The Influence of Barometric Pressure

[Tentacle Toast]

Good morning, friends.

I've observed several times now a correlation between a drop in barometric pressure, & molting/atypical behaviours. The latter is to be expected, but it's the seemingly spontaneous response of the former that I'm curious about; might an impending bout of moisture hasten this usually days-long (at least) process?
For several weeks, we've had daytime temps in the 80's (night drops from low 50'-60's), but we had a couple small systems move in bringing rain, & dropping the daytime temps since Monday evening. Well, I had a geniculata that ate a cricket THAT day (Monday), then dropped molt like a prom dress THAT night. It happened so unexpectedly, that I thought her excuviae her corpse. Then LAST night into this morning, my versicolor did almost the same thing, but took the time to web herself off (in the most precarious position I thought, but she seems to be fine now). I've observed this phenomena with a couple of my Avic species, & my D. diamantinensis before, & thought that perhaps it might have something to do with them sharing a similar geographic distribution... but it's happened once with my P. metallica, as well.
Anyone else notice this as well?
Also, my apologies for the horrendous photo quality; my phone's a busted-up mess, & I've misplaced my camera.

 

[Dorifto]

I made a little experiment regarding this exact question, since I noticed the same behaviour/correlation with my Ts, so my answer is yes.

Molting experiment

Well last week after answering a thread about molting problems and knowing that my Ts molted after a big storm and more humid weather (it can be a coincidence too) I decided knowing that a big storm (summer storm) was coming, to "mimic" the effects of that storm on my vivariums. I moisted the...

arachnoboards.com

 

[Tentacle Toast]

I made a little experiment regarding this exact question, since I noticed the same behaviour/correlation with my Ts, so my answer is yes.

Molting experiment

Well last week after answering a thread about molting problems and knowing that my Ts molted after a big storm and more humid weather (it can be a coincidence too) I decided knowing that a big storm (summer storm) was coming, to "mimic" the effects of that storm on my vivariums. I moisted the...

arachnoboards.com

What a terrific thread, man...bravo! The quality of your set-up was proven by your spider staying put despite the open door... probably left & came back, LoLoL.

Thanks for linking that here...I'm more fascinated by these things every day.

 

[Dorifto]

What a terrific thread, man...bravo! The quality of your set-up was proven by your spider staying put despite the open door... probably left & came back, LoLoL.

Thanks for linking that here...I'm more fascinated by these things every day.

Hahahahahaha you are welcome!!! And thanks of course

I freaked out at first, but when I saw her inside, I feel and instant relief and a good feeling because she liked and likes the enclosure.

Imo she took a stroll outside for sure, hope that my gf don't read this hahahaha, 4 days without exploring... highly unlikely knowing how active my pulchra is. That was the second time someone left her door open, hence Vol. 2 both times found her inside.

 

[Tentacle Toast]

Hahahahahaha you are welcome!!! And thanks of course

I freaked out at first, but when I saw her inside, I feel and instant relief and a good feeling because she liked and likes the enclosure.

Imo she took a stroll outside for sure, hope that my gf don't read this hahahaha, 4 days without exploring... highly unlikely knowing how active my pulchra is. That was the second time someone left her door open, hence Vol. 2 both times found her inside.

She missed her isopod friends ..

 

[Dorifto]

She missed her isopod friends ..

I spent the following week recovering them, at least the survivors

 

[viper69]

Good morning, friends.

I've observed several times now a correlation between a drop in barometric pressure, & molting/atypical behaviours. The latter is to be expected, but it's the seemingly spontaneous response of the former that I'm curious about; might an impending bout of moisture hasten this usually days-long (at least) process?
For several weeks, we've had daytime temps in the 80's (night drops from low 50'-60's), but we had a couple small systems move in bringing rain, & dropping the daytime temps since Monday evening. Well, I had a geniculata that ate a cricket THAT day (Monday), then dropped molt like a prom dress THAT night. It happened so unexpectedly, that I thought her excuviae her corpse. Then LAST night into this morning, my versicolor did almost the same thing, but took the time to web herself off (in the most precarious position I thought, but she seems to be fine now). I've observed this phenomena with a couple of my Avic species, & my D. diamantinensis before, & thought that perhaps it might have something to do with them sharing a similar geographic distribution... but it's happened once with my P. metallica, as well.
Anyone else notice this as well?
Also, my apologies for the horrendous photo quality; my phone's a busted-up mess, & I've misplaced my camera.
View attachment 422268
View attachment 422269

Over the course of time many have made this claim- myself included.

All anecdotal- but I do believe there’s a connection. As we know rains stimulate many things in the wild

 

[AphonopelmaTX]

Sorry to burst everyone's bubble, but you can't prove or disprove a correlation between atmospheric pressure and molting without a barometer in the room your tarantulas are in. Molting usually corresponds to changes in seasons which include changes in temperature and/ or rain/ humidity. I'm not saying atmospheric pressure alone isn't a trigger, but you can't assume it is without keeping all other variables at a constant.

Since I don't have a barometer myself to test for changes in atmospheric pressure, I have been able to use my indoor/ outdoor thermometers in my tarantula room to confirm a correlation between changes in temperature as the seasons change here in Texas and when my tarantulas molt. This observation allows me to predict which tarantulas are due for a molt with a reasonable amount of accuracy. Not all of my tarantulas molt on a seasonal schedule, but the majority do. The tarantulas in my collection that have a predictable molting schedule include species of Aphonopelma and Brachypelma both adults and spiderlings. The tarantulas that do not have a predictable molting schedule include species of Grammostola, Euathlus, and Theraphosa. It is interesting to note that the species with predictable molting schedules occur naturally in the northern hemisphere and the ones that do not in the southern hemisphere.

With the tarantulas in my collection with a predictable molting schedule, there are two phases: spring/ early summer and late summer/ fall. When the temperature in my spider room start rising to a temperature of about 80 F in late May to June, the "spring group" stops eating and eventually molts. The "fall group" stops eating and molts when the temperature starts falling from about 85 F to about 70 F. There is no molting activity during the hottest (July-August) and coldest months (January-February) when temperatures in my spider room are steady at around 85 F and 60 F (give or take a few degrees F) respectively.

I also have a thermo-hygrometer which reads temperature and humidity in the same device. I have not seen any correlation between changes in humidity and molting activity, but it is a variable I have not tested for specifically so can't rule it out as a factor. Keeping temperature at a constant to test for only humidity is practically impossible in my situation. Humidity doesn't appear to be a factor in triggering a molting cycle since I never make any attempt to add water to the soil in my tarantula enclosures or let it dry out.

 

[Tentacle Toast]

Sorry to burst everyone's bubble, but you can't prove or disprove a correlation between atmospheric pressure and molting without a barometer in the room your tarantulas are in. Molting usually corresponds to changes in seasons which include changes in temperature and/ or rain/ humidity. I'm not saying atmospheric pressure alone isn't a trigger, but you can't assume it is without keeping all other variables at a constant.

Since I don't have a barometer myself to test for changes in atmospheric pressure, I have been able to use my indoor/ outdoor thermometers in my tarantula room to confirm a correlation between changes in temperature as the seasons change here in Texas and when my tarantulas molt. This observation allows me to predict which tarantulas are due for a molt with a reasonable amount of accuracy. Not all of my tarantulas molt on a seasonal schedule, but the majority do. The tarantulas in my collection that have a predictable molting schedule include species of Aphonopelma and Brachypelma both adults and spiderlings. The tarantulas that do not have a predictable molting schedule include species of Grammostola, Euathlus, and Theraphosa. It is interesting to note that the species with predictable molting schedules occur naturally in the northern hemisphere and the ones that do not in the southern hemisphere.

With the tarantulas in my collection with a predictable molting schedule, there are two phases: spring/ early summer and late summer/ fall. When the temperature in my spider room start rising to a temperature of about 80 F in late May to June, the "spring group" stops eating and eventually molts. The "fall group" stops eating and molts when the temperature starts falling from about 85 F to about 70 F. There is no molting activity during the hottest (July-August) and coldest months (January-February) when temperatures in my spider room are steady at around 85 F and 60 F (give or take a few degrees F) respectively.

I also have a thermo-hygrometer which reads temperature and humidity in the same device. I have not seen any correlation between changes in humidity and molting activity, but it is a variable I have not tested for specifically so can't rule it out as a factor. Keeping temperature at a constant to test for only humidity is practically impossible in my situation. Humidity doesn't appear to be a factor in triggering a molting cycle since I never make any attempt to add water to the soil in my tarantula enclosures or let it dry out.

I DO happen to have a Fischer weather station (one of those "three dial" thermometer/hydrometer/barometer units boat guys love), & the reason I made this thread is because I have thrice now made this correlation. I explicitly didn't say it CAUSED them to molt, but the the spontaneity is certainly remarkable. I keep my house dark & cool year round through climate control, so outdoor fluctuations in temperature & humidity I don't believe are playing a factor. As mentioned, the majority of species involved share similar distributions (with the metallica as the oddball), so I thought perhaps this was a possible response to spiders in that range.
Certainly seems I'm not the only one who's experienced this. Perhaps it'll be a post grad's thesis one day, yes?

 

[AphonopelmaTX]

I DO happen to have a Fischer weather station (one of those "three dial" thermometer/hydrometer/barometer units boat guys love), & the reason I made this thread is because I have thrice now made this correlation. I explicitly didn't say it CAUSED them to molt, but the the spontaneity is certainly remarkable. I keep my house dark & cool year round through climate control, so outdoor fluctuations in temperature & humidity I don't believe are playing a factor. As mentioned, the majority of species involved share similar distributions (with the metallica as the oddball), so I thought perhaps this was a possible response to spiders in that range.
Certainly seems I'm not the only one who's experienced this. Perhaps it'll be a post grad's thesis one day, yes?

Since your observations are coming from a device measuring multiple data points, your claim is much more credible than the others. I don't pay any attention to those who make a claim based on whether it is raining outside or not or what their weather app says. Since your claim comes from a device in the same room as your tarantulas, I'm much more interested in this thread! LOL

Perhaps you are right in that this topic could make for a good grad student project, but I don't think you need to be a grad student to get meaningful data though. Recording all information shown on your weather station every time a tarantula molts and plotting it on a graph would be extremely revealing as to what abiotic factors contribute to triggering a molting cycle.

Now I want one of those weather station gadgets to find out what the atmospheric pressure is when I notice the temperature changes. Maybe atmospheric pressure contributes more to triggering molts than temperature and I don't even know it because I can't measure it.

 

[Tentacle Toast]

Since your observations are coming from a device measuring multiple data points, your claim is much more credible than the others. I don't pay any attention to those who make a claim based on whether it is raining outside or not or what their weather app says. Since your claim comes from a device in the same room as your tarantulas, I'm much more interested in this thread! LOL

Perhaps you are right in that this topic could make for a good grad student project, but I don't think you need to be a grad student to get meaningful data though. Recording all information shown on your weather station every time a tarantula molts and plotting it on a graph would be extremely revealing as to what abiotic factors contribute to triggering a molting cycle.

Now I want one of those weather station gadgets to find out what the atmospheric pressure is when I notice the temperature changes. Maybe atmospheric pressure contributes more to triggering molts than temperature and I don't even know it because I can't measure it.

Here ya go... pretty much what I have, except mine doesn't have the rounded ends:

https://www.loewen-meta.com/products/fischer-weather-station-9178-us-fahrenheit?variant=41021384655043&gclid=Cj0KCQjw8O-VBhCpARIsACMvVLNSMaOKCySEdOrJpc16q9GkmUnfgfz13s1oVS-eqs6WXYPnUNGfPZgaAmfYEALw_wcB

I'll start keeping a log when storms are forecast, & chart it out like you've suggested. At the very least, it'll make for an interesting update. Perhaps by then, I'll have been buggered into getting a new phone, & can even include decent pictures, LoL

 

[Dorifto]

Unless you were blowing air in and out, pretty much the atmospheric pressure will be the same (+-) than your local meteorologic station, if you are at the same area and same elevation of course.

Here at least there is a huge correlation between storms and a decrease in atmospheric pressure, even we have our own storm, named galerna or embata, where the temps can drop as much as 20°C 68F in matter of minutes, like this month, from 42°C to 20°C...

But yes, I'm agree with you, they are asunptions or hypothesis unless a measured experiment or data collection is made.

Here ya go... pretty much what I have, except mine doesn't have the rounded ends:

https://www.loewen-meta.com/products/fischer-weather-station-9178-us-fahrenheit?variant=41021384655043&gclid=Cj0KCQjw8O-VBhCpARIsACMvVLNSMaOKCySEdOrJpc16q9GkmUnfgfz13s1oVS-eqs6WXYPnUNGfPZgaAmfYEALw_wcB

I'll start keeping a log when storms are forecast, & chart it out like you've suggested. At the very least, it'll make for an interesting update. Perhaps by then, I'll have been buggered into getting a new phone, & can even include decent pictures, LoL

Lol!! I used to have one when I was a child, or at least a pretty similar one. I broke it

 

[dogpack]

No T's yet. I'm still researching/learning, gathering supplies/raaising feeders, and doing what I can to be prepared for new T friends. Finding this thread now has me curious about the molting process and its relationship to external factors. I will need to see what I can find. Many thanks for bringing up this topic.

 

[viper69]

I DO happen to have a Fischer weather station (one of those "three dial" thermometer/hydrometer/barometer units boat guys love), & the reason I made this thread is because I have thrice now made this correlation. I explicitly didn't say it CAUSED them to molt, but the the spontaneity is certainly remarkable. I keep my house dark & cool year round through climate control, so outdoor fluctuations in temperature & humidity I don't believe are playing a factor. As mentioned, the majority of species involved share similar distributions (with the metallica as the oddball), so I thought perhaps this was a possible response to spiders in that range.
Certainly seems I'm not the only one who's experienced this. Perhaps it'll be a post grad's thesis one day, yes?

I knew you had one

 

[Matt Man]

Well I live in So Cal where we presently have high temp, high barometric pressure of 30.03 H and 29.9 L and many of my Ts are presently molting
So my experience presently, does NOT jibe with your theory

 

[Matt Man]

steady @ 29.97, P. rufilata and T. verdezi molted

 

[Tentacle Toast]

steady @ 29.97, P. rufilata and T. verdezi molted

At no point did I imply it a drop was a requirement, I merely noticed a correlation between"spontaneous" molts, & low pressure systems. You're experience neither proves, nor disproves my observation.

 

[l4nsky]

Well I live in So Cal where we presently have high temp, high barometric pressure of 30.03 H and 29.9 L and many of my Ts are presently molting
So my experience presently, does NOT jibe with your theory

What's the humidity like right now, especially in comparison to the rest of the year?

IMO, it's likely that temperature, pressure, humidity, and even nutrition all might have some influence in triggering a molt, or more precisely, in determining a molting schedule as a tarantula matures.

Since your observations are coming from a device measuring multiple data points, your claim is much more credible than the others. I don't pay any attention to those who make a claim based on whether it is raining outside or not or what their weather app says. Since your claim comes from a device in the same room as your tarantulas, I'm much more interested in this thread! LOL

I did have a possible correlation between increased burrow humidity and recent thunderstorms not only triggering molts, but syncing up the molts in 3 Phormingochilus specimens (0.2 Akcaya and 0.1 Sabah Blue). I posted the details of that event in the thread that @Dorifto linked above. It's a small sample size, but it's enough to warrant further investigation.

Perhaps you are right in that this topic could make for a good grad student project, but I don't think you need to be a grad student to get meaningful data though. Recording all information shown on your weather station every time a tarantula molts and plotting it on a graph would be extremely revealing as to what abiotic factors contribute to triggering a molting cycle.

Lol two steps ahead of you sir. My initial observations definently peaked my interest. We'll want to collect a fair bit more data than just the day of the molt if we want to identify any trends or patterns. Hopefully, I'll be able to track temperature and humidity for the burrow as well as temperature, humidity, and barometric pressure for the tarantula room and outdoors, and even food intake by the end of the year.

I have a working theory that I really want to test.

• I think that different species have different minimum times between molts and this minimum time increases as the animal gains size and matures (meaning some species have faster growth rates than others, but they all slow down as they get larger and hit maturity).
• I also think that when the specimens are younger and putting on size quicker, that most species aren't entirely reliant on weather cues as they are smaller and can easily get into hides in trees or small burrows that offer increased humidity. For the smaller specimens of most species, I believe that nutritional intake and temperature are much more important in determining molts as long as they have a consistently humid place (for the species!) to molt, but I think that importance shifts more towards other factors as the specimen matures.
• I also think that each species has preferred weather patterns for reproduction and molting when they mature that are instinctual and tied to the natural habitat that they are adapted to. I'd like to see if they potentially take this instinctually known pattern and try to fit it as best they can to the seasonal variations of their current geography as they grow up to time their maturity to that pattern.

@AphonopelmaTX , If I remember correctly, you're a bit of a data nerd like me. I'll let you know if I get the system up and running before the end of the year or not.

 

[The Snark]

Suggestion. If you want the thread topic, or other environmental conditions to be understood, the basics of proper scientific methodology should be used.

Required
-One offs don't count. Results must be repeatable.
-A control needs to be established. Ordinary conditions compared to the environmental variations.
-As near as possible, test equipment should be in calibration. To standards so anyone with similar test equipment can replicate conditions and get the same results.
-All environment variables need to be monitored and documented. Lighting, minimum, maximum and mean temperature, humidity, and barometric pressure. Air exchange in the room should be nominal norm to assure no accumulations of gasses especially CO2 are present. Also, external stimulus to each animals senses must be similar. Usually labs maintain isolation areas or chambers.

The general plan is obvious. Predictable replication of results. And always discard the top and bottom 10% extremes.

Keep in mind CO2 is well documented to have significant effects on physiology and metabolism (or photosynthesis) with plants and animals. This is a serious pitfall for people who want to have bio-active enclosures. CO2 can accumulate and pool very rapidly.

 

[Jonathan6303]

No T's yet. I'm still researching/learning, gathering supplies/raaising feeders, and doing what I can to be prepared for new T friends. Finding this thread now has me curious about the molting process and its relationship to external factors. I will need to see what I can find. Many thanks for bringing up this topic.

I wouldn’t worry about it in early stages of keeping.