Category Archives: Animals

I am a paleontologist

I love the science of paleontology for many reasons. The science combines so many other areas of study into one bundle, such as geology, biology, functional morphology, evolution, stratigraphy, and systematics.

Not only that, dinosaurs and other prehistoric animals are just fun! And being fun, paleontology is a great way to introduce people to science in an engaging way. How many young people start their interest in science by learning about dinosaurs, and say they want to be a paleontologist when they grow up–a bunch!

Well, someone shared this video with me and I love sharing it with you. Enjoy! (you may need to scroll down).

Dangerous animals—spiders

In this installment of the Dangerous Animals series we look at a group that is very misunderstood, and often erroneously indicted for being dangerous—spiders. In the summary chart of dangerous animals, summarized from various sources, spiders are accused of causing 6 deaths a year, on average, in North America. This is more deaths than caused by bears, mountain lions, and wolves combined, and I am highly suspicious of the figure.

In his review of the Centers for Disease Control and Prevention (CDC) data, Langley (2005) summarizes death by all sorts of wild animals, and spider bites have their own classification code, suggesting that the medical community has decided it is worth watching for. For example, the data suggest that between 1991 and 2001 there were 5 fatalities by alligators, and a whopping 66 deaths by spider. People seem to be dropping dead left and right from spider bites. What gives?

In North America, there are two types of spiders known to cause medically significant envenomations in humans: the widows and the recluse. Let’s look at each.

Latrodectus, the Black Widow

Latrodectus, the black widow, showing a characteristic pose, upside down in the web.

There are currently 30 species of spiders within the genus Latrodectus, commonly called widows in North America. The species are distributed world-wide and are on every continent except Antarctica. The venom of the widow contains neurotoxins that inhibit neurotransmission. The spiders like dark and quiet places, with bites occurring when people unintentionally grab or sit on the spider, perhaps under a porch, on lawn furniture, in the tool shed, or in gloves or other item clothing. In the past bites sometimes occurred in outdoor toilets. Symptoms of bites tend to be local and radiating pain, and sometimes back, abdominal, and chest pain, sometimes accompanied by fever, agitation, hypertension, and interestingly, priapism (Vetter and Isbister 2008). People have described it to me like a case of the flu. Untreated, symptoms can last from hours to days. Despite their infamy, death is very uncommon.

Loxosceles reclusa, the Brown Recluse

Loxosceles reclusa, a Brown Recluse female guarding her egg sac on a cardboard box in Kansas.

Few spiders generate as much passion and aversion as the brown recluse (Loxosceles reclusa). I currently live in an area where black widows are extremely common, and local people are very casual about them, but are terrified of the brown recluse. I have done many educational programs where I have displayed live spiders, including black widows, and unvaryingly I am treated to several stories by visitors about how they (or someone they know) were bitten by a brown recluse, usually with very bad consequences. (I literally had one person tell me that his aunt had her entire arm removed because of a bite). The thing is brown recluse spiders do not live here! Nothing generates fear like the unknown.

Prior to living where I do now, I lived in an area with gobs of brown recluses, and the people there were generally nonchalant about their presence, as there were almost no cases of bites resulting in horrible wounds.

Distribution map of species within the genus Loxosceles, including Loxosceles reclusa, or the Brown Recluse (from Vetter 2008).

To be clear, Loxosceles is confirmed to have bitten people and caused wounds that in rare cases take a long time to heal and can leave disfiguring scars, or even death. They are a spider of medical concern. But, having said this, the threat is far over blown.

They are named “recluse” because they like very quite areas, and can frequent homes and storage sheds in quite places. They like corners of basements, and particularly cardboard boxes. Sometimes they crawl into clothing and shoes left on the floor or in the closet. Like with the widows, people are most often bitten when they catch the spider between their body and where the spider is—the bite is defensive.

In a majority of cases, the bite results in local discomfort and nothing more. In some cases a larger wound forms that is tender, but most of these heal with minimal medical intervention, usually within days. Sometimes the wound heals slower, and in rare instances does grow large and can leave a scar. And in very rare cases (<1%) there are more significant systemic issues that can affect major organs and cause death. (Vetter and Isbister 2008).

As mentioned, I lived in an area with known recluse populations. In fact, in one case, 2,055 individual recluse spiders were captured in 6 months from one home in Kansas where the family lived for many years without a single incident attributed to the spiders (Vetter 2008). However, popular perception about these spiders is very different. Why is this?

The most likely explanation is that when the recluse was implicated in bites the most extreme cases got widely reported, heightening awareness in the public and medical community. Diagnoses of recluse bites have become common place, often in areas where the spiders have not been found in the wild, and usually without clear evidence that the symptoms presented were actually caused by a spider, or any other bite for that matter. For example, in Florida, an area without a known population of recluses, during a six year period, 844 brown recluse bites were reported: 124 by medical personnel, 198 by people seeking information about bites, and 522 from people reporting bites treated at a non-healthcare facility (Vetter and Furbee 2006). Physicians are thus occasionally guilty of “practicing Arachnology” by identifying bites, and even spider species, from clinical symptoms alone. The truth is, there are numerous conditions that have been, or could be, misdiagnosed as a recluse bite (Vetter 2008) (see below).

Given the obvious over-diagnosis and misdiagnosis of spider bites, and of recluse bites in particular, I find the assertion that 6 deaths a year in North America are caused by spiders to be highly doubtful. At the very least, this is an undeserved slam against our eight-legged friends, and at worst is misleading the public and medical community, causing potential misdiagnoses and poor treatment choices.

Conditions that have, or could be, misdiagnosed as a bite from a brown recluse (Loxosceles reclusa), from Vetter 2008.

Infections

Atypical mycobacteria

Bacterial

– Streptococcus

– Staphylococcus (especially MRSA)

– Lyme borreliosis

– Cutaneous anthrax

– Syphilis

– Gonococcemia

– Ricketsial disease

– Tularemia

Deep Fungal

– Sporotrichosis

– Aspergillosis

– Cryptococcosis

Ecthyma gangrenosum (Pseudomonas aeruginosa)

Parasitic (Leishmaniasis)

Viral (herpes simplex, herpes zoster (shingles))

Vascular occlusive or venous disease

Antiphospholipid-antibody syndrome

Livedoid vasculopathy

Small-vessel occlusive arterial disease

Venous statis ulcer

Necrotising vasculitis

Leukocytoclastic vaculitis

Polyarteritis nodosa

Takayasu’s arteritis

Wegeners granulomatosis

Neoplastic disease

Leukemia cutis

Lymphoma (e.g., mycosis fungoides)

Primary skin neoplasms (basal cell carcinoma, malignant melanoma, squamous cell carcinoma)

Lymphomatoid papulosis

Topical and Exogenous Causes

Burns (chemical, thermal)

Toxic plant dermatitis (poison ivy, poison oak)

Factitious injury (i.e., self-induced)

Pressure ulcers (i.e., bed sores)

Other arthropod bites

Radiotherapy

Other Conditions

Calcific uremic arteriolopathy

Cryoglobulinemia

Diabetic ulcer

Langerhans’-cell histiocytosis

Pemphigus vegetans

Pyoderma gangrenosum

Septic embolism

Related posts:
See the rest of the Dangerous Animals series
Pesky house bugs–bed bugs

References:

Langley, R. L. 2005. Animal-related fatalities in the United States–an update. Wilderness & Environmental Medicine 16:67-74.

Vetter, R. S. 2008. Spiders of the genus Loxosceles (Araneae, Sicariidae): a review of biological, medical and psychological aspects regarding envenomations. The Journal of Arachnology 36:150-163.

Vetter, R. S., and R. B. Furbee. 2006. Caveats in interpreting poison control centre data in spider bite epidemiology studies. Public Health 120:179-181.

Vetter, R. S., and G. K. Isbister. 2008. Medical aspects of spider bites. Annual Review of Entomology 53:409-429.

Maintaining the Horse Trailer

If you’ve ever owned a horse trailer then you know just what type of maintenance is needed to keep it in working order and safe for your equine friends to ride in. However, I have found many people who really don’t understand the necessity of routine maintenance. Horrible trailering accidents can easily be prevented with simple routine upkeep of the horse trailer. Hinges can break causing the door to swing open, possibly letting the horse fall out into traffic. I’ve seen accidents caused by flooring giving way or tires blowing out. While accidents can happen at any time, lowering the odds with proper maintenance is really easy to do. One of the best horse gifts that you can give to give your horse is a safe trailer to ride in.

If you’re not mechanically inclined there are many trailer servicing places in most metro areas that you can take your trailer into for a good once over. It doesn’t have to be a big fancy garage. In fact, one of the best places around here is a little Mom and Pop garage just past the place that always has the cheap draft horses for sale. There are some really basic things to have checked out. Checking that the wiring and trailer brakes are working properly is a must. Having the floor boards checked out is also a must. Most places are very good at getting the mats back in place correctly. They can also check the brake bearings and the tire tread and pressure. A good garage will check for rust and will offer to repair it for an extra fee. They will go over all the hinges and lube them if needed or repair them if they’re damaged. Checking the welds and outer shells for breaks, rust, or damage is often included in the basic service, though fixing such problems might entail an extra fee. Whatever garage you use, getting the routine yearly maintenance checks can end up saving your horse’s life.

Why dinosaurs are not extinct

In the twenty plus years I have been involved in paleontology I have been witness to a revolution within science. The revolution has been quiet, not noticed by most of the public. Like any good revolution, the battles of this revolution took place between two camps, the “traditionalists” and the “radicals” who were out to change things. And this shift is illustrative of how science as a whole moves from one way of understanding to a brand new way of looking at the world. It is, in fact, a paradigm shift that has profoundly changed biology and paleontology forever.

At issue is how we explore and classify the relationships of all living things. The traditional view, the one that I was taught as a young student, was the classification of living things into the taxonomy originally begun by Carl Linnaeus. This system started with a group, and then sought to put things into the group. For example, one can make the observation that animals that look like “dogs” could be grouped together, so you would start with the idea of a dog-group and look for animals that should be included.

You might put foxes, wolves, domestic dogs into the group, and call it the dog family. You might also note that “cats” could likewise be grouped, and do the same thing, creating a cat family. In this view, the families were equal in rank—and there could be no overlap. An animal would be included in only one of the equal-ranked families. Any animal was included in only one class, for example Amphibia, Reptilia, Aves, or Mammalia.

The equal-ranked heirarchy of classifications worked well enough when we mainly were concerned with modern animals. Clearly, birds look different than mammals and reptiles, so it seemed evident they belonged in their own class. But this classification scheme, however well it served us as a place to start, is myopic about how evolution actually operates—how organisms actually evolve. This is understandable since it was started 100 years before evolution as a theory was established.

In trying to shoehorn life into the system, we repeatedly ran into problems as we expanded our knowledge of the diversity of living things and our understanding that the history of life is a complex branching bush. We knew that early tetrapods (organisms with four limbs) gave rise to the early amphibians that crawled out on land, and that they in turn evolved into reptiles, mammals and birds. But despite this branching within tetrapods, the class ranks were forced to be exclusive, so somewhere in evolutionary history was an “amphibian” that had to become a “reptile,” and a “reptile” that had to become a “bird.”

The many transitional forms in the fossil record increasing became impossible to classify. These intermediate animals had to be forced into one class or another. Increasingly, it became evident that many times the criteria used to put an organism into one class were the whims of an individual scientist, and another equally qualified expert with different opinions might place the same animal in a different class with equal validity.

The origin of birds was for a long time a great mystery to paleontologists. Birds are a pretty unique and specialized group, and while we knew that they originated from reptiles somehow, exactly how and when was unclear. One early paleontologist noted that dinosaurs had many features in common with birds, but the early concepts of what dinosaurs were like distracted most scientists from comparing them too closely. After all, the common conception of dinosaurs was as big, lumbering, dim-witted, swamp-dwelling beasts. The bird ancestor must have been light, fast moving, and energetic.

However, dinosaur research over the last thirty years has completely changed our view of them. Evidence from many lines, including things like footprints and the cellular structure of the bones, all point to dinosaurs as being very dynamic creatures. With this new view, the notion that birds were linked to dinosaurs became clear too. Now, we have dinosaur fossils with feathers, and birds with teeth and dinosaur tails to attest to their close relationships. In fact, birds are most closely related to the meat-eating raptor-like dinosaurs of Jurassic Park fame.

To go along with the revolution in our view of dinosaurs was that revolution in science that I mentioned above–the emergence of a new way to understand the interrelationships of life on Earth. This new model accommodated the myriad branching events that life actually experienced in order to produce the great variety of living things. So, instead of starting with a conception of the group and looking for members, this new concept looked at the branching patterns evident in life, and then sought to apply names.

Below is an illustration of the branching pattern of selected tetrapods, those vertebrates with four well developed limbs. As the first tetrapods gave rise to new and different groups, the branches split off. An early tetrapod gave rise to amphibians and the other animals above it on the chart (mammals, turtles, etc.). A later tetrapod developed traits related to the production of eggs and young that we recognize as the Amniota. Some of those early amniotes went off on an evolutionary trajectory that we can recognize as being the early mammals, and all the diversity that resulted from them. And so it goes up along the branches.

Branching pattern of the tetrapods, mostly the land vertebrates

We now explore the branches and can apply names to the groups that we find to be meaningful. For example, in the illustration below we can call everything in the box a reptile. Note that it includes things that used to be called reptiles, turtles, lizards, snakes, crocodiles, and dinosaurs, but now also includes birds.

Group that includes all the reptiles

Likewise, if we draw a line around the dinosaurs, they also include the birds. This view of life tells a more complete evolutionary history and retains the branches, letting the animals “fall where they will.” We do not pull birds out of their relationships and give them special consideration. Instead of birds being equal in rank with reptiles, they are included among them. This upsets the tradition that being a bird is somehow equally important to being a reptile, but better reflects the reality of descent, without forcing nature into earlier human conventions of naming and grouping. Of course, birds are a group within their own right, and we could zoom in to explore their branching pattern, but it does not change the group to which they belong.

Group of dinosaurs

This leads to another startling statement. Below I have highlighted the groups that are extant (still around today).

Groups of tetrapods that are alive today (extant)

Because of our grouping scheme, birds are included in the dinosaur group, so dinosaurs are not really extinct! They live among us today flitting about, singing their mating songs in the trees. It is funny how things can change in science. Twenty years ago scientists would have told you the dinosaurs were all extinct, and today we say the opposite. I love scientific progress–it can be so startling.

Dangerous animals–Sharks

We can all hear the ominous music, building slowly, frightfully, until the climax when Jaws attacks! Movies like Jaws have burnt this fearsome group of animals into our psyche, and I think the thought lurks somewhere in our minds whenever we visit the ocean that there are really big fish out there. There are somewhere around 440 species of shark worldwide. They are an ancient group of fish, whose overall lineage dates to before the Age of Dinosaurs. Of these hundreds of species, only 4 are known to have been involved in a significant number of fatal attacks on humans. Worldwide there is an average of 4.3 fatalities per year.

The four most dangerous species have different habits, and therefore the patterns of attacks and their danger to people are different. They are the great white shark (Carcharodon carcharias), oceanic whitetip shark (Carcharhinus longimanus), bull shark (Carcharhinus leucas), and the tiger shark (Galeocerdo cuvier).

Great White Shark

The great white, of Jaws fame, is a fearsome predator. Adult sharks are 12-17 feet in length. They are found along both coasts from Mexico into high latitude waters of Alaska, and along the east coast up to Hudson Bay. However, it is also known from deeper ocean waters, and new findings suggest that at least the west coast populations congregate in the open ocean between California and Hawaii for parts of the year. They are predators of marine mammals, turtles, large fish, and even whales. Humans are incidental targets.

During the hot summer of 1916, the Jersey Shore was the scene of a series of attacks that shuck the public, and was the inspiration for the book Jaws. Between July 1 and July 12, four people were killed. The great white is often blamed, but it could have also been a bull shark. Why there were so many attacks at that time is hard to say, and has not been repeated since.

Oceanic Whitetip Shark

The oceanic whitetip shark is actually responsible for more fatal attacks on humans than all other species combined, and it does not even frequent the coasts. It is found worldwide, and prefers warm waters and deep ocean areas. It is the unfortunate events of the twentieth century that allowed this shark to become superlative in human fatalities—it is the shark reasonable for attacks on survivors of shipwrecks and downed aircraft. During the war in the Pacific, when ships and planes were regularly shot down, many hundreds of stranded sailors were attacked and killed. Horrific stories from survivors testify to this gruesome bloodshed and led to much research by the Navy in shark repellents. Hopefully, this scale of human carnage will never occur again. And while this species is the most deadly shark, its habits make it of little concern to the average beach-goer.

Tiger shark

The tiger shark is found worldwide in mostly equatorial waters. It prefers tropical and sub-tropical warm water, and does not get into the high latitudes like the great white. It tends to stay in deep waters that line reefs, but it does occasionally move into shallow water and channels where it might encounter people. This shark is large, commonly attaining lengths of 10-14 feet, but because of its habits encounters with humans are relatively rare.

Bull shark

In contrast, the bull shark is likely the most dangerous species to humans overall. It too is common in warm waters along coasts, but it also tolerates fresh water, and can migrate into rivers. They have been found far up the Amazon River in South America, and as far north in the Mississippi River as Illinois (yikes!) (Thomerson et al. 1977). These sharks are unpredictable and are often aggressive, and because of their habit of being in shallow waters are probably responsible for the majority of near-shore attacks.

However, having said all of that, the chances of being attacked are very remote. You can see the per year compared with other animals on the chart. Was that deep, ominous music I just heard?

Average number of deaths per year caused by various animals

Thomerson, J. E., T. B. Thorson, and R. L. Hempel. 1977. The bull shark, Carcharhinus leucas, from the upper Mississippi River, near Alton, Illinois. Copeia 1977(1):166-168.

Several of the images come from sources recommended in the Nature Wallpaper post.

Boneblogger: Science and the outdoors

Exploring the natural world