Biological Weapons

About a year ago I started writing occasional articles for the Entomological Society of America’s website “Entomology Today.” These assignments prompted me to delve into some biology I might not have otherwise and it has been so much fun. I’d like to share my entomology articles with my blog readers by posting links to them here. If you are interested, check out what I am doing over there. I hope you enjoy it.

Here’s a look at the diabolical biological weaponry predators and parasites use against one another. Click on the killer photo by entomologist and photographer extraordinaire, Alex Wild, to read the article.

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Biological Weapons

Colorado Ivory

 

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Elk ivories, which are technically vestigial tusks, are small– just over an inch long including the root. Photo by Meredith Swett Walker

 

Elk hunting is a big deal in Colorado, and while many hunters are primarily interested in harvesting an elk for its meat, some hunters are after a trophy bull. Trophy elk are scored based on how large their antlers are and how many “points” or tines they have on each. But if humans had been hunting for trophy elk 25 million years ago or so, they would have been after the animal with the largest tusks, not antlers.

 

Elk are members of the deer family, and while modern male deer are noted for their antlers, prehistoric deer lacked antlers, but had tusks instead. Tusks are technically teeth (usually canine teeth), but are distinctive in that they grow continuously and protrude from the mouth. Today’s elk still bear remnants of their toothy past. Partially hidden in the upper jaw of both male and female elk are vestigial tusks, more commonly known as “ivories.”

 

An elk’s ivories are actually canine teeth. They are not large­– less than an inch of the tooth is exposed in an adult elk– and they aren’t used in chewing. There is no corresponding tooth on the lower jaw for them to make contact with, but they do wear down some over time. While some elk ivories are pearly white, others are stained deep brown by tannins in the plants the elk eats and digestive juices. (Elk aren’t known to use Crest Whitestrips®.)

 

The term “ivory” technically refers to animal tusk material used in art or craft. Humans have used elk ivories to make jewelry and decorate other goods for centuries. Among many Native American tribes, ivories were used to adorn women’s dresses and were a symbol of prosperity.

 

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A Kiowa couple, Eonah-pah and his wife Alma, photographed in the late 1870s by William S. Soule. Alma is wearing a dress decorated with elk ivories.

 

In the late 1800s and early 1900s elk ivory became very fashionable and the teeth were used to decorate watch fobs, the short chains attached to pocket watches. At that time these watch fobs were an unofficial symbol of the Benevolent and Protective Order of Elks (B.P.O.E.), a fraternal order and social club still active today and commonly known at “the Elks.” But elk ivory’s popularity led to a spike in prices for the teeth, which in turn created an elk poaching problem. In 1907, in an effort to stop the poaching, the B.P.O.E spoke out against the use of elk ivories for jewelry and helped establish the National Elk Refuge in Wyoming.

 

While humans use elk ivories for adornment, elk use them in a manner that recalls a time when these teeth were much more impressive– they use them to threaten their rivals. An angry elk will sometimes curl its upper lip in a “sneer display” that reveals its vestigial tusks.

 

It is thought that as ancient deer evolved antlers, they lost their tusks. Only a handful of modern species of deer and deer-relatives still bear prominent tusks. Chinese water deer, muntjacs, and tufted deer, are all relatively small species that live in Asia and still have tusks. These species generally lack antlers. With their diminutive size, big brown eyes and large fang-like tusks, these deer almost look made-up, like Bambi masquerading as a vampire for Halloween.

Siberian Musk Deer
Siberian musk deer live in Northeast Asia. This is a small deer, weighing less than 40 pounds, but it sports impressive tusks. Photo by Николай Усик.

 

Scientists are not entirely sure if any of the prehistoric deer that moved into North America from Asia many millions of years ago had tusks. Most of the fossil remains that paleontologists have found so far are incomplete. According to Dr. Darrin Pagnac, a paleontologist at the South Dakota School of Mines who studies ancient grasslands and the herbivores that grazed on them, “The earliest ‘deer’ in North America is Eocoileus, from the late Miocene (7-5 million years ago).  All we have of it is a partial antler and the back of the skull.  No teeth, so we can’t tell if it had canines or not.”

 

Whether or not any tusked deer ever roamed the plains of North America, elk ivories are a reminder of ancient times, when the wildlife on our continent looked very different than it does today. Once upon a time prehistoric cheetahs and camels roamed here. Giant sloths, weighing a ton, browsed on leaves and the giant beaver, who was over six feet long, presumably cut down really big trees. As magnificent as elk and Colorado’s other wildlife is today, the creatures of the past may have been even more impressive.

This article first appeared in the November 21, 2015 issue of the Grand Junction Daily Sentinel.

Colorado Ivory

Why Does the Three-toed Woodpecker Have Three Toes? (Or: Questions that distract me from things I ought to be doing)

Three-toed Woodpecker (Picoides dorsalis) by Luis Agassiz Fuertes
Three-toed Woodpecker (Picoides dorsalis) by Luis Agassiz Fuertes

Yesterday I got out for my first cross-country ski in an embarrassing number of years. The occasion was a birding field trip on the Grand Mesa organized by my local Audubon Society chapter- the Grand Valley Audubon Society. The weather was overcast with light snow falling- it made for great skiing conditions, but the birds were lying low. We heard some chickadees in the distance and got a glimpse of what might have been a junco darting into the base of a spruce. I only got a good look at one bird, but it was a great one: an American three-toed woodpecker.

This woodpecker gets its name because it has- you guessed it- three toes. Most birds have four toes- three toes pointing forward and the first toe, or hallux, pointing backward. This arrangement of toes is called anisodactyl. Most woodpeckers also have four toes but in a slightly different arrangement. Their first and fourth toes typically point backward with the second and third toe pointing forward. This arrangement is called zygodactyl. But the American three-toed woodpecker has lost the first toe over the course of evolution and has only the fourth toe pointing backward with the second and third pointing forward. Okay, but why does the three-toed woodpecker only have three-toes?

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As a former ornithology TA, I felt like I should know the answer. After all I had enjoyed torturing undergrads with just this kind of trivia. I had other, much more pressing, work that I needed to be doing today, but my obsessive little mind kept circling back to Google search and dig around through old ornithology studies to find an answer. I feel I should share the answer I pieced together with the world. I am sure, somewhere out there in the vastness of the Internet, someone else’s freaky little mind is obsessing over the same question.

According to my informal investigation, American three-toed woodpeckers are not the only woodpeckers with only three toes. There is a Eurasian three-toed woodpecker that was once thought to be the same species as the American three-toed, but is distinct (Zink et al., 2002.) There is also one other species of woodpecker in North America that has three toes, the black-backed woodpecker. Apparently the first toe has been “lost” over the course of evolution in multiple lineages of woodpecker, but why? For a bird that makes a living clinging to the side of a tree with its feet, you would think losing a toe would be a disadvantage. Not so according to an analysis by Walter J. Bock. Bock (1999) used the “Method of Free-Body Analysis” to determine all the physical forces acting on the clinging bird. According to his analysis, the first toe does not supply much support in the clinging woodpecker. Even in woodpecker species that have not lost a toe, one of the rear toes usually points sideways when the bird is climbing, not backwards. The zygodactyl arrangement of toes is ancestral and is advantageous for perching with the foot wrapped around a twig rather than clinging to the side of a trunk. For instance, parrots, old-world cuckoos and some owls all have zygodactyl feet and they do not typically cling to the sides of trees. When a bird is clinging to the side of a tree, the toes doing most of the work are those that are opposing the force of gravity- the forward facing ones (or toes two and three.)

So if over the millennia a woodpecker were to be born without a first toe, it would not be at a disadvantage. Perhaps it might even be advantageous in some way? Weight reduction perhaps? This three-toed mutation could be passed on to its offspring and eventually become the norm for the species. Losing a digit has happened many times and by various mechanisms in the evolution of vertebrates (Cooper, 2014.) Perhaps someday humans will be exploring a future version of the Internet minus a pinkie finger. Of course, in the distant future (if we haven’t driven ourselves extinct, or become enslaved by artificial intelligence) we probably won’t need fingers at all- we will control everything with our freaky little minds.

Bock, W.J. (1999) Functional and evolutionary morphology of woodpeckers. Ostrich 70 (1): 23-31.

Cooper, K.L. et al. (2014) Patterning and post-patterning modes of evolutionary digit loss in mammals. Nature 511: 41-45.

Zink, R.M. et al. (2002) Holarctic phylogeography and species limits of three- toed woodpeckers. The Condor, 104(1): 167-170.

 

Why Does the Three-toed Woodpecker Have Three Toes? (Or: Questions that distract me from things I ought to be doing)