Yakutsk horses, which move little and mainly stand in sleeping positions during the coldest weather. The mammoth fatty acids suggest derivation from certain lichens in the diet.

Willerslev, Eske, et al. 2014. Fifty thousand years of Arctic vegetation and megafaunal diet. Nature 506 (7486): 47. DOI: 10.1038/nature12921 A large, multi-national team went into Pleistocene sediments and mummified gut contents, and used reference DNA from herbarium specimens to characterize vegetational changes over the past 50,000 years. They found that the last ice age caused a significant alteration of northern plant communities, greatly reducing forbs while increasing grasses and woody plants. Many of the megafauna herbivores such as woolly rhinoceros and woolly mammoth depended on the forbs for their protein content, and the authors believe that the failure of forb-rich communities to re-form after the ice receded contributed to or even caused megafaunal extinctions. No mention was made of human hunting in the ScienceDaily article describing the study.

Hoffecker, J. F., S. A. Elias, and D. H. O’Rourke. 2014. Out of Beringia? Science 343 (6174): 979. DOI: 10.1126/science.1250768 They reviewed cores taken from the Bering Sea and found that Beringia was not a barren grassland through the glacial times but had significant areas of tundra shrubs and trees. Animals including elk and moose likely lived there, and the likelihood of long-term human occupation seems good. This could provide a way that the ancestors of Native Americans could have been isolated from Asians for the 10,000 years, between 25,000 and 15,000 years ago, accounting for the genetic differences comparisons show. Beringia was not glaciated, and summers may well have been like those of today, though winters would have been severe. When the glaciers opened a way by melting, the 15,000-year Native American presence in the continent began as the Beringians moved in.


Literature Review: Wolves and Dogs

by Carl Strang

Last year produced a few published studies of wolves and dogs that caught my eye. Dogs are well established as having been domesticated from wild wolves, but the timing and nature of that new relationship have been a contentious topic. Here is a recent contribution to the debate:

Thalmann, O., et al. 2013. Complete mitochondrial genomes of ancient canids suggest a European origin of domestic dogs. Science 342:871-874. This group of researchers previously had suggested that dogs first were domesticated in the Middle East, but this new study with updated methods points to a European origin 18-32,000 years ago. They included DNA from fossil wolves and dogs in their comparisons. From an interpretive article in ScienceDaily: “By comparing this ancient mitochondrial DNA with the modern mitochondrial genomes of 77 domestic dogs, 49 wolves and four coyotes, the researchers determined that the domestic dogs [of today] were genetically grouped with ancient wolves or dogs from Europe — not with wolves found anywhere else in the world or even with modern European wolves. Dogs, they concluded, derived from ancient wolves that inhabited Europe and are now extinct.” This timing and geography point to a likely domestication by hunter-gatherers rather than agriculturalists.

Wolf at Wolf Park in Indiana

Wolf at Wolf Park in Indiana

Once the ancestors of dogs had become genetically isolated from wolves, the two populations were exposed to different selective pressures. The wolves continued to be subject to natural selection, while the dogs were influenced by human-directed selective breeding, and by the different selective pressures of living in human communities. The next study compared the development of dogs and wolves, and discovered some consequences of that divergence.

Kathryn Lord. A Comparison of the Sensory Development of Wolves (Canis lupus lupus) and Dogs (Canis lupus familiaris). Ethology, 2013; 119 (2): 110 DOI: 10.1111/eth.12044 From a ScienceDaily article. She looked at the relationship between the timing of sensory maturation and exploration behavior in wolf and dog puppies. Both acquire smell, hearing and vision in that order, at 2, 4 and 6 weeks of age. Wolves, however, begin exploration and socialization at 2 weeks, dogs at 4 weeks, and so dogs are socializing after they have the ability to perceive their social surroundings more completely. Wolves are getting fearful shocks during this period as new sensory capabilities appear, and so need an earlier and more complete contact with their social community, and never form the same kind of solid bond that dogs do.

Dogs have diverged from their wolf ancestors

Dogs have diverged from their wolf ancestors

A final, sadder note was a news article in Science magazine that explained how Isle Royale’s long-studied wolves are close to dying out.

Wolf tracks on an Isle Royale beach. Are these about to disappear?

Wolf tracks on an Isle Royale beach. Are these about to disappear?

Mlot, Christine. 2013. Are Isle Royale’s wolves chasing extinction? Science 340:919-921. Last year, for the first time in 40 years, there were no wolf pups on the island. The 2013 January count turned up only 8 closely related adults. Rolf Peterson, principal wolf biologist at Isle Royale for many years, thinks they now will die out, with inbreeding the root cause. Moose have increased as their principal predators have declined. The Park Service is considering whether to introduce new wolves to rescue the population (Isle Royale is a national park in northern Lake Superior).

Literature Review: Wolves and Coyotes

by Carl Strang

New information about coyotes and wolves always seems to have a little extra zest.



Hennessy, Cecilia A., Jean Dubach, and Stanley D. Gehrt. 2012. Long-term pair bonding and genetic evidence for monogamy among urban coyotes (Canis latrans). J. Mammal. 93:732-742.

This study was yet another contribution from the group led by Stan Gehrt of Ohio State. Chicago region coyotes are monogamous (litters show common parentage), and pair bonds are long-lasting. (Note how many person-weeks of intensive study can produce a primary result that can be stated in a single sentence.)

Wheeldon, Tyler, and Brent Patterson. 2012. Coyotes in wolves’ clothing. Am. Midl. Nat. 167:416-420.

They examined 3 pups from the northern Lower Peninsula of Michigan which were wolf-like. These proved to be “coyotes but revealed evidence of maternal introgression from a Great Lakes wolf in their pedigree. These findings suggest that Great Lakes wolves are capable of interbreeding with coyotes when conspecifics are rare.” Tracks and trail camera images from the area had shown what appeared to be a wolf, but these results point to an unusually large coyote or a hybrid. They think the most likely scenario is that a wolf immigrated from the Upper Peninsula population and mated with a coyote. This study caught my eye because of my experience of hearing a possible wolf-plus-coyote chorus at Chain O’Lakes State Park last summer.

Wolf at Wolf Park in Indiana

Wolf at Wolf Park in Indiana

William J. Ripple, Robert L. Beschta. Large predators limit herbivore densities in northern forest ecosystems. European Journal of Wildlife Research, 2012; DOI: 10.1007/s10344-012-0623-5

(As described in ScienceDaily article). In a review of data from all around the Northern Hemisphere, they found that the removal of large predators, especially wolves, has had a profound negative effect on forest ecosystems. In their absence, deer and other large herbivores achieve population densities 6 times larger; their overconsumption of plants interferes with tree reproduction, and has a cascading impact on biodiversity generally. Erosion increases, stream and forest quality decreases, and carbon sequestration is greatly reduced. Effects are multiplied by other large and medium-sized predators which are supported in some seasons by scavenging from wolf kills. Because of this, the year-round behavioral response of the herbivores to the wolves, and the more limited removal of the herbivores, human hunting is not a completely equivalent substitute (as Aldo Leopold learned to his chagrin from the Kaibab Plateau fiasco).

Howl in the Night

by Carl Strang

One of the most memorable moments during my visit to Chain O’Lakes State Park last week came in the middle of the night. I was awakened by a long, low howl that immediately was joined by a chorus of high-pitched coyote howls, somewhere not too far from my campsite. There must have been at least 8 coyotes, a good-sized litter having matured to near independence at this point in the season.

Coyote at Mayslake Forest Preserve

But that first howl. Granted, I was awakened by it and therefore still half asleep. But it was a long howl, and its sound was so identical to those of wolf howl recordings I have heard that my waking-up was immediate and complete before the howl finished. I hoped it would repeat, but it did not, and the coyotes quickly subsided as well. I have been speculating since that moment.

Wolf at Indiana’s Wolf Park

A wolf was found road-killed in the vicinity of Chain O’Lakes a few years ago. Wolves have wandered into Illinois occasionally from the nearest population center in central Wisconsin during the past decade. Wolves are known to cross with coyotes, and this is thought to happen more frequently at the fringes of wolf populations in the Great Lakes region. So, what did I hear that night? I am not saying it was a wolf. As I said, I was half asleep. Still, it is conceivable that a wolf came down from Wisconsin and paired with a coyote in that park, which is extensive enough that a shy canid could stay out of sight.

Literature Review: Isle Royale Update

by Carl Strang

As I mentioned in yesterday’s post, there were plenty of wolves and moose on Isle Royale when I visited there in 1996. That is one of the better monitored ecological systems, and I was interested in an update based on the 2011 winter count, as reported in ScienceDaily.

View from a fire tower on the central ridge of Isle Royale.

The year after my trip there, a new male wolf immigrated to the island from the Canadian mainland. For a time the wolves benefited from this boost in genetic diversity, but that influence has begun to decline with a resumption of inbreeding, and the island’s wolves are down to a single pack of 16 individuals.

At the same time, reduced moose numbers have allowed a rebound of vegetation and they are on the verge of an increase. One of the side benefits of travel is a personal connection that lends interest to such stories.

Lessons from Travels: Isle Royale Moose and Wolves

by Carl Strang

My short list of greatest adventures always will include my circumnavigation of Isle Royale by sea kayak in the second half of August, 1996. Isle Royale is the big island in northern Lake Superior that, to me, looks like the eye in the lake’s wolf’s head shape. The paddle around it is a 100-mile journey. I got there by ferry from Houghton, Michigan.

There was plenty of room in the hold for kayaks and camping equipment.

On the way out I had a happy encounter with Rolf Peterson, a fellow graduate of Purdue’s wildlife program, who took over the Isle Royale wolf-moose study from his mentor, Durward Allen. It turned out I was able to help. With my kayak I could reach a few moose carcasses Rolf had spotted from the air during the winter surveys but which were in remote places. There were some data and samples that needed to be collected on the ground.

I never had seen a moose, and Isle Royale is one of the best places in the U.S. to find them. I encountered around a dozen during this trip.

This fellow walked right through camp one morning.

Isle Royale is better known as a backpacking destination, but I’m really glad I did it by sea.

This is the kind of trail the backpackers must negotiate in places. I felt a mixture of respect and pity as I watched them staggering into camp at the end of the day, when I had done my relatively easy paddling in the morning and could explore the trails with a light day pack.

A sea kayak can carry everything one needs for a two-week trip. A micro-filtering pump allows one to strain the lake water for drinking and cooking.

I still have this tent, though it got a tear during a storm on a later sea kayak expedition. Shortly after taking this photo I lost the camera remote I was holding in my left hand.

Along the way I saw occasional moose skeletons previously inventoried by Rolf and his students.

Wolves and weather have scattered some of the bones.

In the southwest quarter of the island there are no established camps, so I set up on the beach that night. There I saw my first wolf sign.

The tracks were very fresh, but I knew my chances were slim of seeing one of these shy canids.

This was a very remote location, with only the occasional calls of golden-crowned kinglets to break the August silence. The following photo, which I took just before pushing off the next day, conveys some of the eerie mood of the place.

I liked to make an early start, so as to have as much of the afternoon as possible for day hiking.

The following camp at Huginnin Cove, on the north shore just east of Isle Royale’s tip, provided the next clue to the presence of wolves.

Stinkin’ fresh wolf scats on the trail near the campground.

There is a long stretch of the north shore which provides no good landing for a sea kayak.

Here you can see why.

Nevertheless, one of Rolf’s moose was there, just inland from a little break in the shoreline. I found the spot, wedged Water Strider (my kayak) between a boulder and the cliff, and climbed up carrying my tow line/anchor rope.

The little waves gave Water Strider some scratches from the rocks which she bears to this day.

After some searching I found the carcass, a female, and I bagged the smelly sample for transport to Rolf. I dubbed her Miss Moosie, and she was my companion for the remainder of the trip.

Moose were part of the northeast Illinois fauna in the wake of the last continental glacier, and wolves still were here in historical times. It was a pleasure to share a landscape with them for a while, and to imagine the days when such creatures left tracks and deposited scats on trails now occupied by Ogden Avenue and Army Trail Road.

Literature Review: Dog Breeds

by Carl Strang

Part of my approach to natural history inquiry is to follow at least some of the scientific literature relevant to my interests. This is by no means necessary for hobby level inquiry. In my case it’s in part to feed my general curiosity, and in part force of habit established as a grad student and assistant professor of biology early in my career. Today I would like to review an article describing a paper that appeared in Nature this year by Bridgett M. vonHoldt and, as expected in a study of this magnitude, a long list of co-authors. The article I saw was here.

The group looked at a large number of nuclear genes in all major dog breeds and worldwide wolf populations. Wolves long have been known as the wild ancestors of dogs, but there has been some debate as to where their domestication occurred.

VonHoldt and company found a strong match to Middle Eastern wolves. An earlier study which pointed to an East Asian origin was based on a small segment of mitochondrial DNA, and so has less credibility. The oldest dog in the archeological record is 31,000 years, from Belgium. The oldest Middle Eastern find is 12,000 years old.

Comparing dog breeds, they found that relatively few genes account for differences in color, size and body proportions.

Focusing on their results for one oddly proportioned breed (and one I knew through Tag, the childhood pet in the above photo), I see that the dachshund is in a group with the basset hound, beagle and bloodhound. The closest (sister) group to them contains the spaniels. Here again I find a childhood connection through the first dog I knew, Timmy the springer spaniel.

The most distant group from these is composed of the basenji and husky-like dogs, which in turn are closest to wolves. Genetic dog groupings correspond well to established breed groupings (for instance those in kennel club dog shows) with exceptions, notably the toy dogs, which are smaller versions of diverse dogs scattered across the various kennel club groupings.

Words of Tracking: Common Walking Gaits

by Carl Strang


In an earlier set of posts (find under Methods category in sidebar to left) I introduced the alphabet of tracking, i.e., identification of the kind of animal that made the track. Today I want to take the next step toward reading the stories that footprints have to tell us. That is, to look at the basic gaits. A gait is a pattern of footprint placement, the building block from which an animal’s trail is built, and it also is the order in which the feet step as the animal moves. You will find the same gaits given different names in different references. I follow the terminology of my teachers at the Tom Brown school (link in left margin of the frame).


The pace gait is the usual traveling gait of certain animals, such as raccoons and bears, whose wide-bodied proportions favor swinging their weight from side to side, stepping with both left feet at once, then both right feet. If you try this, in a comfortable rather than lunging effort, you will find that your feet produce side by side pairs of footprints, left front foot beside right hind foot, right front foot beside left hind foot. Here is the pattern in a set of raccoon tracks.


Pace gait, raccoon

Pace gait, raccoon



The opposite of a wide body is a long skinny body, which we find in weasels. If your body is, to exaggerate, something like a rope with two little feet at each end, the easiest way for you to proceed will be to move both your front feet together, then both your hind feet, with the hind feet landing behind the front feet. This gait is called the bound. Often the feet are somewhat offset, an indication that the animal oriented its body axis at an angle rather than in line with its direction of travel.


Bound gait, mink

Bound gait, mink



Another gait in which the front feet move together and the hind feet move together is the gallop. This is common in rodents and rabbits, animals whose hind legs are more powerful than the front, so that the hind feet land in front of the front feet. Cottontails typically place one front foot in front of the other, while rodents such as mice and squirrels, as well as masked shrews, place their front feet side by side (in the photo the shrew is moving left to right).


Gallop gait, cottontail

Gallop gait, cottontail


Gallop gait, masked shrew

Gallop gait, masked shrew



There is one circumstance in which cottontails place their front feet side by side, however. I will leave this one for you to puzzle over. Look for examples this winter, see if you can figure it out. Here’s a photo so you know what to look for.


Cottontail gait puzzle

Cottontail gait puzzle



The final common walking gait is typical of hoofed animals (white-tailed deer in NE Illinois), the dog family and the cat family, as well as us (when do we walk on all fours?). This one is called the diagonal walk, and unlike the others the feet move separately in a sequence: left front, right hind, right front, left hind. In this case the left feet come down in close to the same place, and so do the right feet. The overall impression is a zigzag between right foot pairs and left foot pairs, hence the name for this gait.


Diagonal walk gait, wolf (Isle Royale)

Diagonal walk gait, wolf (Isle Royale)



There are other gaits, but they are less common or are special cases and will be reserved for later. Also, the connections I have made between animals and gaits are limited to routine travel. When circumstances require, animals shift out of their normal walking gait. For instance, a raccoon in an extreme hurry does not, cartoon like, do a real fast pace gait. Instead, it shifts into a gallop. Tracks outside the normal pattern are a clue that something unusual, therefore interesting, was happening.

%d bloggers like this: