The otters don't have that concern - they don't have a problem if they find a thin spot; on the contrary, they look for the open spots so they can come up and play on the ice. Here's a set of tracks where they were hopping along and sliding on their bellies on the ice last week.
|River Otter Tracks and Slides|
I took a walk up to Arbutus Hill Pond yesterday, and found it well frozen, with about 4 to 6 inches of ice. There was also still some snow up on the slightly higher elevations.
Along the way I found ice crystals growing up out of the wet ground,
as well as some fresh crystals on leaves from the prior day's moisture.
|Fresh Water Leech under the Ice|
In reading about leeches I learned they aren't a risk to humans, as the parasites they carry cannot survive in humans. They are adapted enough that they inject the enzyme hirudin into their host that prevents blood from coagulating, and also release an anesthetic so the host is unaware of their attachment. If you do get a leech on you, it is recommended that you remove it with your finger nail, as they do not leave mouth parts behind like a tic. You should not use heat or salt; that will release the leech, but it will first disgorge its stomach contents into its host - so forget that African Queen movie scene with Humphrey Bogart and Katharine Hepburn!