Pup Mortality Research Articles

Interaction of photoperiod and testes development is associated with paternal care in Microtus pennsylvanicus (meadow voles)

During the summer breeding season, free-living meadow voles do not engage in paternal care. However, in fall when female territoriality declines, social nesting and breeding activity may overlap and adult males nest with females and young. In the laboratory, meadow voles housed under short day (SD) lengths exhibit more and better quality paternal care than those housed under long day (LD) lengths. This observation is commensurate with the hypothesis that SD paternal care may increase fitness by decreasing pup mortality during colder months. However, SD males also demonstrate variability in paternal care. We hypothesize that this variability may be due to male fertility status; SD infertile males, incapable of siring offspring, should be less likely to care for pups than fertile males, for whom paternal care may confer fitness benefits. The goal of this experiment was to determine whether paternal behavior differed between fertile LD males, fertile SD males (i.e. males that were gonadally photoperiod-unresponsive to SD lengths), and infertile SD males (i.e. males that were gonadally photoperiod-responsive to SD lengths), as indexed by paired testes weights and behavioral evaluation. Fertile SD males exhibited proportionally more paternal behavior than infertile SD males or fertile LD males, which did not differ from each other. Fertile SD males also exhibited paternal behavior faster, spent more time in contact with pups, and engaged in longer and more frequent bouts of pup-directed grooming and huddling than either infertile SD males or fertile LD males. Collectively, these data suggest that photoperiod and fertility status may interact to exert both inhibitory and permissive control over the expression of paternal behavior in adult meadow voles.

Small pack size imposes a trade-off between hunting and pup-guarding in the painted hunting dog Lycaon pictus

The painted hunting dog or African wild dog, Lycaon pictus, is one of the most endangered large carnivores in Africa, with extinction predicted within a few decades if their dramatic decline is not stopped. It has recently been hypothesized that because of their constraining need for helpers, group size was of major importance in obligate cooperative breeding species, and that the resulting likely existence of a threshold number of adults could create an Allee effect, increasing the group extinction risk. One example where the importance for a critical number of adults may have major repercussions for painted hunting dogs concerns baby-sitting, or pup-guarding, a behavior typical of obligate cooperative breeders. We propose that, as forgoing this behavior is costly because pup guards have the potential to decrease pup mortality, its use is costly too, especially in small packs, because helpers are strongly needed for their cooperative foraging (hunting, protecting the kill and bringing back food to the pups). We present a simple model showing how pup-guarding imposes a cost because it implies that less food per hunt is brought back to more individuals at the den. We complete these analyses with empirical tests of the effect of pack size on the probability of pup-guarding, from field data from the Hwange population in Zimbabwe. Our model, as well as our 5 years of empirical data, both suggest a critical threshold at a size of about five individuals. Key words: African wild dog conservation, Allee effect, cooperative hunting, inverse density dependence, Lycaon pictus, painted hunting dog, pup-guarding. [Behav Ecol 13:20–27 (2002)]

Pup mortality in southern elephant seals at Marion Island

Pre- and early post-weaning pup mortality of southern elephant seals (Mirounga leonina) at Marion Island from 1990 through 1999 ranged from 1.6% to 7.3% and averaged 3.8%. Mortality of pups after weaning before their first trip to sea accounted for only 12% of the total mortality. We found no relationship between population size and percentage pup mortality, indicating that pup survival is independent of seal density, at least at the densities of breeding seals that prevailed. Indeed, pup mortality was greatest in the smallest harems, apparently owing to a greater number of younger, less experienced mothers. Small harems were generally also found on less suitable beaches than larger harems and this could have contributed to pup injury as a cause of pup mortality on these beaches. Mother–pup separation and injury caused by beachmasters is likely to be responsible for pup mortality in the larger harems. The low rates of pup mortality observed in this study obviate it being a major population regulating agent at Marion Island.

Age structured matrix predation model for the dynamics of wolf and deer populations

A matrix predation model similar to Volterra's predation model was developed and applied to study predation of the wolf ( Canis lupus) on a white tailed deer ( Odocoileus virginianus) population. The Leslie matrix enables an age structured predation model to be stated with just two equations that are similar to the Volterra equations but with parameters that can be estimated from available life history data. The wolf and deer population dynamics with the matrix model were the same damped oscillations observed with the scalar differential equation model, but with the matrix model the changes in age structure are obtained. Addition of random environmental variation to survival of fawns resulted in continuing cyclic fluctuations in both deer and wolf. A sensitivity analysis showed that the dynamics of the populations were sensitive to mortality of wolf pups, and that fluctuations in both the wolf and deer populations could be reduced with removal of wolf pups.

Effect of early fetal irradiation on the postnatal development of mouse.

An earlier study has shown that irradiation at the late fetal stage of Swiss albino mice disturbed postnatal growth and appearance of physiological markers. The present study was done to determine the effect of irradiation at the early fetal stage on the postnatal development of mouse. Fourteen-day pregnant Swiss albino mice were exposed to 0.1-1.5 Gy of cobalt-60 gamma-rays. F1 pups were observed for < or = 6 weeks of age. Postnatal mortality, body weight and length, head length and width, tail length, and the time of appearance of physiological markers (pinna detachment, eye opening, fur development, vaginal opening and testes descent) were noted. There was no increase in congenital anomalies. Postnatal mortality and percentage of growth-retarded pups increased significantly at doses of 0.5-1.5 Gy. A significant delay in the appearance of all the physiological markers was also noted at these doses. Body length, head length, and tail length remained significantly lower than in the controls throughout the observation period at doses of 0.3-1.5 Gy, whereas body weight and head width showed such a persistent change only at > or = 0.5 Gy. The early fetal day 14 in mouse is sensitive to radiation-induced postnatal mortality and impairment of growth and temporal development of physiological markers, but not to induction of congenital anomalies. While mortality and physiological markers are not affected at <0.5 Gy, growth retardation appears to have a lower threshold of approximately 0.3 Gy.

Protection of puppies against canine herpesvirus by vaccination of the dams

Six bitches free of canine herpesvirus 1 (CHV-1) were vaccinated against the virus; a first injection was given 10 days after the presumed date of mating and a second six...

Limits to sustained energy intake. IV. Effect of variation in food quality on lactating mice Mus musculus.

Observations were made on 30 MF1 mice with their litters. The animals were fed either normal pelleted mouse food (SDS BP Nutrition Ltd) containing 13.4 kJ x g(-1) digestible energy or a specially formulated diet that provided 25% less digestible energy (9.75 kJ x g(-1)) but equivalent amounts of protein and essential minerals and vitamins per gram as the normal diet. Half the animals were switched to the low-energy diet during early pregnancy and half after parturition. The food intake of the two groups increased enormously following parturition, reaching an asymptote over the last few days of lactation. In both groups, the asymptotic food intake exceeded that previously observed across 71 litters of this strain of mice fed the normal diet throughout pregnancy and lactation; the intake of the group fed the low-energy diet from early lactation significantly exceeded that of the mice switched to the low-energy diet after parturition. The increased intakes of the experimental groups were, however, insufficient to offset the lower digestible energy content of the food during lactation. The body mass of the mothers at the end of lactation did not differ between the two experimental groups and the controls. Offspring mass at weaning was inversely related to litter size, but also did not differ between the three groups; pup mortality did not differ between the experimental and control groups. Behavioural observations showed that during both the dark and light phases the general activity of the mother declined enormously from early pregnancy to late lactation. In the dark phase, the time spent in general activity was replaced by time spent both feeding and resting (suckling young), but in the light phase it was replaced only by feeding. At peak lactation, the mice fed for 30-50% of the dark phase and for 30-40% of the light phase. The data indicate that a previously observed asymptote in food intake during peak lactation at 23 g x day(-1) is unlikely to be a limit mediated centrally by the alimentary tract. A higher central limit may exist, at 26.9 g x day(-1), but this is unlikely to reflect the time available for feeding. The data are consistent with limits on sustainable daily energy intake being mediated by the performance of the mammary glands. Animals appeared to accommodate the demands for milk production within a constrained total energy budget by compensating their behaviour, most notably by reductions in the time spent in 'general activity'.

Consequences of gene targeting procedures for behavioural responses and morphological development of newborn mice.

In this study the effects of gene targeting procedures on the early behaviour and morphological development of the resulting offspring have been investigated. Six groups of mice, each having undergone a specific aspect of the biotechnological procedure, (including electroporation, microinjection and/or embryo culture) and one control group, were compared. Development of behaviour, morphological characteristics and body weight of the progeny were tested daily from birth to weaning (0-3 weeks) for all groups. No significant differences in behaviour or morphological development were observed. However, the occurrence of increased (perinatal) pup mortality and increased body weight in the procedural groups, indicates that during the production of gene targeted mice, some of the normal physiological and/or developmental processes can be affected. Therefore, gene targeting procedures should always be accompanied by careful monitoring of health and welfare of the resulting offspring.

A low-fat diet but not food restriction improves lactational performance in obese rats.

Rats fed a high-fat diet before and during lactation have difficulty initiating lactation and have high pup mortality rates, low milk production and, consequently, poor pup growth. To determine if these adverse outcomes can be mitigated with dietary changes made after delivery, obese Sprague-Dawley rats (who had previously been fed a high-fat diet [AIN-93M, modified to contain 35% fat, w/w]) were assigned at parturition to continue to be fed this diet (HF) or switched to free access to a corresponding low-fat (LF) diet (AIN-93M, 4% fat w/w) or switched to the LF diet and restricted to consuming only 75% of ad libitum intake (LF/R). Dams lost weight during lactation, but weight loss was much less in the LF group (19g) than in the other two groups (47 and 59g, HF and LF/R, respectively). There was no appreciable change in body water; body fat decreased by about half in all groups, but most substantially in the LF/R group. Compared with the HF group, milk production was 50% higher in the LF group and 12% lower in the LF/R group. Milk lipid concentration tended to be higher and milk water concentration lower in the HF compared with the other two groups. Growth of the litters of the LF dams was significantly higher than both HF and LF/R dams. These results indicate that switching to a low-fat diet mitigates the negative effects of obesity and continued high-fat feeding on lactational performance and pup growth. Consumption of restricted quantities of a low-fat diet negatively affected milk production and failed to improve pup growth, despite the dams' mobilization of body fat in support of lactation.

Shark‐inflicted mortality on a population of harbour seals (Phoca vitulina) at Sable Island, Nova Scotia

AbstractShark‐inflicted mortality on harbour seals Phoca vitulina on Sable Island, Nova Scotia, was studied from 1980 to 1997, based on carcasses washed up on shore. During this period, pup production declined dramatically from over 600 in 1989 to 40 in 1997. Between 1980 and 1992, pup deaths only were recorded, and only during the May–June pupping period, while deaths in all age groups were recorded year‐round between 1993 and 1997; 458 pups, 23 juveniles and 241 adults were found. Shark‐inflicted mortality in pups, as a proportion of total production, was under 10% during 1980–93, roughly 25% in 1994–95, and increased to 45% in 1996. Shark‐inflicted mortality occurred in all months except December, January and February, with c. 80% of the pups killed during the pupping period, and 97% of the adults killed outside the pupping period. The decline in pup production was not only a result of reduced recruitment owing to pup mortality. A greater proportion of reproductive females than males was killed. We estimate that shark‐inflicted mortality on pups and adult females reduced pup production on Sable Island by 43 to 154 pups annually between 1993 and 1997. Our results indicate that sharks are having an impact on Sable Island harbour seals, possibly to the extent of limiting population growth, or contributing to the observed population decline. Potential reasons for this increased mortality are discussed.

VOCAL INDIVIDUALITY IN MOTHER AND PUP SOUTH AMERICAN FUR SEALS, ARCTOCEPHALUS AUSTRALIS

AbstractSouth American fur seals breeding in Peru are subjected to levels of maternal aggression, and subsequent pup mortality, that are higher than has been reported for any other otariid species. For mothers and pups to maintain contact with each other, a mutual recognition system should exist to facilitate reunion and avoid misdirection of maternal effort. We recorded vocalizations of mothers and pups at Punta San Juan, Peru, during the 1994 and 1995 breeding seasons. Sixteen acoustic variables were measured from a total of 560 calls from 15 mothers and 13 pups. Multivariate analysis showed that calls were variable in several acoustic dimensions. While calls of both mothers and pups showed low variability within and high variability among individuals, mothers' calls were more individualistic. On average, discriminant‐function analysis correctly assigned 60% of pup calls and 70% of mother calls to the individual that produced them. Characteristics of the fundamental frequency were most important for distinguishing among mothers, while pup calls, which typically contained less harmonic structure, could be differentiated by formant‐like frequency ranges. Thus, calls of mother and pup South American fur seals appear to exhibit sufficient stereotypy to allow for recognition and discrimination among individuals.

Changes in the abundance of New Zealand fur seals, Arctocephalus forsteri, in Western Australia

New Zealand fur seals, Arctocephalus forsteri, have been increasing in abundance in South Australia for at least the past three decades. A survey of New Zealand fur seals during the 1989/90 breeding season determined that about 20% of the Australian population bred at 16 sites in Western Australia, amounting to 1429 pups and an absolute abundance estimate of 7100 fur seals. A further survey of all fur seal colonies in Western Australia to determine current pup production and abundance estimates, and trends in pup production since the previous survey was undertaken in January 1999. Of the 17 breeding sites now known in Western Australia, 16 were surveyed and pup production had increased at all but one. The rate of change in pup production at the one unsurveyed site (West Island), was estimated as being equivalent to the mean rate of change at other sites. The estimated mean annual, exponential rate of increase (r) for all sites was 0.09, equivalent to a 9.8% annual increase in pup production and an overall increase in pup production in Western Australia of 113.3% between surveys. Total annual pup production has increased to 3090. The estimate of absolute abundance of New Zealand fur seals in Western Australia is now 15 100, in contrast to the 7100 estimated for the 1989/90 season. Mortality of pups at the time of the survey was estimated to be at least 1.3%. It is predicted that New Zealand fur seal populations will continue to increase in Western Australia. This is likely to have important management implications regarding aquaculture and fisheries activities. The increase in fur seal populations appears to be in contrast to populations of Australian sea lions, Neophoca cinerea, for which preliminary data show no evidence for a population increase. It is unknown whether the dynamics affecting these two species are related.

Expansion of a grey seal (Halichoerus grypus) breeding colony: changes in pupping site use at the Isle of May, Scotland

Until the mid 1970s only a few grey seal Halichoerus grypus pups were born each year on the Isle of May, Scotland, but 1408 pups were born there in 1994. We examined changes in overall site use, individual pupping site fidelity and success in relation to local population density and topography. The area of the island used by seals for breeding has increased as the population increased. Between 1988 and 1994 an index of the proportion of the island's northern area occupied by seals increased from 0.48 to 0.65, while the average population density in these occupied areas decreased over the same period. Although seals have begun to breed in southern parts of the island that were unused previously, other apparently suitable breeding areas on the island remain vacant. Fine scale digital elevation models were constructed using a GIS to evaluate the topographic characteristics of occupied areas and assign topographic ‘costs’ to areas used by seals for breeding on the Isle of May. Seals were associated generally with areas close to the numerous access points from the sea. New areas occupied in the later years of the study had a higher topographical ‘cost’ than the traditional sites. Thus, in an expanding colony such as the Isle of May, areas colonized early in the colony's history were those close to access points and/or standing water and at low elevations. Subsequent expansion resulted in an increase in the areas occupied by seals, but these newly colonized areas were less suitable, and their occupiers were subject to increased topographic ‘costs’. Pup mortality rates were similar in areas of high and low breeding density. Aggressive behaviour between breeding females is the likely mechanism which acts to limit local animal density. Mothers marked at the Isle of May since 1987 returned there to breed with few exceptions, and most females that returned were faithful to their previous pupping sites (median distance between sites used in consecutive breeding seasons = 25 m). Site fidelity persisted even when a previous pupping was unsuccessful and most individuals' pupping locations did not change gradually with time. Comparison with other colonies suggests that the spatial scale of site fidelity is related to the scale of topographic variation within the breeding site.

Expansion of a grey seal (Halichoerus grypus) breeding colony: changes in pupping site use at the Isle of May, Scotland

AbstractUntil the mid 1970s only a few grey seal Halichoerus grypus pups were born each year on the Isle of May, Scotland, but 1408 pups were born there in 1994. We examined changes in overall site use, individual pupping site fidelity and success in relation to local population density and topography. The area of the island used by seals for breeding has increased as the population increased. Between 1988 and 1994 an index of the proportion of the island's northern area occupied by seals increased from 0.48 to 0.65, while the average population density in these occupied areas decreased over the same period. Although seals have begun to breed in southern parts of the island that were unused previously, other apparently suitable breeding areas on the island remain vacant. Fine scale digital elevation models were constructed using a GIS to evaluate the topographic characteristics of occupied areas and assign topographic ‘costs’ to areas used by seals for breeding on the Isle of May. Seals were associated generally with areas close to the numerous access points from the sea. New areas occupied in the later years of the study had a higher topographical ‘cost’ than the traditional sites. Thus, in an expanding colony such as the Isle of May, areas colonized early in the colony's history were those close to access points and/or standing water and at low elevations. Subsequent expansion resulted in an increase in the areas occupied by seals, but these newly colonized areas were less suitable, and their occupiers were subject to increased topographic ‘costs’. Pup mortality rates were similar in areas of high and low breeding density. Aggressive behaviour between breeding females is the likely mechanism which acts to limit local animal density. Mothers marked at the Isle of May since 1987 returned there to breed with few exceptions, and most females that returned were faithful to their previous pupping sites (median distance between sites used in consecutive breeding seasons = 25 m). Site fidelity persisted even when a previous pupping was unsuccessful and most individuals' pupping locations did not change gradually with time. Comparison with other colonies suggests that the spatial scale of site fidelity is related to the scale of topographic variation within the breeding site.

Immediate postnatal sucking in the rabbit: its influence on pup survival and growth.

This study was aimed at characterising the impact of immediate postnatal sucking on pup survival and development. The interactive effects of postnatal success with the day 0 weight of pups, the nest-access regimen (controlled or free) or parity of females was investigated. Pups (n = 900) were categorised according to their initial ingestion of colostrum. In primiparous does: (1) pup mortality between d0-d10 was higher for unsuccessful than for successful early suckers; (2) lighter d0-weight reduced survival for unsuccessful but not for successful pups; (3) free nest-access of females annihilated the survival advantage fostered by the initial sucking success. In secondiparous does, these impacts waned. Finally, whatever the does' parity, only d0-weight influenced pup weight-gain between d0-21. Thus, pup survival seemed to depend (at least in primiparae) on their ability to suck right after birth, and to display a pattern of energy saving without being disturbed by the females' nest entries.

PUP SURVIVAL IN THE MEDITERRANEAN MONK SEAL (MONACHUS MONACHUS) COLONY AT CABO BLANCO PENINSULA (WESTERN SAHARA‐MAURITANIA)

AbstractWe surveyed pup survival in Mediterranean monk seals (Monachus monachus), at Cabo Blanco Peninsula (Western Sahara‐Mauritania) colony from May 1993 to December 1997. This species breeds and hauls out on beaches inside two main caves. During the study period we detected a total of 93 pups that died or disappeared. The survival rate of 84 pups through the age of first moult (approximately two months) was 0.47. This value is similar to those reported for other pinnipeds breeding in caves but lower than for those breeding on open beaches. Mortality varied seasonally and appeared to increase as a result of storms, large ocean swells, and high tides. Mother‐pup pair separation (and resulting pup starvation) and physical injury caused by impact against the rock walls of the cave and cliffs were established as the causes of most deaths. Beach surface area inside the caves also appeared to be a mediating factor in the effects of sea conditions. High pup mortality may be a limiting growth factor in this population, although cave dwelling protects the population from predators and human disturbance.

Pupping season, perinatal sex ratio and natality rates of the Mediterranean monk seal (Monachus monachus) from the Cabo Blanco colony

AbstractPupping seasonality, annual pup production, reproductive rate and sex ratio at birth were determined for the Mediterranean monk seal Monachus monachus colony at Cabo Blanco, the only surviving population of the species which still shows a colony structure. Data were collected by means of a monitoring programme that operated continuously in the main reproductive areas of the population during the period March 1993–May 1997. Most (84%) of the pups observed were born in two caves separated by a short distance. Although both caves were used by females to bear the pups, preferences greatly fluctuated from season to season with no apparent trend. Reproduction occurred throughout the year with a small peak of births in October. This unusual lack of seasonality is associated with the low latitudinal location of the colony and the effect of the upwelling that provides constant food throughout the year. The neonatal sex ratio did not differ significantly from 1:1 and the estimated annual productivity ranged from 44–58 pups. Taking into account population numbers, the annual birth rates were estimated to range from 0.3 to 0.43 pups per reproductive female, an extremely low rate when compared to other pinniped populations, particularly those of a similar size. Such low rates may be either an evolutionary determined characteristic of the species or a demographic consequence of the low population density over the last few centuries. Coupled with high pup mortality rates, this may account for the observed non‐recovery of the population.

Effects of the tapeworm Hymenolepis diminuta on maternal investment in rats

Parasites can influence the optimal allocation of energy between present and future reproduction by changing the value of current offspring relative to that of future ones. We examined the effect of the tapeworm parasite Hymenolepis diminuta on maternal investment in rats. Litter sizes and average pup body mass did not differ between parasitised and nonparasitised mothers, either at birth or at weaning. The two groups of mothers also did not differ with respect to pup growth or pup mortality during lactation. Mass change during lactation was similar between parasitised and nonparasitised mothers. However, a pup-retrieval experiment showed that parasitised mothers were quicker at retrieving their pups to safety than nonparasitised mothers, and spent less time checking for potential sources of danger. These differences were particularly pronounced toward the end of the lactation period. It would appear that the parasite increases the relative value of the current litter and current levels of maternal investment, possibly because it reduces future reproductive success.

The evolution of reproductive systems in pinnipeds

The evolution of reproductive systems in pinnipeds

Safety Evaluation of Phytosterol Esters. Part 3. Two-Generation Reproduction Study in Rats with Phytosterol Esters—a Novel Functional Food

Phytosterol esters (PE) are intended for use as a novel food ingredient with plasma cholesterol lowering activity which works by inhibiting the absorption of cholesterol from the gut. Although PE are naturally present in the normal diet, the levels are insufficiently large to ensure lowering of plasma cholesterol levels. Therefore PE may be added to spreads to achieve the desired cholesterol lowering activity. As part of an extensive programme of safety evaluation studies a two-generation reproduction study has been conducted in Wistar rats, in which the possible effect of PE on male and female reproductive performance and on the growth and development of the offspring was studied. Rats were fed diets containing PE at levels of 0, 1.6, 3.2 and 8.1% (w/w) PE over two successive generations, and a wide range of reproductive and developmental parameters, including sexual maturation parameters and oestrous cycle length, were determined. Macroscopic and microscopic examinations were conducted including a histological examination of selected organs from F 1- and F 2-weanlings and from F 0- and F 1-parental animals. Daily clinical observations did not reveal any unusual findings. In both generations, no effects of PE were observed on pup mortality (calculated on litter basis), precoital time, mating index, male and female fertility index, female fecundity index, gestation index, duration of gestation, number of females with stillborn pups, post-implantation loss and pup development. Furthermore, PE had no effect on sexual maturation parameters (preputial separation and vaginal opening) and oestrous cycle length. In addition, there were no dose-related effects on selected organs following histological examination. In conclusion, dietary administration of up to 8.1% PE (equivalent to a dose of 2.5 to 9.1 g PE/kg body weight/day, dependent on the period of the study) during two generations had no effect on reproduction of parental F 0- and F 1-generation Wistar rats, nor on the development of the F 1- and F 2-pups, nor on the sexual maturation of the F 1-weanlings. Therefore, a nominal dietary PE concentration of 8.1% (equivalent to a dose of 2.5–9.1 g PE/kg body weight/day or 1.54–5.62 g phytosterol/kg body weight/day dependent on the period of the study) was considered to be the no-observed-adverse-effect level following daily oral administration of PE for two successive generations.