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Integrated Management of the Greater Prairie Chicken and Livestock on the Sheyenne National Grassland

Disease


Disease-causing organisms and parasites are commonly present in all organisms and ordinarily do not cause a serious problem unless the organism is in a weakened condition due to poor nutrition or the pathogens or parasites are present in excessive numbers. The most comprehensive study of disease and grouse populations was carried out in Great Britain on the red grouse (Lagopus scoticus), described by Herman (1963). A 2-volume report was published in 1911 but included observations dating back to 1797. Red grouse are subject to periodic die-offs due to a build-up of a roundworm known as Trichostrongulus tenuis. It inhabits the caecum and eggs pass out with feces, hatch, then larvae crawl to the tips of heather which are eaten by grouse and the cycle continues. Problems come when too many heather tips harbor larvae resulting in increased parasite loads. By patch-work prescribed burning, the parasite may be controlled and red grouse numbers supported at higher densities. As Herman pointed out, this monumental work stimulated many subsequent studies.

Parasites and disease are rarely mentioned as a serious threat to prairie grouse, probably due to their mobility and generally lower densities reducing the odds of completing parasite life cycles. Prairie chickens, being "more mobile than any other gallinaceous game" (Leopold 1931:176) might be the least susceptible to disease unless they return to a common feeding areas. Hamerstrom et al. (1957:79) pointed out, "the need for a system of well distributed winter feeding places, and gives one more reason for the superiority of food patches over hoppers and other feeding devices which concentrate birds in small spaces. Since prairie chickens are subject to several of the diseases and parasites of domestic chickens and turkeys, food patches should not be placed on ground over which domestic poultry habitually run."

Gross (1930) gives a fairly complete description of grouse parasites and diseases with a particular emphasis on another caecal worm, Heterakis gallinae. He found it in 50% of the prairie chickens he examined in Wisconsin and noted that it was probably an indication that the prairie chickens had fed on ground "polluted" by poultry droppings. Of particular concern with this parasite is that it serves as the host for the protozoan flagellate (Histomonas meleagris) which causes blackhead disease (Noble and Noble 1973). Gross (1930:36), who closely studied the heath hen, noted that, "Blackhead was an important factor in the decline of the heath hen and was probably derived from turkeys which ranged over the feeding and "drumming" fields (booming grounds) of the heath hen until blackhead made the raising of turkeys unprofitable on Martha's Vineyard Island."

Recently, disease considerations have been identified as a contributing factor in the decline of the Attwater's prairie chicken in Texas (Purvis and Silvy 1995). Disease investigations are underway with wild populations and with geese and northern bobwhite quail. Avian cholera and roundworms (Trichostrongulus tenuis) have been implicated but one of the biggest concerns is the reticuloendotheliosis virus (REV), a disease similar to AIDS which disables the immune system (Purvis and Silvy 1995). This virus was found in the Texas A & M University captive flock and in 1 wild male. Apparently this disease is common in many domestic poultry flocks (30% of all domestic chickens have it) and wild geese can carry it (Nova Silvy, personal commun.).

Diseases and parasites have not been investigated with SNG prairie grouse, nor have they been suspected as a mortality factor. One caution however could involve the expansion of confinement turkey operations along the south edge of the SNG; in particular, the disposal of dead birds and manure. If manure is disposed of in areas accessible to or favored by prairie chickens, this could be a concern. Perhaps manure should be spread at a time and place when the likelihood of prairie chicken contact is minimized or it could be worked in (tilled) soon after spreading. Herman (1963) points out the necessity of controlling diseases through manipulation of populations and habitat. When dealing with a population "on the edge", it is prudent to anticipate all the possibilities for problems in order to take protective measures.

Summary

  1. Disease is generally not a limiting factor with prairie grouse, probably due to their high mobility. A notable exception is perhaps the heath hen which allegedly contacted blackhead disease from contact with domestic poultry.

  2. Recent concern has been raised regarding the possible role of disease in the decline of Attwater's prairie chickens. It's range overlaps that of wintering waterfowl (known to carry avian cholera) and an AIDS-like disease, common in poultry, has been discovered in the Attwater's population.

  3. The expansion of commercial turkey operation near the SNG could merit some concern as far as managing manure and dead birds to minimize contact with prairie chickens.

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