Reproduction and health of moose in southern Sweden

Abstract: Moose (Alces alces) is a highly regarded game species in Fennoscandia, where annual harvest numbers in Sweden, Norway, and Finland together exceed 200,000 animals. For successful management, knowledge about male and female reproduction is essential, as well as the extent to which disease and mortality affect the population. In 2006, a sub-normal reproductive output (calf per cow ratio) was reported from the island of Öland, and a pilot study in 2007 revealed embryonic mortality and occurrence of the tick-borne pathogen Anaplasma phagocytophilum. An expansion of the study (including control areas) was conducted due to the need for updated information on moose reproduction From 2008 to 2011, reproductive organs, blood, spleens, mandibles, and ectoparasites were collected from moose in three areas in southern Sweden. Reproductive organs were inspected macroscopically, weighed and measured, and sperm samples were taken. Morphology of spermatozoa, chromatin analyses, histological examinations, and pathogen analyses were performed at SLU or SVA in Uppsala. Male pubertal age varied from 1.5 to 3.5 years, and the proportion of normal spermatozoa increased significantly with increasing body weight, but decreased temporally over the first month of hunting. Male moose had a low testes:body weight ratio compared with other cervids. Cows showed their first oestrus of the season earlier than heifers, and the hunting period appeared to interfere with oestrus in all females. Onset of puberty in females was positively associated with body weight but not with age. Embryonic mortality and unfertilized oocytes accounted for a significant difference (P<0.01) between ovulation rates and the proportion of viable embryos found in pregnant females. Moose were competent hosts of Anaplasma phagocytophilum, and the prevalence of infection, as determined by PCR, varied both temporally and spatially. Moose calf summer survival rates on Öland were significantly lower than in the mainland populations. The studies performed provide updated information on moose reproductive characteristics, calf survival and moose health. Some changes in population management could potentially improve the reproductive success of moose in southern Sweden. Not all of these parameters might be affected by a change in management, as the surrounding environment and climate play a considerable role in forage availability, the spread of diseases, and calf survival rates.