Tar Pits, Dung Beetles, and Megafauna

Today Los Angeles is a city with a reputation for excess, dominated by cars and actors, and there is a reason for this.  Money.  Money in the form of oil.  The combination of oil and money led to the nascent fossil fuel industry teaming up with the budding car industry in the early 20th century to sabotage the successful street and rail car industry in the Los Angeles basin.  Money led to loose laws which led to crime, gambling, and guerrilla movie studios moving into the LA area, searching for places that were outside the influence of the film establishment of the times.  All of these things are interesting, but without the oil it is unlikely Los Angeles would have taken the trajectory it did.

Oil Fields, Signal Hill, Los Angeles 1914

Oil Fields, Signal Hill, Los Angeles 1914 – source: National Geographic archives

Oil is usually found deep under ground, but the greater Los Angeles area up through the Santa Barbara area is one of a few places in the world where oil is not just close to the surface, it is on the surface, bubbling in cold pits of bitumen, also known as asphalt and tar.  This asphaltum has been important to humans for as long as they have lived in the region.  In the past it was primarily used to waterproof boats, water carriers, and cooking vessels or as an adhesive.  Now, of course we use it to make a whole range of products from gasoline to Vaseline, rubber, plastics, pantyhose, parachutes, paint, detergents, antifreeze, golf balls, and more.

Bitumen occurs where vast amounts of living material (plankton, diatoms, or plant material usually) were deposited in a quiet anaerobic environment, such as a lake or sea floor, and left alone for a long, long time.  In essence, it is liquid coal.  Coal beds are sometimes repositories for incredible collections of fossils.  These ancient remains and offer a window into the deep past, but for a window into the more recent past we need something a little different from coal.  Bitumen provides one of the best preserving agents for more recent remains.

Near Hollywood there is a famous bitumen pit redundantly named the La Brea Tar Pits (literally “The Tar Tar Pits”).  Between approximately 38,000 years ago and 11,000 years ago the La Brea Tar Pits were very active.  An enormous variety of animals and insects were lured to the waters of what appeared to be a rich wetland and were trapped by the sticky tar that lay beneath the shallow layer of water.  A few posts back I brought up the fact that condors are representatives of an extinct assemblage of fauna.  The La Brea tar Pits provide a window into that now extinct assemblage.  Los Angeles was a land of giant bears and jaguars, pygmy pronghorn antelope, camels, mammoths, dire-wolves, great birds of prey, giant ground sloths, and numerous other animals.  

Mural of the La Brea Tar Pits during the Quaternary

Mural of the La Brea Tar Pits during the Quaternary

Animals trapped by the sticky tar aroused the interest of predators and scavengers which were themselves trapped by the tar.  Herbivores, carnivores, mammals, birds, and insects all fell prey to the tar pits and many of them have been preserved in astoundingly good condition.

Pygmy Pronghorn (Capromeryx minor)

Pygmy Pronghorn (Capromeryx minor)

Along with the large animals is one of the best collections of preserved insects in the world.  Most people know that insects are important in a sort of general way.  In recent years honeybees have been in the news quite a bit and their importance in maintaining our food supply has reached the mainstream audience.  I’ve mentioned the importance of both ladybugs and dragonflies, but these are iconic and popular insects, very much in the public eye.  There are many other insects that have an importance far beyond what their diminutive size would indicate.  One of these is the dung beetle (Scarabaeinae).

Until recently much of the planet was home to a wide range of large animals, grouped into the catch-all term “megafauna”.  This is a generic term for any animal massing more than 45-100 kg (100-220lbs).  Most of the recent megafauna of each continent (with the exception of Africa) went extinct shortly after humans reached the respective region.  Here in North America we had great mammoths, elephant relatives, standing 4 meters (13 feet) tall at the shoulder and weighing 9 metric tons (10 short tons).  You can walk under the tusks of the mammoth skeleton in the La Brea Tar Pits, reach your hand up as high as you can, and the tusks are still out of reach.

Colombian Mammoth (Mammuthus columbi)

Colombian Mammoth (Mammuthus columbi)

Numerous types of ground sloth roamed the area, including both the Shasta and Harlan’s Sloths.  Harlan’s Ground Sloth was not the largest and even it stood 3 meters (10 feet) tall and weighed more than a ton.

Harlan's Ground Sloth (Paramylodon)

Harlan’s Ground Sloth (Paramylodon)

The Antique Bison, some 15-25% larger than modern bison roamed the region,

Antique Bison (Bison antiquus)

Antique Bison (Bison antiquus)

And there were, or course predators of all sorts.  Dire Wolves are particularly well represented in the La Brea Tar Pit fossils.

Dire Wolf (Canis dirus) skulls.  One panel of a 3-panel display.

Dire Wolf (Canis dirus) skulls. One panel of a 3-panel display.

There were large numbers of these animals and, like all animals, they had to eat.  The larger the animal, the more it eats.  Modern African elephants eat 100-300kg (220-660lbs) of food per day, so it is reasonable to expect that the Colombian mammoth would eat at least that much per day, if not more.  Then, just on the herbivore side of things, there were the giant ground sloths, horses, camelids, bison, elk, antelope, peccaries, deer, and numerous other species.  Additionally there all the predators; giant jaguars, sabre-toothed cats, dire wolves, American cheetahs, bears of all sorts, including the giant short-faced bear, and more besides them.

All animals must eat, and everything they eat must come out eventually.  This is something we don’t really think much about: what happens to all the animal dung?  How much of it was there?

We don’t really have any good idea just what the animal numbers were like in the past, but we do have a very good idea of the numbers of another kind of modern megafauna.  Cows.  The numbers of cows in the US probably only represent a middling-small portion of the total amount of large megafauna in the US portion of North America, but they give some insight into the kinds of numbers we are talking about when it comes to dung quantities.

The 2006 article by Losey and Vaughan provides some insight to those numbers.  Each cow can produce approximately 21 cubic meters of waste per year, that’s a volume roughly equivalent to 1.3 VW buses worth of dung per year per cow.  In 2004 there were nearly 100 million head of cattle in the US, that means more than 2 billion cubic meters of poop per year, just from cows… I’ll let that image settle in.  For comparison that’s enough to cover  Manhattan to a depth of about 70 feet (21 meters) or Disney World to about 60 feet (18 meters) in cow manure every year (in other news: Disney World is larger than Manhattan).  That’s just from the cows and just the ones in the US.

What happens to all that crap?  Enter the humble dung beetle.  For the portion of cattle that are fortunate enough to be in fields, dung beetles take care of the waste.  According to Losey and Vaughan each year dung beetles save ranchers $380 million dollars in clean-up costs.  A 2001 article by Michelle Thomas indicates that without dung beetles each year we would find 5-10% of each cattle acre unusable due to dung pile-up.  Dung beetles are so important that foreign species of dung beetles have been imported to the US and elsewhere for use in areas that experience heavy livestock use.

Dung beetles range in size from just a few millimeters to several inches in length.  Their size is dependent on the size of the dung they have to deal with.  Currently Africa has the largest land animals and the largest dung beetles.  North America used to have an enormous range of very large animals with correspondingly large droppings.  As you might expect there were some very large dung beetles living here to take care of those droppings.  The large beetle on the left is an extinct giant water beetle similar in size the the large, extinct dung beetles.   This beetle is about 2 inches (5 cm) long.

Different species of dung beetles found in the tar pits.  The large one is extinct.

Different species of small dung beetles found in the tar pits and an extinct giant water beetle that is about the size of the large extinct dung beetles.

Ecosystems are delicate things, subject to trophic cascades, as I have previously mentioned, full of unexpected consequences and side effects.  Most of the great predators in North America died out when the large herbivorous megafauna became extinct.  Scavengers also suffered, amongst them the dung beetles.  All the large dung beetles in North America swiftly followed the rest of the megafauna into extinction.  Currently in North America the dung beetles are small, more like the insects to the right in the image above than the large tan one (you can check out photos of them here).

For many people the response to this is a shrug of the shoulders, but the effects of these beetles going missing had a tremendous effect on the ecosystem, in particular on plant growth and distribution.  We don’t know, and probably will never know how great an effect their absence had.  Dung beetles, the Scarabaeinae, are extremely important ecosystem engineers, gathering fresh dung and burying it as a food source for their developing young.  By doing so they fertilize and aerate the soil, speeding up the cycle of nutrient return by putting the nutrients in a safe place where the plant roots can get to them and where they are less likely to be washed away by rain or desiccated by the sun and blown away.  In addition, dung beetles are important in limiting the spread of diseases and parasites by removing fly and pest breeding sites.

Understanding the details of the world, the interactions, the interconnectedness, the causality of it is difficult.  When we look at the present we have the fine resolution, but lack a context.  When we look at the past we establish a context, but lack the fine scale resolution.  When we look to the future, as we must, we need to be able to combine the insights of the past and the present to predict the consequences of our actions.

Hopefully we are getting better at this, but I cannot help but look at connections like that between the mammoth, dung beetle, the dire wolf, the distribution of plants, and the radiating effects of that interleaving and wonder what vital link, or set of links, we are failing to see right now and what what will mean for our future.

The Archives at the La Brea Tar Pits

Archives at the La Brea Tar Pits

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Apologies for the multiple posting.  I made an edit using the WordPress App on my iPad and it deleted the original post.  I had to restore it and repost.

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California Condors, Megafauna, and Trophic Cascades

A long time ago I worked as an archaeologist near Santa Barbara.  I spent most of my days in the field excavating Chumash sites, recording evidence of looting, drawing maps, and hunting for unknown sites.  It was a fun job, I learned a lot, and it was my first exposure to California Condors.

The Chumash left behind a repository of exquisite petroglyphs, painted and carved into the soft sandstone that makes up much of the Transverse Range, an east-west oriented set of coastal Southern California mountains.  One of my jobs was to preserve this rock-art.  In the dust that makes up the floor of the caves and shelters the art is painted lives a bacteria that eats the organic pigments in the paint used by the Chumash.  Visitors would unwittingly kick up the dust, spreading the bacteria and speeding up the degradation of the rock art.  At several sites we paved the floor with stones to trap the dust.  One of these sites was Condor Cave in the San Rafael Wilderness; I’m sure you can guess how it came by that name.

Condor art at Condor Cave – from http://www.parks.ca.gov

It wasn’t until several years later I when was backpacking in the Ventana Wilderness with a friend that I saw my first wild California Condor.  We stopped and sat, mesmerized, watching five large birds swoop and soar around us.  Of course my camera was acting up at the time and the only photos I got were pathetic to say the best.  The experience stuck with me, all the more so because I had been studying anthropology and repercussions of the North American megafauna extinctions.  

About a week ago I was driving from San Francisco to Los Angeles along HWY 1.  It was one of those spectacular California days where the coast is shrouded by pockets of thick fog broken by regions of bright sunlight and the Pacific Ocean lives up to its name lying tranquil in its bed.

Sun, fog, and kelp-beds along the coast between Morro Bay and Big Sur

Sun, fog, and kelp-beds along the coast between Morro Bay and Big Sur

This stretch of road is made up entirely of corners and as I rounded one I saw a pocket of people pulled over in a turn-out looking up at something on the hill-side.   I caught a glimpse of a large bird on the slope, pulled over at the next turn-out, grabbed my camera, and jogged back to find a very calm California Condor sunning itself in the late afternoon light.

California Condor soaking up the last of the sunlight

California Condor (Gymnogyps californianus) soaking up the last of the sunlight

The California Condors are in rough shape.   DDT, hunting by mis-informed ranchers who believe that condors killed calves, egg collecting, habitat loss, and lead-poisoning are all implicated in modern times for the low numbers of  the California Condor (Gymnogyps californianus).   Additionally, these long-lived birds have small clutch sizes (few eggs per breeding cycle) and reproduce extremely slowly; so slowly that a 1996 study by the Fish and Wildlife department found that it would take 1800 years at the current population growth rate of 1.0003 to achieve a stable wild population of 150 individuals.  This low population growth rate is part of why there is a captive breeding program.

California Condor (Gymnogyps californianus) in the Los Padres National Forest

California Condor (Gymnogyps californianus) in the Los Padres National Forest

In historic times the California Condor ranged from British Columbia to Baja, but during the 19th century its range was rapidly diminished to include only California.  Through captive breeding and release strategies the range has been re-expanded and now includes Arizona, northern Mexico, and a little of Utah, in addition to California.  These birds have what is known as a “relict distribution”, that is, they occupy only a fragment of their former range.

California Condor range map - from: IUCN Redlist http://www.iucnredlist.org/

California Condor range map – from: IUCN Redlist http://www.iucnredlist.org/

 

While it is certainly true that lead poisoning, DDT, and all the rest have been massively detrimental to present day condors this overlooks a very important aspect of the condor niche.  These are large birds, the largest flying birds in North America, with up to a 9.5 foot (2.9 me) wingspan and weighing up to 23 pounds (10.4 kg).  These birds are meat eaters and they need a lot of meat.  The historic population was highest along the coast, where aquatic megafauna would, and still does wash up on the beach.  Beached whales, elephant seals, sea lions, dolphins, seals, and large fish may be disturbing to see, but they provide a wealth of food for bears, foxes, coyotes, weasels, wolves, eagles, gulls, ravens, and condors.  It is true that there are still large gatherings of sea mammals along the coast, but it is also true that there are far fewer of them than there used to be and this has imparted an additional stress to the condors, among other species.

Northern Elephant Seals (Mirounga angustirostris) on the California Coast

Northern Elephant Seals (Mirounga angustirostris) on the California Coast

For birds further inland other sources of meat were, and are important.  Terrestrial megafauna is what fed and feeds inland condors.  We have nowhere near the diversity nor the biomass of large free-living terrestrial animals than we did even a few hundred years ago, let alone what we had when humans first arrived in North America.  Shortly after the arrival of humans most of the large animals, the megafauna (generally being defined as an animal with a body-mass greater than 100 pounds (45 kg) began going extinct.  The giant beavers disappeared, the mastodons vanished, the giant sloths, camel relatives, giant tortoises, horses, and various species of deer were wiped from the continent, and along with those animals also went other animals that relied upon them; dire wolves, saber-toothed cats, short-faced bears, American lions, American cheetah, tetratorns (think condors on steroids), dung beetles, and condors.

Tule Elk (Cervus canadensis ssp. nannodes) being restored to California grasslands

Tule Elk (Cervus canadensis ssp. nannodes) being restored to California grasslands

There is vociferous disagreement as to why the megafauna went extinct, but many, if not most, scholars believe that humans hunted these animals to extinction.  Humans arrived during an ice age and the rapid change in climate (rapid in an evolutionary sense) may have placed the animal populations in a position where enthusiastic hunting had a greater impact than would be otherwise expected; but whatever the exact details the short story is that humans arrived and within a few thousand years a majority of the megafauna went extinct.  This triggered what is known as a “trophic cascade”.

You can think of an ecosystem as being analogous to a game of Jenga.  All together the blocks form a solid tower, but as you remove blocks (species) the tower (ecosystem) becomes more and more unstable.  Eventually one too many blocks is removed and the whole structure comes tumbling down.  In essence, this is what a catastrophic trophic cascade looks like.  So many animals were removed from the ecosystem that now, eleven thousand years later, we are still seeing some of the effects.  Just as blocks you never touched in the Jenga game come tumbling down, species of plants, insects, and animals that were never hunted went extinct or had their life patterns radically altered.  Some plants lost their ability to disperse their seeds, forests and grasslands were no-longer grazed as heavily and the composition of species changed drastically, watersheds and rivers changed their patterns, soils changed as they were walked upon by different animals with different behaviors, concentrations of bacteria and fungus changed, altering soil and groundwater chemistry.  Trophic cascades are a big deal.  They are ongoing, but operate in the background, running smoothly and unnoticed until something breaks the chain of events and the whole tower of blocks comes tumbling down.

The current narrow range of Condors is due, in part to the cascading effects of the megafuna extinctions and more recent changes brought by colonizing Europeans.  We know from the fossil record that prior to the megafauna extinctions several species of condors lived in North America over a range that includes the historic range of the California Condor and stretched across the southern states and up the east coast to New York.

Prehistoric US fossil sites for North American condors, courtesy of the San Diego Zoo library

Seeing the California Condors in the wild is like catching a brief glimpse into the distant past, a time when North America had wildlife diversity to rival that of Africa.  The fate of the condors is far from certain.  They are from a time and place that no-longer exists and it remains to be seen if they can adapt to the world as we have made it, even with our assistance.  I hope the condors do succeed, the world is a richer place and better place for their presence.

Preening in the late afternoon sun

Preening in the late afternoon sun