dehydration

mark1

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I've read on here many times of folks causing their hatchling tortoises to die by keeping them on dry substrate without additional humidity for 1-2 months , the cause of death being kidney failure ……… are there any studies done on this scenario ? I ask because it contrast results of K. Nagy in a study done on headstarting desert tortoises ……… during a 16 month drought all the 4 year old tortoises died , 47 and 50% of the 2 and 3yr olds died ….. 94% of the tortoises hatched during drought survived ……….. he wrote in a 2015 publication
juveniles in the natural-rainfall-only pen is puzzling. The 2006 cohort, which hatched near the mid-point of that drought, survived the drought well, whether they lived in a rain-supplemented or a natural rain pen. We suspect that the large amount of yolk that hatchlings contain in their bodies may help account for their drought-durability. There may also be behavioral differences (remaining in burrows longer, staying inactive, withdrawing into shell) and physiological differences (possible ability to shrink during drought [Wikelski and Thom 2000]; reduced water losses via evaporation [Wilson etal. 2001]) between hatchlings and 4-yr olds that influenced survivorship. To examine this further, we looked at survivorship of other cohorts living in the natural-rain-only pens during the drought period. Drought resistance declined with increasing age:
survivorship through the drought by the 2006 (youngest) cohort was 94%, it was 47% in the 2005 cohort, 50% in the 2004 cohort, and 0 % in the 2003 cohort.

our observations of the juveniles living in the three unwatered pens during the dry spring and summer of 2007 led us believe they would not live very long. Their CI values had dropped to near or below 0.4, indicating severe dehydration and starvation (Nagy et al., 2002). Most were lethargic and unable (or unwilling) to open their eyes or respond quickly to touch stimuli when encountered at or near their burrow entrances in early
morning and evening. Substantial rain showers in early September ended the drought and apparently saved the lives of those first-year juveniles in the unwatered pens. They drank rainwater, recovered reasonably good body condition by mid-September, and had high annual survivorship(94%). Stored yolk may help confer drought resistance on first-year tortoises (see discussion below).

https://cloudfront.escholarship.org/dist/prd/content/qt66b156f8/qt66b156f8.pdf




Kenneth A. Nagy is a Professor Emeritus and a Research Professor in the Department of Ecology and Evolutionary Biology at UCLA, where he has been a faculty member since 1971. A native of Southern California, he received his Bachelor(1967) and Ph.D. (1971) from the University of California at Riverside, and his doctoral research was on the physiological ecology of the herbivorous desert lizard Sauromalus obesus (Chuckwalla). He developed the doubly-labeled water method, which can provide determinations of field metabolic rate, water flux rate, and feeding rate in free-living vertebrate animals, and he applied that technique to wild reptiles, birds, and mammals in various habitats around the world. He summarized his results and those of colleagues in three review publications that present allometric equations (“mouse to elephant curves”) in a large variety of terrestrial animal groupings (taxonomic, dietary, habitat, lifestyle). These empirical equations have been useful for predicting the food, water, and energy needs of species that have not yet been studied in the field. Since retiring in 2006, he has switched his research interests from ecophysiology to conservation biology, especially of Desert Tortoises, and has been conducting tortoise head-starting research on three military bases in the Mojave Desert in California

http://ucla.academia.edu/KennethNagy
 

Tom

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Yes. Necropsies have been done. I know of no published studies on individual pet tortoises and their dehydration related causes of death. @Will is a master of finding published studies. Perhaps he can find something.

And again, what happens outside in a wild setting in the natural habitat, testing the extreme limits of survival of desert tortoises, does not equate to optimal care for a captive baby in a typical North American home. Many of us tried the dry methods in many ways for many years. It simply doesn't work. By comparison, keeping them hydrated and allowing them to find, use or create little humid microclimates universally does work with all species.

I'm not interested in providing survivable conditions for my tortoises. I'm interested in providing optimal conditions for my tortoises.
 

mark1

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if you read the paper it actually tells you that supplementing water to a point is extremely beneficial …… and they're not advocating to not give your tortoises water , it actually tells you it killed most of the older tortoises …….. what it demonstrate is the drought/dehydration tolerance of hatchling tortoises in this guys study …….. if they can hatch out and not drink for 8 months or more , and completely recover in a matter of weeks from near death and starvation , how is it a healthy hatchling provided water can die in a matter of a month or two from dehydration ? simply from dry substrate ……… just a little hard for me to put together the two scenarios , the tortoises in the study were not in the wild , they were being raised in pens …… there are similar studys on dehydration and freeze tolerance in hatchling turtles ……… hopefully Will has some more info …...
 

mark1

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I believe the quest for knowledge , to understand the physiological reasons desert species can survived dehydration better than non-desert living species , it's not just knowing that the hatchlings survive it , but what is the biological reason they survived it at such a higher rate than adults ……. like understanding why some turtles are freeze tolerant , to understand it they needed to freeze turtles that couldn't survive it to see the difference …..I actually use that knowledge to keep my turtles , I know why I can leave the na wood turtles out in a frozen pond and I have to bring in the ca wood turtles …. often there is real life human betterment in such knowledge …….. early dog nutrition studies were brutally cruel , understanding cancer and heart disease is pretty cruel in itself …….
 

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The fact that the older tortoises were less successful at surviving in the prolonged drought may be because their bodies had become accustomed over the years to a certain environment, and the drought changed it drastically. The young tortoises had not had time to "adapt" to their "normal" environment and so they were less affected by the change. The change stressed out the older tortoises much more....just a thought.
 

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What I don't understand is, scientific study or not...how could anyone deliberately allow tortoises to die of dehydration?? Did we really need to know that adults die before hatchlings in a drought?
Such experiments are only the top of the iceberg. I don`t want to know how many cruel experiments researchers do with animals. Absolut unnecesseray experiments like this.
 

TammyJ

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Such experiments are only the top of the iceberg. I don`t want to know how many cruel experiments researchers do with animals. Absolut unnecesseray experiments like this.
I understand and I could not take part in anything like this myself - that is why I did not become a scientist!
 

TammyJ

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The way it seems is that experiments like this are necessary in the "big picture" often to actually save the species by sacrificing some of the individuals.
I hate it too.
 

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The set up of this experiment as had been for several that included Dave Morafka was to see the difference between drought and non drought conditions. The pens were huge, some had supplemental water in the form of sprinklers 'raining' on the area, while other were allowed to exists without rain intervention.

The tortoises were observed to die, they were not killed, there is a huge difference. It is not cruelty in any way shape or form. Just because a person was offering supplemental rain in a scattered system of pens, and others that did not get supplemental rain, does not mean the scientists let them die, anymore than anyone else who could have gone out to the desert those years and offered supplemental water to whatever tortoise they found. Those scientists may very well have thought the tortoises would dtay the course and come through. That's the point of using variables in a step wise way. The variable was supplemental rain. let's shut cruelty down right now, shall we, It's just as much you as them.

I found a study that I used in a recent presentation that indicates that about 75% of the shell in neonate tortoises is water. So, it is indeed very critical. As the tortoise ages that % drops. Adults" shell % water was 35%. That study is attached.

@Tom said "I'm not interested in providing survivable conditions for my tortoises. I'm interested in providing optimal conditions for my tortoises." I think that could be the TFO motto if we had one. That's not to say we can't learn from studies and posts regarding what happens in different situations. I have tested the bounds of some dogma myself.
 

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Bee62

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The set up of this experiment as had been for several that included Dave Morafka was to see the difference between drought and non drought conditions. The pens were huge, some had supplemental water in the form of sprinklers 'raining' on the area, while other were allowed to exists without rain intervention.

The tortoises were observed to die, they were not killed, there is a huge difference. It is not cruelty in any way shape or form. Just because a person was offering supplemental rain in a scattered system of pens, and others that did not get supplemental rain, does not mean the scientists let them die, anymore than anyone else who could have gone out to the desert those years and offered supplemental water to whatever tortoise they found. Those scientists may very well have thought the tortoises would dtay the course and come through. That's the point of using variables in a step wise way. The variable was supplemental rain. let's shut cruelty down right now, shall we, It's just as much you as them.

I found a study that I used in a recent presentation that indicates that about 75% of the shell in neonate tortoises is water. So, it is indeed very critical. As the tortoise ages that % drops. Adults" shell % water was 35%. That study is attached.

@Tom said "I'm not interested in providing survivable conditions for my tortoises. I'm interested in providing optimal conditions for my tortoises." I think that could be the TFO motto if we had one. That's not to say we can't learn from studies and posts regarding what happens in different situations. I have tested the bounds of some dogma myself.
Sorry, but I don`t agree with you. You said the tortoises were observed to die, not killed.
To my opinion they were killed because they had been trapped in a pen. No way to escape the experiment. No way to escape their death.
Maybe a lot of tortoises in the wild die when it is not raining but they have the chance to leave the dry region. The tortoises of the experiment doesen`t have this option. So what is the result of the experiment ? To know how long these tortoises can overlive without water ?
 

Kapidolo Farms

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Sorry, but I don`t agree with you. You said the tortoises were observed to die, not killed.
To my opinion they were killed because they had been trapped in a pen. No way to escape the experiment. No way to escape their death.
Maybe a lot of tortoises in the wild die when it is not raining but they have the chance to leave the dry region. The tortoises of the experiment doesen`t have this option. So what is the result of the experiment ? To know how long these tortoises can overlive without water ?

And what of the tortoises in the same area but not in a pen(?), they could be predated, part of the reason for the pens was to reduce depredation. Would there be a size pen that would make it so the tortoises were not in a sense confined? The pens had an area of 314 square meters (3390 square feet), that does not equate with confined. They were not denied anything other than artificial rain. I get the impression you think (metaphorically) they could have hailed a cab and gone somewhere else, when a region is in drought, it is often the whole water shed or one whole side of a mountain or a mountains rain shadow. Tortoises do not migrate for the most part (with a few notable exceptions). Maybe be happy for the tortoises that got the artificial rain. All were protected from Ravens, that's a good thing, yes?
 

Bee62

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And what of the tortoises in the same area but not in a pen(?), they could be predated, part of the reason for the pens was to reduce depredation. Would there be a size pen that would make it so the tortoises were not in a sense confined? The pens had an area of 314 square meters (3390 square feet), that does not equate with confined. They were not denied anything other than artificial rain. I get the impression you think (metaphorically) they could have hailed a cab and gone somewhere else, when a region is in drought, it is often the whole water shed or one whole side of a mountain or a mountains rain shadow. Tortoises do not migrate for the most part (with a few notable exceptions). Maybe be happy for the tortoises that got the artificial rain. All were protected from Ravens, that's a good thing, yes?
They had been protected from Ravens to not disturb the experiment. I think that is the one and only reason.
When you are so convinced of this experiment would you please explain me what the groundbreaking result of it was ? Maybe I am to blonde to understand it.
 

TammyJ

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The fact that the older tortoises were less successful at surviving in the prolonged drought may be because their bodies had become accustomed over the years to a certain environment, and the drought changed it drastically. The young tortoises had not had time to "adapt" to their "normal" environment and so they were less affected by the change. The change stressed out the older tortoises much more....just a thought.
Tammy, this is interesting. But now you know also that not only did the younger tortoises suffer less from the stress of changed conditions, but they had more water in their shells than the older ones!
 

Kapidolo Farms

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They had been protected from Ravens to not disturb the experiment. I think that is the one and only reason.
When you are so convinced of this experiment would you please explain me what the groundbreaking result of it was ? Maybe I am to blonde to understand it.
That's a hella good question. I believe it was one in a series of experiments at the location to look at differences between one situation over another. Though climate change was not the trendy topic than as it is now, this experiment can explain the difference that occurs based on rain fall.

These are other studies that used the result of this study
https://scholar.google.com/scholar?cites=7545491045622080834&as_sdt=2005&sciodt=0,5&hl=en

The actual reason a scientist does one experiment or another are rarely revealed with a direct statement, it is inferred by the background information placed at the beginning of the experiment. In this case the reasons why are well stated.

In the abstract they state two reasons for the experiment.

"1)We subjected neonate Desert Tortoises (Gopherus agassizii) that hatched inside fenced, predator-resistant field enclosures containing natural vegetation to either a natural rainfall regime or a regime of natural rainfall plus irrigation (supplemental precipitation) over a five-year period, to test the hypothesis that mimicking an above-average rainfall regime in years of average or low natural rainfall will improve rates of survival and growth.

2)We also tested the hypothesis that survivor-ship of released 1-yr olds will be high, due to a decline in predation susceptibility once the vulnerable nesting and hatchling phases are completed."

I am guessing if you were on a safari type trip somewhere and saw predators stalking and eating something you might be compelled to make the predator starve so the potential prey item could live anther day. I totally get that impulse. So, in a way the scientists could also be considered cruel for denying the ravens something they might eat, naturally.

Way outside the box of this conversation was an experiment many years ago, where island biology scientist fumigated a whole small island that only supported insects. They studied colonization by insects. By today's standard that would not be considered ethical.

Here is that experiment... https://www.researchgate.net/profil...Islands-The-Colonization-of-Empty-Islands.pdf
...which has been used by 750 other scientist to better understand many many principles of ecology.
 

KarenSoCal

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I think that not giving them artificial rain, even though they were in dire conditions, is the same as killing them.

The "experimenters" had what they needed to save lives, but didn't provide it.

If we have a person suffering from diabetes, and purposely withhold insulin to see how long he lives...aren't we killing him?

Will, I respect you and value your opinions. But on this, I just can't agree.
 

Bee62

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@Will said:
"I am guessing if you were on a safari type trip somewhere and saw predators stalking and eating something you might be compelled to make the predator starve so the potential prey item could live anther day. I totally get that impulse. So, in a way the scientists could also be considered cruel for denying the ravens something they might eat, naturally."

No, you are guessing wrong. Predators and non predators ( prey ) mostly living in a well balanced relationship together as long as humans don`t disturb this balance. I would never want a predator to starve that the prey can overlive.
But I am strictly against unnecessary experiments and to my opinion this experiment was one. There are too many cruel, unnecessary experiments done. We don`t have the rights to do them.
You mentioned the group "Waltham". They sell dog and cat food. But at first they make a lot of sometimes painful experiments with dogs and cats. The animals in the laboratories of "Waltham" were made sick to test the special developed food for several deseases.
When I feed my pet at home a hundred other non-pet dogs in the laboratories had to suffer painful deseases before so that my pet at home has a "wonderful and healthy" life. I think that is sick !
Do you get what I mean with unnecsessary experiments ?
 

mark1

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I believe during drought they hunker down in their burrows and it either rains or they die , they don't go out looking for water ….. at least that's the finding from some of the radio tracking/home range studies I've seen …..
 

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@Will said:
"I am guessing if you were on a safari type trip somewhere and saw predators stalking and eating something you might be compelled to make the predator starve so the potential prey item could live anther day. I totally get that impulse. So, in a way the scientists could also be considered cruel for denying the ravens something they might eat, naturally."

No, you are guessing wrong. Predators and non predators ( prey ) mostly living in a well balanced relationship together as long as humans don`t disturb this balance. I would never want a predator to starve that the prey can overlive.
But I am strictly against unnecessary experiments and to my opinion this experiment was one. There are too many cruel, unnecessary experiments done. We don`t have the rights to do them.
You mentioned the group "Waltham". They sell dog and cat food. But at first they make a lot of sometimes painful experiments with dogs and cats. The animals in the laboratories of "Waltham" were made sick to test the special developed food for several deseases.
When I feed my pet at home a hundred other non-pet dogs in the laboratories had to suffer painful deseases before so that my pet at home has a "wonderful and healthy" life. I think that is sick !
Do you get what I mean with unnecsessary experiments ?

I didn't talk about dog food, that was someone else. That is an entirely different situation. There, dogs were forced into a situation that was not natural. In the tortoise experiment is was intervention by adding rain, against the natural situation that helped some animals overcome a natural adverse situation. The same experiment could have been done by mark and recapture of tortoises over ever more years and just record under which situation more survived. In the tortoise experiment, the scientists simply applied good year conditions alongside natural bad years.

There is another such experiment where a drought year was compared to a non drought year all with free ranging tortoises of two species in Africa. No pens were used, they just let weak ones starve, not reproduce, or thrive. I'll try and find that paper and post it here. The same situation with two species of tortoise, however predators were not excluded and the drought hit them all. In this case the observers wanted to see what plants were utilized in what way by the two species. No intervention at all. Were those scientist cruel?
 
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