Someone commented recently that resistance to parasites drops in spring (or
at lambing? which usually are together - but not always). This got me
pondering. I once spent a summer in the Northwest Territories (Canada)
doing biological research work for a minerals exploration giant. The area
of the work included a band of Dall's sheep and caribou, and there was a
hotsprings where animals would come to eat mud, presumably for the minerals.
I had the not-so-fun task of once a week changing the film in a time-lapse
camera, and at season's end I got to view every frame of film and count
numbers of animals at the hotsprings. The Dall's sheep in particular had to
leave their preferred habitat (grassy mountain sides and cliffs) and come
down in to the forested valley bottom to use the hotspring. After all the
films were counted it was blatantly obvious that the animals used the spring
almost solely in late winter/early spring. For a week or two the sheep were
at the spring often, and then they disappeared back to the cliffs for the
rest of the summer. From that time on there were virtually no large animal
visitors (once a bear) until late summer, when there was a small peak in
visits (which I think were only caribou - I don't remember clearly).
Something like 90 or 95% of the visits were in the late winter/early spring
period, and 5 or 10% in later summer/early fall (in that part of the world
fall is a very brief season.
I am wondering if the known increase in parasites during spring and my
observation of the visits to the hotspring could be related.
This has got me thinking that livestock might consume much greater
quantities of minerals in spring. I've never before thought to watch for
this. What are your observations?
Ann
Vermont
