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Discussion Starter · #1 ·
As most owners of any Rhacodactylus species will undoubtedly be aware, “room temperature” is “ideal” for species within this genus. Of course, this is suitably vague, but “room temperature” can be further refined as being between 70-80°f (21-27°C). This temperature is generally easy to maintain, and in most cases, does not require the use of any additional heat sources. While it is clear that this heating routine is relatively successful (in so far as there are large numbers of Rhacodactylus geckos kept and bred in the UK annually), I am not fully convinced as to its suitability for the sustained health, and performance of these animals.

Thermoregulation, as you will all likely be aware, is the act of maintaining body temperature within given thermal limits in order for normal bodily processes to take place at optimal (or near optimal) efficiency. The key to successful thermoregulation then, relies on being able to heat and cool the body, according to predefined requirements, using available temperature gradients within the environment. This therefore means that unless your tank is set at the thermal optimal for your species (or indeed specific individual), then you must provide a thermal gradient, and allow the animal to thermoregulate independently. Failure to do this, will likely result in sub-optimal performance, which generally manifests itself as lower than expected appetite, reduced growth rate, impaired digestive ability and other similar symptoms.

Further to this, it has been conclusively demonstrated that other nocturnal gecko species thermoregulate diurnally (Autumn & De Nardo, 1995 – Behavioural thermoregulation increases growth rate in a nocturnal lizard) and so maintaining them at temperature, which mimic their active period (i.e. the night time), is probably inappropriate. OK, so if we accept that maintaining the enclosure at a single temperature is not ideal physiologically for these species, then delimiting a suitable temperature gradient for these species becomes very important.

Many of you will likely be aware of the suggestion that temperatures above 82-83°f (28°C) will induce stress, and possibly cause overheating and death for Rhacodactylus geckos (particularly mentioned for R. cilliatus, although this may simply be due to the numbers of this species kept compared to the other species in the genus). Given the ability of cold-blooded animals to cope with sub-optimal temperatures (both above and below optimal), I find it difficult to believe that a difference in temperature of less than 5°f (2°C) could potentially cause such problems to a species. For this reason I tested experimentally preferred temperature (Tp) in Crested geckos (R. cillatus) over a gradient ranging from 90°f (32°C) to 70°f (21°C) for 26 non-full sibling individuals. Somewhat surprisingly, given the claim of high fatality rate over temperatures of 80°f (27°C), Tp for this species was 86°f (30°C), and higher temperature was tolerated without issue.

With this in mind, I decided that testing growth rate between individuals which were maintained at the generally recommended “room temperature” (in this case, a constant temperature of 75°f or 24°C), and individuals maintained with a diurnal temperature gradient ranging from their Tp of 86°f (30°C) to 70°f (21°C), and a nocturnal temperature of 70°f (21°C). Fifty two (52) hatchlings (with no genetic bias) were divided into the two test categories, and growth rate, along with volume of food eaten was recorded. All other environmental parameters were kept constant, UVb light (5%) was provided, and the food source was exclusively black crickets, appropriately gut-loaded and supplemented at every feed with Nutrobal.

Figure 1: Mean body mass over time in captive R. ciliatus raised from hatching under two separate thermal conditions. Circles represent mean body mass of geckos allowed to thermoregulate at diurnal temperatures. Squares represent mean body mass of those maintained at constant nocturnal temperatures. Bars represent standard error.

The results were pretty conclusive, and show that geckos maintained at a constant ‘room’ temperature (75˚f), grew at a rate of 0.047g/day, while geckos allowed to thermoregulate independently grew at a rate of 0.058g/day. The difference in growth rate is statistically significant (P = 0.002), suggesting that there is a real improvement in performance (measured here as growth rate) in the animals allowed to thermoregulate independently, compared to those maintained at a sub-optimal single temperature. The number of prey items consumed per individual was higher in the thermoregulating group, and because volume of prey consumed could be linked to mass of the animal, when we controlled for body mass, prey consumption showed no significant effect of treatment.

So what do these experiments show, and how could they influence the way you maintain your Rhacodactylus species?

Well, perhaps the most important finding, is that you must provide a thermal gradient for your animals. A single temperature maintained across the entire enclosure is inappropriate for any cold-blooded species, and maybe significantly affecting the performance (in this case, the ability of you animal to function at optimal capacity) of your animal. I am fully aware that the suggested ‘risk’ of overheating may not be fully removed by this experiment (although the evidence is very clear that the risk is unfounded), and so I am not suggesting that everyone simply increase their enclosure temperatures if they do not feel safe doing so. However, these finding should remove some of the worry over potential overheating with summer just around the corner. However, to clarify, raising the temperature across the whole enclosure is not ideal, as this also will not allow correct thermoregulation to take place.
 

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A very well written and interesting read but as my thermometers state my enclosure gets to around 18-20 at night and about 23-25 at day which seems to be fine but i will create a thermal gradient
 

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Discussion Starter · #3 ·
I'm not sure I understand, seems to be fine for what?

Do you have a heat source creating a thermal gradient in the tank, or is the tank heated by the ambient room temperature? Without comparing both, how can you know which performs better, or if the animal is experienced sub-optimal conditions?

Thanks for the reply,

Andy

Ah, just seen your edit. I'd be interested to know if you see any difference.
 

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i have no heat source at the moment and the animal in question eats the cgd fine but i will test out a heat gradient as i have a spare pulse thermostat should i use a ceramic or heat bulb if i am going to test this out?
 

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A very interesting article - thanks!

A few questions though...

Can I ask what heat source/enclosure was used in this research as there has been a lot of debate on here about mat vrs lamp.

Would I be right in assuming, from these findings, that, in actual fact, the 'typical' crestie set up of a 45x45x60 exo is incorrect as it would be difficult to provide a thermo gradient?

Also, is faster growth considered a better way to grow? There is a lot of evidence that shows in other species (including humans) that growing fast is actually detrimental to low term health...?

Can I just ask too why you chose to feed a diet of just black crickets to them when the collective belief is that they live on fruit with the odd insect?

Thanks

Kat
 

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Discussion Starter · #7 ·
So I just noticed your edit... I was clearly too eager to reply. Choice of heat source is entirely up to you, and both will have their merits. If you are currently happy with your current lighting regime, and your tank layout allows it, I would suggest going with the ceramic (obviously take the required precautions to avoid the risk of burns etc..).

Andy
 

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So I just noticed your edit... I was clearly too eager to reply. Choice of heat source is entirely up to you, and both will have their merits. If you are currently happy with your current lighting regime, and your tank layout allows it, I would suggest going with the ceramic (obviously take the required precautions to avoid the risk of burns etc..).

Andy
yes i will but an interesting point was made what tanks were used and which sources as i too have an exo terra and can imaging since it as an arboreal one that a thermo-gradient will not be as easy?
 

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oh and is the reason they ate more because they had a choice of temperature in which to digest so could digest faster and thus grow quicker and another question do they deficate more with a thermo-gradient. you may not have the answer to this but i would find this interesting
 

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Awesome right up, very to the point, and aids a belief of my own, Basking points are important, and should be used, even a gradient with only a few Celsius difference can make all the difference in behaviour and growth rate.

Spot on buddy.

:2thumb:

Just out of curiosity, was humidity uniform?
 

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Discussion Starter · #11 ·
A very interesting article - thanks!

A few questions though...

Can I ask what heat source/enclosure was used in this research as there has been a lot of debate on here about mat vrs lamp.

Would I be right in assuming, from these findings, that, in actual fact, the 'typical' crestie set up of a 45x45x60 exo is incorrect as it would be difficult to provide a thermo gradient?

Also, is faster growth considered a better way to grow? There is a lot of evidence that shows in other species (including humans) that growing fast is actually detrimental to low term health...?

Can I just ask too why you chose to feed a diet of just black crickets to them when the collective belief is that they live on fruit with the odd insect?

Thanks

Kat
Hi Kat, thanks for the response. I will endeavor to answer as fully as possible.

For the Tp experiment, heat cable was used, in a "specially designed" (perhaps this is too grandiose way of saying it purpose built) horizontally oriented chamber. However for the growth experiments, normal vertically oriented tanks with ceramic heat bulbs were used (the temperature gradient was therefore vertical, and not horizontal). I think this is quite important, as mats do not create ambient temperature, and so cannot create a gradient (but more a hot, and then not hot choice).

Appropriate growth rate? It's a very good question, and I guess it is possible to speculate reasons why this could be positive and negative. It is however a typically used character for this type of experiment, and I would suggest it makes some evolutionary sense as that increased growth rate infers a fitness advantage.

Your final point is also interesting, I have seen no conclusive evidence that these fruit makes up a significant proportion of the diet of any of these species in the 'wild', it seems this bias is imposed in captivity. I'd be happy to see evidence to the contrary though!

Kind regards,

Andy
 

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A very interesting read the only way to ascertain if this indeed is beneficial to this species would be to see which method produces a) the most offspring and b) the longest lived cresteds on average faster growth is not always a good thing and could lead to shorter lifespans and increased risk of health problems

Theres no way of knowing i think this is just one part of a larger study of rhacs :2thumb:
 
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Discussion Starter · #13 ·
oh and is the reason they ate more because they had a choice of temperature in which to digest so could digest faster and thus grow quicker and another question do they deficate more with a thermo-gradient. you may not have the answer to this but i would find this interesting
Yes the group that was allowed to thermoregulate independently ate more, however when body mass was controlled for statistically, the treatment (thermoregulation, or constant) had no effect on consumption. So, larger gecko, the more it will consume.

Awesome right up, very to the point, and aids a belief of my own, Basking points are important, and should be used, even a gradient with only a few Celsius difference can make all the difference in behaviour and growth rate.

Spot on buddy.

:2thumb:

Just out of curiosity, was humidity uniform?
Humidity was maintained ad hoc based on the general rule that: The substrate should not be water logged, and standing water should not be present from previous misting when you mist again. In general it meant misting 2-3 times daily, with clear temporal variation in humidity depending on when it was last misted.

Andy
 

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Very well written article there Andy, I have been meaning to convert all my tanks to have a thermal gradient and UV source in time.

A note about the exo terra and creating a thermal gradient, I have my palm gecko in a 45x45x60, with a heat source set to give a max temperature of 95f in the top left hand side, and giver a good thermal gradient down to about 70f-75f at floor level. So this thermal gradient can be achieved. Also my carpet chameleon in a 45x45x45 has UV and a heat source, which produce a warm area of around 85f and again a cool area of between 70f-75f can be found.
 

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Discussion Starter · #15 ·
A very interesting read the only way to ascertain if this indeed is beneficial to this species would be to see which method produces a) the most offspring and b) the longest lived cresteds on average faster growth is not always a good thing and could lead to shorter lifespans and increased risk of health problems

Theres no way of knowing i think this is just one part of a larger study of rhacs :2thumb:
I think you raise an interesting point. While the growth rate was indeed faster in the group allowed to thermoregulate independently, it is perhaps incorrect to think this growth rate represents inappropriately fast growth which could negatively impact long-term fitness characters. It is more likely, in my opinion at least, that the constant temperature treatment is causing inappropriately slow growth. A character which is similarly detrimental to long term health.

Andy
 

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I think you raise an interesting point. While the growth rate was indeed faster in the group allowed to thermoregulate independently, it is perhaps incorrect to think this growth rate represents inappropriately fast growth which could negatively impact long-term fitness characters. It is more likely, in my opinion at least, that the constant temperature treatment is causing inappropriately slow growth. A character which is similarly detrimental to long term health.

Andy
Another question, did the two groups show any differences once adults? Or did one group just get there faster than the other?
 

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Discussion Starter · #17 ·
Another question, did the two groups show any differences once adults? Or did one group just get there faster than the other?
Differences in what respect mate? The experiment for each animal ceased after their 5 month trial, and so experimental conditions were not maintained after this point. Unfortunately long term fitness trials are difficult to fund and maintain...

'Adulthood' or sexual maturity can be affected by body mass and growth rate, so it is reasonable to think that there may be some decrease in the time it takes to reach sexual maturity. However, it is likely that individuals of R. cilliatus reach this at around the 7-9 month mark (irrespective of sex), 'we' then impose weight restrictions on breeding for the long term health of the animal, not because it is not capable of reproducing (and this is of course a good thing).

Andy
 

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I think you raise an interesting point. While the growth rate was indeed faster in the group allowed to thermoregulate independently, it is perhaps incorrect to think this growth rate represents inappropriately fast growth which could negatively impact long-term fitness characters. It is more likely, in my opinion at least, that the constant temperature treatment is causing inappropriately slow growth. A character which is similarly detrimental to long term health.

Andy
Oh i deffinetly agree with you it is more than likely detrimental slow growth as opposed to the thermo gradients faster growth being detrimental to there health id say all lizards need a way of thermoregulating there bodies are hardwired to do so.

if that makes any sense whatsoever im not so sure i know what im trying to say lol
 

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Discussion Starter · #19 ·
Oh i deffinetly agree with you it is more than likely detrimental slow growth as opposed to the thermo gradients faster growth being detrimental to there health id say all lizards need a way of thermoregulating there bodies are hardwired to do so its just temperature fiddling after that.
This is exactly what I hope the take home message will be Shane, providing a thermal gradient (somewhat irrespective of the range) is essential for reptiles to properly maintain their body temperature within its optimal range. Failure to do this, can and will have negative impacts on a range of physiological and behavioral traits, and may negatively impact the overall health of the animal.

Cheers again for the input.

Andy
 

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I dont know why but this thtreadhas got my mind buzzing lol
 
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