Author Archives: Greg

Dangerous animals—bears

Truth is stranger than fiction. The most recent human fatality caused by a bear took place in the wilds of Ohio. Well, sort of the wilds—just outside of Cleveland.

It seems that a young man, Brent Kandra, was tending to a captive bear when the bear attacked and killed him. The bear was owned by a man who has kept exotic animals for display in the past, and the event has sparked debate about the wisdom, and regulation, of large exotic animals being kept by private individuals (Associate Press 2010).

Whether in a cage or in the wild, bears are undeniably dangerous animals. This is the next in our series exploring dangerous animals. Unlike most of the other species we have looked at whose danger to humans is really more imagined than real, bears do come in contact with humans with some regularity, sometimes with unfortunate consequences.

In North America there are three bear species: the black bear (Ursus americanus); the brown bear (Ursus acrtos); and the polar bear (Ursus maritimus).

Black bear

Black bear in the Canadian Rockies

Like so many common names, the name black bear is really not very good since the animals are often many other colors than black. The fur comes in shades of blond, black, brown, cinnamon, and gray. Interestingly, the bears tend to be black in the eastern forests, and more color variation is introduced as you survey the populations to the west, such that in California most of the bears are brown.

The black bear is the smallest of the bear species, and the most common, with the widest current distribution. They are found across Canada and south through New England into the Appalachian Mountains. There are populations in the Ozarks and in the southern states. In the west they can be found through the Pacific Northwest, and through the Rocky Mountains south into Mexico.

Black bears are generally shy and reclusive, but they can become accustom to humans, especially when they learn to associate human activity with food—through trash or handouts. In many backcountry areas where bears are common officials try to keep bears and people separate, but it is not always possible. Food storage is a great concern when camping. For example, while camping at one remote location in the Great Smoky Mountains campers were to hang their food from a cable over a stream.

Hanging a food pack over a stream in bear country

Hanging a food pack over a stream in bear country

Incorrectly hanging your bag could lead to a bad time.

Results of improperly hanging your food pack

Results of improperly hanging your food pack

Brown bears are similarly misnamed, although the color variation is less dramatic than their black bear cousins. There are several subspecies, or races, of brown bears that you may have heard of, dividing them into coastal Kodiak and inland grizzly populations, but they are all the same species.

Brown bear

Brown bear

While once much more wide-spread in their distribution, brown bears are limited today to Alaska and northwest Canada, with several populations in western United States parks such as Glacier and Yellowstone.

Encounters with polar bears are understandably rare given the remoteness of their habitat. (See why polar bears are sensitive to climate change.) Polar bears spend much of their time out on sea ice, hunting seals. However, unlike other bear encounters, most encounters between humans and polar bears seem to be motivated by predation—that is, the bear is looking to eat them.

Bear encounters do sometimes lead to injury or even fatalities, and as people spend more time in bear country, the chances for an encounter naturally go up. In encounters that go badly, injury is more common than fatality as bears most often attack when they feel threatened, and once the threat is over they tend to leave. Rarely do bears prey on humans as a food source, but it does happen. In general there are about 1.8 bear-caused fatalities per year (see Clark 2003, Gunther and Hoekstra 1998, Herrero and Fleck 1990, Herrero and Higgins 1999 for discussions).

Of the dangerous animals discussed in the series, bears are the ones that most people need to be aware of, and to think about when entering the woods. Do not do stupid things in bear country, like walk around imitating the sounds of animals to attract bears (yes, it has happened), improperly store your food, try to feed the bears, get too close while taking pictures, or tease or taunt the bears. Common sense and awareness that these majestic creatures are sharing our woods will ensure that your adventures will have only the typical amount of excitement.

Associate Press. 2010. Bear who mauled caretaker is put to death in Ohio. NPR. http://www.npr.org/templates/story/story.php?storyId=129321688.

Clark, D. 2003. Polar Bear – human interactions in Canadian National Parks, 1986-2000. Ursus 14(1):65-71.

Gunther, K. A., and H. E. Hoekstra. 1998. Bear-inflicted human injuries in Yellowstone National Park, 1970-1994. Ursus 10:377-384.

Herrero, S., and S. Fleck. 1990. Injury to people inflicted by Black, Grizzly or Polar Bears: recent trends and new insights. Bears: Their Biology and Management 8:25-32.

Herrero, S., and A. Higgins. 1999. Human injuries inflicted by bears in British Columbia: 1960 – 97. Ursus 11:209-218.

Fossil tells a new tail

Mosasaurs lived in the world’s oceans during the Late Cretaceous, the last Period from the Age of Dinosaurs (see the geologic time scale). They are close relatives of modern snakes and lizards, and during the Cretaceous they become fully aquatic sea monsters, growing to tremendous sizes, and were the top predators of their environments.

Their fossil remains occur in great numbers in the marine chalk deposits of the Central Plains, and numerous specimens have been preserved in museums all over the world (see posts on the chalk formation and on rock formations in general). Yet despite the great numbers of specimens collected, we still have much to learn about these great beasts.

For example, examination of their bones shows that they are elongate animals, with enlarged tails for propelling their bodies through the water. Their limbs are modified into flippers, useful in controlling the direction and orientation of their bodies in the fluid medium. So, it is clear that they are primarily tail-swimmers.

Early restorations based upon this evidence imagined a tail sort of like a modern crocodile, a thick tail that was slightly compressed laterally, making it taller than thick, but remaining relatively snake-like. Early restorations of the skeleton articulated the tail as a long chain of vertebrate, continuous from base to tip without any remarkable difference along the way.

Here is an illustration of the skeleton of the mosasaur Platecarpus from a classic work on mosasaurs (Williston 1898). Note the rod-like straightness of the back.

Mosasaur Platecarpus from Williston

Mosasaur Platecarpus from Williston

And here is an artist’s illustration of Tylosaurus, the largest of the mosasaurs, from Mike Everhart’s Book, Oceans of Kansas, showing the tail with a slight thickening near the end, but mostly being straight (Everhart 2005, recommended in the Boneblogger store).

Mosasaur Tylosaurus

Mosasaur Tylosaurus from Oceans in Kansas by Mike Everhart

However, frequently the skeletons of mosasaurs were found preserved in the rock with the last third of the tail bent downward, away from the main axis of the base of the tail. And this was not just found in a few skeletons, but it was found frequently enough that scientists speculated, at least in conversations with each other, that perhaps the down turned tip was not an artifact of preservation, but maybe meant something.

Well, a newly described mosasaurs fossil, which has exceptional preservation, provides the answer. This specimen collected in Kansas and now at the L.A. County Museum, preserves not only the bones, but also impressions of skin, impressions of internal organs, and even some of the body outline. The bones of the tail are clearly down-turned, giving the authors of this new study enough confidence to state what has been quietly talked about before—mosasaurs had a bi-lobed tail fluke (Lindgren et al. 2010).

Mosasaur Platecarpus

Mosasaur Platecarpus showing revised body outline

It only takes a single fossil to help overturn past notions about prehistoric life. The next big discoveries are out there, in the rocks and sitting in the museum drawers, waiting to be examined in detail. What will we find next?

Everhart, M. J. 2005. Oceans of Kansas: A Natural History of the Western Interior Sea. Indiana University Press, Bloomington.

Lindgren, J., M. W. Caldwell, T. Konishi, and L. M. Chiappe. 2010. Convergent evolution in aquatic tetrapods: insights from an exceptional fossil mosasaur. PLoS ONE 5(8):e11998.

Williston, S. W. 1898. Mosasaurs. University of Kansas Geological Survey 4(1):81-347.

Science in dinosaur movies: Jurassic Park, then and now

The 1993 movie Jurassic Park, based on the book by Michael Crichton and directed by Steven Spielberg, is seen by most enthusiasts as the best dinosaur movie that Hollywood has produced. It set a high-water mark in the genre for many reasons: it took dinosaurs seriously as a topic, and did not portray the animals simply as ridiculous extras; and the movie was amazing for its visual effects. For any movie from Jurassic Park onward, your dinosaurs had better look real, scary, and believable.

Jurassic Park was also important in that it showed dinosaurs more or less accurately, consulting with real paleontologists in its making, and working to utilize the latest and greatest views on dinosaurs. This is not to say that they did not put in a Hollywood spin, or as I have called it in the past, “Spielbergize” some of the dinosaurs, but as a paleontologist I could really see that the ideas were not completely out of the blue. In fact, Spielberg foreshadowed some of the findings about dinosaurs that were to come.

I want to review some of the key features of Jurassic Park as they were thought of in Hollywood in 1993 and compare that with the state of the art today.

Dinosaur DNA

The entire premise of Jurassic Park is that DNA from extinct species was collected and cloned in order to bring the animals back to life. Are we any closer to being able to do this? Well, not really.

The complete DNA code of any single species is very long and complex, and it is very unlikely that any DNA molecule will survive intact for millions of years. We cannot even clone species that are modern or recently extinct with much success, and we have access to their DNA. The technical difficulties of getting DNA intact, knowing how to put that DNA together on chromosomes, knowing how to trigger the genes on the chromosomes to turn on and off during development, means that even if we could somehow get a complete dinosaur DNA sequence, we could not make a living animal.

However, there have been some amazing advances in molecular paleontology, where protein fragments and amino acids have been shown to be able to survive within fossil bone for an extraordinarily long time, much to the surprise of scientists who assumed that fossilization would destroy the tissues at the molecular level. Making predictions is difficult, especially about the future. Who knows what discoveries await us, but for now, the current best answer is that we will never be able to clone a dinosaur. (See Mammoth protein designed to be cool for more on molecular paleontology).

Excavation Scene

Early in the movie we are treated to a scene of a paleontology excavation as modern paleontologists dig into the past to understand dinosaurs. As with any profession, portrayal in a movie is not often close to reality. Cop movies do not realistically show what it is like to be a cop. Lawyer and doctor movies stretch the true on those professions, and the excavation scene was the one where me and my professional colleagues got a good laugh.

We see the field crew effortlessly dusting sand away from crisp fossil bone. We see the team firing off seismic charges to send waves into the rock to visualize complete dinosaur skeletons underground, just waiting to be effortlessly dug out. Oh boy. This is so far from the truth.

We cannot simply use a type of remote sensing technology to visualize unexposed fossils, however there are a few technologies that people have tried to use. Sometimes the minerals that fill fossil bone have a higher concentration of radioactive elements, and so mapping the concentration of radioactivity over a site has helped to locate concentrations of fossils in those cases.  There is a technology called ground-penetrating radar which under certain circumstances could be applied to fossils, but its use is limited. The main problem with both of these techniques is that to find fossils underground, you have to be able to tell them apart from the surrounding rock, and too often the fossils are very similar to the rock that encases them.

Fossils are still found the old fashioned way—by looking for bones weathering out on the surface, and digging around them in hopes that something more is there.

And of course, it is not as simple as dusting them off. Fossils are often enclosed in a hard matrix of rock, which can take many hours of tedious labor to remove. Frequently in the field the fossils are exposed enough to understand how they are laid out, and then removed in giant blocks to be worked on back in the museum lab for the next several years.

Velociraptor

The undeniable stars of the movie were the “raptors.” As shown, they were cunning and relentless killers, bent upon creating havoc for their human character counterparts. In the movie, the velociraptors were shown to be about as tall as an adult human and perhaps 12 feet long nose to tail. That was an exaggeration to say the least.

Real velociraptors have been excavated in Central Asia, and are not known from North America as fossils. However, there are Velociraptor relatives known from this continent. But in life, real velociraptors were only about half the size shown in the movie, maybe the size of a mid-sized dog.

However, Spielberg did not know it, but his velociraptors did not have to be exaggerated in size if he had just said that they were a dinosaur species that was discovered in 1991, and named in 1993—Utahraptor (Kirkland et al. 1993). The same year that Jurassic Park was released also saw the emergence of Utahraptor, a dinosaur that much better fits the dinosaur shown on film. It was discovered in North America, as was suggested for Velociraptor in the movie, and was the size of the animals shown in the film. So, in a way, Spielberg was showing a real dinosaur, just not the one he thought.

Tyrannosaurs Running

It might be a close call as to which was more popular in the movie, Velociraptor or the seminal favorite dinosaur Tyrannosaurus. Who did not thrill to see the giant animal trash Jeeps, eat lawyers, and run amuck? In a harrowing scene, tourists of Jurassic Park are chased at top speed by the Tyrannosaurus and only just manage to escape in their vehicle.

Could Tyrannosaurus almost outrun a Jeep? Well, likely not.

Large animals today do not run well. The heavier an animal is, the more force there is on the animal’s joints and bones, and running compounds the effects of those forces. Modern elephants cannot run, but rather trot. They can move quickly, but they are too large to achieve a full-scale run.

How to kill Tyrannosaurus

How to kill Tyrannosaurus, from Farlow, Smith, and Robinson, Journal of Vertebrate Paleontology, vol 15(4).

Likewise, tyrannosaurs were very large and heavy animals, and there are physical constraints based upon the strength of their bones and joints. And unlike an elephant, Tyrannosaurus supported all their weight upon two legs, teeter-tottered over their hips. Running would have placed tremendous stresses on the hip joint.

Also, unlike an elephant, the large head of a tyrannosaur was extended out over the ground, as much as 15 feet above the surface, and they did not have forelimbs of any size to speak of. This means that if they did get up to a significant running speed and were to stumble, their heads would fall with great force to the ground without any way to break the fall. In short, if they did run and fall they would bash their brains out on the ground. Running, in this case, would be fatal.

Venomous dinosaurs

In Jurassic Park, the dinosaur Dilophosaurus was portrayed as being able to spit blinding venom into its victim’s eyes. The suggestion that a dinosaur was venomous was groundbreaking. Earlier this year there was a report of the discovery of a venom delivery system in a raptor dinosaur, Sinornithosaurus (Gong et al. 2010), seeming to once again make Spielberg a paleontological prognosticator.

However, it does not seem likely that the interpretation of Sinornithosaurus as being venomous will stand up to further scrutiny. Secondary investigations of the fossils suggest that characters which were viewed as supporting a venom delivery system are actually not what they were first thought (Gianechini and Agnolin 2010), so it looks like we still have to wait to find a venomous dinosaur, much less one that can spit!

Jurassic Park stands as one of the greatest dinosaur movies. From a paleontology stand point, while the movie is fiction several interesting propositions were shown, and this is, after all, what drives our curiosity to explore.

Dinosaur movies at Amazon

References:

Gianechini, F. A., and F. L. Agnolin. 2010. A reassessment of the purported venom delivery system of the bird-like raptor Sinornithosaurus. Paläontologische Zeitschrift.

Gong, E., L. D. Martin, D. A. Burnham, and A. R. Falk. 2010. The birdlike raptor Sinornithosaurus was venomous. Proceedings of the National Academy of Sciences 107(2):766-768.

Kirkland, J. I., R. Gaston, and D. Burge. 1993. A large dromaeosaur (Theropoda) from the Lower Cretaceous of eastern Utah. Hunteria 2(10):1-16.

Related Posts:
Learn about dinosaur toys
Dinosaur excavation in the Purgatoire River Canyon

Effects of climate change on polar bears

Polar bears (Ursus maritimus) are in the news again because of dire predictions for the coming decades on their population numbers. The effects of climate change have been predicted to impact the polar regions first and most dramatically according to most models, and indeed, it is at the poles where we are recording some of the most dramatic examples of climate change. Polar bears, being the largest of the living bear species, are charismatic and popular, and because of the likely impact that climate change will have on them they have become a poster species for the climate issue.

polar bear

Polar bear, Ursus maritimus.

In a recent interview bear expert Andrew Derocher predicted that one population of polar bears (western Hudson Bay) could see its numbers drop too low to be viable within three decades (Yale Environment 360 2010). We have explored polar bears and their populations in other posts. Here I want to examine why changes in sea ice and warmer periods are such a concern for polar bears.

Polar bears evolved relatively recently, diverging from an ancestral brown bear population about 150,000 years ago (Lindqvist et al. 2010). There is a unique population of brown bears that live on Admiralty, Baranof, and Chichagof (ABC) islands of southeastern Alaska’s Alexander Archipelago. This population, called the ABC bears, is the closest brown bear relatives of the polar bears—early members of this population split off to live full time on the sea ice, evolving into the modern polar bear species. Thus, polar bears are an example of rapid mammalian evolution, undergoing morphologic changes such as elongated snouts, overall size changes, furry padded feet, and color changes, as well as social and metabolic changes to adapt to the rhythms of the arctic seasons.

It is their complex adaptations to living on the rugged ice that makes them most susceptible to changes in that habitat. They use the ice as a platform for hunting seals, as a habitat for finding mates and mating, and for traveling long distances. As the ice breaks up earlier in the spring, and re-freezes later in the winter, several weeks of prime hunting time are taken away from the polar bears. Today, they are able to spend almost three weeks less on the ice hunting than they were able to several decades ago. This is critical because after the ice breaks up for the year, the bears must fast until the next season, and longer times of open water means long fasting periods.

This can be critical for a female bear that must gestate her young, birth them, and begin to nurse them to a size large enough that they can accompany her onto the ice for hunting the next season. So, she is expending a great deal of energy in contributing to the growth of her young while fasting. If she did not build enough fat reserves the year before to withstand this metabolic marathon, she and her offspring will not survive into the following year. A few additional weeks of having to fast can be the difference between life and death.

The intimate connection that polar bears have evolved with their arctic habitat means that they are finely tuned to changes in that world. And with the effects of climate change appearing in the arctic regions first, they are in fact akin to the “canary in the coal mine,” a harbinger of things to come.

References:

Lindqvist, C., S. C. Schuster, Y. Sun, S. L. Talbot, J. Qi, A. Ratan, L. P. Tomsho, L. Kasson, E. Zeyl, J. Aars, W. Miller, Ó. Ingólfsson, L. Bachmann, and Ø. Wiig. 2010. Complete mitochondrial genome of a Pleistocene jawbone unveils the origin of polar bear. Proceeding of the National Academy of Sciences.

Yale Environment 360. 2010. For Hudson Bay polar bears, the end is already in sight. http://e360.yale.edu/content/feature.msp?id=2293.

Additional related posts:
Polar Bear Populations
Public Opinion and a Geologic Perspective on the Effects of Global Warming
IPCC

Aquarium Backgrounds Explored

So, you are looking at setting up an aquarium. Perhaps you have already looked over the essential advice page, and now want to look at aquarium backgrounds. How can you add some pizzazz to your set up, really making it attractive? A simple, or complex, background can give the aquarium a more finished look.

A really simple aquarium background can be made from an attractive piece of cloth attached to the back of the tank. This will help hide the tubes and wires that come off the tank. Cloth is simple and inexpensive. You can get unusual printed patterns, even mimicking natural textures, or go wild with colorful designs. Being inexpensive, you can change the background easily from time to time, and keep things fresh.

If you want something that looks a bit more finished consider a pre-printed adhesive background. There is a wide variety of images you can select from, including solid colors, reef scenes, and even cartoon characters like Sponge Bob. Sometimes you get a two for one deal with a printed image on both sides that you can reverse out. For example, one side might be a tropic reef scene, and the other might be a land scene for a terrarium, like this one offered by Amazon.

Finally, for a full three-dimensional background that gives true depth and interest to your aquarium, you could by pre-fabricated backdrops made out of Styrofoam. These are really only suitable for large fish tanks, but they really give your display that museum or professional aquarium look. You can get natural looking rock walls, Amazon tree roots, and individual rocks to make your own patterns. Overhangs in the water, caves, and crevasses provide a lot of depth as well as places for the fish in your tank to hide. However, these pre-made backgrounds are not inexpensive, generally starting at $200 and quickly going up in price.

Make your own background

There is another alternative if you are on a budget but are a bit handy, and that is to make your own aquarium background. It is not as hard as it might seem. A materials list is below.

How do museums and zoos get realistic looking rocks in their displays? This same way, and you can do it too. Start with a basic plan for your aquarium set up. Consider up front where you will put hoses, pumps, and heaters so you can leave room in your design. If you have some really interesting tree branches, you may want to incorporate that into the design. Be creative.

With the design thought about, get several sheets of thick Styrofoam from your local hardware store. Cut the foam to fit the back of the tank, and then layer several pieces, like blocks, to the background to create depth and basic texture. The pieces can be stuck together with a bit of silicone caulk. Be creative in giving texture, create overhangs and ledges. Think about the basic shapes of natural stone outcrops you have seen and mimic them. You may want to make sure the bottom of the design is wide enough that the final background is stable. This first step is just your basic landform so don’t worry too much about the details yet.

After you have a rough form, begin to shape the Styrofoam to remove the edges and give it a natural look. Gently brush it with a steel wire brush to rough it up, giving it a pitted surface all over. Use a hair dryer on the foam to melt it into different shapes, but do be careful that you do not catch it on fire. Your goal is to give it a weathered shape.

Next, you will create a firm surface over your basic form. Use ready mix Quickrete from your local hardware store, mix it up and cover your form. The concrete adds to the rock look. You can use a paint brush to dab texture into the concrete as well. You will want a relatively smooth surface, but some shallow texture is good.

Let the cement cure fully, a day or two is best. Now, it is time to add color. Use paints in earth tones, or whatever you like. Make sure you use 100% latex paint. This is so the paint has fewer chemicals that might later leach into the water and harm the fish. Remember, this is not like painting a wall in your house. It is more like layering on color to give it complexity and depth. First, give the surface a basic coat, often one of the darker colors in your palette. Then, dab on lighter colors in varying patterns to add interest. Try the tips of a paint brush, a sponge, a paper towel with paint, a rag—anything you can think of, just have fun.

Let your paint cure fully, again at least a couple of days. The last step is to seal the whole thing with an epoxy resin to seal in the paint and protect it from water corrosion. Epoxy is a two-part material with a resin and a hardener. They are mixed in order to create a chemical reaction which hardens the material. A word of caution—be sure to measure the amounts of resin and hardener and follow the directions for the ratios, AND be sure to really mix the hardener into the resin before applying. The biggest source of failure for the epoxy to set up is the incorrect amount of hardener or it not being mixed evenly. It will result in your epoxy hardening in spotty patches, and some areas might not cure at all.

Give the painted concrete side a detailed covering of epoxy. Be sure to get under your ledges and in caves. Let it set up for several days. Now you are ready to put it in your aquarium. You can use silicon to tack it back to the wall, then seal around the edges with silicone caulk. It helps keep water from getting behind your rock formation.

Fill your aquarium after the caulk has fully set and circulate the water for about three days. Do a complete water change and allow it to circulate several more times. This is to help wash out any toxins that are in the paints and epoxies before you set up with fish and plants.

Now, finally, you have your own custom aquarium background. It was a bit of time, but overall should not cost your too much, and you did it yourself! Much better than something you buy.

Materials list:
Several Styrofoam sheets for base, maybe of various thicknesses
Silicone caulk
Wire brushes
Hair dryer
Knives and other tools for shaping
Ready mix Quickrete
Paint, 100% latex in a variety of colors (3-4)
Brushes, sponges, rags, paper towels, for painting
Epoxy for sealing the surface

Other posts:
Aquarium stands, options and considerations
Wall aquariums and wall-mounted aquariums
Aquarium hoods