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 1981. 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 1981 , and in the 1990's fecal samples were tested for parvovirus, and live capture wolves were assessed for probable mange (Table F1). Disease testing was conducted on 115 serum samples through 1996 for canine parvovirus (CPV), infectious 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.

Table F1.
Disease testing of live-captured wolves in Wisconsin 1991-1996
(Positive Test/Total Tested)
YEAR CPV
Serum
CPV
Feces
ICH CDV HW Lyme Blasto Mange-like
Condition
1981 5/6 --- --- --- --- --- --- ---
1982 6/7 --- 3/3 6/6 --- --- 1/3 ---
1983 4/5 --- 2/5 0/5 --- --- --- ---
1984 1/4 --- --- 0/1 --- --- 0/2 ---
1985 4/5 --- 0/1 --- --- --- 0/5 ---
1986 4/4 --- --- --- --- --- --- ---
1987 --- --- --- --- --- --- 0/2 ---
1988 1/4 --- 2/4 0/4 --- 3/4 --- ---
1989 --- --- --- --- --- 3/4 --- ---
1990 --- --- --- --- --- 2/3 --- ---
1991 5/12 --- 5/12 1/1 1/11 8/12 0/12 2/11
1992 2/10 --- 4/9 1/10 0/8 4/9 0/9 5/10
1993 0/6 2/4 0/6 1/6 0/7 3/6 --- 6/9
1994 3/9 2/6 3/10 2/10 0/10 4/9 --- 3/11
1995 7/13 4/7 4/13 1/13 0/13 2/13 --- 2/16
1996 4/9 3/6 5/9 3/9 0/9 4/9 --- 1/14
Total 46/94 11/23 28/72 15/65 1/58 33/69 1/33 19/71
+81-89 71% --- 54% 38% --- 75% 8% ---
+90-96 36% 48% 36% 18% 2% 44% 0% 27%
CPV = Canine Parvovirus
ICH = Infectious Canine Hepatitis
CDV = Canine Distemper Virus
HW = Heartworm
Lyme = Lyme Disease
Blasto = Blastomycosis

Canine parvovirus was tested on 94 wolf serum samples and 23 wolf scats. Overall 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 F2 illustrates mortality factors of 63 radio collared wolves found dead in the field from 1979 through 1998. Some of these wolves were no longer being actively monitored. Human's caused 61% of known wolf mortality, and more than half was caused by shooting. Disease caused 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.

Table F2
MortalitySummary of Radio-Collared wolves from Wisconsin and adjacent areas of Minnesota Oct. 1997-Dec, 1988
Cause of Death: Number

Percent Known Mortality

Human Caused
Capture-Related

2

4%

Shooting

18

32%

Trapping

3

6%

Vehicle Collision

8

14%

Unknown Human Cause

4

7%

Total Human Caused:

35

61%

Natural Causes:
Birthing Complications

1

2%

Disease

11

19%

Killed by Other Wolves

6

12%

Unknown Natural Cause

3

5%

Total, Natural Caused: 22 39%
Total Known Mortality:

57

100%

Unknown Mortality:

6

Total All Mortality:

63

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