About the only time Muskrats travel any distance from water is in the spring when they are seeking new territory, in the fall if their habitat dries out, or anytime their wetland is drained. The Muskrats at the FWG are probably a result of spring or fall dispersal as those are the seasons when they are most visible at the garden.
Although very common, Muskrats can be surprisingly difficult to see, mainly because they are most active very early and very late in the day. Their habitat also doesn’t make for easy observation. However, if you are patient (or lucky), you should be able to observe them swimming and feeding, moving across mats of aquatic vegetation, or even trundling across dry land.
Apart from a sort of “chittering” sound when they have been distressed by my presence, I have never heard any Muskrat vocalization, nor have I been able to find any descriptions apart from a vague mention of squeals and grunts when they are agitated or cornered.
Their biggest enemy is probably us. Not only do we kill countless numbers on the road, but we trap millions every year for their pelts. They also fall prey to a number of other species, although at the FWG their most serious predator would be dogs, Red Foxes (Vulpes vulpes), and possibly some of the large raptors that sometimes occur there. I have heard that weasels (Mustelidae) and Raccoons (Procyon lotor) will also take muskrats and both these species occur at FWG, although in small numbers. Of course, in other areas of Ottawa, Coyotes (Canis latrans) can be added to the list of predators, along with American Mink (Mustela vison).
During most of the year, Muskrats inhabit a fairly small territory, and population density varies considerably: Banfield (1974) gives anywhere from 3 animals per 0.5 ha to 3 per 14 ha of wetland. As with so many rodents, populations are cyclical. Muskrats seem to reach their peak every 6-10 years after which, numbers crash. No particular reason is given, but Forsyth (1985) probably correctly, assumes the cycle is related to food supply and water fluctuation. He also comments that the greater (10-year) cycle, which typically occurs in the northern part of their range, is likely related to a shorter breeding season and slower growth rates, meaning it takes longer for northern animals to recover to their previous numbers.
At the FWG, we had never seen more than one muskrat at a time in our pond, until spring 2008 when a pair appeared. They were very active for a couple of days, but after that we had only sporadic sightings of a single animal and, by mid-summer, it was unclear whether they were still around. As to whether they actually bred, or moved on to better prospects, I don’t know for sure, but if they’d had young, our pond is small enough that we’d have eventually noticed them, and we didn’t. Furthermore, as you will see below, the pond doesn’t provide particularly good natal sites.