Ever See These Parasites Before?

A. bonasae (Dan Craven photo)

When we were in Minnesota last year, we heard tell of a worm-like parasite that was suspected to have been bringing down the grouse population. Never saw it ourselves – probably didn’t kill enough birds (lol) – but recently a compadre of ours sent us these photos of parasitic worms he found in his first grouse of the year.

Nasty, eh?

Anyone ever seen these before?

Since our buddy Dan lives in Minnesota, we contacted Ted Dick, MN DNR’s grouse biologist, and asked him if he could ID the worm. He could: It’s called Ascaridia bonasae. That last piece of Latin should be familiar to ruffie hunters because the taxonomic name of the wily furry forest chicken is: Bonasa umbellus.

[Btw: Bonasa means “good when roasted” and umbellus is “sunshade,” aka umbrella, meaning the male’s ruff. Sort of a crime the bird isn’t named after Superman or something else that can dodge “bullets.”]

A little more on the parasite, from this website:

> Ascaridia bonasae is a large, whitish nematode normally located in the small intestine of ruffed grouse. Hunters may find this roundworm in the body cavity when it escapes through holes in the small intestine created by pellets of shot.

> The life cycle of A. bonasae is direct, i.e., no intermediate host is necessary. Eggs are laid by adult female worms in the intestine of the host and are eliminated with the droppings. These eggs are in turn picked up by susceptible birds in feed and water.

> Adult female worms measure up to about 50 mm and males to approximately 35 mm in length. There are usually only a few worms present in each grouse although more than 75 worms have been reported from a single bird.

> Dorney and Kabat (1960) reported that the extent of infection of young grouse with A. bonasae during the summer is directly related to the abundance of grouse during the latter months of the previous winter.

> A. bonasae is not considered a serious pathogen of ruffed grouse and does not affect the edibility of the birds.

In other words:

Another shot of the invaders (Dan Craven photo)

> These parasites are normal, and elsewhere it says these things can be found throughout the grouse range.

> These things apparently don’t take up residence in people, should you have the misfortune to eat one.

We found the reference to the 1960 study interesting, tracked down and found these tidbits from it:

> Parasitic disease was density-related since the abundance of grouse in late winter was found to be directly related to the extent of infection with Ascaridia bonasae in young birds the following summer. [In other words, more birds = more infected birds.]

> During [peak population] years, the incidence of parasitic disease is higher, overwinter losses and brood mortality are increased….

In view of the second bullet, the scientists recommended (for northern WI) an “experimental overharvest of high [grouse] populations in the north [with] hunting season starting in mid-September and with removal of the bag limit – along with “an experimental spring hunting season…similar to the spring hunting of tetraonid cocks in Europe.”

More:

A spring hunt should be restricted to the last three weeks in May. It would be biologically feasible for the following reasons:

1. A current low fall harvest of adult males in the north is evident.

2. A reservoir of nonterritorial cocks is able to replace lost males.

3. Areas having low population densities would be made huntable in spring since the cock drumming behavior pin-points the quarry.

4. Few hens are seen once incubation has started, almost eliminating the likelihood of their being shot, especially with hunting activity centering around drumming logs.

5. There is an apparently low inclination of ruffed grouse to renest, hence there is a decreased importance of the cock in the last three weeks of May.

Such a season could provide a million recreational hours annually to hunters in northern Wisconsin. The sporting qualities of such a hunt are high, judging by its widespread acceptance in Europe.

Bowhunting for drumming cocks might be more acceptable to the general public and reduce accidental hen losses.

Pretty funny, eh? Although bird hunting in the spring sounds would mean half the wait each year….

Tags: Featured

Category: Disease, MN, Ruffed Grouse, WI