Litter size data from a breeding program of endangered Common hamster (Cricetus cricetus)
Date of Archiving2020
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Animal Ecology & Ecophysiology
Key wordsLitter size; genetic rescue; breeding program; endangered rodent; Common hamster
Reduced genetic variation is a severe threat for long-term persistence of endangered animals. Immigration or translocation of new individuals may result in genetic rescue and increase of the population viability of the endangered population or species. Studying genetic rescue breeding programs of endangered species can contribute to our knowledge of the diverse effects of genetic rescue. In the breeding program of Common hamsters in the Netherlands as a few wild founders from two nearby and also highly threatened populations were added to the breeding stock. As a result of the introduction of new founders the litter size increased over the years, but no relation between inbreeding levels and litter size was found. Average litter size mainly benefited from the genetic variation introduced by a hamster from Germany. The analysis of the data is based on the registration in the Hamster Studbook managed by the Rotterdam Zoo, version April 2009. The pedigree which was used in the analysis is based on this Studbook and extended with ‘virtual ancestral parents and grandparents’ for the wild trapped founders of the breeding program. The father (Sire) and mother (Dame) of the grandparents in the dataset are indicated with a ‘0’ (= unknown). The use of virtual ancestors was needed for calculating inbreeding coefficients and relatedness of all individuals. Without these virtual ancestors each founder would have the same inbreeding coefficient and the same relatedness to other founders, while it is for sure that founders from the same population are more related to each other than to founders from other populations. This approach resulted in a basic inbreeding coefficient of 0.25 for all founders and no relatedness with individuals from other populations. This version of pedigree includes information on 1013 different hamsters, of which 14 were trapped in the wild (= wild trapped founders), 11 virtual ancestors and 994 individuals born in captivity from these 14 founders. Litter size was measured as the number of juveniles alive at an age of six weeks. At six weeks after birth litters are separated and each individual is equipped with a transponder. Before an age of six weeks the exact number of juveniles is unknown, because breeding females are left alone as much as possible to prevent infant-mortality. In total 185 litter were used in the analysis. In the pedigree all founders got virtual ancestral parents and grandparents (the same parents and grandparents for individuals from the same population). Furthermore, one of the founding females (W11) in the Dutch breeding line was trapped with six of her young and the father of this offspring was presumed to be a single untrapped individual. The file Pedigree_total_200520_csv has the following columns: A) ID = Unique individual number B) Individual = Unique studbook number for each (artificial) hamster) C) Gender = male, female or ? (unknown) D) Day_birth E) Month_birth F) Year_birth G) Sire = Father H) Dame = Mother Each row is an individual and extra information on artificial parents is also given in the file. The file Litter_size_total_200520.csv has the following columns A) Year (of breeding) B) Breeding location (Blijdorp, D&B, GAIA) C) Cpt-Sire = Studbook code of the father (W = wild-trapped, CPT = born in captivity) D) DNA Percentage of founder population for the father E) Age of the father (Sire) in years F) Cpt-Dame = Studbook code of the female (W = wildtrapped, CPT = born in captvity) G) DNA Percentage of founder population for the mother H) Age of the mother (Dame) in years I) Litter size of this couple J) Breeding line (NL = Netherlands, NL-W = individuals from the wild with 100% NL DNA, B = mix Belgium-Netherlands, D = mix Germany-Netherlands, BD = mix Netherlands, Belgium, Germany). Each row is a litter from a specific male x female.