Fieldwork in EALAT Working Package 5: Weighing and collecting blood samples from a herd of reindeer
It is a remarkable how little is known to science about either the ways or the extent to which weather conditions affects the growth, survival and reproductive performance of semi-domesticated reindeer. What is clear – at least in populations of wild ruminants - is that weather can affect the performance of animals and other in a variety of ways and over a variety of timescales.
There are, for instance, concurrent effects, such as the way in which weather conditions in summer can influence the growth and quality of forage plants which, in turn, can influence the growth of juveniles. There are also delayed effects, such as they way in which weather-induced variation in the growth of animals early in life can influence their performance as adults. Two important parameters related to these aspects which we can measure in reindeer are (i) the survival of calves during their first four months of life and (ii) the age at which females first breed. The survival of juveniles during their first summer may be influenced by the weather conditions their dams experienced in winter while they were pregnant or by weather conditions at calving itself. The age at which an animal begins to breed, which in reindeer may vary from 0 to 4 years of age, may be influenced by the rate at which it grew during its first and second summers.
To measure these things requires information on whether particular females were pregnant in a given season. Armed with this information, we can determine the survival of calves by confirming, later in summer, the presence or absence of calves with those females known to have been pregnant in spring. Similarly, we can determine age at first breeding by examining the reproductive status of each reindeer in spring in relation to its age in every year of its early life. This work, which is now part of EALAT Working Package 5, is carried out in a herd of reindeer belonging to the Sara family of Karasjok.
The Sara herd is unique in Finnmark because every reindeer in it is marked as a calf with a numbered tag which enables scientists to maintain unambiguous individual records of each animal throughout its life. The herd was gathered in a paddock near Karasjok on 21st March. Blood samples for pregnancy testing were taken from all females aged one year or older and these, and all last year’s calves, were weighed. This sounds straightforward but, in fact, requires great skill and considerable cooperation. It requires skill to bring a herd of reindeer down from its pasture on the taiga and to place it in exactly the right place – in the paddock – at exactly the right time.
It requires considerable cooperation between herders and scientists to have dozens of female reindeer presented one after the other in exactly the right position for collecting blood, and then weighed and then released in one or more paddocks - all done neatly and precisely during a furiously hectic six hours.
Besides the herders, the scientific team included staff and students from the Universities of Tromsø and Copenhagen and the Norwegian College of Veterinary Medicine.
