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STATEWIDE UNGULATE ECOLOGY Study I: Population Performance of Mule Deer and Elk Populations Study II: Effects of Predation on Mule Deer and Elk Populations Study III: Effects of Habitat and Nutrition on Mule Deer and Elk Populations
| Content Provider | Semantic Scholar |
|---|---|
| Author | Zager, Peter Pauley, George R. Hurley, Mark A. White, Craig |
| Copyright Year | 2007 |
| Abstract | We measured survival and cause-specific mortality of adult female mule deer and elk in Idaho during 2005-2006 and 2006-2007. Survival of mule deer was similar across both years ranging from 0.83 in 2005-2006 to 0.86 in 2006-2007. Likewise, cow elk survival was 0.86 in 20052006 and 0.88 in 2006-2007. Predation and hunter harvest were the most common proximate causes of mortality. Losses to malnutrition we negligible. Job 1. Survival, Cause-specific Mortality, and Pregnancy Rates of Elk and Mule Deer in Idaho Introduction Mule deer and elk are Idaho’s most important big game animals. Currently, a range of 78,000 to 84,000 hunters participate in Idaho elk hunts and harvest over 16,000 elk, while over 110,000 mule deer hunters harvest 23,000 to 26,000 mule deer. In 2001, deer hunting in Idaho contributed over $181,000,000 in economic benefits to the state, including nearly 2,000 jobs and 1.3 million dollars in state tax revenues (IAFWA 2002). More than half of all deer hunting in Idaho is dedicated to mule deer. Elk hunting in Idaho contributes over 150 million dollars to the state’s economic condition (Cooper and Unsworth 2000). Mule deer populations in Idaho have followed a trend similar to populations across the western United States. Mule deer generally achieved high historical densities in the 1950s and 1960s followed by significant declines across the western states. These declines have been the subject of intense debates within professional circles (Workman and Low 1976) and among the hunting public. More recently, populations in Idaho and some surrounding states experienced growth through the 1980s and a subsequent decline in the 1990s (Compton 2004a). There is little consensus and, even less definitive evidence, on the causes driving these trends. Elk populations in Idaho grew steadily into the 1960s and subsequently declined until general, antlerless hunting was discontinued in 1975. Subsequently, populations grew steadily through the 1980s. Over much of the more arid habitats of southern Idaho, elk populations grew and expanded into previously unoccupied habitats. In the late 1980s, calf recruitment began 1 Ungulate Ecology Study I-III PR07.doc declining in many areas of Idaho (Compton 2004b). In the more productive areas, recruitment rates declined from high levels to moderate levels, while in less productive areas, recruitment rates declined to extremely low levels, often below 15 calves:100 cows. Low recruitment led to declining populations, which precipitated intense interest in the problem. Since that time, elk research in Idaho has focused on the causes of elk calf recruitment. Habitat potential is generally recognized as the ultimate determinant of population density. Ungulate populations are limited to habitat potential and vital rates presumably respond in a density-dependent fashion (Caughley 1977). The classic model of ungulate population growth assumes a logistic form with the inflection point, and associated maximum growth rate, at approximately half of carrying capacity. However, some evidence suggests that yield is asymptotic nearer the upper level of population potential. Regardless, the fundamental assumption is that habitat, primarily forage, and its effect on animal condition regulates population growth, yield, and density. As populations approach habitat potential, yield approaches zero. In ungulate populations, the functional response may be reflected in lower survival of subadults, primarily neonates, and lower subadult fecundity (Cook et al. 2004). The literature is replete with accounts of ungulate mortality factors running the full gamut from additive to compensatory variously depending on predator and prey population densities, habitat conditions, alternate prey, and a variety of other factors including human exploitation. Connolly (1978) cited 45 references that tended to support the hypothesis of population regulation by predators, and another 27 that suggested predation was compensatory. Predation was identified as a controlling factor (Keith 1974), limiting factor (Bergerud et al. 1983, Bergerud and Snider 1988, Larsen et al. 1989), and regulating factor (Messier and Crete 1985, Ballard et al. 1990) of North American ungulate populations. However, Thompson and Petersen (1988) challenged the conclusion of Bergerud et al. (1983) that wolf predation limited moose populations in 2 areas, and Boutin (1992) questioned the wide acceptance of predation as the major regulatory factor of moose. In general, much of the work failed to consider alternate explanations and failed to test hypotheses with experimental manipulation. In some instances, experiments were conducted providing more reliable evidence. Gasaway et al. (1983) revealed a significant increase in moose calf recruitment and population growth in areas with wolf removal while there was no change in control areas. In another area, moose recruitment did not change with wolf removal (Ballard et al. 1987), but did increase with bear removal (Ballard and Miller 1990). Experimental manipulation in the Yukon revealed that wolf predation limited caribou and moose recruitment, and adult moose survival, but did not affect adult caribou survival or Dall sheep recruitment and survival (Hayes et al. 2003). Zager and White (2003) found that elk calf survival increased with a reduction in black bear and mountain lion densities in Game Management Unit (GMU) 12, while survival declined when predator densities were increased in GMU 15. These findings might corroborate the previous work of Schlegel (1976) who demonstrated increased elk calf survival following the removal of black bears. This work suggests an additive component of calf elk losses to predation. Mortality is expected to be largely compensatory when population density is near habitat potential. Bartmann et al. (1992) demonstrated a strong compensatory element of mule deer 2 Ungulate Ecology Study I-III PR07.doc fawn mortality in both a penned and free-ranging setting. When coyote densities were reduced, coyote-caused mortality decreased while starvation increased. Fawn survival was directly related to fawn weights, and varied inversely with density in penned pastures. Similarly, Clutton-Brock et al. (1987) demonstrated a density-dependent decrease in calf survival with increasing red deer (Cervus elaphus) cow density. Franzmann and Schwartz (1986) found a relationship between habitat quality and bear predation on moose calves. In Yellowstone National Park, winter elk calf mortality was inversely related to elk population density, and summer mortality was related to birth weight (Singer et al. 1997). Moreover, calves killed by predators tended to be late-born and lighter. Predation Bears may be a significant predator of ungulate neonates. A combination of black bears and brown bears took 34-52% of radio-collared moose calves in Alaska and the Yukon (Ballard et al. 1981, 1990; Larsen et al.1989; Schwartz and Franzmann 1990). In each case, bear mortality was the largest proximate source of mortality and Larsen et al. (1989) concluded that bear predation was the most significant limiting factor of moose on their study area. Schlegel (1976) found that black bears took at least 67% of radio-collared elk calves that died at Coolwater Ridge in Idaho. The current research effort revealed a similar magnitude of black bear-caused mortality in GMUs 10 and 12, with lesser bear-caused mortality in GMU 15 (Zager and White 2003). Singer et al. (1997) found relatively low black bear predation on calves (3% of deaths), while grizzly bears caused 28% of calf deaths. Myers et al. (1996) found that black bears accounted for 21% of elk calf deaths. Van Ballenberghe and Ballard (1994) argued that bear predation on moose calves is additive and density dependent. In southern Idaho, black bear predation was not detected on mule deer fawns (Hurley et al. In prep). However, their study areas were located in areas of low black bear occurrence. In mule deer habitats with higher black bear densities, bear-caused fawn mortality may be a factor. Mountain lions consume a wide variety of foods including lagomorphs, rodents, and small predators, but deer typically dominate their diet (Robinette et al. 1959, Hornocker 1970, Toweill and Meslow 1977, Ackerman et al. 1984, Hemker et al. 1984). Mountain lions are significant predators of elk (Hornocker 1970, Schlegel 1976, Myers et al. 1996, Singer et al. 1997, Smith and Anderson 1998, Zager and White 2003). Coyote predation of mule deer fawns and elk calves is well documented (Hamlin and Schweitzer 1979, Johnson and Hansen 1979, Gese and Grothe 1995, Singer et al. 1997, Hurley et al. In prep). The findings of Hurley et al. (In prep) revealed that, while coyotes prey heavily on mule deer fawns in southern Idaho, efforts to reduce coyote densities to improve fawn survival are largely ineffective. In 1995 and 1996, 35 gray wolves were reintroduced into Idaho under provisions of the Endangered Species Act. From the initial 35, wolf numbers subsequently increased to 71 in 1997 and by December 2004, at least 400 wolves were present in Idaho. Wolf populations continue to grow as new packs form and wolves spread into previously unoccupied areas. 3 Ungulate Ecology Study I-III PR07.doc Wolf diets throughout the world tend to be highly variable, but wolves tend to subsist largely on ungulates, where they are available. In the multiple ungulate systems of the northern Rocky Mountains, wolves tend to select elk over other ungulate prey (Huggard 1993, Husseman et al. 2003). Huggard (1993) suggested elk were selected over deer because large elk groups could be found in predictable locations. Like other predators, wolves tend to select more vulnerable prey. Several investigations revealed that wolves select elk that are old, young, or somewhat debilitated (Carbyn 1983, Kunkel et al. 1999). Wolves also tend to select bull elk, possibly due to lower condition caused by rut activity (B |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://collaboration.idfg.idaho.gov/WildlifeTechnicalReports/Ungulate%20Ecology%20Study%20I-III%20PR07.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
