After a frosty fifty years, the United States and Cuba are now warming up to one another,
and we may be about to learn a lot more about a fascinating group of snakes that reaches
its peak variety in Cuba.
These are the dwarf boas.
Their name is a little deceptive, as they were originally assumed to be connected to
true boas, just like the splitjaw snakes.
Even though we now know better, the name persists.
Most dwarf boas are only 1 to 2 feet long, therefore the dwarf side is correct.
But, at first appearance, this inconspicuous group of drab, nocturnal, live-bearing snakes
has more surprises and lessons about snake evolution than one might think.
There's also a lot of interesting natural history to be found.
Dwarf boas feed primarily frogs and lizards, and they constrict their prey similarly to
true boas.
By carefully twisting the front half of their body around its prey, much like a rope around
a windlass.
Typically, the first loop is twisted such that the snake's belly faces its head.
This habit, combined with their unusually big gape size, seemed to indicate that they
belonged to the Boidae family of true boas.
Tree boas, boa constrictors, and anacondas are among the most well-known.
All true boas are found in the tropics.
There are a lot of them in the West Indies.
As a result, unlike many other boid "hangers-on" (such as the Malagasy Sanzinia and Acrantophis,
African Calabaria, North American rosy and rubber boas, Pacific Candoia, and Old World
sand boas).
In terms of live species biogeography, a close link between dwarf boas and booids was easy
to accept.
According to Harry Greene and Gordon Burghardt's comparative research of constriction behavior
in extant alethinophidia snakes, this form of constriction is shared by practically all
"henophidian" snakes, including booids, pythonoids, and some uropeltoids.
Nonetheless, because constriction behavior does not work in small places, a few fossorial
species have presumably lost it entirely.
Dwarf boas, in particular, were assumed to be particularly closely related to two other
small neotropical booids genera, Exiliboa and Ungaliophis.
Both morphologically and ecologically, they resemble each other.
Although they are still known as "dwarf boas," a new picture began to emerge approximately
15 years ago.
Exiliboa and Ungaliophis DNA revealed that they were certainly linked to true boas.
Tropidophis and Trachyboa were most closely linked to the monotypic family Aniliidae,
according to evidence from mitochondrial, nuclear DNA, and immunological proteins, as
well as characteristics of their muscular, circulatory, and reproductive structure.
The Red Pipe snake is a unique South American species found in this area.
Anilius, like several Asian pipe snakes to which it was formerly considered to be closely
related, does not generally constrict its prey since it forages underground on elongate
vertebrates like eels, caecilians, amphisbaenians, and other snakes.
However, we can now say with certainty that these Asian pipe snakes are related to Anilius.
The closeness between the gape size and constriction behavior of dwarf boas and that of pythons
possibly still shows the shared retention of a paired morphology or action pattern adopted
by their common ancestor.
It's simply a common ancestor who is far older than we previously believed.
Dwarf boas and American pipe snakes diverged 60 to 110 million years ago in South America,
according to estimates.
Following the mid-Cretaceous split-up of west Gondwana 70 to 120 million years ago, their
common ancestors were isolated from those of all other current alethinophidia snakes,
which spread in Africa.
This was the dividing line that separated South America from Africa.
And we've been used to categorizing alethinophidia into two primary lineages: Amerophidia and
Alethinophidia.
Instead of being divided into a monophyletic Macrostomata that includes boas, pythons,
and caenophidia, and a basal group of non-macrostomata pipe snakes that are more scolecophidia-like
in ecology.
Surprisingly, numerous snake taxonomy publications from 2013 are out of date when it comes to
this fundamental alteration in snake taxonomy.
Because it was still uncertain at the time (and there are still some strong arguments
from paleontologists that the molecular data may be misleading).
The "new" family of dwarf boas consists of two species of "eyelash dwarf boas".
In the mainland genus Trachyboa (there we go with the boa thing again).
And there's the Tropidophis genus, which has 32 species in total, five of which are from
mainland South America, and a West Indian radiation with 17 Cuban species (one of which
is shared with Jamaica and one with both Jamaica and Hispaniola).
One on Hispaniola (which Cuba shares), five in Jamaica (two of which are shared with Cuba),
two in the Bahamas, and one from the Turks and Caicos Islands.
Each of the three Cayman Islands has one (Grand Cayman, Little Cayman, and Cayman Brac).
And there's one that's only found on Navassa Island, a small, deserted, contested island
in the Caribbean Sea between Cuba, Jamaica, and Hispaniola (which is known from four specimens
and has not been seen in over 100 years).
The species of the West Indies, notably those of Cuba, demonstrate a diversification that
rivals and parallels that of Darwin's finches.
According to morphological and molecular evidence, Cuba's 17 species are descended from a single
migration event.
Furthermore, the island species appear to be more distantly linked to mainland species
than Trachyboa.
However, because four-fifths of Tropidophis species have no published sequencing data,
both of those results could alter.
These snakes were captured by early explorers and biologists from bromeliads, stone walls,
and beneath rocks.
They saw that Tropidophis species did not try to evade capture, but instead coiled themselves
into tight balls when caught.
Auto bleeding of the nose and mouth was rapidly seen as a strange defense action.
To put it another way, when these snakes are handled, they spontaneously bleed from these
orifices and smear the blood all over themselves.
The gap between their spectacles and their eyes filled with blood briefly before they
blink, giving their eyes the appearance of flashing red.
Blood collected from their mouths takes over half an hour to coagulate, whereas blood collected
from their tails takes only 10 minutes to clot.
In addition, the blood in the mouth is more acidic and contains fewer red blood cells.
Because it's combined with saliva, we're guessing.
It is not a substitute for venom because it is harmless to frogs and lizards.
The specific purpose is unknown, although it appears to aim to frighten off potential
predators.
Dwarf boas, like many snakes, becomes accustomed to captivity and finally ceases to display
this behavior.
Just when you thought things couldn't get any more intriguing, remember that most Tropidophis
have the ability to change color!
When they are active at night, they are pale silver-white, and when they are not, they
are dark grayish-brown.
A dwarf boa may swing from totally light to completely dark in 1 to 2 hours.
They achieve this by mobilizing melanosomes (organelles carrying the light-absorbing pigment
melanin) from the centre of a melanophore cell deep under their skin to finger-like
extensions of the melanophore closer to the skin's surface.
Partially blocking stationary xanthophores and iridophores, which contain yellow, blue,
or green pigments.
Both adults and juveniles undergo diel color change.
And it does not seem to be affected by age, sex, pregnancy, or feeding, although prior
to shedding snakes remain dark and inactive for several days.
Although photoperiod is most likely to be responsible, exposure to low temperatures
(less than 63 degrees Fahrenheit) can cause a partial shift from dark to light even in
the middle of the day.
Captive snakes that were moved from Cuba to Czechoslovakia developed jet lag.
It took many days for them to adjust their circadian rhythm to the new photoperiod.
And keeping them in utter darkness for several days caused them to lose touch with the sun's
rhythm.
This color change is thought to aid nocturnally active snakes in keeping their body heat.
Because light-colored things lose heat more slowly than dark-colored ones, they are more
energy efficient.
Most species have had little ecological data collected on them to date, partly due to their
rarity and partly due to the difficulty of operating in the area.
How do five or six sympatric species in different sections of Cuba share resources and coexist?
What was the order of island biodiversity and migration, and when did it occur?
Dwarf boas, hopefully, will remain around long enough for us to find out.
They are under attack from a variety of sources.
Locals dislike them, as they do in many areas, despite the fact that no Greater Antillean
snakes are deadly to humans.
It's also possible that capturing for the pet trade is a problem.
Especially since a previous Turks and Caicos Islands government official allegedly allowed
reptile traffickers to take thousands of Tropidophis greenway for the pet trade from North Caicos.
Supposedly hinting that it would be preferable if all of the snakes were removed!
Most native ecosystems have been extinct in the West Indies for centuries.
And increasingly rapid development, especially due to tourism, threatens what little remains.
Non-native predators, particularly the Small Indian Mongoose, may pose the greatest threat
to them.
"In Jamaica Spotted red dwarf boas is virtually extinct owing to the appetite of the introduced
mongoose," herpetologist Thomas Barbour noted in 1919.
Operation Mongoose, ironically, was the codename for the Kennedy administration's endeavor
to isolate Cuba diplomatically, politically, and economically in order to destabilize Castro's
rule.
Dwarf boas, as well as the 120 or so snake species unique to the West Indies, are threatened
by cats, dogs, rodents, goats, pigs, cane toads, and even other introduced snakes.
As well as the rest of the local wildlife.
Several lizard species have benefited from improved public relations and conservation
campaigns, and snakes may benefit as well.
We're going to take a chance and predict that we'll find a few new dwarf boa species in
the not-too-distant future.
Also, the mainland species may be reclassified into a new genus.
We also believe they require a more imaginative common name than "dwarf boa," especially one
that does not contain the word "boa."
"Wood snakes" is one available alternative, which is at best decent.
In the Caicos Islands, they're also known as "rock pythons," a name that's just as misleading
as "dwarf boa."
In Cuba, there are dumb snakes, while on Andros Island in the Bahamas, there are "shame snakes."
Both of these terms could refer to their defensive head-covering behavior.
Our favorite name for them is "thunder-snakes," as they are known in many places of the West
Indies because they are more frequently seen after strong rainstorms.
The name "Caribbean Thundersnakes" has a wonderful ring to it, and it can help them boost their
image.
So, that’s all we have for you today!
Thanks for watching.
See you guys in the next video.