“Mink aren't typically found up trees, but they're known to climb when they're startled, as was likely the case in the picture below”.............”So what was this mink up to (other than a tree)?”...........“Perhaps it was looking for romance”...........“It's mating season for the animals, and they range widely during this time”..........”Kits will be born in late spring”..........”Minks travel on land and in the water”.........“They walk, run, and bound on land, and may attain speed of 13 km/hr (8 mph) for brief periods”............”This semiaquatic species swims on the surface and underwater, covering as much as 15 m (50 ft) or more when submerged”........”A mink may remain in its den for several days after severe winter storms, but otherwise is active throughout the year”.............“Much activity occurs at twilight and at night, but it is not unusual for a mink to forage during the day in winter and while caring for young”..........”Minks are carnivores, preying on muskrats, chipmunks, mice, rabbits, fish, snakes, frogs and water fowl”........”Leftovers from a kill are often kept in the mink's den for later”

by Northern Woodlands

March 19, 2020

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by Northern Woodlands

March 19, 2020

0 

Sandy Dannis shared this photo of a mink that she encountered while walking on her land in Dalton, New Hampshire. Mink aren't typically found up trees, but they're known to climb when they're startled, as was likely the case here.

So what was this mink up to (other than a tree)? Perhaps it was looking for romance. It's mating season for the animals, and they range widely during this time. Kits will be born in late spring.

http://r20.rs6.net/tn.jsp?f=001edFa3v48RNUJOMvvARLvMepMBf_1CyGSksE2gR4_Il-aUJ3Qq8hM6FqEwO7CAXQFQmI8wNnmDbLdQiq_9NTKOrXL4nEuh0XVfmbD3eUiVceEuG0AOKD6lLmfD0747nFvj8bH7zk1b-YsNS9mkHVITHxJ_1APMQSiZiyNHrxDkmsZU9qOSUcp5AIbImkhrtglERaYHByXCkVZmLXDKRI4KA==&c=YxF4rWHUxwE5wNr1zAXZZNZIFGz6eS2T8q02dLjcwij80veqgjzLWw==&ch=fzD_qU-IoB6t1Yv7M0x3cWh_rLePs0jblHpGo7QxKw3nTzFum39xNw==

“Often, dozens of snakes of different species will share winter dens, called hibernacula”..........”In the den, snakes enter a state of hibernation, with their body temperature dropping to between 35 and 45 degrees”.............“Congregating like this helps snakes retain moisture”.........”Group denning also facilitates springtime mating for some species”..........“As snakes do not eat once their internal temperatures reach 60 degrees, a milk snake Will not kill a garter snake(which happens during the warm weather months)”............“Snakes will appropriate dens created by woodchucks, chipmunks, and other animals”.........”They’ll also use human-made structures like stone walls, cisterns, and building foundations”..............“Some species, like the timber rattlesnake, seek out rocky crevices and talus slopes with a southern exposure”...........”The rocks warm quickly in the sun and retain heat well after dusk, providing a relatively temperate environment, even in winter”

http://r20.rs6.net/tn.jsp?f=001edFa3v48RNUJOMvvARLvMepMBf_1CyGSksE2gR4_Il-aUJ3Qq8hM6FqEwO7CAXQFg6Zag2UuCqDaAOSG-irQgq0m1TfAorKWKjGq4Gzh_ENrb2jaaFV8GVhHTuxrVH98tO1VNAgxuiD8etV-YsTWKgqmdIPG9XGyud-_klHlQmKS82z9zQyAKf7UAOVdpfgnJq6fLc-Zm8u6Th13QbBn4vETTTb2wjXSnpCxFf9yk98=&c=YxF4rWHUxwE5wNr1zAXZZNZIFGz6eS2T8q02dLjcwij80veqgjzLWw==&ch=fzD_qU-IoB6t1Yv7M0x3cWh_rLePs0jblHpGo7QxKw3nTzFum39xNw==

by Sandra Mitchell

March 9, 2020

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During the summer, I often spy common garter snakes sunning themselves in my garden. As the snow piles up through winter, covering the landscape in cold white, I wonder where these warmth-seeking creatures have gone. Without fur or fluffed-up feathers for insulation, how do these ectotherms survive the long months between autumn’s fading warmth and spring’s arrival?

The short answer is: they seek shelter underground. Often, dozens of snakes will share winter dens. These dens (also called hibernacula) take many forms.

“Since our snakes are unable to dig their own holes, they are reliant on what they are able to find in the environment to help them successfully overwinter,” said herpetologist Jim Andrews, coordinator for the Vermont Reptile and Amphibian Atlas Project.

Suitable hibernacula sites are either below the frost line or in locations with enough radiant heat to prevent freezing. Andrews explained that some species have traditional denning areas, places snakes will return year after year to weather the cold. They may follow other snakes’ pheromone trails to locate denning sites, and may travel a mile or more to reach a suitable winter location. Other snakes are more opportunistic, settling for whatever site they find when the time comes to curl up for the winter.  

Snakes will appropriate dens created by woodchucks, chipmunks, and other animals. They’ll also use human-made structures like stone walls, cisterns, and building foundations. Some species, like the timber rattlesnake, seek out rocky crevices and talus slopes with a southern exposure. The rocks warm quickly in the sun and retain heat well after dusk, providing a relatively temperate environment, even in winter.

In these dens, snakes enter a state of hibernation, meaning their metabolic rate decreases drastically, and their body temperature can drop to between 35 and 45 degrees. A hibernaculum may, surprisingly, contain multiple snake species. While an eastern milk snake may, during other seasons, actually consume a garter snake, reptiles generally do not eat once their internal temperatures drop below about 60 degrees, making this unusual arrangement between predator and prey possible.

Congregating like this helps snakes retain moisture. Group denning also facilitates springtime mating for some species.

Andrews said snakes that return to the same winter sites for many years and through multiple generations may have higher winter survival rates. But he noted local snake populations can be nearly wiped out after cold, snowless winters. As an example of this, he pointed to the winter of 1987-88, when many snakes perished and reptiles moved in from the surrounding areas to recolonize.

Andrews also noted some snake species, including garter snakes, are viviparous, meaning they give birth to live young, rather than laying eggs. Viviparous snakes tend to be more successful than oviparous snakes in climates like ours, where summers are relatively short. The mother snake cannot move her eggs to be sure they are incubated in the warmest possible area – but she can move her body. A female garter snake may also store sperm in her body and delay fertilization until the weather becomes favorable for baby snakes.

Although we don’t know all the details of how these ectotherms survive winter extremes, the many snakes gracing my yard and garden in the spring provide living proof that they have managed to survive and thrive. And just as the snakes are perhaps anxious to escape their dens into a flood of warm sunshine, come spring I am ready for my first garter snake visitor of the year.

Sandra Mitchell is an avid amateur naturalist, certified wildlife tracker, registered Maine Guide, and a student in the Maine Master Naturalist Program.

“Recently, the Idaho Fish and Game changed its rules to allow any hunter or trapper to kill up to 30 wolves per year”............“And the state is considering a proposal to open much of the state to year-round wolf killing”.............“In Montana, the MDFWP is discussing increases from 5 to 10 wolf tags for some parts of the state”...........”The one take-home message from these actions is that the prediction that once the states were given management of wolves, we would see a rational, biologically informed management is inaccurate”..........“The old bias against predators is based more on a cultural attitude as any scientific value”

https://www.thewildlifenews.com/2020/02/07/wolf-opposition-is-part-of-the-cultural-war/

Wolf Opposition Is Part Of The Cultural War

by GEORGE WUERTHNER on FEBRUARY 7, 2020 

Recently, the Idaho Fish and Game changed its rules to allow any hunter or trapper to kill up to 30 wolves per year. And the state is considering a proposal to open much of the state to year-round wolf killing.

In Montana, the MDFWP is discussing increases from 5 to 10 wolf tags for some parts of the state.

In both states, we will be eliminating the ecological function of predators. Predators can change how large animals like elk use the landscape and can also preclude excessive browsing of critical areas like riparian zones. Also, wolf kills can provide an essential source of food for scavengers from magpies and eagles up to and including even grizzlies.

Is this hatred of wolves based on massive livestock losses or huge declines in elk numbers?

In 2019, Montana had about 2,550,000 cattle[i], and 108 confirmed cattle losses attributed to all predators, including wolves.[ii] That is such a small percentage as to be laughable.

By contrast, in 2018, Montana ranchers lost 37,000 cattle just to winter storms. The federal Livestock Indemnity Program (one of many rancher welfare programs) paid ranchers more $11.1 million of taxpayer funds.[iii]

How about predator impacts on hunting? In, 1995 when wolves were first restored to Yellowstone and Central Idaho, the Montana elk population was 109,500.

In 2019, Montana’s elk population was estimated at (134,557)[iv] Twenty-five percent over upper objective) and the 2018 elk harvest was 27,793.[v]

A similar situation exists in Idaho. The 1995 Idaho elk population was estimated to be 112,333, and the harvest that year was 22,400. In 2017, the Idaho elk population stood at 116,800 (4,000 more than when wolves arrived. In 2017 elk harvest in Idaho was 22,751—300 more animals that in 1995.

Ironically there is some scientific evidence that random (non-surgical killing) of wolves increase livestock conflicts and elk losses to predators.

Wolves are social animals. They work together to hunt their prey. When members of the pack are killed, it can disrupt the pack’s ability to hold its territory as well as hunt efficiently. Also, smaller packs kill more prey per animal than larger packs.

If a single or small group of wolves kill prey, they often must leave the kill site to bring food back to pups. During their absence, scavengers can consume much of a carcass, forcing the small pack to kill another animal. By contrast, a larger pack can guard its kill and consume it entirely.

Many of my colleagues, particularly in the larger middle of the road conservation groups, supported delisting of wolves arguing that once ranchers saw that wolves were responsible for almost insignificant losses and hunters found out that elk would continue to thrive over much of the West, opposition to predators would dissipate.

I disagreed because I did not think the opposition was based on rational ideas. Wolves, I suggested, were symbolic animals.  As wild animals, wolves represented the forces that neither ranchers nor hunters could control.

Wolves also represent to some people the actions of distant people (despised coastal residents) or a federal government which they too hate—except, of course, for all the federal welfare bestowed on them—also coming primarily from the same coastal residents who pay the bulk of all taxes.

The one take-home message from these actions is that the prediction that once the states were given management of wolves, we would see a rational, biologically informed management is inaccurate. The old bias against predators is based more on a cultural attitude as any scientific value.

I hope that younger ranchers and hunters will have a more sophisticated view of wolves and other predators. In the meantime, the only option for predator proponents is to continue to educate people on why wolves are an essential part of our wildlife heritage.

[i] https://beef2live.com/story-cattle-inventory-vs-human-population-state-0-114255

[ii] http://liv.mt.gov/Attached-Agency-Boards/Livestock-Loss-Board/Livestock-Loss-Statistics-2019

[iii] https://www.usnews.com/news/best-states/montana/articles/2019-06-16/over-37-000-cattle-lost-during-brutal-2018-winter-in-montana

[iv] http://fwp.mt.gov/fishAndWildlife/management/elk/

[v] https://myfwp.mt.gov/fwpPub/harvestReports

"Keeping cats indoors could blunt adverse effects to wildlife"............."Some estimates show that cats in North America kill from 10 to 30 billion wildlife animals per year"..........."They often have a two- to 10-time larger impact on wildlife than wild predators—a striking effect".............."A new North Carolina State and North Carolina Museum of Natural Sciences study shows that hunting by house cats can have big effects on local animal populations because they kill more prey in a given area than similar-sized wild predators"............."The study showed that house cats killed an average of 14.2 to 38.9 prey per 100 acres, or hectare, per year"............."This effect is mostly concentrated relatively close to a pet cat's home, since most of their movement is in a 100-meter radius of their homes, usually encompassing a few of their neighborhood's yards on either side"

https://phys.org/news/2020-03-cats-indoors-blunt-adverse-effects.html

view video--https://youtu.be/SYJATBgQlY0

MARCH 11, 2020

Keeping cats indoors could blunt adverse effects to wildlife

by Mick Kulikowski, North Carolina State University

Birds alighting on driveways and baby bunnies munching on lawn grass should keep something in mind: Beware the house cat.

A new study shows that hunting by house cats can have big effects on local animal populations because they kill more prey, in a given area, than similar-sized wild predators. This effect is mostly concentrated relatively close to a pet cat's home, since most of their movement was a 100-meter radius of their homes, usually encompassing a few of their neighborhood's yards on either side.

Researchers from NC State University and the North Carolina Museum of Natural Sciences collaborated with scientists and citizen scientists from six countries to collect GPS cat-tracking data and prey-capture reports from 925 pet cats, with most coming from the U.S., U.K, Australia and New Zealand.

"Since they are fed cat food, pets kill fewer prey per day then wild predators, but their home ranges were so small that this effect on local prey ends up getting really concentrated," said Roland Kays, the paper's lead author. "Add to this the unnaturally high density of pet cats in some areas, and the risk to bird and small mammal population gets even worse.

"We found that house cats have a two- to 10-time larger impact on wildlife than wild predators—a striking effect," he said.The researchers focused on the ecological impact of house cats—as opposed to feral cats—and enlisted hundreds of pet owners to track their cats to see where they went and report on the number of dead critters they brought home. Inexpensive GPS tracking devices measured distances traveled by these house cats, which spent their days both indoors and outdoors.

"We knew cats were killing lots of animals—some estimates show that cats in North America kill from 10 to 30 billion wildlife animals per year—but we didn't know the area in which that was happening, or how this compared with what we see in nature," Kays said.

The researchers calculated the amount of prey killed per year by house cats and divided the number by the area in which the cats hunted. Some adjustments were made to the prey count as cats don't necessarily bring all their kills home.

The study showed that house cats killed an average of 14.2 to 38.9 prey per 100 acres, or hectare, per year.

The study also showed that cats do much of their damage to wildlife in disturbed habitats, like housing developments.

"Because the negative impact of cats is so local, we create a situation in which the positive aspects of wildlife, be they the songs of birds or the beneficial effects of lizards on pests, are least common where we would appreciate them most," said study co-author Rob Dunn, William Neal Reynolds Distinguished Professor of Applied Ecology at NC State. "Humans find joy in biodiversity, but we have, by letting cats go outdoors, unwittingly engineered a world in which such joys are ever harder to experience."

NC State's Arielle W. Parsons and Brandon Mcdonald co-authored the paper. Other co-authors include Troi Perkins from Dartmouth College; Shelby Powers from East Carolina University; Leonora Shell from SciStarter; Jenni L. McDonald and Holly Cole from University of Exeter; Heidy Kikillus and Lisa Woods from Victoria University of Wellington; and Hayley Tindle and Philip Roetman from the University of South Australia.

A video presenting the findings of this study, for embedding in articles, is here: https://youtu.be/SYJATBgQlY0

More information: Roland Kays et al. The small home ranges and large local ecological impacts of pet cats.
Animal Conservation March 11, 2020. DOI: 10.1111/acv.12563

"As ectotherms, frogs’ core body temperature rises and falls with that of their surroundings"............... "So when outside temps drop below 32 degrees, they need to either avoid the cold or learn to live with it".............. "Most amphibians opt for freeze-avoidance, either by burrowing below the frost line (woodland salamanders) or by overwintering on the ice-free bottoms of lakes and streams (stream salamanders and aquatic frogs)"............"While freeze-avoidant frogs eke out an existence beneath the ice, freeze-tolerant species wait out winter as living ice cubes"............."In the eastern woodlands, gray tree frogs, spring peepers and wood frogs all possess this superpower"........."When the cold descends, the frogs mobilize glycogen from their livers".............."The glycogen converts to glucose, which serves as a natural antifreeze, lowering the temperature at which internal ice crystals can form".................."Eventually, the frogs’ hearts stop beating, their lungs stop breathing, and up to 65 percent of the water in their bodies freezes solid"..............."During this time, the frogs have no detectable brain activity".............."When spring arrives, they thaw in as few as four hours, though it takes about a day for them to fully rouse"

http://r20.rs6.net/tn.jsp?f=001Bt7_jnb0zwyuQ2wwVMKA8F2Og6-Vo8spNBCHRbPmVck5xtvFEYY1WC__xGio_8Pgt4505tkVpFVZlXYy42PktoyoFYnD78v3vlWU14w0vNomNhf2mdjliY8AUby92LaSmmSzHJiECGzR-4a5mua9yyDvy3tav7mDqU8FaaqJLcS7xmXJ9-vpORLc7Gqw4SWxBNRnnVlsjzxue0iHAPiJqa7xryAsOMNW&c=vTIgOx3mNj54NNNqc4FaJUetRtKwZhTg4iguVYrFeCkzD6Ak7s3-Pw==&ch=xvGVSkquiA1JLMHLbyk3wCUgIeBoJsHb8lClFy0Y_nZZlAbQIaVHQA==

Frozen Frogs Underfoot

by Brett Amy Thelen

February 24, 2020

2 Comments

Illustration by Adelaide Tyrol

Every once in a while, as I’m tramping through the winter woods on my snowshoes, it occurs to me that I am walking on top of frogs.

In winter, our thoughts naturally turn to the species who remain within our sight – the chickadees at our feeders or the foxes who leave records of their travels in the snow – but any creature whose life spans more than one season, and who cannot fly away to warmer climes, must find a way to endure the cold. In February, our amphibians are all still here. They’ve just tucked themselves away for safekeeping.

As ectotherms, frogs’ core body temperature rises and falls with that of their surroundings, so when outside temps drop below 32 degrees, they need to either avoid the cold or learn to live with it. Most amphibians opt for freeze-avoidance, either by burrowing below the frost line (woodland salamanders) or by overwintering on the ice-free bottoms of lakes and streams (stream salamanders and aquatic frogs).

In the 1970s, Canadian biologists who lowered themselves through a hole in the ice on an Ontario pond in full SCUBA gear to search for rainbow trout (no, I am not making this up) were surprised to discover 15 northern leopard frogs (Lithobates pipiens) resting in small pits on the pond bottom. A decade later, another fish biologist conducting winter snorkeling surveys in an unfrozen Ontario river found leopard frogs resting dormant under rocks in the stream bed, their eyes covered by the nictitating membranes, or translucent “third eyelids,” that provide protection from floating debris. In both cases, the frogs were motionless – their metabolism slowed to a crawl, with oxygen exchange taking place entirely through their skin – but they were still capable of swimming away slowly when disturbed.

A study of bullfrogs (Lithobates catesbeianus) overwintering in two Ohio ponds – conducted by less masochistic biologists, who relied on radio transmitters instead of submersion in frigid water – found that the frogs moved about during even the coldest months, preferring shallow areas near inlet streams. The researchers hypothesized that the bullfrogs selected these sites because they were warmer and better-oxygenated than areas of slower-moving water.

While freeze-avoidant frogs eke out an existence beneath the ice, freeze-tolerant species wait out winter as living ice cubes. In our neck of the woods, gray tree frogs (Hyla versicolor), spring peepers (Pseudacris crucifer), and wood frogs (Lithobates sylvaticus) all possess this superpower, with wood frogs being the most well-studied.

Each autumn, as frost creeps ever closer, wood frogs ready for winter by fasting. Even in captivity, wood frogs kept under temperature and daylight regimes similar to those experienced in the wild refuse food once nighttime temperatures dip into the 30s. They then burrow under the leaf litter, where they create small cavities by rotating themselves to compress the surrounding soil. There, they crouch, drawing their legs in close and tucking their heads down in order to minimize surface area exposure.

When the cold descends, the frogs mobilize glycogen from their livers. The glycogen converts to glucose, which serves as a natural antifreeze, lowering the temperature at which internal ice crystals can form. Eventually, the frogs’ hearts stop beating, their lungs stop breathing, and up to 65 percent of the water in their bodies freezes solid. During this time, the frogs have no detectable brain activity. When spring arrives, they thaw in as few as four hours, though it takes about a day for them to fully rouse.

Remarkably, wood frogs spend the entire winter a mere one to five inches below the forest floor. Although above the frost line, these shallow burrows provide important protection from the elements. A recent study found that wood frog hibernacula in north-central Maine never dropped below 20 degrees, even when aboveground temperatures sunk to negative 13. The snowpack insulates; the deeper and fluffier the snow, the warmer it is inside a wood frog’s hibernacula. In an ironic twist, warmer winters associated with climate change could result in colder, more challenging conditions for overwintering frogs.

The next time you find yourself standing atop a blanket of deep snow, pause for a moment. Let your mind travel down through the snow to the leaf litter, and a few inches further still, into the darkness of the soil and to the wood frog curled up, frozen but not lifeless, beneath your feet. Give thanks for the snow, which swaddles the frog, and for the frog, which is proof – if ever you needed it – of the miracles that take place unseen, every day, in the woods.

Brett Amy Thelen is Science Director at the Harris Center for Conservation Education in Hancock, New Hampshire.

"The Great Dying of the Indigenous Peoples of the Americas resulted in a human-driven global impact on the Earth System in the two centuries prior to the Industrial Revolution"............."The arrival of Europeans in the Americas in 1492 CE marks the onset of disease epidemics resulting in the loss of up to 90% of indigenous people living in the Americas over the subsequent century"............"There is wide agreement about the effects of diseases and epidemics associated with European contact".............."The first well-documented, widespread epidemic in what was to become New Mexico was smallpox in 1636"..............."Shortly thereafter, measles entered the area, and many Pueblos lost as many as a quarter of their inhabitants"................."After the founding of Spanish settlements and missions, there was substantially more contact, and throughout the 17th century, epidemic disease was repeatedly imported"................"It should be noted that Osteologic data demonstrate that native groups were most definitely not living in a pristine, disease-free environment before contact".........."Diseases such as treponemiasis and tuberculosis were already present in the New World, along with diseases such as tularemia, giardia, rabies, amebic dysentery, hepatitis, herpes, pertussis, and poliomyelitis, although the prevalence of almost all of these was probably low in any given group"............."Old World diseases that were not present in the Americas until contact include bubonic plague, measles, smallpox, mumps, chickenpox, influenza, cholera, diphtheria, typhus, malaria, leprosy, and yellow fever"............. "Indians in the Americas had no acquired immunity to these infectious diseases"..............."Europeans began to colonize North America (defined here as the United States of America and Canada) after Central and South America, thus regional and continent wide estimates are largely based on archaeological evidence, tribe-by-tribe counts and environmental carrying capacities"............ "The lower range of population estimates for North America lies between 900,000 and 2.4 million, based on tribe-by-tribe counts for the period 1600 CE to mid-1800 CE"..............."The highest estimate of 18 million, established from analyzing environmental carrying capacities, has been criticized for its assumptions on food acquisition strategies".............."More recent estimates derived from geospatial interpolation of archaeological sites range between 2.8 million and 5.7 million"................."These intermediate figures are supported by a recent comprehensive regional-scale archaeological study"

https://www.sciencedirect.com/science/article/pii/S0277379118307261

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1071659/

Earth system impacts of the European arrival and Great Dying in the Americas after 1492

12/4/2018

Author links open overlay panelAlexanderKochahrisBrierleyaMark M.MaslinaSimon L.Lewis

The population of the Americas in 1492

The first population groups to arrive in North America between 20,000 and 15,000 years ago were of east Asian- and north Eurasian ancestry (e.g. Amick, 2017; Moreno-Mayar et al., 2018; Pedersen et al., 2016). The adoption of a sedentary, agricultural way of life in the Americas began 10,000–8000 BP (Piperno and Dillehay, 2008; Piperno et al., 2009). Large, complex civilizations emerged in North, Central and South America, further increasing population density, with abundant evidence for a large population living in the Americas prior to European arrival (e.g. Bolt and van Zanden, 2014; Canuto et al., 2018; Clement et al., 2015; Cook, 1998; Denevan, 1992a). However, as the epidemics spread, often ahead of the European explorers, pre-European population estimates were never formally documented in colonial censuses (Diamond, 1997; Dobyns, 1993). Hence, Native American populations were only documented in the decades after European contact, necessitating the use of indirect methods to estimate the pre-1492 population of the Americas. Here, we summarize all existing methodologies applied to reconstruct pre-contract indigenous population, and extract published regional estimates to calculate a revised hemispheric population estimate with uncertainty ranges.

2.1. Approaches to estimating the indigenous population at European arrival

Historical anthropologists and archaeologists estimate indigenous population numbers at contact by utilizing a range of documentary evidence, including sizes of armies, number of adult males, census data, tribute records, numbers of buildings, depopulation ratios, and historic clerical chronicles such as the number of baptisms and number of deaths in a community (Borah and Cook, 1960, 1969; Dobyns, 1966, 1983). The conversion from such evidence into population estimates has several limitations. Records of the sizes of armies and the sizes of settlements from just after Spanish arrival may be prone to miscounting and exaggeration (Denevan, 1992a) while the conversion from tributes to population numbers requires contentious assumptions to be made (Henige, 1998; Zambardino, 1980). These include the proportion of a population excluded from tributes, average tribute paid per house, number of people per house, conversion from goods into monetary value, spatial homogeneity of population structure and analogies to present day population structures (Borah and Cook, 1960; Sanders, 1976; Sanders et al., 1979).

Colonial census estimates are generally considered more reliable (Denevan, 1992a), but do not capture population levels before European contact (Borah and Cook, 1960). Accepting such censuses as representative of pre-contact populations led to studies from the early and mid-20th century giving very low 1492 CE population estimates (e.g. Kroeber, 1939; Rosenblat, 1954). Some estimate of the population loss on contact is necessary to provide more robust population numbers.

Archaeological data can also be used to estimate pre-contact population size, but again involves several assumptions, such as the number of houses in a settlement that are occupied at one time (Schacht, 1984). But in contrast to historical documents, new archaeological sites are regularly discovered and new and innovative multidisciplinary approaches are being applied to the data, adding new constraints on regional pre-contact population sizes (e.g. Canuto et al., 2018; Goldberg et al., 2016; Liebmann et al., 2016; Storey, 2012). Population densities can be inferred from the number of archaeological sites (Heckenberger et al., 2003), the number of archaeological features such as pottery, charcoal and fertile anthropogenic soils known as Amazonian Dark Earth (ADEs Heckenberger et al., 1999; Meggers, 2001). Expanding on this, the “habitat density method” projects well-studied local population densities to other regions with similar environmental characteristics to calculate the total population under the assumption that population densities in different locations with the same habitat are similar (e.g. Denevan, 1970, 2003; Newson, 1996). Thus, all 1492 CE population estimates require data to be combined with assumptions to arrive at estimates.

Fig. 2. Regions known to have been affected by disease outbreaks by 1600 CE and pre-Columbian land use. Disease outbreak data derives from Dobyns (1993) and Cook (1998). Land use extent is based on high densities of archaeological sites, earthworks and Amazonian Dark Earths occurrence (Clement et al., 2015; De Souza et al., 2018; McMichael et al., 2014; Whitmore and Turner, 1992). The locations of sites and records referred to in the text and later figures are also shown. 

2.2. New pre-Columbian population estimates

We summarize the existing evidence for pre-Columbian populations using seven geographical regions: the Caribbean, Mexico, Central America, the Inca Territory, Amazonia and contiguous forested area, North America and the Rest of the Americas. The Inca Territory at contact encompassed Peru, Bolivia, Ecuador, Colombia, Chile and parts of north-western Argentina; the Rest of Americas is composed of Venezuela, Uruguay, Paraguay and the rest of Argentina. We complied 129 estimates from 82 studies (Caribbean, n = 18; Mexico, n = 17; Central America, n = 23; Inca Territory, n = 26; Amazonia, n = 20; North America, n = 9; Rest of Americas, n = 6; total hemisphere, n = 10; Table 1). Below we discuss the range of estimates for each region and use them to calculate a total population estimate of the Americas in 1492 CE based on all existing data available at the time of this review.

Caribbean. The first contact between Europeans and Amerindians occurred when Columbus arrived in 1492 CE on the Caribbean island of Hispaniola (what is now Haiti and the Dominican Republic). The primary source for most modern estimates of the contact population is a contemporary eyewitness report by the Dominican friar Bartolomé de las Casas who reported a Hispaniola population of 4 million at the time of contact (Denevan, 1992a). However, studies based on this same report range from 60,000 that neglects contemporaneous reports of post-contact deaths (Verlinden, 1973, in Henige, 1978), to acknowledging some degree of depopulation with initial populations estimated at between 100,000 (Amiama, 1959; Rosenblat, 1976) and 8 million (Cook and Borah, 1971, Table S1).

The 8 million estimate has drawn criticism for the worker-to-population ratio used, the assumption of a logarithmic population decline during 1492–1496 CE, and the inclusion of a controversial tribute count from 1496 CE (Henige, 1978). Most estimates are between 300,000 and 500,000 people in the Caribbean before European contact (Córdova, 1968; Dobyns, 1966; Morison, 1948; Moya Pons, 1979; Williams, 1970).

Mexico. Europeans arrived in what is now Mexico in 1519 CE. Yet, the first comprehensive census only took place in 1568 CE, and tribute records are only available as documentary evidence from the late 1540s (Cook and Borah, 1960; Whitmore, 1991). For central Mexico (the most populous region in Mexico) a population of 25.3 million in 1519 CE has been estimated from tribute records (Borah and Cook, 1969), which would make it one of the most populous regions in the world at the time. Zambardino (1980) highlights the uncertainties in Borah and Cook's approach and arrived at a population between 2.2 and 28 million. Dobyns (1966, 1983) suggests the highest numbers, up to 52 million for central Mexico, based on an extrapolation of depopulation ratios from the Valley of Mexico. These values are higher than some estimates for all of Mexico. For the other region with a substantial pre-Columbian population, the Yucatan peninsula, estimates range between 2.3 million (historic documents, Lange, 1971) and 13 million (extrapolation from number of houses, Morley, 1968). Considering all of Mexico, the lowest estimates, which either outright reject (Rosenblat, 1954) or question the accuracy (Sanders, 1972) of the early tribute records, are between 4.5 and 6 million. Intermediate estimates are ∼16 million, based on a linear extrapolation from results of a modelling study incorporating a combination of population, agricultural and epidemiological models for the Valley of Mexico (Fig. 2, near Valle de Mezquital, Whitmore, 1991) and 17.2 million as a best-estimate based on a synthesis of previous estimates by (Denevan, 1992a). Pre-contact population estimates for central Mexico and Yucatan combined, which is considered representative for all of Mexico, range from less than 3 million to over 52 million with many at around 20 million (Table S1).

North America. Europeans began to colonize North America (defined here as the United States of America and Canada) after Central and South America, thus regional and continent wide estimates are largely based on archaeological evidence, tribe-by-tribe counts and environmental carrying capacities (Milner and Chaplin, 2010, see Table S1). The lower range of population estimates for North America lies between 900,000 and 2.4 million, based on tribe-by-tribe counts for the period 1600 CE to mid-1800 CE (Kroeber, 1939; Ubelaker, 1976, 2006). The highest estimate of 18 million, established from analysing environmental carrying capacities (Dobyns, 1983), has been criticized for its assumptions on food acquisition strategies (Milner and Chaplin, 2010). More recent estimates derived from geospatial interpolation of archaeological sites range between 2.8 million and 5.7 million (Milner and Chaplin, 2010). These intermediate figures are supported by a recent comprehensive regional-scale archaeological study (Liebmann et al., 2016).

Table 1. Population and land use at 1500 CE and 1600 CE in P08 (Pongratz et al., 2008a), HYDE 3.1 (Klein Goldewijk et al., 2010), KK10 (Kaplan et al., 2011), and this study. Also shown are their implied net global carbon uptakes as published in Pongratz et al. (2011) (for P08) and Kaplan et al. (2011) (for KK10 and HYDE 3.1) and the calculated net global carbon uptake from this study.

	P08	HYDE 3.1	KK10	This study (IQR)
Population at 1500 CE (million)	41.1	41.2	60	60.5 (44.8–78.2)
Land use per capita (ha per capita)	0.18	0.67	6.25	1.04 (0.98–1.11)
Land use area at 1500 CE (million ha)	7.5	27.7	372	61.9 (43.3–87.1)
Depopulation (%)	65%	76%	90%	90%
Population at 1600 CE (million)	14.2	9.7	6	6.1 (4.5–7.8)
Land use area at 1600 CE (million ha)	4.9	8.7	123	6.1 (4.8–7.4)
Land use change 1500–1600 CE	4	−6.9	−249.9	−55.8 (−38.5–79.7)
Net global carbon uptake (Pg C)	0.009	<0 .1="" td="">	40	7.4 (4.9–10.8)