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Statistics for wildlifers: how much and what kind?

Quantitative methods are playing increasingly important roles in wildlife ecology and, ultimately, management. This change poses a challenge for wildlife practitioners and students who are not well-educated in mathematics and statistics. Here we give our opinions on what wildlife biologists should know about statistics, while recognizing that not everyone is inclined mathematically. For those who are, we recommend that they take mathematics coursework at least through calculus and linear algebra. They should take statistics courses that are focused conceptually , stressing the Why rather than the How of doing statistics. For less mathematically oriented wildlifers, introductory classes in statistical techniques will furnish some useful background in basic methods but may provide little appreciation of when the methods are appropriate. These wildlifers will have to rely much more on advice from statisticians. Far more important than knowing how to analyze data is an understanding of how to obtain and recognize good data. Regardless of the statistical education they receive, all wildlife biologists should appreciate the importance of controls, replication, and randomization in studies they conduct. Understanding these concepts requires little mathematical sophistication, but is critical to advancing the science of wildlife ecology.

Wildlife Society Bulletin

A rural mail-carrier index of North Dakota red foxes

Rural mail-carrier sightings of red foxes (Vulpes vulpes) during mid-April, -July, and -September of 1969-73 were compared to spring fox family estimates derived by aerial searches of six townships. The mid-April mail-carrier index reflected annual fox density changes on the six townships (correlation coefficient = 0.958) . Random exclusions of individual mail-carrier reports indicated participation could decline 40 percent without affecting index accuracy.

Wildlife Society Bulletin

Monitoring black-tailed prairie dog colonies with high-resolution satellite imagery

The United States Fish and Wildlife Service has determined that the black-tailed prairie dog (Cynomys ludovicianus) warrants listing as a threatened species under the Endangered Species Act. Central to any conservation planning for the black-tailed prairie dog is an appropriate detection and monitoring technique. Because coarse-resolution satellite imagery is not adequate to detect black-tailed prairie dog colonies, we examined the usefulness of recently available high-resolution (1-m) satellite imagery. In 6 purchased scenes of national grasslands, we were easily able to visually detect small and large colonies without using image-processing algorithms. The Ikonos (Space Imaging(tm)) satellite imagery was as adequate as large-scale aerial photography to delineate colonies. Based on the high quality of imagery, we discuss a possible monitoring program for black-tailed prairie dog colonies throughout the Great Plains, using the species' distribution in North Dakota as an example. Monitoring plots could be established and imagery acquired periodically to track the expansion and contraction of colonies.

Wildlife Society Bulletin

Assessing factors that may predispose Minnesota farms to wolf predation on cattle

Wolf (Canis lupus) depredations on livestock cause considerable conflict and expense in Minnesota. Furthermore, claims are made that such depredations are fostered by the type of animal husbandry practiced. Thus, we tried to detect factors that might predispose farms in Minnesota to wolf depredations. We compared results of interviews with 41 cattle farmers experiencing chronic cattle losses to wolves (chronic farms) with results from 41 nearby matched farms with no wolf losses to determine farm characteristics or husbandry practices that differed and that therefore might have affected wolf depredations. We also used a Geographic Information System (GIS) to detect any habitat differences between the 2 types of farms. We found no differences between chronic and matched farms in the 11 farm characteristics and management practices that we surveyed, except that farms with chronic losses were larger, had more cattle, and had herds farther from human dwellings. Habitat types were the same around farms with and without losses. The role of proper carcass disposal as a possible factor predisposing farms to wolf depredations remains unclear

Wildlife Society Bulletin

Canvasback mortality from illegal hunting on the upper Mississippi River

To quantify the consequences of local hunting on illegal kill of canvasbacks ( Aythya valisineria ), we studied the behavior of hunters on a 646-ha area open to duck hunting (closed to canvasback hunting) on Lake Onalaska, Navigation Pool 7, Wisconsin, during the 1991 and 1992 waterfowl hunting seasons. Law enforcement officers observed 258 hunting parties for 419 hours. Of 94 hunting parties encountering canvasbacks, 41 (44%) shot at the ducks on 56 occasions, or 27% of 207 encounters observed, Based on a ratio estimator, there were 790 (95% CI = 376) attempts to shoot at canvasbacks on the Lake Onalaska study area during 1991 and 837 (95% CI = 390) during 1992. Mortality of canvasbacks, excluding crippling loss, was estimated to be 128 during 1991 and 166 during 1992. Thus, total canvasback losses may be higher than currently estimated on a flyway or national basis. This estimating technique offers a promising method for enumerating hunter take of protected and legal species.

Wisconsin

Avian cholera mortality in lesser snow geese nesting on Banks Island, Northwest Territories

Avian cholera is one of the most important diseases affecting waterfowl in North America, but little is known about its ecology and its impact on waterfowl populations. We documented avian cholera mortality in breeding lesser snow geese (Chen c. caerulescens) at the Egg River colony on Banks Island, Northwest Territories, Canada, in 1995 and 1996. Area of the breeding colony, core nesting area, and number of nesting geese were greater in 1996 (colony=7,537 ha, core area=1,581 ha, 401,000 nesting geese) than in 1995 (colony=6,637 ha, core area=996 ha, 318,000 nesting geese). Density of nesting geese also was greater in the core area during 1995 (120 geese/ha) than in 1996 (90 geese/ha). Pasteurella multocida (serotype 1) was cultured from the leg bones of adult snow goose carcasses collected after outbreaks. Mortality from avian cholera began during nesting and continued until birds dispersed at hatch. Mortality appeared to be in foci scattered throughout the nesting colony, but generally was greater where there were greater densities of nesting geese. We estimated that 30,000 and 20,000 geese died in 1995 and 1996, respectively, about 5-9% of the nesting colony. Between 1991 and 1997, at least 4 avian cholera outbreaks occurred at Banks Island. It appears that avian cholera has become endemic in this population of snow geese, and these birds have the potential to transmit the disease to other waterfowl, especially on wintering areas where waterfowl are very concentrated.

Northwest Terrritories

Spent shot availability and ingestion on areas managed for mourning doves

Mourning dove (Zenaida macroura) hunting is becoming increasingly popular, especially in managed shooting fields. Given the possible increase in the availability of lead (Pb) shot on these areas, our objective was to estimate availability and ingestion of spent shot at the Eagle Bluffs Conservation Area (EBCA, hunted with nontoxic shot) and the James A. Reed Memorial Wildlife Area (JARWA, hunted with Pb shot) in Missouri. During 1998, we collected soil samples one or 2 weeks prior to the hunting season (prehunt) and after 4 days of dove hunting (posthunt). We also collected information on number of doves harvested, number of shots fired, shotgun gauge, and shotshell size used. Dove carcasses were collected on both areas during 1998-99. At EBCA, 60 hunters deposited an estimated 64,775 pellets/ha of nontoxic shot on or around the managed field. At JARWA, approximately 1,086,275 pellets/ha of Pb shot were deposited by 728 hunters. Our posthunt estimates of spent-shot availability from soil sampling were 0 pellets/ha for EBCA and 6,342 pellets/ha for JARWA. Our findings suggest that existing soil sampling protocols may not provide accurate estimates of spent-shot availability in managed dove shooting fields. During 1998-99, 15 of 310 (4.8%) mourning doves collected from EBCA had ingested nontoxic shot. Of those doves, 6 (40.0%) contained a?Y7 shot pellets. In comparison, only 2 of 574 (0.3%) doves collected from JARWA had ingested Pb shot. Because a greater proportion of doves ingested multiple steel pellets compared to Pb pellets, we suggest that doves feeding in fields hunted with Pb shot may succumb to acute Pb toxicosis and thus become unavailable to harvest, resulting in an underestimate of ingestion rates. Although further research is needed to test this hypothesis, our findings may partially explain why previous studies have shown few doves with ingested Pb shot despite their feeding on areas with high Pb shot availability.

Missouri

Chlamydiosis in 2 biologists investigating disease occurrences in wild waterfowl

Chlamydiosis (ornithosis, psittacosis) is an infectious disease of birds that can be transmitted to humans. Human infections are probably acquired by inhalation of aerosols containing elementary bodies of the causative agent Chlamydia psittaci , from bird droppings, or from tissues. Infected birds do not have to be ill to transmit the organism (Schachter and Dawson 1978). The disease in humans is considered an occupational risk for people working with pet birds (particularly psittacine species) and poultry, but all avian species can be considered as potential reservoirs (Schachter and Dawson 1978). Burkhart and Page (1971) listed >130 species of wild birds as being infected. The purpose of this report is to draw the disease to the attention of those working with wild birds by describing 2 cases acquired from wild waterfowl and by reviewing other information on human infections associated with wild birds. We do this because the disease can be serious if not treated properly, and because the disease is not usually associated with wild birds the diagnosis may not be considered by physicians without some prompting from the patient.

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