An effective realization of breeding programs in zoos is strongly determined by completeness of animal pedigree information. The knowledge of pedigree structure allows to maintain optimal genetic variability of a given population. The aim of this study was to estimate the parameters describing the pedigree structure of American bison housed in zoos in the context of further management of the population. Finally, 4269 American bison were analysed (1883 males, 2217 females, and 169 with unknown sex). The registered animals were born between years 1874 and 2013. The following pedigree parameters were estimated: number of fully traced generations, number of complete generations equivalent, index of pedigree completeness, individual inbreeding coefficients, increase of inbreeding for each individual, effective population size, and genetic diversity. The maximum number of fully traced generations was 3 (the mean value is 0.693). The mean inbreeding coefficient for the population studied was 3.26%, whereas individual increase in inbreeding ranged from 0 to 25.12%. Although the pedigree parameters (including the inbreeding level) in the American bison obtained in the present study seem to be acceptable (from the perspective of other wild animal populations), they can be over/underestimated due to incomplete pedigree.

Survival is one of the most important traits to consider for limited animal populations under conservation programs. Here, we estimate the effects of inbreeding, geographical region (Europe, North America and other) and sex on survival at six points of life in American bison populations kept in zoological gardens. The data set consisted of 3893 animals, 1812 males and 2081 females, born between the years 1874 and 2013. We analyzed survival in terms of longevity and survival of the first day after birth. We applied regression analysis with a logistic model. Longevity was examined in terms of six time categories whereas the survival of the first day after birth as a binary trait. We find that the average longevity for the studied population was 5.21 years with a standard deviation of 6.75. The longevity was significantly affected by the sex: females survived on average longer than males. The median values of longevity were considerably lower than the averages and also conditioned by the sex. The largest number of individuals was recorded in survival up to the age of sexual maturity, equal to 43.6% of males and 30.75% of females. More females survived after reaching the age of sexual maturity. Survival of the first day after birth was not influenced by the calf's sex. There was also detected that the survival of individuals decreased with an increasing level of inbreeding, under relative small pedigree parameters for the population studied. It was also demonstrated that geographical region has a significant effect on the longevity of captive bison.

Inbreeding and offspring sex ratio in the pygmy hippopotamus (Cheoropsis liberiensis) population kept in zoological gardens. Folia Biologica (Kraków) 63: 35-42. The aim of this study was to estimate the inbreeding level and its impact on offspring sex ratio in the pygmy hippopotamus population kept in zoological gardens. Records of pygmy hippopotamus born between 1873-2013 were extracted from the international studbook. Totally, 1357 individuals originating from 148 breeding units were included (individuals with unknown sex were omitted). The offspring sex ratio is defined as the number of sons to the total number of progeny of each dam and sire. Spearman's rank correlation was employed to examine the relationships between the inbreeding level and offspring sex ratio. Inbreeding coefficients and individual increase in inbreeding coefficients (included as a linear co-variable) were examined as well as the geographic region and birth period using general linear models. The average inbreeding coefficient was 5.39%. The following sex proportion was observed for the inbred population: 57% and 43% for females and males, respectively. A significant relationship between inbreeding level of parents and their offspring sex ratio were estimated for European zoological gardens, whereas in others geographic regions the dependencies were insignificant.

This study aimed to evaluate the genetic and environmental factors affecting the survival of the pygmy hippopotamus (Choeropsis liberiensis) population kept in zoological gardens, including the estimation of the inbreeding level. Survival was examined at three time points: birth (0–1 days), 1 month (30 days) and 5 years of age. The data were obtained from the Zoological Information Management System, and covered observations on 1196 pygmy hippo, collected between 1873 and April 2016 and grouped into five geographical regions (Africa, Australasia, Europe, USA and Canada, and South America). The analyses were performed using LOGIT and PROBIT transformations of the binominal survival data. No statistically significant differences (P-value > 0.05) were observed between the results obtained from the two transformations. The survival of individuals was found to decrease with increased level of inbreeding, the most significant effect being on survival at birth. At all three survival time points the highest survival was observed among females. Additionally, the Australasia region showed the highest overall survival. We hypothesize that the environment, climate and similarity of local food to the native diet of pygmy hippo allows animals kept in zoological gardens in that region to perform better than in other regions. The results of this study indicated that it is necessary to exercise vigilance in reducing inbreeding as it negatively impacts survival. This can be achieved by continued efforts to maintain and improve genetic diversity through management of breeding and associated transfer of animals between zoological facilities to reduce relatedness in breeding pairs.