Tag Archives: conservation

Crocodiles and Cane Toads

You can see them from a helicopter: the white, bloated bellies of dead crocodiles, limply floating down the Victoria River. Australian freshwater crocodiles live hard lives, and most hatchlings are quickly eaten by fish, herons, frogs, turtles, or adult crocodiles. By the time they reach adulthood, at more than 7 feet long, they’ve already proven themselves to be the toughest reptiles around, so finding dead ones didn’t used to be common. Starting in 2002 that began to change (Letnic et al. 2002). Bodies started turning up, floating on their backs, by the hundreds. In their stomachs, researchers found the culprit: cane toads.

Cane toads, an invasive species in Australia, are extremely toxic. Their skin and organs are filled with cardiac glycosides, molecules that induce heart failure. Pets that eat them often die. So do a few humans, who lick the toads hoping to experience the hallucinogenic effects* of toad poison.

A dead freshwater crocodile, after eating a cane toad. Photo by Adam Britton, used with permission.

A dead freshwater crocodile, after eating a cane toad. Photo by Adam Britton, used with permission.

The toads’ natural predators, to varying degrees, have evolved to handle toad poison (also called bufotoxin). Examples include certain army ants and the cat-eyed snakes, which eat the toads and their tadpoles with ease. Even outside the toads’ native range (tropical Latin America), predators are often able to tolerate them because they have already adapted to the toxins of their own local toads.

Australia has a special problem: the country has no native toads. None at all. Since the cane toads’ introduction, scientists have observed dramatic population declines in predatory reptiles, from monitor lizards to pythons to crocodiles. These reptiles are not adapted to living with toads: they don’t instinctively leave toads alone, and when they venture eat one, death by poison is often the result.

Australia is home to two crocodile species. The smaller of the two is the freshwater crocodile (Crocodylus johnstoni), which lives in ponds and the upper reaches of rivers, away from the northern coastline. At 7-10 feet in length, this species is not dangerous to humans unless provoked, instead subsisting on a diet of fish, amphibians, small mammals, and the like.

A freshwater crocodile. Photo by Richard Fisher, licensed under CC BY 2.0.

A freshwater crocodile. Photo by Richard Fisher, licensed under CC BY 2.0.

The larger is the saltwater crocodile (Crocodylus porosus), males of which are the largest crocodiles on earth, reaching lengths up to 20 feet. Although they often live alongside (and sometimes prey upon) freshwater crocodiles, saltwater crocodiles truly thrive in the more coastal habitats: estuaries, mangrove swamps, and sea-bound river deltas.

Both species are opportunists, and will happily snap up a toad if given the opportunity.

A saltwater crocodile. Photo by Lip Kee Yap, licensed under CC BY-SA 2.0.

A saltwater crocodile. Photo by Lip Kee Yap, licensed under CC BY-SA 2.0.

Dr.’s James Smith and Ben Phillips (2006) wanted to find out just how dangerous cane toads were to Australia’s native predators. They harvested the toxins from cane toads and then administered them to various Australian reptiles, including predatory lizards, pythons, and both crocodile species.

When scientists want to know how deadly a toxin is, they calculate LD50. The LD50, or median lethal dose, is simply the amount of poison that will on average cause the death of 50% of victims.

The LD50 depends both on the toxin and on the animal that ingests it. A rat, for example, has a 50% chance of death if it drinks 192 milligrams of caffeine for every kilogram that the rat weighs. Rats typically weigh about 1/3 of a kilogram, so the total LD50 for caffeine is 1/3 of 192, or 64 mg. More toxic substances have lower LD50’s, since it takes less poison to cause death. Caffeine isn’t that toxic. Aren’t numbers fun?

The mangrove monitor, a predator easily poisoned by cane toads. Photo by Jebulon, in public domain.

The mangrove monitor, a predator easily poisoned by cane toads. Photo by Jebulon, in public domain.

Smith and Phillips calculated that the LD50 for bufotoxin fed to freshwater crocodiles was about 2.76 milligrams. Cane toads, which can weigh up to 2 kilograms, are perfectly capable of killing freshwater crocodiles that eat them.

Here’s the odd thing: while freshwater crocodiles often died as a result of cane toad poisoning, none of the saltwater crocodiles did. To see if the poison was affecting them in other ways, the scientists conducted athletic tests — if the crocodile couldn’t run as fast after poisoning, that was interpreted as a sign the poison was harming the reptile. While the freshwater crocodiles slowed down after ingesting bufotoxin, saltwater crocodiles were just as energetic before as after their toxic meal.

Are saltwater crocodiles immune to bufotoxin? It’s hard to say. The scientists wanted to kill as few crocodiles as possible, and they didn’t have enough crocodiles on hand to test much higher doses. Perhaps extremely high doses of bufotoxin would kill saltwater crocodiles, but the data is lacking.

What we do know is that saltwater crocodiles are much more resistant to cane toad poison than freshwater crocodiles. There are two potential reasons for this, and the most obvious is size. Saltwater crocodiles, males of which can weigh more than 2,000 pounds, are the largest crocodilians and the largest non-marine predators in the world. An adult saltwater crocodile simply cannot eat a toad large enough to reach a lethal dose.

A saltwater crocodile. Photo by fvanrenterghem, licensed under CC BY-SA 2.0.

A saltwater crocodile. Photo by fvanrenterghem, licensed under CC BY-SA 2.0.

Smaller crocodiles are more vulnerable. In 2013, an expedition to remote areas of northern Australia revealed that some populations of pygmy freshwater crocodiles, which only grow to 5 feet, have suffered declines upwards of 60% due to toad poisoning (Britton et al. 2013). The same research team, led by Dr. Adam Britton, is trying to raise money with a crowd-funding campaign to return to these remote sites, to study and help protect pygmy crocodiles. I strongly encourage you to visit the crowd-funding site here, as Britton has prepared a terrific video on pygmy crocodiles and the unique challenges they face.

A pygmy freshwater crocodile. Photo via Adam Britton, used with permission.

An adult pygmy freshwater crocodile. Photo by Adam Britton, used with permission.

The saltwater crocodiles in the Smith and Phillips study were not even close to 2,000 pounds — they were subadults, less than three feet long and closer to five pounds. So a few milligrams of cane toad poison should have killed at least some of them. Instead the walked away un-fazed, without so much as a skip in their gait.

Why? It may have to with the two crocodiles’ evolutionary history. In addition to being the largest, saltwater crocodiles are some of the widest-ranging** crocodiles, distributed from eastern India through Southeast Asia, Indonesia, and New Guinea. Because they can live in saltwater, they have been able to colonize many Pacific Islands (e.g., the Solomons) that are out of reach of other crocodilians.

A cane toad. Photo by Sam Fraser-Smith, licensed under CC BY 4.0.

A cane toad. Photo by Sam Fraser-Smith, licensed under CC BY 4.0.

Throughout their range they encounter a tremendous variety of potential prey. Saltwater crocodiles are not picky eaters, and have been observed feeding on fish (including sharks), frogs, lizards, snakes, turtles, crabs, snails, octopuses (during marine forays), deer, monkeys, pigs, cows, rats, otters, rabbits, porcupines, kangaroos, squirrels, wild cats, jackals, emus, geese, miscellaneous birds, and bats that fly just a little too close to the water.

Also, toads.

Even though Australian crocodiles never encounter toads, they have almost exactly the same DNA as their relatives in Asia and Indonesia. Perhaps they have inherited a tolerance for bufotoxin, while the freshwater crocodile, alone and isolated in Australia, has not.

Freshwater crocodiles might seem like the evolutionary dopes in this story, but there is hope for them. While some populations have been hit hard, others appear to be unaffected, perhaps because cane toads tend to avoid the habitats where freshwater crocodiles do most of their hunting (Somaweera et al. 2012). Research (like the pygmy crocodile project) is continuing to shed light on where cane toads are affecting crocodiles the most, why, and what can be done to protect them.

Finally, crocodilians are more intelligent than most reptiles. Studies with captive specimens have shown that after just a few encounters, hatchling freshwater crocodiles are able to quickly learn to avoid cane toads. Back in the field, some populations of crocodiles are already showing signs of learning, as cane toads are attacked less often and less enthusiastically than native frogs (Somaweera et al. 2011). As with humans, the best hope for freshwater crocodiles is in the next generation.

A young freshwater crocodile. Photo by Mike Peel, licensed under CC BY-SA 4.0.

A young freshwater crocodile. Photo by Mike Peel, licensed under CC BY-SA 4.0.

*Don’t even think about it.

**Saltwater crocodiles, while secure in Australia, are endangered in Southeast Asia, where many populations have gone extinct.

Cited:

Britton A.R.C., E.K. Britton, and C.R. McMahon. 2013. Impact of a toxic invasive species on freshwater crocodile (Crocodylus johnstoni) populations in upstream escarpments. Wildlife Research 40: 312-317.

Letnic M., J.K. Webb, and R. Shine. 2008. Invasive cane toads (Bufo marinus) cause mass mortality of freshwater crocodiles (Crocodylus johnstoni) in tropical Australia. Biological Conservation 141: 1773-1782.

Smith J.G. and B.L. Phillips. 2006. Toxic tucker: the potential impact of cane toads on Australian reptiles. Pacific Conservation Biology 12(1): 40-49.

Somaweera R., J.K. Webb, G.P. Brown, and R. Shine. 2011. Hatchling Australian freshwater crocodiles rapidly learn to avoid toxic invasive cane toads. Behaviour 148(4): 501-517.

Somaweera R., R. Shine, J. Webb, T. Dempster, and M. Letnic. 2012. Why does vulnerability to toxic invasive cane toads vary among populations of Australian freshwater crocodiles? Animal Conservation 16(1): 86-96.

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Scaly and Adorable: Australia’s Pygmy Crocodiles

Yesterday I wrote about crocodile evolution, and some of their amazing extinct relatives (here). I wrote about them partly because prehistoric crocodylomorphs are amazing, and that’s as good a reason as any. But it was also to prove a point: modern crocodilians, 23 species all with similar appearances, might seem like ancient members of a group that has hardly changed at all. This is not so. Crocodilians are instead the only survivors of a vast and hugely diverse lineage of animals, most of which looked nothing like the crocodilians alive today.

Like the finned sea-crocodiles of the Jurassic, modern crocodilians are an off-shoot, just one branch in a massive crocodylomorph tree. Unlike the sea-crocodiles, by some combination of chance and adaptation, modern crocodilians have managed to avoid extinction (so far). Unlike the sea-crocodiles, crocodilians are still evolving.

NileCrocodile--Etiopia-Omo-River-Valley-01.jpg

A Nile crocodile (Crocodylus niloticus). Photo by Gianfranco Gori, licensed under CC BY-SA 4.0.

Dr. Adam Britton, a world-renowned crocodilian biologist, points out that his favorite animals are far more advanced than they look. “I do see them as highly refined survivors of their ancient lineage. The analogy I use when talking about croc evolution is to compare modern crocodiles to Ferraris: they might superficially look and function similarly to a Model T Ford, but they are so much more refined.”

One of Dr. Britton’s favorite species is the Australian freshwater crocodile (Crocodylus johnstoni), the smaller of Australia’s two native crocodiles. Freshwater crocodiles typically reach 7-10 feet in length — impressive, but dwarfed by the saltwater crocodile (Crocodylus porosus), males of which can grow to over 20 feet. The two species share Australia, but because saltwater crocodiles are larger and fiercely territorial, freshwater crocodiles are often relegated to sub-optimal habitats, such as smaller rivers and ponds.

A young freshwater crocodile. Photo by Mike Peel, licensed under CC BY-SA 4.0.

A young freshwater crocodile. Photo by Mike Peel, licensed under CC BY-SA 4.0.

Such habitats include the remote, rocky upstream gorges of the Victoria and Liverpool Rivers (Webb 1985). Here, and at a few other sites in northern Australia, unique freshwater crocodiles live in relative isolation from humans and saltwater crocodiles. Unfortunately, they also live without much food — small streams mean few fish, which make for malnourished crocodiles.

So they evolved. Over time, the crocodiles became smaller to make up for a poor diet, and now they are truly tiny, with the largest reaching 5 feet in length. They became the pygmy crocodiles, small enough that you could (unadvisedly) pick one up and carry it around with you.

A pygmy freshwater crocodile. Photo via Adam Britton, used with permission.

A pygmy freshwater crocodile. Photo by Adam Britton, used with permission.

Stunted growth is one thing — any crocodile, fed a poor diet, will fail to reach its maximum size potential. Pygmy crocodiles are different. They have been growing this way for enough time that they are now genetically predisposed to small size. If you took a pygmy croc from the wild and fed it the same diet as a normal freshwater crocodile, the former would still be much smaller than its cousin.

A pygmy crocodile. Photo by Adam Britton, used with permission.

A pygmy crocodile. Photo by Adam Britton, used with permission.

Pygmy crocodiles aren’t quite distinct enough to be classified as their own species — yet. They haven’t been isolated for very long, so for now they are still considered an unusual population of freshwater crocodiles. They may interbreed with larger crocodiles, in which case they will never fully separate. A more exciting possibility is that they may continue to evolve and diverge in isolation, in which case they may someday become genetically unique enough to constitute a new species.

There is another possibility: pygmy crocodiles may go extinct before they get a chance to evolve any further. Although their habitat is isolated and relatively secure, they are threatened by invasive cane toads, introduced to Australia in 1935. A hungry crocodile will happily snap up a toad, but because cane toads are extremely toxic, they are often the crocodile’s last meal.

Curiosity killed this crocodile -- it tried to eat a poisonous cane toad. Photo by Adam Britton, used with permission.

Curiosity killed this crocodile — it tried to eat a poisonous cane toad. Photo by Adam Britton, used with permission.

Pygmy crocodiles, because they are so small, are especially vulnerable to the poison. Although some populations have been unaffected (Doody et al. 2014). others have declined in abundance by more than 60% since the toads’ introduction (Britton et al. 2013). Why some populations are more vulnerable than others is one of many crucial questions that remain unanswered (Somaweera et al. 2012).

A cane toad. Photo by Sam Fraser-Smith, licensed under CC BY 4.0.

A cane toad. Photo by Sam Fraser-Smith, licensed under CC BY 4.0.

Dr. Britton is leading an effort to study pygmy crocodiles in their natural habitat. The goals of his research are two-fold. First, he means to assess their wild populations to determine if the crocodiles might be endangered. Second, Britton and his team wish to collect DNA from the pygmy crocodiles, to better understand their evolutionary history, and their genetic relationship with larger freshwater crocodiles.

This is an achievable and worthy project, but an ambitious one. Field work is always costly, but pygmy crocodiles live in isolated, hard-to-reach places, and getting there requires use of a helicopter. Dr. Britton and his team have started a crowd-funding effort to raise funds to support pygmy crocodile research — I’ve donated, and if you think pygmy crocodiles are amazing, I strongly encourage you to do so as well. There are some great prizes for donors, including crocodile-themed artwork and jewelry!

You can learn more about the project at its crowd-funding site, here. On the website is a short video in which Dr. Britton discusses and handles pygmy crocodiles. They are positively adorable.*

If crocodiles are Ferraris, then pygmy crocodiles are Smart Cars — tiny and vulnerable, but awesome in an enticingly bizarre sort of way. Pygmy crocodiles are an evolutionary quirk, just like the prehistoric pelican-snouted crocodile Stomatosuchus, or the armadillo-backed Armadillosuchus, or the shark-tailed … you get the picture. There’s just one important difference: pygmy crocodiles are alive. We, as residents of a special time in the history of life, get to appreciate them for the amazing creatures that they are. Let’s try and keep it that way.

*The crocodiles, I mean. Although if you like listening to British scientists get super-duper excited about wildlife, it’ll be a happy three minutes for you.

A big thank you is owed to Dr. Britton, who graciously allowed me to use his images for this article. Once again, I encourage you to donate to his effort to study these amazing crocodiles. You can learn more about crocodilians at Dr. Britton’s encyclopedic and lavishly illustrated website here.

Cited:

Britton A.R.C., E.K. Britton, and C.R. McMahon. 2013. Impact of a toxic invasive species on freshwater crocodile (Crocodylus johnstoni) populations in upstream escarpments. Wildlife Research 40: 312-317.

Doody J.S., P. Mayes, S. Clulow, D. Rhind, B. Green, C.M. Castellano, D. D’Amore, and C. Mchenry. 2014. Impacts of the invasive cane toad on aquatic reptiles in a highly modified ecosystem: the importance of replicating impact studies. Biological Invasions 16(11): 2303-2309.

Somaweera R., R. Shine, J. Webb, T. Dempster, and M. Letnic. 2012. Why does vulnerability to toxic invasive cane toads vary among populations of Australian freshwater crocodiles? Animal Conservation 16(1): 86-96.

Webb G.J.W. 1985. Survey of a pristine population of freshwater crocodiles in the Liverpool River, Arnhem Land, Australia. National Geographic Society Research Report 1979: 841-852

The Bucktoothed Slopefish

by Joseph DeSisto

We all love tales of rare sharks and squid, hauled up from the depths in nets and traps. Just a few days ago, an extremely rare deep-sea shark (the false catshark) was found off the coast of Scotland. Yet it is important to remember that the ocean is a big place and, in a paradoxical sort of way, it’s quite common for fish to be rare.

Enter the slopefishes, a handsome if under-appreciated family of marine fishes. All of the family’s 12 species live in rocky reefs at moderate depths. Most are rare, some extremely so. One species is known only from two specimens which were removed from the stomach of a coelacanth (a much larger fish) near the Comoros Islands. The slopefish were partially digested, so even though they represent new species, scientists have been unable to formally describe and name them (Anderson and Springer 2005). After 36 years, those two fish remain the only known representatives of their kind.

The bucktoothed slopefish. Photo by M.V. Chesalin, licensed under CC BY 3.0.

The bucktoothed slopefish. Photo by M.V. Chesalin, licensed under CC BY 3.0.

The bucktoothed slopefish’s tale might have ended similarly. Scientists named the species in 1974 based on only one specimen, found near the Gulf of Aden between Yemen and Somalia. Later efforts to capture more were fruitless. Finally, earlier this year, a bucktoothed slopefish made its way into a deep-sea fish trap off the coast of Oman (Anderson et al. 2015).

Now that a new specimen is available, we can appreciate the species for what it is: a thing of beauty, scarlet red and stream-lined, with rigid spines along the back. This discovery serves to remind us that the best finds in nature come not merely from knowledge, or even luck, but from days, weeks, or even decades of patience, persistence, and hard work.

Cited:

Anderson Jr. W.D. and V.G. Springer. 2005. Review of the perciform fish genus Symphysanodon Bleeker (Symphysanodontidae), with descriptions of three new species, S. mona, S. parini, and S. rhax. Zootaxa 996: 1-44.

Anderson Jr. W.D., M.V. Chesalin, L.A. Jawad, and S.R. Al Shajibi. 2015. Redescription of the percoid fish Symphysanodon andersoni Kotthaus (Symphysanodontidae) from the northwestern Indian Ocean, based on the holotype and the second known specimen. Zootaxa 4021(3): 475-481.

Saving the Easter Island Springtails

by Joseph DeSisto

By the time European settlers reached tiny Easter Island (Rapa Nui), far off the Pacific coast of Chile, it was already in ecological turmoil. The island had first been colonized by Polynesians as late as 1200 B.C.E. — their descendents comprise the Rapa Nui people, now the island’s indigenous population. They had at least 500 years before European colonization, and in that time the Rapa Nui people did great things — they constructed the world-renowned moai statues, for example:

Fifteen maoi -- on average, each of these is 13 feet tall and weighs 14 tons, but many are much larger. Photo by Ian Sewell, licensed under CC BY-SA 3.0.

Fifteen maoi — on average, each of these is 13 feet tall and weighs 14 tons, but many are much larger. Photo by Ian Sewell, licensed under CC BY-SA 3.0.

Despite the grandeur of the sometimes 30-foot-high moai, Easter Island already had its own wonders — the island was dominated by a species of palm tree, with trunks easily large enough to make a sea-faring canoe. That palm tree (Paschalococos disperta) existed only on Easter Island. I wish the picture below showed one of these trees, but that would be impossible — the Easter Island palm has been extinct for centuries. When European settlers arrived in 1722, the island was already almost completely deforested, with just a few pockets of forest left. Over the next few centuries, intensive sheep-grazing sealed the palm’s fate.

The Chilean wine palm (Jubaea chilensis) is the Easter Island palm's closest living relative. Photo by Scott Zona, licensed under CC BY 2.0.

The Chilean wine palm (Jubaea chilensis) is the extinct Easter Island palm’s closest living relative. Photo by Scott Zona, licensed under CC BY 2.0.

Today, the only evidence that palms ever existed on Easter Island come from petrified pollen grains and nut fragments (Flenley et al. 2006). The microscopic pollen grains are virtually indestructible and, in a cruel irony, have long outlasted the shepherds and, indeed, many of the moai themselves.

After such an environmental tragedy, it would be surprising to find any new species on Easter Island. And yet, even though every native vertebrate and many native plants have been driven to extinction, invertebrates that live exclusively on Easter Island continue to be discovered.

Just last week, biologists Taiti and Wynne (2015) published a survey of the woodlice (i.e., roly-polies) of the island, documenting two new species, one of which is only known from Easter Island. And that’s not all — a few months ago, five new springtails were introduced to science, unique to Easter Island (Bernard et al. 2015). Springtails are tiny, near-microscopic insect relatives that move by leaping extraordinary distances — if woodlice are the bumper-cars, then springtails are the bunnies of the micro-scape.

In profile: two new woodlouse species from Easter Island. Photo from Taiti and Wynne (2015), licensed under CC BY 3.0.

Two new cave-dwelling woodlouse species from Easter Island: Styloniscus manuvaka (left) and Hawaiioscia rapui (right). Photo from Taiti and Wynne (2015), licensed under CC BY 3.0.

So where are all these new species coming from? It turns out that even in such a desolate place as Easter Island, where almost all native wildlife and flora are gone, caves continue to provide a haven for undiscovered species (Wynne et al. 2014). All eight of these new species were found deep in caves, where humans have had less impact.

This is good news for those woodlice and springtails — now that we know they exist, perhaps we can keep them from following so many of their surface-dwelling brethren into extinction. After all, caves may be isolated, but they are not immune to our footprints. Keeping human traffic away from caves, and making sure the surrounding fern-moss habitat stays healthy, are both steps in the right direction (Wynne et al. 2014).

As a species, we have all but destroyed Easter Island’s fragile and unique ecosystems. Even so, in spite of our best efforts, a few native species, deep in the unexplored reaches of caves, persist. There is hope for them — and us — yet.

Cited:

Bernard E.C., F.N. Soto-Adames, and J.J. Wynne. 2015. Collembola of Rapa Nui (Easter Island) with descriptions of five endemic cave-restricted species. Zootaxa 3949(2): 239-267.

Flenley J.R., A.S.M. King, J. Jackson, C. Chew, J.T. Teller, and M.E. Prentice. 2006. The Late Quaternary vegetational and climatic history of Easter Island. Journal of Quaternary Science 6(2): 85-115.

Taiti S. and J. Wynne. 2015. The terrestrial Isopoda (Crustacea, Oniscidea) of Rapa Nui (Easter Island), with descriptions of two new species. ZooKeys 515: 27-49.

Wynne J.J., E.C. Bernard, F.G. Howarth, S. Sommer, F.N. Soto-Adames, S. Taiti, E.L. Mockford, M. Horrocks, L. Pakarati, and C. Pakarati-Hotus. 2014. Disturbance relicts in a rapidly changing world: The Rapa Nui (Easter Island) factor. BioScience 64: 711-718.

The Milk Adder

by Joseph DeSisto

Many times I was told, growing up in Maine, that if I looked hard enough I could find adders. People alleged to find them in parks, along rock walls, even in their homes. The word “adder” confused me, because this is the “true” adder:

The European adder, Vipera berus. Photo by Zdeněk Fric, licensed under GFDL.

The European adder, Vipera berus. Photo by Zdeněk Fric, licensed under GFDL.

That’s the European adder, a viper found in Europe and northern Asia. It is venomous, like all vipers, although not especially prone to biting. In New England, we only have two vipers, the copperhead and the timber rattlesnake. Neither are known to occur in Maine. Presumably copperheads never occurred here, prohibited by the cold winters.

The timber rattlesnake, meanwhile, is absent from Maine not because of the climate, but because the species was systematically exterminated through rattlesnake hunts. In Maine as in much of the United States, the timber rattlesnake has been stoned, burnt, and bulldozed out of our lives. Now it has become something of a legend, a name whispered when a rustle in the leaves is heard, or when a large snake slithers out of sight, just quickly enough to evade scrutiny.

A timber rattlesnake from Iowa. Photo by Psychotic Nature, licensed under CC BY-SA 3.0.

A timber rattlesnake (Crotalus horridus) from Iowa. Photo by Psychotic Nature, licensed under CC BY-SA 3.0.

Yet the adder of Maine is neither copperhead nor rattlesnake, but the harmless eastern milk snake. Why they should be called adders, I haven’t a clue. Despite looking nothing like a viper, milk snakes are sometimes confused with rattlesnakes and copperheads because they

a) shake their tails in dead leaves to mimic the sound made by a rattle,

b) aren’t afraid to hold their ground and defend themselves, and

c) are snakes.

That they should be killed is shameful, because milk snakes happen to be some of the most beautiful snakes in New England. As hatchlings they are creamy-white, with brick-red spots running down the back, each outlined in black as if traced with a fountain pen. With each year the snake loses a bit of its color — by adulthood most milk snakes are a pale gray, with red spots faded to a duller, but still handsome, chestnut brown.

A young milk snake or "milk adder" from Iowa. Photo by Psychotic Nature, licensed under CC BY-SA 3.0.

A young milk snake (Lampropeltis triangulum) or “milk adder” from Iowa. Photo by Psychotic Nature, licensed under CC BY-SA 3.0.

For most of my childhood, the eastern milk snake was my herpetological holy grail. I spent hours wandering through fields, digging in wood piles, and painstakingly tracing the edges of rock walls. Finally I tried my luck at a car junkyard, where I was told that snakes liked to hide under the heat-soaked, mouse-infested hoods and spare parts. When I asked the manager if he had seen any snakes with red spots, he told me that yes, many of the snakes had red spots, but only after he killed them and nailed them to trees like the Old Testament bronze serpent.

Milk snakes are not uncommon, but they are very secretive. Unlike the sun-loving garter snakes and racers, milk snakes are mostly nocturnal and subterranean, emerging from hiding only when necessary to track their rodent prey. When they are uncovered, milk snakes often defend themselves violently, shaking their tail, rearing up, and striking. The six-inch-long hatchlings are just as tenacious, although their bite amounts to little more than a soft pinch.

An adult eastern milk snake -- less striking than a hatchling, but still a handsome snake. Photo by Trisha Shears, licensed under CC BY-SA 3.0.

An adult eastern milk snake — less striking than a hatchling, but still a handsome snake. Photo by Trisha Shears, licensed under CC BY-SA 3.0.

I never did find my milk snake, but I like to think those years taught me something about nature. Milk snakes, like so many wonders of the natural world, are not found – they appear, like angels or shooting stars or gusts of wind. I don’t look for milk snakes any more, but I still go for long walks, flip logs, and scrutinize rock walls. Without fail, something amazing is there, and with luck one day that amazing thing might be a milk snake. Until then I look forward to a few moments reveling in its beauty before, with a flick of its muscular body, it vanishes.

This blog is mostly focused on invertebrates, but you can expect me to write more about reptiles as well, because I love them. My last article on snakes focused on vipers, and the chemicals they use to track their prey.

Happy World Snake Day!