Survival Rate Of Pups Research Articles

Re-feeding evokes reproductive overcompensation of food-restricted Brandt's voles

In natural conditions, animals have to cope with fluctuations of food resources. Animals having experienced prolonged decrease in feeding opportunities may increase their reproductive success when meeting abundant food. Though food restriction is well known to reduce reproductive success of animals, it is not clear whether re-feeding can restore or even overcompensate the reproductive success. In this study, we investigated the differences in reproductive parameters between food-restricted and refed (FR–RF) group and control group of Brandt's vole (Lasiopodomys brandtii). For 4weeks, FR–RF voles were provided with 70% of their normal daily food intake and then they were fed ad libitum for the next 4weeks. Voles of control group were fed ad libitum for 8weeks. Females (FR–RF or control) were mated to non-littermate males of the same group (FR–RF or control), and we found that the mean litter size and survival rate of F1 pups of FR–RF group were significantly higher than those of control group. We also provided a field example showing that the litter size of Brandt's voles tended to be higher if they experienced two consecutive dry and wet months than that of voles didn't have this experience. Our results suggest that re-feeding may have evoked an overcompensatory mechanism of food-restricted voles in reproductive success. This may be an adaptive strategy for Brandt's voles (with oscillating populations) to cope with the fluctuating food resources in natural conditions by adjusting their reproductive success.

The effects of Cannabis sativa L. seed (hemp seed) on reproductive and neurobehavioral end points in rats

This study determined the effects of maternal dietary intake of hemp seed on reproductive and neurobehavioral end points of Wistar rats. Time-mated rats were fed 100% hemp seed (n = 15), 50% hemp seed (n = 15) or basal diet (n = 15) once a day. The amount of food made available was based on control feed consumption records. All dams remained on their respective diets from premating (14 days) throughout gestation and lactation. After weaning, all pups were given their maternal diet until puberty. Mating and delivery weights of dams in all groups did not show significant changes. Number of pregnancies, number and post-natal survival rate of total rat pups, litter size and milk yield were lower in the group that received 100% hemp seed. Offspring that received 50% hemp seed diet expressed reproductive and neurobehavioral end points from a modified Fox battery earlier than rats on 100% hemp seed or basal diet, except acoustic startle results where no differences appeared. In conclusion, this study shows that hemp seed supplementation does not improve the reproductive and neurobehavioral performances of rats. Pregnant women and nursing mothers should be cautious about the using of Cannabis sativa L. byproducts in their diets.

CircadianClockMutation in Dams Disrupts Nursing Behavior and Growth of Pups

To understand the role of the circadian molecular clock in mouse reproduction, we investigated the daily rhythms associated with nursing and pup growth in Clock-mutant mice maintained under light-dark housing conditions. The daily rhythm associated with the maternal behavior of crouching had a strong diurnal peak and two weak nocturnal peaks in wild-type dams, whereas homozygotes (Clock/Clock) exhibited no significant peaks in activity. Wild-type, but not Clock-mutant, dams showed high, rhythmic levels of prolactin content in serum that corresponded with crouching. Pup body weight increased at a significantly slower rate in Clock-mutant dams compared with wild-type dams under all experimental conditions when the pups ranged from 10-15 in number. Heterozygote dams equally bred wild-type, heterozygote, or homozygote pups. The amount of milk secreted from dams, as calculated by the increase in pup body weight through suckling, was lower in Clock-mutant mothers vs. wild-type mice. When Clock-mutant dams gave birth to more than 10 pups, survival was poor for offspring until the time of weaning. The present results demonstrate that Clock mutation disrupts daily maternal behavior and the growth and survival rate of pups, especially with the breeding of more than 10 pups.

Patterns of helping effort in co‐operatively breeding banded mongooses (Mungos mungo)

AbstractIn most co‐operative breeding species, some individuals contribute much more to helping behaviour than others. The most well‐established explanation of such variation is based on kin selection and suggests that, in the absence of detectable differences in relatedness, individuals who suffer lower costs for a given level of help should contribute more. Differences in helping effort between dominance/sex categories were investigated in co‐operatively breeding banded mongooses Mungos mungo in Uganda. The most conspicuous form of help in this species is provided by individuals who babysit offspring at the den while the rest of the pack goes off to forage. Across eight groups, the survival rate of pups increased with the average number of babysitters guarding them, consistent with the hypothesis that helpers benefit the brood that they guard. There was no difference between dominant males, subordinate males and breeding females in total contributions to babysitting. Subordinate males, however, contributed more to babysitting in the mornings, which were the longest and presumably the most energetically expensive sessions of the day. In six litters in one well‐studied pack, dominant males and breeding females reduced their contribution to babysitting for the period that females were in oestrus. By contrast, subordinate males increased their contribution to become the main babysitters during this time. These results are consistent with the hypothesis that, where helping conflicts with breeding, individuals with little chance of direct reproduction can help at a lower fitness cost than those with a high probability of successful reproduction.

SURVIVAL RATES OF SEA OTTER PUPS IN ALASKA AND CALIFORNIA

AbstractAdult female sea otters (Enhydra lutris) were instrumented with implanted radio‐transmitters in Prince William Sound (PWS), Alaska, and survival rates were estimated for their dependent pups. Overall, 94 of 141 (67%) of the pups studied survived to a minimum age of 120 d and were assumed to have successfully weaned. Survival of pups in six cohorts ranged from 53% to 88%. The mean interval between successive visual observations was 12.5 d. For these calculations, the assumption was made that pups were successfully weaned if they accompanied mothers for at least 120 d. Estimated survival rates were different when this assumption was changed to either 90 d or 150 d (73% and 52%, respectively).Females were palpated for pregnancy when instrumented. Of 19 believed to be pregnant, 17 were subsequently seen with young pups giving a detection rate for births of 89.5%. When the above observed survival rate of pups was adjusted for undetected births, the estimated overall survival rate for the study population was 60% (120 d minimum dependency).Survival rates of pups in PWS and a population at Kodiak Archipelago (KOD) (Monson and DeGange 1995) were compared with that of pups in the population in California (CA, four studies). These data did not support the hypothesis that survival rates were lower in California (CA: 103/160, Psurv. 0.64; PWS: 94/141, Psurv.= 0.67; KOD: 19/23, Psurv.= 0.83; pairwise comparisons, X2, P > 0.05). Comparison of pup survival rates among studies was hindered by small sample sizes, methodological differences, and lack of detail about assumptions underlying estimates.

The effects of future consumption by the Cape fur seal on catches and catch rates of the Cape hakes. 3. Modelling the dynamics of the Cape fur sealArctocephalus pusillus pusillus

The current status of and future trends for the Cape fur seal Arctocephalus pusillus pusillus population are assessed using information from aerial counts of pup abundance. The model used in the analyses is age- and sex-structured, and assumes density-dependence in the survival rate of pups. Uncertainty is assessed by conducting sensitivity tests and estimating 90% confidence intervals by the percentile method. The results confirm the increase of the seal population since the introduction of legal controls at the end of the 19th century, and the estimate of 1,7 million animals of Age 1 and older at the start of 1993 is relatively robust to model assumptions and values for biological parameters. The food consumption by the seal population is estimated to have almost doubled between 1973 and 1993, and to be roughly 2 million tons annually at present. Future trajectories of seal numbers and annual consumption of food cannot be determined with great precision and are sensitive to the values assumed for the post-first-year survival rate and the degree of compensation in density-dependence. Depending on such assumptions, the seal population could already have reached its pre-exploitation equilibrium level or still be well below this level. Data from the 1993 aerial survey have considerable influence on the model results, and particularly on inferences concerning whether the population is now approaching its pre-exploitation level. This suggests that further surveys should be conducted to ascertain the reliability of the changed trend in pup abundance indicated by that 1993 count.

Significance of wounding to female reproductive success in Hawaiian monk seals (Monachus schauinslandi) at Laysan Island

We studied reproductive rate, length of lactation period, pup survival, and mortality of injured and uninjured female Hawaiian monk seals (Monachus schauinslandi) on Laysan Island, northwestern Hawaiian Islands, in 1983 – 1989. The severity and timing of nonfatal injuries were influential in determining their effect on female reproductive success. There was a tendency towards a shorter mean lactation period and lower survival rate of pups for females with major injuries than for uninjured females. Females with minor injuries were similar to uninjured females in terms of reproductive rate, length of lactation, and pup survival. For females injured shortly before the birth of their pup or during lactation, pup survival was lower than for uninjured females, whereas for females injured during the year prior to pupping, measures of reproductive success were not significantly different from those for uninjured females. Immature (aged 4 – 8 years) females entering the reproductive population were injured by adult male seals significantly more often than females aged 0 – 3 years, but at a similar rate to adult females. The major effect of injuries on female reproductive success is an increase in female mortality: 87.5 % of the adult females (n = 16) that died on Laysan Island in 1983 – 1989 sustained injuries from adult male seals.

The inheritance and breeding results of hairless descendants of Mexican hairless dogs

The inheritance and breeding results of hairless descendants of Mexican hairless dogs (MHDs) were investigated. When the male hairless dogs were bred to female beagles, the birth ratio of hairless and haired dogs was 1:1. Mating between MHDs gave both hairless and haired pups. The results indicated that an autosomal dominant monogenic gene was responsible for their hairless characteristics. We propose the symbol Hm for this gene (hairless, Mexican type). The survival rate of hairless pups was markedly lower than that of haired ones. It was elevated to 50-90% by warming their cages to a minimum of 25 degrees C.

Vasopressin, maternal behavior, and pup well-being

The brain peptide, vasopressin (VP), was studied with respect to its effects on maternal care in rearing natural and cross-fostered pups. Long-Evans (LE) rats synthesize hypothalamic VP; whereas, Brattleboro (DI) rats do not produce this peptide. Long-Evans dams exhibited superior maternal care when compared with DI dams when rearing their own as well as foster pups. This enhanced behavior was evidenced by the higher survival rate of pups reared by LE mothers compared to those reared by DI mothers. Later, when the offspring were subjected to the stress of 23 hours of food restriction each day, LE animals reared by their natural mothers survived for a significantly longer period of time and developed significantly less stomach pathology than DI animals reared by their natural mothers or LE foster mothers. The results demonstrated that the secondary factor of maternal care in the absence of VP was of little consequence in the characteristic difficulties observed in DI offspring.

Exposure of rats to lead nitrate in utero or postpartum; effects on morphology and behavior.

Female rats were administered lead (Pb), as the nitrate salt, on day 17 of pregnancy (5 or 25 mg/kg i.v.) or throughout lactation (5 or 25 mg/kg/day p.o.). There were adverse effects on weights of females receiving Pb on day 17. At 25 mg/kg i.v. gestation was significantly prolonged. In both groups treated intravenously, average pup weight on day 1 postpartum was significantly reduced and there was a significantly higher mortality than in controls, and hydrocephalus occurred. Survival rate and weight gain of pups from dams that received Pb throughout lactation was not different from controls. Brain weights and histomorphology of all groups was normal. Behavior in male offspring, as measured by open-field activity, rotorod or passive avoidance tests, was unaffected by exposure to Pb.

The effect of flunitrazepam on reproduction in the rat. The use of cross-fostering in the evaluation of postnatal parameters in rat reproduction studies

During the course of reproduction studies in rats with flunitrazepam, a benzodiazepine derivative, a high incidence of neonatal loss at delivery and during the first 2 days of the lactation period was observed. At delivery the female rats treated with 25 mg/kg/day flunitrazepam exhibited signs of central nervous system depression and were indifferent during parturition resulting in an increased incidence of dead pups at delivery. In addition, flunitrazepam induced a peculiar voracious behavior causing some animals to cannibalize their litter shortly after dosing. A crossfostering experiment was conducted in order to determine whether the observed neonatal loss was the result of a direct toxic effect of flunitrazepam on the neonates or was secondary to aberrant maternal behavior. Cross-fostering in itself did not produce adverse neonatal effects since the survival of control neonates in litters that had been fostered was equivalent to control animals whose litters were not fostered. Treated dams nursing neonates from control litters cannibalized these apparently normal pups indicating that the observed cannibalism after delivery was due to abnormal maternal behavior. Treated neonates placed with control dams exhibited a survival rate which although much better than control pups with treated dams, was still somewhat lower than controls, suggesting that decreased viability of pups delivered from treated dams was an additional factor in the neonatal loss. The survival rate of Cesarean-delivered pups, however, from treated dams and fostered by untreated dams was not significantly different from control neonates similarly handled. This latter result demonstrated that the decreased viability of pups from treated dams appears to be the result of trauma during delivery rather than a direct toxic effect of flunitrazepam on the neonate or on the fetus in utero.