Archive for the ‘Ecology’ Category

Railroad Ecology

September 15, 2022

George Stephenson invented the first workable steam engine locomotive in 1814, and he designed the first working rail system in 1820. The British government approved the construction of this first track used for hauling coal. The first rails were made of wood, but they wouldn’t hold locomotives filled with heavy loads of coal. The type of iron available then was also not strong enough to hold all that weight, so Stephenson invented an improved type of iron that could. Americans bought this technology and constructed our first working railway track in 1828. It was the Baltimore-Ohio Railroad and was 8 miles long. Tavern keepers opposed the construction of railways because they feared losing business when railway tracks were constructed far from their establishments, and religious nuts who thought railroads were sinful also fought against their construction, but the free market eventually won. Today, there are over 800,000 miles of railway tracks around the world.

George Stephenson invented the first workable locomotive steam engine in 1814. He also invented the iron used on railway tracks.

The many miles of railway tracks across the world have a big impact on the environment. They increase mortality of large animals, and they serve as migratory barriers for smaller animals, especially amphibians. Herbicides used to suppress vegetation influence the types of species that can live near railway embankments. Grassland corridors on railway embankments cut through forest facilitate the spread of invasive plant species. The impact is so extensive that railroad ecology has become a subset within the science of ecology. Railroad ecology has been more studied in Europe than the United States, but more and more scientists here are starting to pay attention to it.

A study in southern Poland looked at the influence of railway embankments on bird populations. This study counted 1644 individuals of 67 species. They found railway embankments hosted a greater diversity of species, but total number of birds was about the same as found in agricultural fields. They counted 923 individuals of 58 species found on railway embankments. The 3 most abundant in order were starlings, skylarks, and white-throated sparrows. 17 species were only found on railroad embankments, while 9 species were only found in agricultural fields. Railway transects had higher diversity, but birds were most abundant where railway embankments passed over wetlands, wet meadows, slopes, and bushy areas.

A scientific study found skylarks were the 2nd most common species of bird found on railroad embankments in southern Poland.

A study in Alberta Canada looked at wildlife mortality caused by train collisions with large mammals. This study determined 646 large mammals were killed by trains along 1 major track between 1995-2018. Species killed by trains here included grizzly and black bears, white tail and mule deer, bighorn sheep, moose, wolf, coyote, and Canadian lynx. 50 bears, 27 large carnivores, and 560 ungulates were killed. Areas with increased train speed and near water resulted in greater casualties. Trains coming around bends also caught large mammals by surprise.

This moose was rescued, but many large mammals are killed by trains every year.

References:

Cassady, Colleen, V. Whittingham, A. Forshner, A. Gangadhare, and D. Lietze

“Railway Mortality for several Mammal Species Increases with Train Speed, Proximity to Water, and Truck Curvature”

Scientific Reports 20776 2020

Kajzer-Bonk, J. et. al.

“The Effect of Railways on Bird Diversity in Farmland”

Environmental Science and Pollution Research 26 2019

2 Uninhabited Forests in Mozambique

September 1, 2022

Scientists used google earth to find 2 uninhabited forests in Mozambique. Outside of isolated mountain forests like these, Mozambique has 0% virgin forest left. The first is Mount Lico, a granite mountain surrounded by agricultural lowlands. Mt. Lico is classified as an inselberg or isolated mountain. It is made of erosion-resistant granite. Formerly, it was about the same elevation as the surrounding land, but over time precipitation caused the surrounding land to erode away, leaving this isolated mountain. The forest growing on top of this mountain has been isolated for millions of years. Scientists first explored Mt. Lico in 2018, and every expedition finds species new to science. Though pottery has been found on Mt. Lico, the locals say no one in recent history has scaled the cliffs to get there. Scientists have already named 9 new species found here including mistletoe, 2 snakes, 2 pygmy chameleons, a bat, and 3 kinds of butterflies. Potentially, there will be more new species named because they found numerous amphibians, a catfish, more butterflies, crabs, and small mammals not known to science. There are hundreds of unknown species of fungi here as well. Mt. Lico is an important refuge for species of birds that prefer closed canopy forests, now rare elsewhere in the region. Of the 126 species of birds found here, 9 are considered endangered. Mt. Lico is now protected.

Mt. Lico in Mozambique. The sheer walls protect it from human settlement.
Scientists had to scale a cliff to explore Mt. Lico.
Mt. Lico is an inselberg–a granite mountain that resists erosion. The land surrounding it was formerly the same height, but rain has eroded it away.
Amphibians abound on Mt. Lico.
Pygmy chameleons and hundreds of other animal and plant species new to science live on Mt. Lico.
Mt. Lico from inside the forest.
Mt. Mabu is uninhabited because the natives think the spirits of the dead reside here.
This is 1 of 7 rare species of birds that live on these isolated tropical mountains in Mozambique.

Mt. Mabu is uninhabited for a different reason. The local natives believe spirits of the dead reside here, and they avoid it for superstitious reasons, though limited hunting and gathering takes place here. Researchers say it is eerily quiet, and animal tracks are everywhere. Caterpillars are so abundant that caterpillar scat falls like rain from the treetops. Mt. Mabu is 5600 feet above sea level and 27 square miles in extent. Uninhabited forests like these are getting harder and harder to find as the human population on earth heads towards 10 billion.

References:

Silva, Bettencourt, G., J. Bayless, and W. Conradson

“First Herpetological Survey of Mount Lico and Mount Socone, Mozambique”

Amphibian and Reptile Conservation 14 (2) 2020

Spotteswood, G., and J. Bayless

“Threatened Bird Species on 2 Little Known Mountains (Cheperone and Mabu) in Northern Mozambique

Ostrich–The Journal of African Ornithology 74 (1) 2008

Everglades Hammocks and Snails

June 8, 2022

During Pleistocene climate phases of high sea levels, the Everglades region of south Florida was flat sea bottom dotted with limestone outcrops and coral, and Lake Okeechobee was a saltwater bay. Today, the Everglades is a sea of sawgrass (Cladium jamaicense) dotted with hardwood hammocks that grow on top of the formerly inundated limestone outcrops and coral. Fresh water from Lake Okeechobee, funneled by a coastal ridge, flows south through the Everglades landscape. Sawgrass (technically a sedge not a grass) is a fire-adapted species, and during dry spells it burns, but hardwood hammocks are usually protected from the fires. Trees growing on the limestone-enriched elevated soils drop leaves, and the acidity from the decomposing leaf litter dissolves the limestone surrounding the hammock, creating moats filled with water that serve as fire breaks. Most hardwood hammocks also have an eroded solution hole in their middle, and they are elliptically shaped with 1 end pointed in the direction of the southward water flow.

Typical Everglades landscape–sawgrass wet prairie dotted with hardwood hammocks.

The composition of trees on Everglades hardwood hammocks includes a mix of tropical and temperate species. Tropical species are more common on southern Everglades hammocks, while temperate species predominate on the northern Everglades hammocks. The list of tree species found on these hammocks includes gumbo-limbo, mahogany, cocoplum, wax myrtle, live oak, red maple, hackberry, mulberry, Everglades palm, royal palm, and strangler fig.

Gumbo limbo tree. This is a tropical species common in hardwood hammocks of the southern Everglades. Everglades hardwood hammocks contain a mix of temperate and tropical species of plants.
Royal palms cannot survive frequent frost. Therefore, they are more common in the southern Everglades.

A diverse snail fauna thrives on Everglades hammocks because the limestone outcrops provide a rich source of calcium. Snails need calcium to develop their shells. The relatively frost-free climate also helps them breed year-round. Each hammock hosts a variation of tree snail (Liguus fasciatus) with a different color pattern. Over 58 variations are known. Tree snails feed upon fungus, lichen, and algae. 4 species of large apple snails live on these hammocks. 3 non-native apple snail species from South America are outcompeting the native species (Pomacea paludosa). Apple snails graze on green plant material and are a pest on south Florida vegetable farms. However, the rapidly expanding population of non-native apple snails benefit snail-eating bird species such as limpkins and the Everglades snail kite. The latter species is endangered, but the increase in snail populations has led to a rebound in Everglades kite numbers.

Native Florida apple snail. 3 species of non-native apple snails also thrive on Everglades hammocks.
Over 58 color variations of tree snails have been found on Everglades hammocks. Each hammock hosts a snail with a different color variation.
Limpkins primarily eat snails.
Endangered snail kites are increasing in population, thanks to rapidly spreading populations of non-native apple snails.

I’ve seen apple snails for sale in Asian food markets. I was not impressed with my lone snail-eating experience after I bought a can of imported escargot. They were relatively inexpensive, but they had no flavor at all. Escargots are traditionally served with butter and garlic sauce. I think eating snails is an excuse to dunk French bread in the butter and garlic sauce.

Survival of the Fittest During the Anthropocene

December 9, 2021

Humans are a part of the natural world, and human activities have an enormous impact on worldwide ecosystems. The impact is so great, some scientists think the current geological era we live in now should be known as the Anthropocene. The animals and plants that are best able to adapt to Anthropocene living conditions have the best chance of surviving into the future. I call it survival of the fittest during the Anthropocene. When I used this phrase on twitter in defense of cats, whiny woke wimps showered their fury at me. One anonymous jerk called me a ninny, short for pickaninny, a derogatory term for a black child. Darren Naish, a world-renowned vertebrate zoologist, clicked on the like button for this racist tweet, then blocked me because I don’t agree that cats are detrimental to the environment. I don’t think Naish is a racist–he probably didn’t know ninny was a racist term. He may be an expert on vertebrate zoology, but his knowledge of other topics is apparently limited.

Darren Naish liked a post from someone who referred to me using a racist term, then he blocked me because I don’t agree that feral cats are detrimental to the ecosystem.
A man on twitter called me a ninny, short for pickaninny, a derogatory racist term. Darren Naish clicked on the like button.

I like animals capable of thriving during the Anthropocene. Cats are 1 of the best examples of an organism well adapted to living alongside humans. They can survive with or without people, existing in conditions ranging from being pampered to total neglect. Cats are a commensal species with humans and will occur wherever humans live, whether woke ecologists like it or not. Some scientists unfairly demonize cats. Most of the studies purporting to show how cats are detrimental to ecosystems are so bad I can’t understand how they get published in peer-reviewed scientific journals. Perhaps, the most famous paper (widely regurgitated without question in the media) claimed cats killed an estimated 94 million birds per year in the U.S. The author of that paper simply made-up numbers using wild guessing. Cats do kill birds on occasion, but they are taking the place of natural predators that would live in the area, if it had remained wilderness. Some species of songbirds have artificially inflated populations in suburban locations because humans create favorable nesting structures, maintain bird feeders, and suppress natural predator populations. A cat killing a songbird in the suburbs is actually restoring a balance. Moreover, cats control rodents and rabbits, species that spread disease and actually compete with humans for food.

My outdoor cats. They control rodent populations and provide companionship.

Ross Barnett is another scientist always whining about cats on twitter. The sadistic hypocrite favors bringing the lynx back to Great Britain where they have been extirpated, but he participated in a cat eradication program in Australia. Cat eradication programs in that part of the world have been disastrous. Rat and rabbit populations exploded wherever cats were eliminated. Rats ate all the birds the eradication programs were supposed to protect, and rabbits denuded the landscape. How can Barnett lament the loss of the lynx, but favor the destruction of an animal so similar? His reasoning makes no sense.

I don’t like the term, invasive species. Every successful organism has been invasive at some point in its evolutionary history. They originated at 1 location and invaded surrounding territory. I prefer to call them newly colonizing species, and I think they increase diversity. House sparrows are 1 of my favorite newly colonizing species, and they are well adapted to surviving the Anthropocene. They are commonly found in grocery store parking lots, and some even live inside the stores. Few other birds (with the exceptions of pigeons and ring-billed gulls) can be found thriving in parking lots.

House sparrows are one of my favorite newly colonizing species. They are common in grocery store parking lots, and some times even live inside the stores.

Bradford pears are another 1 of my favorite newly colonizing species. Many ecologists revile this species because of the way they take over abandoned fields at the expense of native species. I think they contribute greatly to the beauty of the landscape. They provide white flowers in spring, attractive foliage in fall, and food and nesting for birds.

Flowering Bradford pear tree in an old field. I love this species. Woke horticulturalists suggest replacing them with native serviceberry. What a stupid suggestion. Serviceberry won’t successfully grow in most locations, like Bradford pear trees can.

Instead of lamenting all of the organisms incapable of surviving during the Anthropocene, people should appreciate the tough species that can survive in a world dominated by humans.

Wet Climate Phases during the Pleistocene Probably Supported Higher Megafauna Populations in Southeastern North America

October 8, 2021

I love the fungus that grows on manure. I know that sounds weird, but the dung fungus spore concentration in sediment samples is the best evidence paleo-ecologists have of determining past megafauna populations. It is the perfect proxy because if dung fungus spores are high in a sample, megafauna populations must have been high during that time period. There is no hiding all the defecation that was occurring then. Low dung fungus spore concentrations are evidence of low megafauna populations. The latest dung fungus spore study was from a core of sediment taken beneath Lake Peten-Itza in Guatemala. The core was over 120 feet long and included radio-carbon dated time periods from 42,000 years BP-4,000 years BP. The dung fungus concentrations were compared with the pollen composition within each time period to determine what types of environments existed when megafauna populations were high or low. The types of environments fluctuated with known climate phases, alternating between oak and myrtle-dominated woodlands, pine-dominated woodlands, dry acacia-grassland scrub, and seasonal rain forest (the predominating present day environment). Oak-dominated woodlands prevailed during wet interstadials; acacia scrub grasslands prevailed during dry stadials. Megafauna populations were highest in this region during phases of climate that favored oak-dominated woodlands. I also noticed on the chart below that grass pollen was higher during this phase as well, suggesting wildlife had abundant grass and acorns to eat. Nearby fossil sites show horse, llama, mammoth, gompothere, and glyptodont occurred in this region during these time periods. Megafauna populations were lowest during dry stadials.

Location of the study site. Image from the below referenced study. Scientists took the core from 1 of the deepest parts of the lake that never dried out during dry climate phases.
Chart showing abundance of dung fungus (sporomiella) with pollen composition from a >120 foot core taken from sediment beneath Lake Peten-Itza. Megafauna populations were most abundant during wetter climate phases. Chart from the below reference.
Lake Peten-Itza today. It is surrounded by a seasonal rain forest, but during different climatic phases of the Pleistocene the surrounding environment varied between oak-dominated woodlands, pine-dominated woodlands, poor quality scrub grasslands, and seasonal rain forests. This lake is old and over 500 feet deep in some places.
Lucky Oak Woodland in Indiana. Much of central Georgia probably looked like this during wet interstadials of the Pleistocene.
Oak woodland in Ellijay, Georgia. Over 10,000 years ago this was prime habitat for Jefferson’s ground sloths, long-nosed peccaries, and tapirs. At least deer still occur here.

Other regions of the world weren’t the same. The mammoth steppe, a grassland and forb-dominated environment, located from northern Europe across Asia to Beringia, supported higher megafauna populations during cold stadials than other climate phases that favored forests and woodlands. The arid acacia scrub grasslands that occurred in Central America during stadials may have been nutrient poor and just did not support high populations of megafauna. Much of the region may have been bare soil.

I hypothesize populations of megafauna in the piedmont region of southeastern North America were also higher during interstadials. Pollen evidence indicates oak trees increased in abundance during these climate phases. Wetlands expanded and more grass, herbaceous plant growth, and acorns were available with increased precipitation; thus providing more potential food for wildlife. I think megafauna were likely limited to oasis-like habitats in this region during cold dry stadials. These habitats probably occurred in river valleys where stream flow was much reduced, and instead of meandering continuous rivers like those of today, the waterway was more like a chain of pools clogged with sand bars.

Many folks imagine Pleistocene-environments to resemble the modern day Serengeti, but this was not always the case. During cold dry climatic phases large areas may have hosted scarce wildlife populations restricted to shrinking water holes. Wildlife populations rebounded whenever climate phases shifted to more moist conditions. I’m sure wildlife populations fluctuated in parts of North America just like they did in Guatemala.

Reference:

Rozas-Davila, A.; A. Correa-Metreo, N. McMichael, M. Bush

“When the Grass wasn’t Green: Megafaunal Ecology and Paleodroughts”

Quaternary Science Review 266 August 2021

Deer Herbivory Alters Plant and Bird Species Composition

May 20, 2021

Cades Cove, located within Great Smoky Mountains National Park, is 1 of my favorite places in the world. I visited Cades Cove during June of 2017 and saw lots of deer, a few black bears, a turkey, and an herd of tame horses. It’s 1 of the best places to see wildlife east of the Mississippi. Cades Cove is known for its high density of white-tailed deer and is 1 of many areas where deer herbivory and its effect on plant species diversity and abundance has been studied. High density deer populations reduce tree regeneration and alter plant species composition and forest successional patterns. Areas where deer are abundant can also see a shift in natural communities to an alternate state, while plant species diversity becomes reduced, influencing other species of wildlife. Results of studies on the interaction between deer and plant community vary, depending upon geographical location. Some species thrive or can at least survive in high density deer locations, while these same species in a different geographical location my suffer. I’ll review some of these studies below.

Plant growth inside and outside a deer exclosure in Wisconsin.

Cades Cove, located within the Great Smoky Mountains National Park, is an area considered to have an high density of deer.
Deer in Cades Cover are not hunted, and they have little fear of people.
Look at how close these stupid asses got to this bear in Cades Cove. That bear could be mauling them in about 2 seconds.

Scientists studying the effect of deer herbivory on plant species composition use exclosures, or in other words they construct deer proof fences on certain plots to prevent deer from feeding on the plants inside the fence. They then compare plant composition and abundance inside and outside the fence. A study at the Clemson Experimental Forest found that after 2 years the difference between inside and outside exclosures was negligible. The differences aren’t noticeable until 5-20 years after the exclosure is constructed. At Callaway Gardens near Columbus, Georgia deer exclosures were in use for 20 years. Here, there were significant differences between the inside and outside of the enclosures. Inside the exclosures strawberry bush (Eunonymous americanus not to be confused with the strawberry people eat–Fragaria virginianus) and greenbriar, 2 favorite deer foods, grew taller and more dense than outside the exclosure. There was also an increase in red maple, black cherry, white oak, and sassafras inside the exclosure. Outside the exclosures there was an increase in sweetgum, wax myrtle, hop hornbeam, shining sumac, water oak, and willow oak. Black cherry benefitted from the absence of deer at this location, but at a site in northwest Pennsylvania, this species was found to be resistant to deer browsing.

Violet responds differently to deer herbivory at different locations as well. Scientists studying deer herbivory on the upper peninsula of Michigan found deer eradicated violets, but at Cades Code, though it is often eaten by deer, violet still regenerates. The scientists in Michigan identified “winners” and “losers” among plants in high density deer sites. “Winners included wind pollinated sedges and grasses in the Poa genus, along with hazelnut, blueberry, wood anemone, and wood fern. “Losers” in addition to violets were forbs such as big leaf aster, blue beard lily, strawberry, and thimbleberry. In some areas of Wisconsin deer can reduce tree sapling abundance by 90%, and they can eliminate white cedar and red oak. Oddly enough, yellow birch trees require moderate deer population densities. This species didn’t regenerate if deer populations were too low or too high.

The effects of deer herbivory were studied in a forest located in northwest Pennsylvania. The forest consisted of sugar maple, striped maple, black cherry, fire cherry, beech, and sweet birch. Tree regeneration failed in 25%-40% of clear cut plots. Species of trees that were browse resistant included beech, black cherry, striped maple, ash, and hackberry. A number of common bird species were absent from Pennsylvania forests with high deer population densities. This list includes wood peewees, cerulean warblers, yellow-billed cuckoos, and indigo buntings.

Ironically, heavy deer populations can accelerate forest successional patterns. By feeding upon pioneer species of plants, deer reduce competition for space with species that normally don’t dominate until later stages of forest succession.

References:

Thrift, J.

“Effects of White-Tailed Deer Herbivory on Forest Plant Communities”

Clemson University Thesis 2007

Wiegmann, S.; and D. Waller

“Fifty Years of Change in Northern Upland Forest Understory. Identity and Traits of “Winner” and “Loser Plant Species”

Biological Conservation 129 2006

Chinese Privet (Ligustrum sinense) is Beneficial for Birds

May 13, 2021

During the 1927 college football season the Georgia Bulldogs won 9 consecutive games before playing their hated rival, the Georgia Tech Yellow Jackets. The Bulldogs always played the Yellow Jackets in Atlanta during this era because their own home games were played at rocky Herty Field–a poor quality gridiron. The Bulldogs were a fast team that year, so some Yellow Jacket officials watered down the field before the game, turning it into a muddy quagmire that negated Georgia’s speed advantage, and the Yellow Jackets upset the Bulldogs 12-0, ruining their unbeaten season. Georgia officials were furious and vowed to build their own stadium where they could play Tech at home every other year. Sanford Stadium was completed in 1929. Hedges of Chinese privet were planted near the sidelines, and Georgia home games are referred to as being played “between the hedges.” I’m a big Georgia Bulldog fan, and I was excited to discover 1 specimen of Chinese privet that recently popped up on its own near my back door.

Gardeners planted Chinese privet in Sanford Stadium during 1929. Traditionally, college football games played in Athens, Georgia are said to be played “between the hedges.” Photo from Gun and Garden Magazine.
I’m a big Georgia Bulldog fan, so I was excited to discover this Chinese privet that popped up near my back door.
Cardinal eating a privet berry. At least 16 species of birds use privet thickets for food and/or cover. Photo ripped off from google images.

Chinese privet, as the name would suggest, is native to China, and it was introduced to North America during 1852 as an ornamental plant. Privet is a tough species and thrives in both wet and dry locations on just about any kind of soil. In the wild privet grows on disturbed sites and originally depended upon elephant foraging, human activity, fires, or wind storms to open up the forest canopy, so it could take over a location. Privet can survive fire and will come back from the roots. In addition to spreading through sucker roots, privet is spread by birds eating its fruit and defecating the still viable seeds throughout the environment. It grows fast. The 1996 Olympic soccer matches were played at Sanford Stadium, and the privet hedges were temporarily removed and transplanted. Upon their return to Sanford Stadium they grew enough in 1 week that one couldn’t tell they’d ever been moved.

Chinese privet flowers are very fragrant. This is what attracted my attention to the bush, but I did not recognize it. I posted a photo on a Facebook page known as Weakley’s Flora of Southeastern North America. I learned plant conservationists revile Chinese privet because it crowds out native plants. The man who identified it for me told me to destroy it. I told him I liked it and was not destroying it. Numerous other shmucks called me a troll, and one suggested I was a fake account who signed up for this group just to troll about Chinese privet. (Facebook suggested the group based on my interests. That’s why I joined.) Another person suggested I use an app for plant identification because I must not be interested in ecology and didn’t belong in the group. (I’ve been writing this blog about Pleistocene ecology for over 10 years.) Yet another putz encouraged me to breath the flowers in deeply in the hopes I would suffer an uncomfortable allergic response. The internet makes it easy to expose people for their mean spirited attitudes.

Now, I am trolling them. I found a scientific study that determined Chinese privet benefits birds. Thickets of Chinese privet host the same abundance and species diversity of birds as other more natural areas during spring, summer, and fall; but during winter bird species diversity and abundance is even higher than in the surrounding landscape. Privet berries ripen in late fall/early winter when most native berries are gone. Birds that benefit from food and/or cover provided by privet include cedar waxwings, cardinals, bluebirds, robins, Carolina wrens, chickadees, brown thrashers, flickers, mockingbirds, purple finches, blackbirds, blue jays, crows, doves, sparrows, bobwhite quail, turkey, and feral chickens. Mockingbirds are the most common songbird in my neighborhood, and I suspect this was the species that inadvertently planted the bush in my backyard when it defecated the seed. The berries are toxic to humans. Deer and cotton rats eat privet foliage and also benefit from the presence of the plant. This same study did find privet does crowd out native plants.

Another study determined privet thickets host fewer bees and butterflies than privet-free zones, but this study is misleading and seriously flawed. Privet was mechanically removed from locations in a botanical garden and a nature reserve in Athens, Georgia. Forest service scientists trapped bees and butterflies 5 years after the removal and counted species abundance and diversity. The title of the article is misleading–“Removing Chinese Privet from a Riparian Corridor Benefits Pollinators 5 years later.” From the title one would assume they counted bees and butterflies at the same location before the privet was removed, but this is not what they did. Instead, they compared bee and butterfly composition from this location to different locations within the Oconee National Forest including 2 sites with privet and 2 sites without. This is quite flawed because some sites might be better for pollinators based on factors unrelated to privet. (And see below…an obvious factor.) Moreover, the sites where privet was removed were embedded within a botanical garden and a nature reserve where humans deliberately plant flowers that attract bees and butterflies. Populations of pollinators in these areas are artificially boosted due to anthropogenic activities. They are even higher than in the natural privet-free zones used as control groups in the study. A better study would take inventory of pollinators before and after privet removal in the same location.

Even without human interference nature would eventually control privet populations. During the 1996 transplanting of the Sanford Stadium privet, horticulturalists discovered the privet was slowly dying of a nematode infestation. They treated it, but many wild stands of privet may be dying from nematode infestations. Left alone, after centuries, native plants could retake space where privet previously took over.

References:

Hudson, J.; J. Handa, and S. Kim

“Removing Chinese Privet from Riparian Forest Still Benefits Pollinators 5 Years Later”

Biological Conservation 167 November 2017

Wilcox, J; and C. Beck

“Effects of Ligustrum sinense (Chinese privet) on Abundance and Diversity of Songbirds and Native Plants in a Southeastern Nature Preserve”

Southeastern Naturalist 6 (3) 2007

Tigers (Panthera tigris) Suppress Dhole (Cuon alpinus) Populations.

April 1, 2021

A new study determined tigers suppress dhole pack sizes in India. Dhole packs are smaller in areas with higher densities of tigers, even if there is an higher density of potential prey species. The scientists conducting the study used camera traps to estimate pack size and tiger numbers. In Tadoba-Andhari Tiger Reserve where tiger density is high, there were 7 dhole packs averaging 6.4 dholes per pack. In Navegaon-Naziri Tiger Reserve where tiger density is lower, there were 5 dhole packs averaging 16.8 dogs per pack. Pack sizes were 2.6 times greater in areas with lower tiger density. Both reserves are in a subtropical dry deciduous forest zone dominated by teak, argun, and giant crepe myrtle trees. The terrain is somewhat hilly. Leopards are another important large predator in the reserves, and the leopard population is also negatively impacted by tigers. Common prey species in the reserves include spotted deer, sambar deer, barking deer, nilgai antelope, wild boar, and gaur–a large species of cattle. Dhole pack sizes do increase in areas with greater prey density, but the abundance of tigers is a greater influence on pack size. Dholes tend to prey on smaller animals in areas with lots of tigers, so they can consume more of the animal before a tiger drives them away from the kill. Tigers depress dhole populations by directly hunting them and by chasing packs away from their kills.

Map of tiger reserves where the below referenced study took place. Map from the below referenced study.

Tigers totally dominate dholes. The authors of the study saw tigers kill dholes on 5 different occasions and drive packs away from their kills 23 times. They saw no instances of dholes killing tigers or driving them away from their kills.

Spotted deer are an important prey item for tigers and dholes.
Nilgai antelope, also known as blue buck are another important prey item for tigers and dholes. Hunters introduced nilgai antelope to Texas about 100 years ago, and now there is a feral population of 37,000 in that state.

India has the highest dhole population in the world. There are small packs in the northern montane forest, and larger packs in the dry deciduous forests of central and south India. Since tigers were eliminated from Laos, dhole populations have increased there. Dholes formerly ranged across most of Asia, and during the Pleistocene they ranged into North America, though fossil evidence there is limited to 1 site in Mexico.

Siberian tigers are known to depress wolf populations, and lions depress hyena and hunting dog populations in Africa. I wonder if big cats suppressed canid populations in Pleistocene North America. Saber-tooths were very powerful fanged cats, and American lions grew larger than any big cat species. Pleistocene jaguars grew as large or larger than modern tigers and are at least as common as dire wolves in the fossil record of Florida. There really is no way to know because abundance in the fossil record doesn’t necessarily reflect actual abundance in life.

Reference:

Bhanda, A.; P. Ghaskodbi, P. Nigram, and B. Habib

“Dhole Pack Size Variation: Assessing the Effect of Prey Availability and Apex Predator”

Ecology and Evolution March 29, 2021

Squirrels and Blue Jays vs Acorn Tannins

December 12, 2020

For over 10,000 years acorns were the most important source of food for Native Americans wherever oak trees were common.  Acorns are an important source of food for animals too for everything from mice to bison.  However, acorns contain tannins, a substance difficult to digest and even toxic for some animals.  For example horses that eat too many acorns may die. Oak trees rely on animals to spread their seed, but if too much of their seed is consumed, their populations will decline.  The nutritional value in acorns attracts hungry animals, but the tannins act as a semi-deterrent.  Acorns from species in the white oak family evolved a different strategy for coping with acorn predation than species in the red oak family.  White oak acorns contain less tannins and are more palatable, so squirrels and jays prefer these and spread them throughout the landscape, but they germinate as soon as they are buried in the fall.  When a squirrel or jay tries to retrieve them later, it is too late.  White oaks only lose acorns that are consumed immediately.  Acorns from oaks in the red oak family are high in tannins, but the tannins are concentrated in the bottom half of the acorn.  Squirrels gnaw on the top half and abandon the bottom half.  If enough of the bottom half is left, the acorn can still germinate, though red oak acorns don’t need to germinate until spring because squirrels and other animals don’t want to eat the part of the acorn with such an high concentration of tannins. This year the sand laurel oaks (Quercus hemispherica), the most common oak species in my neighborhood, are producing a bumper crop of acorns, and the squirrels are gnawing the tops of them but leaving the bottoms.

Squirrels eat the tops of acorns from oak trees in the red oak family.  These acorns, found in my backyard, are from a sand laurel oak. also known as Darlington oak.  The top part of acorns have less tannins which are hard for most animals to digest.  Nevertheless, squirrels risk death from the 8 cats that live in my backyard to exploit this food source.  Oaks can germinate from acorns with the tops gnawed off.

Squirrels fed a diet of just red oak acorns in an experiment ate less.  Blue jays fed a diet of red oak acorns in an experiment actually lost weight.  Squirrels living in a location with mostly red oaks must vary their diet with other foods such as white oak acorns, nuts, fungi, berries, and insects.  Blue jays fed a diet of red oak acorns and acorn weevil larva maintained their weight, showing how blue jays can survive in the wild on a diet of mostly red oak acorns because the infestation rates of acorns by weevil larva are high.  Incidentally, oak trees were able to quickly colonize New England and southern Canada following deglaciation at the end of the Ice Age because of the acorns that were spread by blue jays.

Tannins posed an obstacle for hungry Native Americans as well.  According to Euell Gibbons, Native Americans processed the acorns by boiling them in water to leech out the tannins.  It’s necessary to periodically change the water–a tedious process.  I tried this years ago with the sand laurel oak acorns in my yard.  After dumping the water out and replacing it 8 times, I got tired of the process and gave up.  The acorns were becoming less bitter, but still not palatable enough to eat in a satisfying quantity.  Native Americans with no modern day supermarkets were most persistent from necessity.

References:

Chang-Macoubrey, A;  A.E. Hagerman, and R. L. Kirkpatrick

“Effects of Tannins on Digestion and Detoxification Activity in Gray Squirrel (Sciurus carolinensis)”

Physiological Zoology 20 (3) 1997

Johnson, W., Libby Thomas, and Curtis Adkinson

“Dietary Circumvention of Acorn Tannins by Blue Jays: Implications for Oak Demography”

Oecologia 99 (2) 1993

 

 

Wilderness Rebounded Following the Black Death

August 24, 2020

The recent ill-advised lockdown that failed to stop the spread of the coronavirus reduced human activity for several months, and the wildlife noticed.  Deer and coyote, normally more active at night, began roaming big city streets in broad day light.  It doesn’t take long for wilderness to rebound when the presence of humans is diminished or eliminated.  The Chernobyl Exclusion Zone is now 1 of the greatest nature reserves in the world, thanks to radiation fallout which makes the area an unpopular place for people to reside.  Past epidemics have led to the rebound of wilderness.  Europeans introduced many infectious diseases to the Americas, resulting in an 80% reduction in Indian populations.  Many Europeans then mistakenly believed the Americas had always been a sparsely populated segment of the world.  They collectively forgot their own past history with the bubonic plague.

The bubonic plague is believed to have originated in the Gobi Desert, possibly in the gerbil population.  Fleas spread the dangerous bacteria (Yersinia pestis) to the Mongolian raiders descended from Ghengis Khan who then carried it to Europe during hostile invasions and through free trade.  During 1347 a merchant ship with an 100% infection rate arrived in Venice, Italy and soon the plague spread throughout Europe in fleas carried by rats.  People slept on straw mats, crowded together in unsanitary condition, and bubonic plague outbreaks exploded.  In addition to being flea-borne the bacteria could be transmitted through the air between people in close contact with each other. The plague is an horrible disease, killing people in 3-4 days, and the victims die in agony–their lymph glands literally burst with toxic bacterial waste and white blood cells.  The victims turn black, hence the name “Black Death.”  50% of the population died.  Not enough agricultural workers remained alive to harvest the crops, and combined with bad weather from the onset of The Little Ice Age, famine soon followed the plague.  Wild animals and wilderness soon took over much of rural Europe.

Fast and lethal, the Black Death spread more than a mile per day

Bubonic plague, originating in Asia, decimated European populations for 2 centuries and wilderness areas rebounded.

Aspen Glow. A Limited Edition Fine Art Print from Peter Lik. – LIK ...

Birch and aspen trees quickly sprouted in abandoned fields that were soon replaced by oak forests with trees that eventually grew 150 feet tall.

Białowieża

Huge oak trees like this grew on abandoned agricultural land following the Black Death.

Grass growing in abandoned grain fields fed herds of wild cattle and horses recently freed from their dead human masters, and these escapees interbred with their wild cousins.  Bison expanded their range.  Soon birch and aspen forests sprouted in the fields, and moose invaded the new natural areas to feed on the saplings.  Brown bears enjoyed the fruits of long neglected orchards.  Eventually, oak trees shaded out the birch forests, and they grew to enormous size–the acorns feeding wild boars and roe deer.  Lynx and wolves reclaimed land they’d lost in the previous centuries.

The Significance of Aurochs | borderslynn

The aurochs, the ancestor of modern cows, along with cattle that went feral roamed the European countryside in the years following the Black Death.  The Black Death likely delayed the extinction of the aurochs by centuries.  They didn’t become extinct until 1527.

The Odd Couple!! (Wild Red Deer Stag & Horse) | Horses, Animals ...

Red deer and horse populations increased when human populations decreased.

King Jagiello escaped an outbreak of the plague in 1426 when he retreated to an hunting manor in the Bialowitza woods.  No roads or bridges penetrated this vast wilderness.  Royalty protected this wilderness for centuries, and today it is just a partial remnant of the post Black Death rebound of nature.

Author Mimi Matthews

Wolf packs took over when humans disappeared from large areas of Europe.