And it's a formidable task, because we grow up often with prejudices against snakes. So the way I go about it is to show people how cool snakes are. So just for starters, snakes move around without any limbs. And if you think that's no big deal, just get down on the floor, fold your arms up, and try to wiggle to the back door. You can do it, but you will be very slow and very inefficient and very awkward.
So imagine me eating a cheeseburger weighing say, pounds without carving it into pieces or using my hands to stuff it in my mouth. That's what some snakes can do. This is a moderately large meal for a snake. This is a picture taken in the wild in Costa Rica by Dan Jansen.
That's a, I'm guessing, 30 to pound boa constrictor about 10 feet long. Now she did eat that white-tailed deer fawn, which I'm guessing might have weighed 20 pounds, something like that. And actually, after she finished eating that fawn, she didn't look that stuffed. Remember that-- like this? She looked like an enlarged tube, but she didn't look that stuffed.
And I hope you'll agree it's a pretty impressive thing to do that. And the consequences are enormous. It's quite likely that this is something like a third of this snake's annual energy budget. So with just one risky foray, hunting expedition, so to speak, and swallowing event, this snake has consumed about third of its energy needs. Might have taken an hour to do so. Three times a year, and that's it, it's all set. It doesn't have to get out there and take risks and so forth. It's a very different way of living from being like a hummingbird or a shrew. So of course, the question is how can they do this?
And I'm going to teach you how they do it using a method that I developed about 30 years ago at Berkeley. And I'm going to show you how some 9-year-olds in Houston a couple of years ago showed me how to do it better. And the first thing you probably notice is that the lower jaws are not connected at their front ends, OK?
In most vertebrates, including us, during embryonic development, the two halves of the lower jaw fuse at the front of the jaws in a joint called the mandibular symphysis. And if you put your finger here, you can feel a little groove between two bumps. Does everybody feel it? It's really fun to do this in a room of about people.
And if any of you-- a few of us are old enough to remember an actor called Kirk Douglas. He had a very obvious mandibular symphysis, big groove here, you know? So snakes never make that. The second thing, which is a little less obvious but I'll show it to you, is that in most vertebrates, the lower jaw articulates with the skull. So if you put your hand on the side of your face right here and open and close your mouth, you can feel your lower jaw articulating at the temporomandibular joint with your skull.
But in snakes, the lower jaws aren't articulating with the skull, they're articulating with one or more long movable bones, in this case, two, that suspend the mandibles from the skull, OK? These two things together make possible incredible gape. And you can make a model of how this works-- a model you can show, by the way, to six-year-olds, so I've had whole classes of six-year-olds doing this-- with your own body.
So if you clasp your hands like this and hold them up to your chest, and imagine that you are a lizard's head. And when your lizard is hungry and wants to eat an insect, it opens and closes its mouth like this, OK? And when its mouth is open, the biggest thing it's going to eat has to go through this triangular hole right there.
Does that makes sense? So are you imagining you are now a lizard head? So if you're a snake head of the same size and you have no mandibular symphysis, and your jaws are connected to long swinging struts that hang out from the skull, you could open your mouth this big. Remember, it's the same head size, OK?
Tracks & Shadows Field Biology as Art: Harry W Greene: Hardcover: Powell's Books
So you can only eat something that goes through this hole, or you can eat something that goes through this hole. And that's a significant reason why snakes can eat such big food. There's one more thing that's a little more complicated and more difficult to explain. You probably know this, there are a lot of teeth up here. And if we were directly underneath looking up at it, you would see basically, two upper jaws, a right one and a lower one. But instead of being like this one continuous row of teeth like we have, it consists of two sets of bones. So this is the right upper jaw of a snake.
And this bone right here, called the maxillary, is the one we have teeth on. But snakes also have teeth down the middle rows like this. And this whole thing, unlike our maxillary bones, is highly movable. So it's actually suspended from the roof of the brain case. And it floats in the mouth like this. And it can move back and forth like this. And the way a snake eats is not to actually pull that deer into itself. We used to say that, and then somebody finally thought, how could it do that?
How could those tiny muscles in that head move that deer? And we finally realized-- it's kind of absurd how long it took to figure this out-- it doesn't have to move the deer. It just has to move its head. And that's what a snake does is essentially hand over hand-- so it opens one side, goes like this, pulls its head forward. And while it's pulling with the left side, the right side's opening, moving forward, putting the teeth in, and pulling that side of the head forward.
And it literally, hand over hand pulls its head over the big food items. Does that make sense? So you notice, that wasn't in my model. And that's because I only have two arms. I never figured out how to do it any better. And so a couple of years ago-- I have a friend who has a brilliant daughter named Sadie who really likes snakes.
And he's an amateur videographer, actually makes a whole second income just with his YouTube videos. And so we got this idea of going to her Montessori school and asking the kids how to do it better. And so I won't go into it, and I'm not going to show you the video now. But you can go to YouTube and see this. And basically, these kids invented this way to use two kids to be the head of a snake.
And so this is them doing it.
Review: Tracks and Shadows, Field Biology as Art
Sadie's being the upper jaws, and Kristy's being the lower jaws. Took just a little bit to get coordinated. There is a bit of confusion. But they finally got it, and it works really well. OK, if I'm trying to convince people to like dangerous snakes I think the next thing I have to do is be honest with them about the danger.
So there's a subset of nature lovers who think that we basically should minimize the dangers that animals pose to us, or the problems that animals cause for our livestock and so forth. And I'm not part of that group. I think to tell ranchers, for example, that wolves don't eat large ungulates is to assume that ranchers are stupid. And I can tell you ranchers are by and large not stupid.
So if I were trying to convince ranchers to like wolves, I would not start out telling them that wolves don't eat large ungulates. I'd start with the truth, and then move from there. And it's the same way with snakes. I don't think you can tell people that rattlesnakes and copperheads aren't dangerous. They kill people. It's all a matter of sort of circumstance. This is the tombstone of a young man who died at the age of It took him eight days to die. It would have been absolutely hideous death, right after the Civil War in south Texas.
On the other hand, this problem, as I would maintain, are most of the risks associated with the dangerous and large animals is relatively easily solved by research and education. So for most of the problems that spring from our potential conflicts with animals, we can figure out ways to ameliorate them, get them almost down to zero, get them down to tolerable levels. And certainly, that's true of snake bite in this country.
In this country, the average snake bite victim is a young male who's been drinking and picks up a venomous snake, OK? So it's not a hard problem to solve in the United States. In this country, the average snake bite victim survives, probably even without treatment. In this country, we know exactly why you would die from a rattlesnake or a copperhead bite, or even a coral snake bite.
And we know exactly what to do about that medical situation. So the truth is in this country, snake bite's essentially not a public health problem anymore of any significance. And it shouldn't keep us from appreciating snakes as parts of nature. The next thing that turns out to be useful is to try to get past the idea that these are objects of evil. Now this is an animal with no eyelids. It's an animal without sucking lips. So it's an animal without conventional, to us, facial expressions.
It's not an animal with which we easily empathize. And my experience is the way to get around this is to convey some details of the lives of individual snakes. And doing this has been enormously facilitated over the last 25, 30 years by the advent of a spectacular way for studying snakes in the wild. And that is to put a tiny radio transmitter inside them. Once you have a radio transmitter inside them, you can find the snake over and over again. And I was part of a year field study in Arizona where we did just that.
We made about 4, observations on 50 radio-telemetered black-tailed rattlesnakes. So this is a big adult male black-tailed rattlesnake, probably about four feet long, probably weighed about two pounds. A female would be about three feet long and weigh about a pound. There's actually a female in this picture. She's super female 21, my favorite snake in my whole life. And she's sitting right at the entrance that hole right there. You probably can't see her, because that's one of the things snakes do is try to keep you from seeing them.
But once we have a radio inside them, we can watch them all the time. Well, I could give a long talk just about the things we found out in 15 years of watching these animals. But I'm just going to tell you one thing, and that's that we discovered that they had maternal care.
Tracks and shadows : field biology as art
Prior to this field study, there had been observations of rattlesnakes and other pit vipers in the field with their babies, and it had always been dismissed as coincidence. It was always dismissed as oh, we just happened to come along when one had just had its young. And that's in spite of the fact in some of the accounts-- there were details in the written accounts that made it very clear they weren't newborn young. But by having these snakes with radio transmitters in them while they went through this very shy period of being pregnant, we could spy on them every day.
We could watch them all through gestation, from late March until late July when they gave birth. And then we could watch them continuously once they had the babies, all day long. We'd get up there before dawn, set up our spotting scopes, and we'd watch their interactions with babies. And it turns out what happens is they routinely stay with the babies. This species usually chooses a abandoned rock squirrel burrow as a gestation site, stays there for several months till it's ready to give birth.
Gives birth, but then even though the snake hasn't eaten in about 11 months, she sticks around for about 10 days during a very delicate period in the babies' lives, when they're getting ready to shed their first skin. So every morning, we'd go up there, and there'd be the female sitting outside the gestation site with the babies piled up on top of her. If you get too close, the babies zoom into the hole, and the mother starts rattling and backs in after. We did experiments later in captivity that shows that she's more defensive during this time attending babies than she is either before or after.
We did experiments that showed in captivity that mom and baby are mutually attracted from birth until the babies shed their first skin, and then the attraction is over. And in fact, because of these females we watched, especially super female 21, who was so unconcerned with our presence, we were able to show that the female sits and watches the babies shed their first skin. And so this is the morning of about 10 days after birth. Here's super female 21 watching.
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This is the first of six babies that comes out one by one and sheds its skin right in front of its mom. The next morning, there's six intertwined skins, no babies to be found. And when we follow 21's transmitter, we find her 40 yards away at a wood rat nest trying to get her first meal in almost a year.
Well, it turns out this being a good mom is a really big deal, OK? If anything will make people empathize with a rattlesnake, it's being a good mom. Now I want to take you back to about or '91, when I was still at Berkeley. And so I had a rattlesnake in a tube. It's a way we have safely handling venomous snakes.
And I was letting her touch it. And I was talking about how I had this pipe dream that one day-- not today, but one day-- things would change so much that people would actually sign up as eco-tourists to go see timber rattlesnakes at a den in the fall like they sign up to go see birds, you know? That was my dream. And I picked timber rattlesnakes, which don't occur in Berkeley, where I lived at the time-- but I picked timber rattlesnakes because at the time of the American Revolution, they were abundant in the eastern half of the US, very widespread, major large forest predator.
Ben Franklin wrote a very, very laudatory essay about the timber rattlesnake. And yet years later, it's endangered in most of the states in the Northeast, entirely because of human persecution, and despite the fact that it's essentially not a public health problem at all. So I thought if the day comes when we've changed our attitudes towards dangerous animals enough that people will sign up to go see timber rattlesnakes, then we're really getting somewhere. And Natalie wrote in the article, ah, yes, get my travel agent.
Like that'll be the day. So fast forward to , I moved to Cornell. Finger Lakes Land Trust was buying Steege Hill across the river near Corning specifically to preserve a timber rattlesnake den. And they had a series they called "Talks and Treks" in which somebody would give a talk on a Thursday night, and then lead a hike on a Saturday. And so it might be about lichens, or it might be about fall warblers, or whatever. And they'd have somebody talk about that topic.
And then on Saturday, there'd be this hike. So this in fact, as far as I know, is the first rattlesnake eco-tourism trip ever. I gave my talk on Thursday night. I told them about maternal care. I had a live timber rattlesnake I set out on the floor so they could see that it didn't run around the room chasing and killing everybody. I told them that we would not be picking up this snake, mashing down its head, showing off its fangs with a pencil, holding it by the tail and talking about how dangerous it is, and doing disrespectful things like that.
We would be very respectful. They were to bring binoculars. We would not be catching the snakes or anything. And so doesn't this look like a bunch of birdwatchers except for one thing? They're looking down. Isn't that cool? He and I have a year friendly quarrel going on with the emphasis on the friendly and not the quarrel. So these people are all looking at a single rattlesnake.
We walked them for four hours. We saw one rattlesnake in four hours, and it did not twitch. It could have been a plastic rattlesnake for all they knew. When we got back to the parking lot, they were all just bubbling. Wait till I tell my husband I saw a live rattlesnake. Wait till I tell my son. Did you notice how the skin between the scales was kind of purple, because it's a pregnant female like Dr. Greene said it was? You would've thought they'd seen a golden eagle or a bobcat. They were just glowing. And I think it's because they'd had a sublime aesthetic experience in terms of these snakes.
OK, I'm going to close with three brief vignettes. So this is sort of looking a little bit more outwardly. In the book, I talk about three gifts I would give young naturalists if I could. So if I could-- anybody, let's say, 30 or younger that was a naturalist and if I had the money, I would give you these three things. And I'm just going to tell you about one of them here.
But one of them is I would send you to Africa. And I would put you on foot, not in a safari van. I'd put you on foot among the megafauna. You can do this. I mean, there are various ways to do it. You could know somebody who's a researcher there and go with them. That would be one way, and I've done it that way. You could go as a teacher for a Cornell course, and I've done it that way with my colleague [? So in fact, you can go to South Africa's Kruger National Park and not have to pay all that money to be in a safari van.
You can go on safari by yourself in a rental car in Kruger. And you can pay a little bit extra and get taken hiking way off-road in Kruger. So I once walked about 25 miles off-road in two days in Kruger, just six tourists and two armed national park rangers. And it's a profoundly moving and thought-provoking thing to be on foot in Africa among the megafauna.
And I want to tell you the three things I've gotten out of it over the course of three trips. The first one is in this country-- and I really do think it's mainly in the United States. It's certainly mainly in North America. It's not a way of thinking that's so prevalent in Europe, Africa, and South America. But in this country, we tend to idealize wilderness as a place where there are no humans, or at least a place where humans leave nothing but tracks, not even a fire pit or anything like that.
When you're in Africa-- it hit me after a while-- you can't apply that notion of wilderness to Africa. Because if you want Africa with no people-- you can talk about too many people. You can talk about technology. You can talk about pollution, on and on and on. I buy all that. But if you want to talk about a conceptual ideal of Africa as wilderness with no people, you have to go back to when we were Australopithecines. Because we started in Africa.
There's never been in Africa without people until you go back to when we weren't people, OK? And actually, there hasn't been a North America without people for about the last 12, to 20, years, depending on what the evidence is. So I think that's a very thought-provoking thing in terms of how we think of wilderness. The second thing is-- I'll put this as politely as possible-- poop is pristine. It is everywhere. There is dung everywhere. There is dung, and it's in the waterholes. They even poop in the waterholes. I mean, there's just dung, dung, dung everywhere.
It's so abundant and so diverse, and so identifiable species by species that we do class projects in our tropical behavioral ecology course in Kenya, where we walk line transects and count different kinds of dung, OK? We don't see that mostly in this country.
And when we do find a cow pie or something like that, we get all exercised about it. And I think that's because we live in a kind of a weird anachronism here in North America. We lost our megafauna about 10, years ago. You know that until about 10, years ago, we had six species of elephants in the United States? Elephant relatives? I mean, that's how North America came to be what it is today, is in the presence of megafauna. And we don't have ours anymore. And the last thing is, always worry, sometimes terrified, OK? You just do not walk around on foot among the megafauna without being very humble in a special way that you don't have to be humble in most parts of the United States.
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You have to be respectful of the possibility there's an elephant in that thicket, or a buffalo in that thicket, or a lion behind that boulder. You can never forget that that's a possibility.
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I found that after a few weeks in Kenya, I always knew which way the wind was blowing. I didn't get out the car without knowing which way the wind was blowing. And I didn't get out of the car with my students without looking around to see where is the nearest thicket that might hide something that could hurt us? It's a very different way of thinking. And I think again, it's something that has to do with our notions of wilderness.
Second thing, New World cattle. So environmentalists, especially in the western US, tend to think of cattle as a scourge on the landscape. And I do understand that the ranching situation out west is peculiar in terms of most of it happens on public land. It's not a place where there was a megafauna in many places, and so on and so forth. I get all that. But I think it's a little more nuanced when you take the country as a whole, and here's why. Cattle evolved from a thing called aurochsen, the Old World aurochs.
This was the original wild cattle. And it actually only went extinct in about in Western Europe. In or , Columbus brought Iberian cattle to the New World for the first time.
And he first brought them to an island in the Caribbean. And within a couple of years, some of them went to Mexico on Columbus's ships. And some went to South Florida on Columbus's ships. And after years of largely natural selection in those two very different landscapes-- very arid out west and Mexico and the southwestern US, subtropical in Florida-- we now have two very different-looking-- we could say natural breeds of New World cattle.
In Florida, they're called Cracker cattle. They're resistant to tropical diseases. They're resistant to hoof rot and things like that. Out west, we have longhorns, as shown in this picture. Now I spent a lot of time on a ranch in the Texas hill country that has only longhorns on it. And it's an interesting place. These animals require basically no care.
So for example, with the so-called European improved breeds, it's not uncommon to have to pull the first calf. And that's because we've selected for giant fat calves. That's our modus for producing beef in this country. And we haven't selected concomitantly for the size of the birth canal. So it's not uncommon for so-called improved European breeds to have trouble giving birth the first time. And in fact, some people breed their cows to a longhorn the first time so it'll have a small calf. Well, David's cows never have trouble giving birth.
They give birth to pound calves. So there's a half-ton cow gives birth to a pound calf, no problem, you know? Being a careful observer increases the likelihood of caring, and communicating that caring might mean less destruction of vital habitats such as the rainforests and deserts.
Alongside such thoughts, there are detailed descriptions of research and teaching, as well as plenty of information about reptile biology. The book's target audience is probably academics, scientists and natural historians. At times the flowery and colloquial language is slightly offputting. At other times, it is refreshing to read a scientific narrative that verges on the poetic.