Muskrat population declining significantly

The tall, feather-like reeds that have been crowding out native plants along the coastline are claiming another victim — the lowly muskrat.

Wildlife biologists throughout the Northeast and eastern Canada say that they have observed significant declines in muskrat populations, and the culprit seems to be phragmites australis, also known as the common reed.

Paul Rego, a wildlife biologist with the state Department of Environment Protection, said that muskrats — an aquatic rodent that resembles a small beaver — have been in steep decline since the 1990s.

“The most widely accepted reason for this has been a change in wetland vegetation,” Rego said. “The cattails — their principal source of food — have been replaced by phragmites and also by the purple loose-strife.”

Rego said that muskrats have no use for either of these invasive plants. “Cattails are an important source of food for muskrats,” he said, noting the muskrat population drop was discovered after analyzing the records of fur trappers. About 400 trapping licenses are issued annually in Connecticut.

Muskrats also use cattails to make their nests.

According to the DEP, about 24,000 muskrat pelts were harvested in 1984. In recent years, the number is about 4,000 or less. This decline has corresponded closely with the spread of phragmites, which creates a plant “monoculture” once it invades a marsh, biologists say.

“Phragmites had definitely expanded its range in the last couple of decades,” said Todd Mervosh, a weed scientist with the Connecticut Agricultural Experiment Station’s Windsor office. “It’s a very aggressive plant — it’s tall — other plants can’t get sunlight,” Mervosh said. “And it spreads through rhizomes — they look like roots but actually they’re underground branches that spread out 20 feet or more.”

He said that phragmites can only be effectively controlled with herbicides, and that there are only a few companies in the Northeast with the training and equipment to do this work in the marshes where the weed grows.

Rego said that there are three other hypotheses being considered, none of which have gained much traction in the scientific community.

The first of these includes the so-called “succession” of marshland, in which it gradually changes from an “open marsh,” with mostly grass-like plants, to a “closed marsh” with more trees.

Another has to do with an increase in predators, such as owls, hawks and mink. The third involves the gradual improvement of water quality in the last 40 years, which has, paradoxically, led to a reduction in marsh plant life because cleaner water doesn’t have as many organic nutrients.

Trapping, he said, has not had a significant impact on muskrats’ numbers.

The muskrat decline comes at a time when some woodland creatures are thriving while others are struggling.

The Audubon Society reported last summer that many once-common feathered species, such as the whippoorwill, grosbeak and bobwhite, are in sharp decline in New England. Also not doing well are amphibians and many pollinating insect species, such as feral bees. Another medium-sized mammal with declining numbers in Connecticut is the northeastern cottontail rabbit, according to Howard Kilpatrick, a wildlife biologist with DEP’s Franklin office. “That’s probably due to habitat loss,” he said. “When woodlands begin to grow, you have eight to 10 years of good rabbit habitat with lots of underbrush, but as the forest matures, the underbrush disappears, and so do the rabbits.”

He added that suburban tracts have taken their toll, both in fragmenting cottontail habitat and introducing stray dogs and cats, which eat or stress the young. Conversely, some species, particularly those that live on the fringes of human activities, are seeing their numbers increase in Connecticut — such as deer, bears, moose and coyotes, Rego said.

Skunk and raccoon populations can be difficult to measure because of their boom-and-bust nature, but Rego said that both short- and long-tail weasels are threatened, too. “The ones that do well are the generalists,” he said. “The muskrat occupies a rather specific aquatic niche and doesn’t have much contact with humans.” In spite of the 1970s mega-hit “Muskrat Love,” muskrats aren’t particularly amorous, and appear to be content to live their lives in solitary fashion. “Yes, they have territorial issues,” Rego said.

Still, males and females do get together — however briefly — to mate, resulting in litters of about six young. Adult females produce as many a three litters per year, meaning that muskrats have, in the past, rebounded quickly from threats imposed by disease, human activity and predators. But the invasion of the phragmites has left the muskrat with an almost foreign landscape, populated with plants that are of little use.

The animal’s name refers to musk glands located in its hindquarters, and because it looks a little like a rat. Its appearance is more like that of a small beaver; they’ll reach a length of 18 to 25 inches, including its eight- to 10-inch tail.

Muskrats are nocturnal and are not commonly seen in daylight hours. They live about one or two years in the wild.

Rego said that the DEP has studied muskrats in the Quinnipiac River Marsh Wildlife Area — bounded by New Haven, Hamden and North Haven — most extensively. But, he said, it’s likely that similar declines have taken place in the marsh at the mouth of the Housatonic River — the Charles E. Wheeler Wildlife Area — and other marshy sites between New Haven and Greenwich.

Rego said that phragmites involve two different plants that have a similar appearance. The invasive variety can be traced to a reed that originated in Europe.

“There is actually a domestic version of the plant which isn’t nearly as bad,” he said.

Mervosh said that the invasive phragmites are quite likely a hybrid of the native and European species. He doesn’t see much letup in its advancement, either. “Unfortunately, it doesn’t need a marsh — it can spread to upland areas, too.”

By: JOHN BURGESON – CONNPOST.com