Evolution of Old Worlds x New Worlds

[Benzen]

I always wondered why OW and NW Ts are so different in temperament.
While NW Ts are mostly chill, slow and have urticating hairs, OW Ts are fast as heck, defensive and love to bite.
What made them develop so differently?
Is the OW so much more dangerous for small critters such as Ts? More predators which requires to be more feisty and bold?

If someone has an idea or theory, lemme know!

 

[0311usmc]

I always wondered why OW and NW Ts are so different in temperament.
While NW Ts are mostly chill, slow and have urticating hairs, OW Ts are fast as heck, defensive and love to bite.
What made them develop so differently?
Is the OW so much more dangerous for small critters such as Ts? More predators which requires to be more feisty and bold?

If someone has an idea or theory, lemme know!

I keep mainly old world tarantulas, have been since i started keeping since 2007 and they are not as you describe, they dont threat posture me they retreat to burrows, they never try to bite because to busy bolting their hide and all tarantulas are fast as heck ALL of them NW or OW dosent matter FYI.

 

[Benzen]

When you compare an OBT to a Brachy you can clearly see a difference. But interesting nonetheless that your OW seem to react like most NW Ts. Then let's get specific: why is an OBT so much more defensive (generally) than a Brachy?

 

[DaveM]

The first spiders that we would call tarantulas evolved almost certainly in the supercontinent Gondwana, which was a landmass of Old World and New World connected, but toward the end of Gondwana's existence when it was starting to break up into new continents. Old and New World were separated in this breakup around 100 million years ago. The time since then is the great majority of the time that tarantulas have been on this earth, evolving separately, and that's a lot of evolutionary time (most speciation events that generated what we keep in the hobby today happened within the last 10 million years). SO, it would be surprising if Old World and New World tarantulas were not quite different. In fact, I think it's surprising how similar they are, which must be due to convergent evolution, pressure to remain in similar forms, because they were successful forms and nature doesn't abandon what works.

 

[Benson1990]

I think it's a big misconception to think new world species are chill and slow...out of the ones I own the OW species are the easiest, they'll retreat to the den if disturbed, I've never faced a threat pose yet, but the NW who don't burrow and are out all the time are the ones to be careful of, mine can be very skittish and have a real turn of pace when they want to, my T. albo is a total spaz you just never no what it's going to do and it never retreats, I'll add it's not being particularly defensive it's just it's very jumpy and prone to erratic movements when disturbed.

 

[Seemannnni]

I think it's a big misconception to think new world species are chill and slow...out of the ones I own the OW species are the easiest, they'll retreat to the den if disturbed, I've never faced a threat pose yet, but the NW who don't burrow and are out all the time are the ones to be careful of, mine can be very skittish and have a real turn of pace when they want to, my T. albo is a total spaz you just never no what it's going to do and it never retreats, I'll add it's not being particularly defensive it's just it's very jumpy and prone to erratic movements when disturbed.

I second this. Psalmos. are NO. JOKE.

 

[Tarantuland]

When you compare an OBT to a Brachy you can clearly see a difference. But interesting nonetheless that your OW seem to react like most NW Ts. Then let's get specific: why is an OBT so much more defensive (generally) than a Brachy?

OBTs are bolty, especially as slings, but much more prone to hiding than the hair kicking and threat postures I’ve gotten from boehmei.

i actually did a presentation related to this last year, I’ll try to remember to link my sources later

 

[Wolfram1]

My 0.1.1 Brachypelma hamorii kick hairs if i so much as open the enclosures without cracking it very carefully and feeding them right away. That somehow seems to calm them down a little. And all that despite having a deep burrow they could retreat into.
I would consider this much more defensive than my old world tarantulas who just jump and run.

If you try to catch them it is a different matter, but even then i would say old-worlds that have somewhere to retreat to do so.


As for the biting, if you had one less defence mechanism it is only logical they resort to the default.

 

[Tarantuland]

Tarantula’s Ubiquity Traced Back to the Cretaceous - Biological Sciences - Mellon College of Science - Carnegie Mellon University

Tarantulas are among the most notorious spiders, due in part to their size, vibrant colors and prevalence throughout the world. But one thing most people don’t know is that tarantulas are homebodies. Females and their young rarely leave their burrows and only mature males will wander to seek out...

www.cmu.edu

 

[Benja84]

Even my OBTs always resort to bolting to the burrow. In my experience, aggressive OBTs are because people don't give them the room for adequate burrowing. I don't have a ridiculous sample size, as I only keep around 15 Ts at a time, but it's a pretty even spread between old and new. I've never gotten a threat posture from an OW in the 12 years I've kept.

 

[AphonopelmaTX]

I think it's a big misconception to think new world species are chill and slow...out of the ones I own the OW species are the easiest, they'll retreat to the den if disturbed, I've never faced a threat pose yet, but the NW who don't burrow and are out all the time are the ones to be careful of, mine can be very skittish and have a real turn of pace when they want to, my T. albo is a total spaz you just never no what it's going to do and it never retreats, I'll add it's not being particularly defensive it's just it's very jumpy and prone to erratic movements when disturbed.

I 100% agree with this. Any tarantula, regardless of its taxonomic placement or where it occurs in the world, will always resort to running away and hiding before physical confrontation. The challenge with some tarantulas, especially the larger ones, is giving them enough space and housing them correctly so they have a place to run to.

I also think the perception of old worlds being more aggressive or defensive in general than the new worlds has to do with how our primate brains are wired to view the baring of big pointy teeth as being more threatening than any other displays of aggression. When a large old world tarantula is quick to bare its fangs and start biting, we perceive that as being more threatening than a new world tarantula that is quick to kick off clouds of urticatious setae even though both are equal as displays of defensive behavior.

As far as when the urticatious setae developed in tarantulas from the Americas, I think the jury is still out on when and how that happened. The challenge being they only appear in the Theraphosinae, Aviculariinae, and in part the Psalmopoeinae (genus Ephebopus), which only appear in the Americas along side other tarantula subfamilies that do not have urticatious setae. Therefore the urticatious setae had to have developed sometime well after the continents split. Behavior-wise, there appears to be a correlation between a tarantula's level of defensiveness and the hostility of the environment. I don't think it is a coincidence that the tarantulas considered highly defensive/ aggressive are the ones appearing in places such as tropical rainforests where there is a continual evolutionary arms race between predator and prey.

 

[viper69]

I always wondered why OW and NW Ts are so different in temperament.
While NW Ts are mostly chill, slow and have urticating hairs, OW Ts are fast as heck, defensive and love to bite.
What made them develop so differently?
Is the OW so much more dangerous for small critters such as Ts? More predators which requires to be more feisty and bold?

If someone has an idea or theory, lemme know!

NWs are not mostly docile nor slow
Not all NWs have UrS
Love to bite—FALSE!!

 

[UtilityTurkey]

Some NWs don't have urticating hairs and are fast as heck, like Psalmopoeus. I have a P. chordatus that is more chill than half of my NWs.

Also the main thing I think about when it comes to OW/NW evolution is how the heck S. hoffmanni and Ceratogyrus sp both evolved horns independently... THAT is perplexing. It's like how you find pyramids in NW and OW in ancient cultures, despite them not having contact as far as we know...

How did these two genera evolve horns despite being worlds apart?