Appendix F
Wolf Health and Monitoring
and Mortality Factors
by Kerry Beheler-Amass,
Adrian P. Wydeven, and Richard P. Thiel
Disease testing and assessment of mortality factors has been a critical
aspect of wolf monitoring in Wisconsin since 1991. Such examinations
have been important for determining overall health of the wolf
population and determining how various factors have affected wolf
mortality.
Six diseases have been tested on wolf serum samples since 1991, and in
the 1990's fecal samples were tested for parvovirus, and live capture
wolves were assessed for probable mange (Table 1). Disease testing was
conducted on 115 serum samples for canine parvovirus (CPV), infections
canine hepatitis (ICH), canine distemper virus (CDV), heartworm (HTW),
Lyme disease, and Blastomycosis. Most of the animals tested represented
adults and yearlings, because few pups were captured during the
spring-summer live trapping period. Test procedures changed during the
monitoring period, therefore some difference in positive results may be
due to varying test sensitivity. Positive results indicate that the
animal was exposed to the disease, but not necessarily clinically
infected. Rate of positive titer values indicate prevalence of various
diseases in the wolf population, but not specifically the number of
animals affected by the disease.
Canine parvovirus was tested on 94 wolf serum samples and 23 wolf scats.
Over all results were near 50% positive for both tests. Positive test
were more prevalent on samples in the 1980's then in the 1990's (x2
=5.967, P<0.025 1 d.f.). The high levels of positive testing
corresponded with a period of population decline between 1982 to 1985
when the population declined 44% from 27 to 15 wolves. CPV was also
considered a major factor in the decline of Isle Royale wolves between
1980 and 1982 (Peterson 1995). Mech and Goyal (1995) indicated that
when 76% of adults tested positive, the wolf population would be
expected to decline. Parvovirus probably mainly affect young pups by
causing severe diarrhea leading to dehydration, but can also cause
mortality in wolves 9 months old in the wild (Mech et al. 1997).
Lyme Disease tested positive in 48% of 69 wolf serum samples. The rate
in Wisconsin is higher than most of Minnesota (Thieking et al. 1992).
Lyme Disease has only been identified in wolves of the Great Lakes
region. Although Lyme Disease has not been shown to cause specific
mortality with wild wolves, it perhaps does have some subtle impacts on
the wolf population. Annual pup survival has been estimated at only 30%
in Wisconsin (WDNR files), and possibly Lyme Disease is a factor.
Sarcoptic mange was first identified in a Great Lakes wolf in 1991.
(Wydeven et al. 1996). Although sarcoptic mites were difficult to
retrieve from live-trapped wolves, several wolves showed external signs
of mange including extensive hair loss (alopecia), darkened hairless
skin, and flaky crusting skin. Since 1991 mange sign was detected on
27% of wolves, and was as high as 58% in 1992-1993. In 1993 a 11%
decline was detected in the Wisconsin wolf population; Todd et al. 1981
indicate that population impact of mange is generally most severe during
the second or third year of infestation. Although Wisconsin wolves
continue to be infested with mange, it does not appear to have slowed
population growth in recent years.
Only 1 of 33 wolves tested positive for Blastomycosis, although 2 others
were "suspicious" (Thiel, unpublished data). One wolf was found to have
died with Blastomycosis in Minnesota (Thiel et al. 1987).
Other positive disease test included 39% of 72 samples for infections
canine hepatitis and 23% of 65 samples for canine distemper. These
rates as with other disease test indicate exposure to antibodies, but
not necessarily active disease status. Only one serum sample of
positive heartworm infection was detected; this disease seems to be a
rare disease among wild wolves in Wisconsin.
Table 2 illustrates mortality factors of 55 radio collared wolves found
dead in the field from 1979 through 1997. Some of these wolves were no
longer being actively monitored. Human's caused 60% of wolf mortality,
and more than half was caused by shooting. Disease caused at least half
of natural mortality. During the early 1980's annual adult survival was
only 61% and most mortality was caused by humans (Wydeven et al. 1995).
In recent years annual adult survival has generally exceeded 80% and
human-causes have been reduced to 50% of mortality. Shootings have
declined in recent years, but vehicle collisions have increased and
equal shooting mortality in the 1990's. Decrease in the illegal kill
was probably due to educational efforts and increased law enforcement.
Although the Wisconsin wolf populations are affected by a variety of
diseases and mortality factors, overall the wolf population seems
relatively healthy and is showing good growth in recent years. Health
monitoring will need to continue in the future to further assess impacts
of disease on the wolf population, and to detect any new mortality
factors that may affect wolves in the future.
Literature Cited
Mech, L.D.and S.M.Goyal. 1995. Effect of canine parvovirus on gray
wolves in Minnesota. J.Wildl. Manage. 59:565-570
Mech,L.D., H.J.Kurts, and S.Goyal. 1997. Death of a wild wolf from
canine parvoviral enteritis. J.Wildl. Dis. 33:321-322
Peterson, R.O. The wolves of Isle Royale: A broken balance. Willow
Creek Press, Minocqua, WI U.S.A. 190 pp.
Thiel, R.P., L.D.Mech, G.R.Ruth, J.R.Archer, and L.Kaufman. 1987.
Blastomycosis in wild wolves. J.Wildl. Dis. 23:321-323
Thieking, A., S.M.Goyal, R.F.Berg, K.I.Loken, L.D.Mech, and R.P. Thiel.
1992. Seroprevalence of Lyme disease in Minnesota and Wisconsin wolves.
J. Wildl. Dis. 28:177-182.
Todd, A.W., J.R.Gunson, and W.M.Samuel. 1981. Sarcoptic mange: An
important disease of coyotes and wolves of Alberta, Canada. Proc. World
Wide Furbearer Conf. 1:706-729.
Wydeven, A.P., R.N.Schultz, and R.P.Thiel. 1995. Monitoring of a
Recovering gray wolf population in Wisconsin, 1979-1991. p.147-156 in
L.N.Carbyn, S.H.Fritts, and D.R.Seip. eds., Ecology and Conservation of
Wolves in a Changing World. Canadian Circumpolar Institute, Occ. Publ.
No.35, 642 pp.
Wydeven, A.P., K. Beheler-Amass, N.J.Thomas, R.N.Schultz, S.M.Schmitt,
D.P.Shelley, and T.M.Gehring. 1996. Occurrence of sarcoptic mange in
Great Lakes States gray wolves (Canis lupus): 1991-1994. 14th Midwest
Furbearer Work shop, Ironwood, MI U.S.A. April 2-4.
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