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
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
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