Some Aspects of the Population Ecology of Wolves, Alaska

Information on Alaskan wolf populations was obtained from examinationof bounty records, 4,150 wolf radii and ulnae, 1,262 wolf carcasses,and from observations of wolves inhabiting an area of 20,000square miles where wolves were protected. Pregnant adult female wolves averaged 6.5 fetuses; two-year-oldfemales averaged 5.3 fetuses;female pups were not sexually mature. In Alaska, wolves conceive from late February through earlyApril but most females breed in March. Multiparous females breedearlier than first breeders. Multiparous females produce anaverage of 7.3 ova and 6.5 implanted fetuses. The loss of ovafrom ovulation to implantation is significant. Multiparous femalesproduce more ova than first breeders; the difference is highlysignificant. Mortality of pups rather than the lack of initial productionof pups is believed to be the reason for the observed variationsin the proportion of pups in wolf populations. Wolf packs includemembers in all categories of sex and age during the breedingseason. Size of the pack is an indicator of abundance. Wolves in an area where they were protected increased at anaverage rate of 20–30% per year during an 11-year period.     

Major histocompatibility complex variation and age‐specific endoparasite load in subadult European rabbits

Genes of the major histocompatibility complex (MHC) play a fundamental role in the vertebrate immune response and are amongst the most polymorphic genes in vertebrate genomes. It is generally agreed that the highly polymorphic nature of the MHC is maintained through host–parasite co‐evolution. Two nonexclusive mechanisms of selection are supposed to act on MHC genes: superiority of MHC heterozygous individuals (overdominance) and an advantage for rare MHC alleles. However, the precise mechanisms and their relative importance are still unknown. Here, we examined MHC dependent parasite load in European rabbits (Oryctolagus cuniculus) from a distinct population with low MHC diversity (three alleles, six genotypes). Using a multivariate approach, we tested for associations of individual MHC class II DRB constitution and the rabbits’ intestinal burden with nematodes and coccidia. Rabbits having a particular allele showed lower infestations with hepatic coccidia (E. stiedai). However, a comparison of all six genotypes in the population revealed that carriers of this allele only benefit when they are heterozygous, and furthermore, MHC heterozygosity in general did not affect individual parasite load. In conclusion, this study suggests an immunogenetic basis of European rabbit resistance to hepatic coccidiosis, which can strongly limit survival to maturity in this species. Our study gives a complex picture of MHC–parasite correlations, unveiling the limits of the classical hypotheses of how MHC polymorphism is maintained in natural systems.