Tarantulas and moisture requirements

A recent thread about G. pulchra husbandry got me really thinking about tarantulas and their moisture requirements as it pertains to substrate. In that thread, it sounded like some folks keep them on moist sub while other keep them dry. Although these are obviously quite different on husbandry needs, it sounds as if both set of folks are keeping healthy animals with no ill effect despite the opposing conditions.

When I think about moisture dependent species, T. blondi, H. gigas, and L. violaceopes immediately come to mind. These seem to be three species that require moist substrate to insure their good health. But what about some of the other species that many of us keep moist but others keep dry?

Poecilotheria, Asian terrestrials, South American tropicals, etc. are usually kept on moist substrate. However, I've heard of folks keeping Lasiordora and Phormictopus both moist and dry. I recently spoke to a keeper who had been successfully keeping pokies dry for years without issue. Then there are avics, who often hail from humid parts, but keepers have discovered that humid enclosures with improper ventilation can kill them. Personally, I used to keep my phormictopus species on moist sub, but I noticed that they would tend to gravitate toward the dry side and burrow. I now keep them on mostly dry with water dishes, and they are all still growing like weeds.

Are there physiological differences between species that make some more susceptible to dry conditions, or is it a case in most instances of tarantulas being hardy enough to tolerate a variety conditions? For example, I live in Connecticut where it can be 90 degrees with 100% humidity one day, and 50 degrees with 40% humidity the next. Even though I can survive in the high humidity, I certainly don't like it. Is it possibly like this for some tarantula species?

Now, obviously when breeding comes into play, some species require extra attention to environmental factors and closer conditions to their regions of origin. I'm talking about general husbandry here. Also, I am in no way advocating that we should desert what experience has taught us constitutes proper husbandry.

What are others' thoughts? I'm just really curious as to what other keepers think. Which species need to be kept moist in order to thrive, and which seem to do well in conditions different from the conditions in the wild? Are any of you folks keeping something differently and having success with it?

Humidity doesn't kill Avics, it's humid containers that don't have proper ventilation that kill them.

Megaphobema robustum is another to add to that "moist" list of your comment. My Ephebopus murinus is more on the moist side as well.

I always kept Asians Theraphosidae on moist/slighty moist substrate (depends) with a water dish. As for Phormictopus sp. just a bit moist, i never kept those "moist" like Asians or particular NW like Megaphobema robustum or a Theraphosa sp.

Grammostola pulchra adults here are fine with "bone dry substrate and water dish". In the city where i live humidity is a bit higher (never lower than 60) so this helps me.

I wouldn't keep an Asian, no matter, on bone dry substrate, however. Another thing IMO to consider is ventilation, ventilation is extremely important, and good air circulation.

viper69 said:

Humidity doesn't kill Avics, it's humid containers that don't have proper ventilation that kill them.

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What I meant was the majority of folks were keeping them super humid with moist substrate and constant spraying, and now the rule is generally dry sub, a water dish, and good ventilation. The high humidity requirements for many of these guys seem to be a thing of the past.

---------- Post added 10-03-2015 at 08:21 PM ----------

Chris LXXIX said:

Megaphobema robustum is another to add to that "moist" list of your comment. My Ephebopus murinus is more on the moist side as well.

I always kept Asians Theraphosidae on moist/slighty moist substrate (depends) with a water dish. As for Phormictopus sp. just a bit moist, i never kept those "moist" like Asians or particular NW like Megaphobema robustum or a Theraphosa sp.

Grammostola pulchra adults here are fine with "bone dry substrate and water dish". In the city where i live humidity is a bit higher (never lower than 60) so this helps me.

I wouldn't keep an Asian, no matter, on bone dry substrate, however. Another thing IMO to consider is ventilation, ventilation is extremely important, and good air circulation.

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Yup, both M. robustom and E. murinus are two others! I'm sure that there are more as well; I just spoke off the top of my head.

I also keep all of my Asian terrestrials on moist as well; I definitely wouldn't mess with that. However, when I first got into Phormictopus, I was very careful to keep them moist, but I noticed that they really didn't seem to care. I still overflow the bowls a bit, but I'm not too worried about it.

Tomoran said:

Yes, I know that. What I meant was the majority of folks were keeping them super humid with moist substrate and constant spraying, and now the rule is generally dry sub, a water dish, and good ventilation.

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I can talk for me; never sprayed or misting, always pour water on the substrate. The rest is up to the water dish. This for the "moist substrate" T's (Asians, Hysterocrates gigas, Megaphobema robustum etc)

The rest are: bone dry with a water dish (Grammostola sp. Brachypelma sp. GBB, OBT, Ceratogyrus sp. etc) and some T's with parts of the substrate a bit moist, with a water dish (Psalmopoeus cambridgei, Ephebopus murinus etc).

There isn't a rule, for me, except the water dish (can't stand T's enclosures without a cork bark and a water dish). There's, more or less, to try to "replicate" (impossible, i know) the enviroment where the T's come from, starting to work from the point of where we live for that.

An Indian one, or another tropical, housed in totally bone substrate like a Pterinochilus murinus IMO isn't the best.

Chris LXXIX said:

I can talk for me; never sprayed or misting, always pour water on the substrate. The rest is up to the water dish. This for the "moist substrate" T's (Asians, Hysterocrates gigas, Megaphobema robustum etc)

The rest are: bone dry with a water dish (Grammostola sp. Brachypelma sp. GBB, OBT, Ceratogyrus sp. etc) and some T's with parts of the substrate a bit moist, with a water dish (Psalmopoeus cambridgei, Ephebopus murinus etc)

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Yeah, I don't do the misting either. I have a bottle with holes in the top I use to make it rain for the ones that need a bit of moisture. I stopped moistening my Avics substrate and just keep the water dishes full. My Lasiodora species are also kept mostly dry.

I do wonder what the physical differences are between the tarantulas that need this moist substrate and the ones that don't.

Tomoran said:

Yeah, I don't do the misting either. I have a bottle with holes in the top I use to make it rain for the ones that need a bit of moisture. I stopped moistening my Avics substrate and just keep the water dishes full. My Lasiodora species are also kept mostly dry.

I do wonder what the physical differences are between the tarantulas that need this moist substrate and the ones that don't.

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I think is due to the fact of how they evolved to live in arid or more humid enviroments and things like that. They are probably more delicate and would not survive in too dry enviroments, just like a GBB or a Grammostola rosea abhor moist substrate.

Again, to be clear, I'm not in any way advocating that folks should stop keeping tarantulas on moist substrate that need it. I'm just curious about the species that seem to do well on either (even if they are from tropical locales), and why some are more adaptable than others.

---------- Post added 10-03-2015 at 08:34 PM ----------

Chris LXXIX said:

I think is due to the fact of how they evolved to live in arid or more humid enviroments and things like that. They are probably more delicate and would not survive in too dry enviroments, just like a GBB or a Grammostola rosea abhor moist substrate.

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Great point about the arid species!

Tomoran said:

I'm just curious about the species that seem to do well on either (even if they are from tropical locales), and why some are more adaptable than others.

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there's no mystery to it. They've adapted to their climates. Some areas have relatively consistent rainfall throughout the year, other places have wet/dry seasons, and some of those dry seasons may include droughts. Plants also adapt to rainfall, which is why some are hardier to dry conditions than others.

Poec54 said:

there's no mystery to it. They've adapted to their climates. Some areas have relatively consistent rainfall throughout the year, other places have wet/dry seasons, and some of those dry seasons may include droughts. Plants also adapt to rainfall, which is why some are hardier to dry conditions than others.

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Oh, I definitely get that they have adapted. I was just curious as to how, physiologically, these adaptations might have manifested. For example, did species that are able to thrive in arid conditions develop a thicker coating over their exoskeletons to hold in moisture and prevent desiccation? I'm guessing that there has been little research or study into this, but it's been something I've wondered about.

I only keep three kinds of tarantula moist in my collection. OW Asian burrowers (My haplos and chilobrachys), my Hapalopus species, and slings/ spiders with eggsacs. Other than that everything else stays on dry substrate with occasional overfilling of the waterdish. I've found that most species adapt easily to dry substrate and as long as there is access to water for them to drink they do just fine.
Slings are more prone to desiccation so until they are large enough to get a water dish they stay on moist/ more humid sub so that they don't lose much water.

Tomoran said:

Oh, I definitely get that they have adapted. I was just curious as to how, physiologically, these adaptations might have manifested. For example, did species that are able to thrive in arid conditions develop a thicker coating over their exoskeletons to hold in moisture and prevent desiccation? I'm guessing that there has been little research or study into this, but it's been something I've wondered about.

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I bet their book lungs are different, that's where I'd start.

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Tomoran said:

What I meant...

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And what you wrote were 2 totally different things! hah :laugh:

viper69 said:

I bet their book lungs are different, that's where I'd start.

---------- Post added 10-04-2015 at 11:55 AM ----------



And what you wrote were 2 totally different things! hah :laugh:

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That was also something I wondered about, the book lungs. I just wish that there was more on it, as I bet it would be quite fascinating.

Haha. Hey, I gave you full props in my edit! I was trying to keep this post from being a novel! :tongue: :biggrin:

Tomoran said:

That was also something I wondered about, the book lungs. I just wish that there was more on it, as I bet it would be quite fascinating.

Haha. Hey, I gave you full props in my edit! I was trying to keep this post from being a novel! :tongue: :biggrin:

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I really can't say why some need higher humidity and others appear to adapt well (eg Avics). It does remind me of certain snakes though. For example some species out of S. America absolutely require higher humidity otherwise they develop respiratory problems in captivity.

klawfran3 said:

I only keep three kinds of tarantula moist in my collection. OW Asian burrowers (My haplos and chilobrachys), my Hapalopus species, and slings/ spiders with eggsacs. Other than that everything else stays on dry substrate with occasional overfilling of the waterdish. I've found that most species adapt easily to dry substrate and as long as there is access to water for them to drink they do just fine.
Slings are more prone to desiccation so until they are large enough to get a water dish they stay on moist/ more humid sub so that they don't lose much water.

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Thanks so much for the response. I keep most of my slings slightly moist as well, and all of my Chilobrachy species are moist. I was just intrigued by this as it seems as keepers gain more experience, more species are showing that they can be adaptable to a variety of conditions. Like you say, many can be kept on dry with a water dish with little issue. Still, there are those ones (either arid species or ones that require more moisture) that can't handle the extremes.

---------- Post added 10-04-2015 at 03:17 PM ----------

viper69 said:

I really can't say why some need higher humidity and others appear to adapt well (eg Avics). It does remind me of certain snakes though. For example some species out of S. America absolutely require higher humidity otherwise they develop respiratory problems in captivity.

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Yes! I was actually thinking about snakes as well, having kept some that absolutely needed the higher humidity. I suppose there will probably be no real answer for the foreseeable future. I just find them to be such tough and adaptable animals overall, so it intrigues me that some would evolve to be a bit more sensitive than others.

Tomoran said:

I was just curious as to how, physiologically, these adaptations might have manifested. For example, did species that are able to thrive in arid conditions develop a thicker coating over their exoskeletons to hold in moisture and prevent desiccation? I'm guessing that there has been little research or study into this, but it's been something I've wondered about.

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Plants have used similar adaptations: Thicker outer layers, less loss thru respiration, greater fluid efficiency, slower growth, etc. They learn to live with less and make the most use of what they have. For plants and animals from high rainfall climates, this isn't a top priority, and they're freed up from constantly dealing with water conservation. Growing plants and molting spiders can't afford to outrun their resources, so rainfall dictates how fast they can grow.