The increased density is because of the immature ,alveolarization of the lung, so that in reality the neonate has less reserve than the adult. Thus, increased respiratory reserve is not the explanation of lung edema resistance in the neonate.Previous reports (14) of increased sensitivity of young rats to ozone and NOZ toxicity did not include the neonatal period. As far as we can find, this is the first report of resistance to lung edema in the newborn. The fact that both thiourea and NO2 produce less edema in the neonata indicate that neurohumoral differences rather than resistance to anoxia is responsible for the lowered mortalities in neonata when compared to adults. Other possibilities are structural differences in the lung (15) and differences in the mechanics of breathing (15) as well as biochemical differences (7) (possibly increased sulfhydryl stores in the neonate).Summary. Two species of Muridae ne0nat.a are more resistant to the lung edema produced by inhalation of nitrogen dioxide and to the lung edema produced by intraperitone-a1 injections of thiourea than comparable weight-adjusted adults. These results are in direct contrast to both original data and data from the literature on the ordinarily increased sensitivity of neonata to most drugs and toxic agents. The normal lung-body weight percentage in rats decreases from 1.7% a t birth to 0.5% at 90 days.

Captive rearing conservation programs focus primarily on maximizing post-release survival. Survival increases with size in a variety of taxa, often leading to the use of enhanced size as a means to minimize post-release losses. Head-starting is a specific captive rearing approach used to accelerate growth in captivity prior to release in the wild. We explored the effect of size at release, among other potential factors, on post-release survival in head-started Mojave desert tortoises Gopherus agassizii . Juvenile tortoises were reared for different durations of captivity (2–7 y) and under varying husbandry protocols, resulting in a wide range of juvenile sizes (68–145 mm midline carapace length) at release. We released all animals ( n = 78) in the Mojave National Preserve, California, United States, on 25 September 2018. Release size and surface activity were the only significant predictors of fate during the first year post-release. Larger head-starts had higher predicted survival rates when compared to smaller individuals. This trend was also observed in animals of the same age but reared under different protocols, suggesting that accelerating the growth of head-started tortoises may increase efficiency of head-starting programs without decreasing post-release success. Excluding five missing animals, released head-starts had 82.2% survival in their first year post-release (September 2018–September 2019), with all mortalities resulting from predation. No animals with >90 mm midline carapace length were predated by ravens. Our findings suggest the utility of head-starting may be substantially improved by incorporating indoor rearing to accelerate growth. Target release size for head-started chelonians will vary among head-start programs based on release site conditions and project-specific constraints.

The effects of indoor rearing versus the conventional method of solely outdoor head-starting on post-release cover and burrow use of juvenile Mojave desert tortoises (Gopherus agassizii), a threatened endemic species, were investigated. We found that partially indoor-reared tortoises exhibited similar post-release behaviours when compared to both same-aged, but smaller, and similar-sized, but older outdoor-reared head-started tortoises, thus increasing the success and decreasing the costs of head-starting.