Abstract

The distribution and abundance of the white-tailed jackrabbit Lepus townsendii have declined significantly since 1950, continuing a trend that began in some regions of its range in the late 1800s. We reviewed museum records and the literature to evaluate the status of the white-tailed jackrabbit in each state and province in its historical range and evaluated possible reasons for its decline. Our evaluation revealed its extirpation or decline throughout much of its range, but its legal or conservation status does generally not reflect this precarious status. We note its extirpation in Missouri, Kansas and Oklahoma, and potential extirpation in British Columbia, Oregon, Illinois, and Wisconsin. We classified the white-tailed jackrabbit to be broadly extirpated in Iowa, Minnesota, Washington, Nebraska and California, and declining with local extirpations in Wyoming, Nevada, Utah, Colorado, New Mexico, and South Dakota. We consider it to be a relict in Ontario, and possibly declining in Alberta, Saskatchewan, North Dakota, Idaho, and Montana. We consider only Manitoba to have a possibly stable population. Determining the reasons for the species' reduced distribution is difficult, as the decline appears to be due to multiple factors, none of which provide a universal explanation. We dismissed road kills, recreational hunting, disease and parasites, and competition with black-tailed jackrabbits Lepus californicus as causes of the widespread population declines and extirpations. We concluded that habitat alterations and climate change are overriding factors, and that past depredation measures and increased predator populations have likely contributed to the decline. These hypotheses require further testing. We recommend more research on the distribution, abundance, ecology, and population dynamics of white-tailed jackrabbits, and management that includes a frank appraisal of the species' status, the potential for grassland restoration, and programs to reintroduce populations into prairie preserves and restored grasslands.

Introduction

The dominant Lepus in North America's intermountain region prior to the Holocene, the grassland-adapted white-tailed jackrabbit Lepus townsendii (Figure 1), began giving way to the black-tailed jackrabbit Lepus californicus with the onset of warming temperatures and changing vegetation between 2,000 and 8,000 y ago (Grayson 1977; Schimitt et al. 2002; Fisher 2012). Reduction in the numbers and distribution of this Nearctic crossover from Eurasia, while subject to periodic fluctuations, continues today (Anthony 1928; Simes et al. 2015; Gilcrease et al. 2016; Brown et al. 2018). Cold tolerant, with large furry feet and thick winter pelage that turns white in winter in its northern range (Hanson and Bear 1971), the white-tailed jackrabbit exhibits higher body temperatures and metabolic rates in winter than in summer (Rogowitz 1990). Thermal conductance is low as befits a cold-adapted animal, and white-tailed jackrabbits can survive frigid conditions by seeking shelter beneath the snow and using ice caves, allowing persistence in cold environments (Rogowitz 1990).

Figure 1.

Startled white-tailed jackrabbit Lepus townsendii in full flight in native grass cover at elevation of ca. 1,368 m above sea level near Thermopolis, Wyoming. Photo by Randall D. Babb in September 2006.

Figure 1.

Startled white-tailed jackrabbit Lepus townsendii in full flight in native grass cover at elevation of ca. 1,368 m above sea level near Thermopolis, Wyoming. Photo by Randall D. Babb in September 2006.

Mammalogists recognize two subspecies of white-tailed jackrabbits, although differences may be slight in areas of contact (Rogowitz and Wolfe 1991). A Great Plains subspecies, L. townsendii campestris, originally inhabited primarily midgrass and shortgrass communities within the Plains grassland ecosystem, while an intermountain subspecies, L. t. townsendii, occupied intermountain and subalpine grasslands (Brown and Makings 2017).

Lepus townsendii campestris normally favors grasslands dominated by midgrasses, but in some instances also can use human-modified environments such as hay fields, airports, and certain croplands. At the eastern edge of its range, forest ecosystems curtail its distribution. Across the Great Plains and Intermountain West, its preferred habitats included tallgrass prairie, mid- and shortgrass plains, sagebrush Artemisia spp.–steppe (Figure 2), subalpine grasslands, and alpine meadows above timberline (Figure 3; Orr 1940; Braun and Streeter 1968). In sagebrush-steppe, it chooses bunchgrass and rabbitbrush Ericameria spp. (Hoeman 1964) communities over sagebrush, which it uses mostly in winter. It uses shrubs primarily as cover, as well as stunted conifers at or above timberline. Summertime diets are composed mostly of forbs, with less than 2% being grasses, and which overlap with those taken by black-tailed jackrabbits which Lim (1987) described as more competitive in obtaining food.

Figure 2.

Shrub-steppe habitat of the white-tailed jackrabbit Lepus townsendii at elevation of ca. 2,027 m above sea level in October 2017, south of Wildhorse Reservoir, Nevada. Photo by David E. Brown.

Figure 2.

Shrub-steppe habitat of the white-tailed jackrabbit Lepus townsendii at elevation of ca. 2,027 m above sea level in October 2017, south of Wildhorse Reservoir, Nevada. Photo by David E. Brown.

Figure 3.

Alpine grassland habitat of the white-tailed jackrabbit Lepus townsendii elevation of > 3,600 m above sea level in the White Mountains of California. Photo by Joe Medeiros in 2016.

Figure 3.

Alpine grassland habitat of the white-tailed jackrabbit Lepus townsendii elevation of > 3,600 m above sea level in the White Mountains of California. Photo by Joe Medeiros in 2016.

The white-tailed jackrabbit is under-studied despite its wide distribution, ecological importance as a prey species, and economic importance as a game animal (Beever et al. 2018). Discussions of its natural history are generally limited to inclusion within larger mammalian inventories within regional summaries (e.g., Colorado: Armstrong [1972]; Nevada: Hall [1946]; New Mexico: Bailey [1932]; North Dakota: Bailey [1926]). Some exceptions include studies in the states of Colorado (Bear and Hansen 1966), Kansas (Carter 1939), South Dakota (Dieter and Schaible 2014), North Dakota (James and Seabloom 1969a, 1969b), and Washington (Ferguson and Atamian 2014). Here we scrutinize the available literature and accessible data from natural resource agencies to portray the global status of the white-tailed jackrabbit, evaluate causes of its decline, and make recommendations for its conservation and management.

Methods

We compiled, read, and evaluated 210 articles in the popular and peer-reviewed literature on white-tailed jackrabbit status, abundance, population trends, survey results, and responses to environmental stimuli. We obtained additional content and references from the white-tailed jackrabbit IUCN Red List account (Brown and Smith 2019) and overarching species accounts (Lim 1987; Simes et al. 2015; Beever et al. 2018). To determine white-tailed jackrabbit population trends, we also sought agency reports, wildlife surveys, and harvest information collected by state natural resource agencies within the species' present and former range. From these sources we evaluated the white-tailed jackrabbit's status and responses to land use changes, the effects of weather on recruitment and mortality, management, and the impacts of disease, predation, pest control, and competition. Because patterns of decline and potential reasons for decline varied by geographic region, we synthesized the evaluation of status in each state and province into seven regions: Northern Plains (Alberta, Manitoba, Saskatchewan), Southern Plains (Kansas, Oklahoma, Nebraska, North Dakota, South Dakota), Eastern Plains–Forest Ecotone (Illinois, Iowa, Minnesota, Missouri, Ontario, Wisconsin), Rocky Mountains (Colorado, Idaho, Montana, New Mexico, Wyoming), Great Basin (Nevada, Utah), Pacific Northwest (British Columbia, Oregon, Washington), and Sierra Nevada (California; Figure 4).

Figure 4.

Regions used to summarize the current (2020) status of the white-tailed jackrabbit Lepus townsendii by state and province. Historical distribution of the white-tailed jackrabbit is represented by the black line, and states and provinces are indicated by white lines and two-letter abbreviations. BC = British Columbia; WA = Washington; OR = Oregon; AB = Alberta; SK = Saskatchewan; MB = Manitoba; MT = Montana; ID = Idaho; WY = Wyoming; CO = Colorado; NM = New Mexico; CA = California; NV = Nevada; UT = Utah; ND = North Dakota; SD = South Dakota; NE = Nebraska; KS = Kansas; OK = Oklahoma; ON = Ontario; MN = Minnesota; WI = Wisconsin; IA = Iowa; MO = Missouri; IL = Illinois.

Figure 4.

Regions used to summarize the current (2020) status of the white-tailed jackrabbit Lepus townsendii by state and province. Historical distribution of the white-tailed jackrabbit is represented by the black line, and states and provinces are indicated by white lines and two-letter abbreviations. BC = British Columbia; WA = Washington; OR = Oregon; AB = Alberta; SK = Saskatchewan; MB = Manitoba; MT = Montana; ID = Idaho; WY = Wyoming; CO = Colorado; NM = New Mexico; CA = California; NV = Nevada; UT = Utah; ND = North Dakota; SD = South Dakota; NE = Nebraska; KS = Kansas; OK = Oklahoma; ON = Ontario; MN = Minnesota; WI = Wisconsin; IA = Iowa; MO = Missouri; IL = Illinois.

We compiled museum specimen records of L. townsendii from VertNet (2018), ARCTOS (2018), and GBIF (2018). We georeferenced specific locations using DeLorme Topo North America 10.0, and excluded records that did not provide specific enough location information to georeference. We used ArcGIS Pro to create a map of white-tailed jackrabbit locations by period.

Results

Our review of information on the distribution and abundance of the white-tailed jackrabbit in each state and province revealed an overall picture of population declines and range contractions (Table 1; Figure 5; Table S1, Supplemental Material; Text S1, Supplemental Material; Figure S1, Supplemental Material). The nature, extent, and temporal patterns of these changes varied by region (Table 1; Figure 5). Alarmingly, the current legal and conservation status of the species in each state is often at odds with the apparent current status of the species, which likely has forestalled needed conservation actions (Table 1). Below we summarize our detailed reviews by state and province that we present in Text S1 and Figure S1.

Table 1.

Current (2020) status of the white-tailed jackrabbit Lepus townsendii by state and province, including legal status according to state statutes, hunting status according to state regulations, special concern status according to State Wildlife Action Plan or Species of Concern list, NatureServe status, and the author's assessment based on review of information.

Current (2020) status of the white-tailed jackrabbit Lepus townsendii by state and province, including legal status according to state statutes, hunting status according to state regulations, special concern status according to State Wildlife Action Plan or Species of Concern list, NatureServe status, and the author's assessment based on review of information.
Current (2020) status of the white-tailed jackrabbit Lepus townsendii by state and province, including legal status according to state statutes, hunting status according to state regulations, special concern status according to State Wildlife Action Plan or Species of Concern list, NatureServe status, and the author's assessment based on review of information.
Figure 5.

Synopsis of the current (2020) status of the white-tailed jackrabbit Lepus townsendii by state and province within its historical range (see Table 1; Table S1, Supplemental Material; Text S1, Supplemental Material; and Figure S1, Supplemental Material for additional detail). BC = British Columbia; WA = Washington; OR = Oregon; AB = Alberta; SK = Saskatchewan; MB = Manitoba; MT = Montana; ID = Idaho; WY = Wyoming; CO = Colorado; NM = New Mexico; CA = California; NV = Nevada; UT = Utah; ND = North Dakota; SD = South Dakota; NE = Nebraska; KS = Kansas; OK = Oklahoma; ON = Ontario; MN = Minnesota; WI = Wisconsin; IA = Iowa; MO = Missouri; IL = Illinois.

Figure 5.

Synopsis of the current (2020) status of the white-tailed jackrabbit Lepus townsendii by state and province within its historical range (see Table 1; Table S1, Supplemental Material; Text S1, Supplemental Material; and Figure S1, Supplemental Material for additional detail). BC = British Columbia; WA = Washington; OR = Oregon; AB = Alberta; SK = Saskatchewan; MB = Manitoba; MT = Montana; ID = Idaho; WY = Wyoming; CO = Colorado; NM = New Mexico; CA = California; NV = Nevada; UT = Utah; ND = North Dakota; SD = South Dakota; NE = Nebraska; KS = Kansas; OK = Oklahoma; ON = Ontario; MN = Minnesota; WI = Wisconsin; IA = Iowa; MO = Missouri; IL = Illinois.

The current status of the white-tailed jackrabbit appears to be most secure in the Northern Plains. However, there is little information on the historical or current status of the species in this region, which represents the northern range limit of the white-tailed jackrabbit. The species expanded its range both north and east with the clearing of forests, resulting in the animal occurring in suburban and industrial areas, where winter densities may be higher than in surrounding rural areas. In the Southern Plains region, which represents the southern extent of the species range, there has been a dramatic retraction of the species range due to extirpations in Oklahoma, Kansas, and southern Nebraska. Within its current range, there also is a marked latitudinal gradient in population declines, with more severe losses at the southern portion of the range. The Eastern Plains–Forest Ecotone region represents the eastern range limits of the white-tailed jackrabbit; forest edges this region. Here, researchers have suggested that the species range initially expanded eastward with the clearing of forests for settlement and agriculture, but populations of white-tailed jackrabbits then declined and were broadly extirpated due to wholesale loss of prairie habitats. Some localized introductions of white-tailed jackrabbits occurred in Wisconsin, but there is no evidence that these introductions were successful or contributed to range expansion. The Rocky Mountains region includes both plains and montane populations of the white-tailed jackrabbit. The status of the white-tailed jackrabbit is more precarious in the three southern states (Wyoming, Colorado, New Mexico) where it has been extirpated from many areas including possible extirpation in a national park (Grand Teton). However, most of the population losses appear to be due to agriculture and degradation of native grasslands via livestock grazing. Similar to the southern portion of the Rocky Mountain region, the species has declined with broad extirpations in the Sierra Nevada region, where researchers now mostly find it only in isolated areas at high elevation. There has been little study of the status of the white-tailed jackrabbit in the Great Basin region. There are evident declines with at least local extirpations, but, given patterns of desertification of former grasslands, we suspect the extent of decline may be more severe than indicated by our assessment. The Pacific Northwest region represents a northern extension of the intermontane sage-steppe communities of the Great Basin. The white-tailed jackrabbit is now almost totally gone from this region, with its possible extirpation from British Columbia and Oregon, and with only relict populations remaining in Washington.

Concomitant with the historical decline of the white-tailed jackrabbit, the black-tailed jackrabbit experienced a range expansion to the north, as well as upward in elevation in some places. Some have presumed these range shifts were due to competition, but other factors can produce the same patterns. Compared to the white-tailed jackrabbit, the black-tailed jackrabbit has a smaller average home range (Smith 1990), greater recruitment potential, and lower mortality rate, and Simes et al. (2015) suggest it is more adaptable to disturbed habitats and reduced forage quality. Readers should note, however, that populations of most western leporid populations, including black-tailed jackrabbits, declined after the early 1970s (Brown et al. 2018). White-tailed jackrabbits also appear to have declined in areas where black-tailed jackrabbits are absent (e.g., Grand Teton National Park).

Discussion

Determining the reasons for the decline of the white-tailed jackrabbit is complex and appears to be due to multiple factors, often varying by region, and none of which in isolation is completely satisfactory. In addition, we consider it important to distinguish between proximate and ultimate drivers of population declines, because identifying ultimate causes can suggest conservation measures to mitigate losses and recover the species. We considered depredation control, competition with black-tailed jackrabbits, altered predator communities, habitat loss, and climate change as possible ultimate causes for the decline and widespread extirpation of white-tailed jackrabbits.

We dismissed road kills, recreational hunting, and disease and parasites as causes of the widespread population declines and extirpations. Although researchers have reported large numbers of road-killed white-tailed jackrabbits (Williams and Nelson 1939; Over and Churchill 1941), such losses are local and do not explain the reported population declines in large areas lacking improved roads (Simes et al. 2015; Brown et al. 2018). Several observers have suggested that intense hunting pressure on white-tailed jackrabbits may have contributed to local and even regional extirpations (Fry 1924; Brown 1947; Watkins and Nowak 1973; Flinders and Chapman 2003; Ferguson and Atamian 2014). However, populations have declined, or failed to increase, in areas closed to hunting (Rickard and Poole 1989; Fitzner and Gray 1991; Cox and Franklin 1989). Although tularemia is a common disease in jackrabbits, researchers have reported no widespread or lasting decline of either white-tailed or black-tailed jackrabbits due to parasites or disease (Simes et al. 2015; Brown et al. 2018). Bailey (1936) noted that white-tailed jackrabbits were not as prone to declines due to parasites as some other lagomorphs. A study of 314 jackrabbit livers collected from 44 counties in South Dakota showed no evidence of disease or parasitism being the cause for reduced numbers (Schaible et al. 2011).

Depredation control

Mass killing of jackrabbits via the use of bounties, “drives,” and poison removed astounding numbers of jackrabbits over a relatively short period of time, likely contributing to early regional declines in the Pacific Northwest, Great Basin, Sierra Nevada, and Southern Plains regions. Palmer (1897) summarized the count of rabbits killed in California, Idaho, Oregon, and Utah from 1875 to 1897 to be 635,546 jackrabbits. In 1922, farmers and the Oregon Extension Service poisoned 110,000 jackrabbits in eastern Oregon (Hogstad 2016). In the 1930s, a single drive in Kansas killed 35,000 jackrabbits and one county, Hodgeman County, issued bounties for 44,000 jackrabbits collected from drives before ceasing to offer a bounty because the costs were unsustainable (Kansas Historical Society 2015). Beginning in the 1930s, the use of the poison strychnine became the preferred method of control over jackrabbit drives (Becker 2006; Hogstad 2016). Jackrabbits are able to travel long distances (> 50 km; Grant 1987) and congregate in large numbers at local food sources (Lahrman 1980; Brunton 1981; Simes et al. 2015). Because of these factors, it is likely that jackrabbit drives and other control methods removed jackrabbits from a much larger area than the local drive site. Thus, drives could have contributed to the early decline of white-tailed jackrabbits in agricultural regions, possibility facilitating replacement by black-tailed jackrabbits.

Competition with black-tailed jackrabbits

The literature is replete with examples of an apparent coupling of the decline and northward contraction of the range of the white-tailed jackrabbit with a northward expansion of the black-tailed jackrabbit, suggesting that competition between the two species could be responsible for these distributional changes (Lim 1987). Wildlife biologists consider the black-tailed jackrabbit to be the more adaptable of the two species in grassland habitats subject to grazing, shrub encroachment, and conversion to cropland (Flinders and Hansen 1972; Lim 1987). Some researchers think that the black-tailed jackrabbit, which may have a smaller average home range (Smith 1990), is more adaptable to disturbed habitats, reduced forage quality, and has a greater recruitment rate potential and a lower mortality rate than the white-tailed jackrabbit (Simes et al. 2015). However, both species coexist naturally in some areas and use different niches when they are present in the same area (Couch 1927; Flinders and Hansen 1972; Simes et al. 2015). Thus, the replacement of white-tailed jackrabbits by black-tailed jackrabbits appears to be the result of altered habitat that favors black-tailed jackrabbits, rather than competition per se.

Altered predator communities

Several accounts attribute the decline or disappearance of white-tailed jackrabbits to increased predation, at least in part (Nelson 1909; Wooster 1935; Carter 1939; Brown 1947; Rogowitz and Wolfe 1991; Dieter and Schaible 2014). Predation rates influence the survival rate of a population, and if the mortality rate exceeds the recruitment rate the number of jackrabbits declines. For species such as the white-tailed jackrabbit, increased recruitment rates may not compensate for increased predation and predation can thus result in long-term population declines. Although there has been very little study of predation determining population changes in white-tailed jackrabbits (Simes et al. 2015), there is abundant evidence that white-tailed jackrabbit predators such as coyotes Canis latrans, bobcats Lynx rufus, and ferruginous hawks Buteo regalis have recently increased virtually throughout the hare's range (Brown et al. 2018). These increases, plus other factors resulting from habitat alteration can cause predation rates to increase. Examples include a loss of concealment cover for prey species, a loss of escape cover, seasonal pelage color changes not in synchronization with weather patterns (e.g., white winter pelage when there is no snow on the ground; Zimova et al. 2014), and poor body condition due to inadequate nutrition. Any of these factors could contribute to a decline in white-tailed jackrabbit numbers.

Lim (1987) notes that a wide range of avian and mammalian predators prey on white-tailed jackrabbits. The golden eagle Aquila chrysaetos and possibly the ferruginous hawk select jackrabbits as a large proportion of their diet (Woodgerd 1952; Olendorff 1976; Collopy 1983, Steenhof et al. 1997). Among the mammalian predators, researchers have reported the abundances of bobcat (Knick 1990) and coyote (Clark 1972; Cypher et al. 1994) are at least partially controlled by an abundance of jackrabbits. For instance, Stoddart (1970) found that more than two-thirds of a semiannual mortality rate of 41% on black-tailed jackrabbits was due to coyote predation, with another 20% attributable to raptors and scavengers.

Conversely, several researchers have concluded that predators at least partially control populations of jackrabbits (Eberhardt and Van Voris 1986; Boutin and Cluff 1989; Sosa Burgos 1991; Steenhof et al. 1997; Bartle el al. 2008), although the relationship is complex and other factors such as precipitation may also contribute (Sosa Burgos 1991; Bartel et al. 2008). For instance, Wagner and Stoddart (1972) determined that an increasing population of coyotes was the major source of increased jackrabbit mortality from 1962 to 1970 in Curlew Valley, Utah, hastening if not causing a 1963 to 1967 jackrabbit population decline. Contributing to this conclusion are observations of increases in jackrabbit populations following predator-control activities that reduced the abundance of coyotes (Henke and Bryant 1999).

A change in predator numbers could potentially cause a decline of white-tailed jackrabbits by either of two processes: apparent competition or mesopredator release. Apparent competition is a process in which a predator's population is bolstered by an abundant prey species (black-tailed jackrabbits), resulting in a decline of another prey species (white-tailed jackrabbits; Holt 1977). This process could occur in areas where white-tailed jackrabbits are relatively scarce and black-tailed jackrabbits are abundant. In this way, it is conceivable the retraction of the range of the white-tailed jackrabbit is due indirectly to the expansion of the range of the black-tailed jackrabbit. Mesopredator release occurs when midsized carnivores become more abundant as a result of the decline or extirpation of larger carnivores that would otherwise control numbers of the smaller carnivores (Soulé et al. 1988). Grey wolves Canis lupus formerly occurred throughout the range of the white-tailed jackrabbit, but conflicts with livestock in the early 20th century led to their extirpation. Ripple et al. (2013) suggest that, as a result, coyotes have both increased in abundance and expanded their range. Wolves are pack hunters that specialize on ungulate prey, whereas coyotes primarily prey on medium-sized and small mammals. Thus, it is plausible that increases in coyote populations caused decline in white-tailed jackrabbit populations (Ripple et al. 2013). Other factors favoring an increase in coyote numbers and distributions include greater water availability, human-supplied food sources, and additional scavenging opportunities, all of which could result in increased predation pressure on white-tailed jackrabbits (Brown et al. 2018).

Habitat loss

Researchers generally agree that loss of grassland habitat has caused population declines of the white-tailed jackrabbit (Lim 1987; Simes et al. 2015; Brown et al. 2018), and our review supports this view. Humans have converted much of the original grasslands of the Great Plains to annual crop production (Gage et al. 2016). This conversion is almost complete in the more productive eastern tallgrass prairie, and new conversion is continuing to happen in the more arid portions of the central and western plains (Gage et al. 2016). In the Southern Plains and the Eastern Plains–Forest Ecotone regions, the “plow-print area” (areas where grasslands have been plowed for crop production) closely parallels the areas where the white-tailed jackrabbit has been extirpated. The plow-print area also suggests that the status of the white-tailed jackrabbit in the Northern Plains may be in worse condition than is realized, as the vast majority of this region is under cultivation (Gage et al. 2016).

In the West, crop production, while less widespread, has also resulted in substantial loss of grassland habitat in key white-tailed jackrabbit areas, including central Washington in the Pacific Northwest region, and high-elevation valleys in the Great Basin, Sierra Nevada, and Rocky Mountain plains region. In arid areas that cannot be cultivated, the primary cause of habitat loss is livestock grazing resulting in habitat alteration. Even partial changes in grassland ecosystems could negatively impact white-tailed jackrabbits by changing nutritional availability or removing concealment cover. With enough intensity or duration, livestock grazing can ultimately lead to a process of desertification that results in loss of grasses and increase in shrubs. These shrub-dominated communities provide habitat for black-tailed jackrabbits, but not for white-tailed jackrabbits (Simes et al. 2015). More recently, Brown et al. (2018) posit that the spread of invasive cheatgrass Bromus tectorum, a species known to increase wildfire frequency, is a contributing threat to white-tailed jackrabbits in the Great Basin region.

One less obvious proximate cause for declining white-tailed jackrabbit populations related to habitat alteration is the decrease of nutritious vegetation, which results in subpar reproductive performance (Brown 1947; Beaudoin and Beaudoin 2012). Schaible and Dieter (2011) noted reduced kidney fat in a declining population of white-tailed jackrabbits in South Dakota, and Gilcrease et al. (2016) thought depleted farm soils with poor concentrations of carbohydrates and reduced glucose might explain declining white-tailed jackrabbit numbers in South Dakota. This process could also be applicable to deteriorated rangelands.

Climate change

Researchers have long suggested that climate change is a factor responsible for the disappearance of white-tailed jackrabbits, particularly in the Southern Great Plains region (Wooster 1935; Carter 1939; James and Seabloom 1969b; Rogowitz 1992; Benedict et al. 2000). The Southern Great Plains is prone to droughts, and researchers thought that long periods of low precipitation were associated with both declining populations of white-tailed jackrabbits and increasing populations of black-tailed jackrabbits. In contrast, in the Eastern Plains–Forest Ecotone region, which is at the wet edge of the species distribution, relatively wet years were associated with low white-tailed jackrabbit populations (Kline 1963). Climate warming causes shifts in climatic zones, forcing species ranges farther north and upward in elevation as vegetation and timing of the seasons change (Karl et al. 2009). A long-term warming trend could pose an increased threat to white-tailed jackrabbits, as this species is more adapted to cold weather than the black-tailed jackrabbit, although the mechanisms are uncertain. One possible mechanism is a mismatch between the evolved seasonal molt to camouflaged pelage coloration and the ambient conditions resulting from a changing climate, as has been demonstrated for snowshoe hares Lepus americanus (Zimova et al. 2014) and mountain hares Lepus timidus (Pedersen et al. 2017). There are nearly 2 wk fewer of snow cover in the United States since 1972 (Rutgers University Global Snow Laboratory 2016), which could expose white-tailed jackrabbits in white winter pelage to increased risk of predation.

Conclusions and Recommendations

We suggest that altered predator communities, habitat loss, and climate change are mostly responsible for the decline and extirpation of white-tailed jackrabbits. Evidence suggests that these threats are continuing and may accelerate in the future. The white-tailed jackrabbit is already lost from a large proportion of its historical range and evidence indicates that declines are continuing, with little proactive conservation efforts by states and provinces to understand or reverse these trends. As a consequence, many populations are nearing extirpation, becoming increasingly isolated, and possibly subject to inbreeding depression, resulting in a decline in fitness and accelerated mortality rates. If so, the result will be a continuation of this decline, more limited distributions, and increased disappearances from marginal areas.

Although little can ameliorate the effects of climate change and drought, and detrimental land use practices will continue to degrade habitats, white-tailed jackrabbit populations may benefit from better land management practices. The provision of more and better grass cover might increase white-tailed jackrabbit survival rates, as would the preservation of open landscapes of native perennial grasses. Additional investigations into the effects of weather and climate on both jackrabbit species are needed, and future studies need to determine which habitat improvements might most improve the survival rates of white-tailed jackrabbits as opposed to black-tailed jackrabbits. We also encourage investigations into the impacts of agricultural chemicals and crop selection on white-tailed jackrabbits.

To accomplish the above, research needs to focus on achieving a better understanding of white-tailed jackrabbit population dynamics, particularly in relation to different land management practices. If, for example, jackrabbit numbers can be increased by reducing juvenile mortality rates from predation through habitat enhancement, then testing the ability to manipulate predation-based mortality could not only lead to increased population numbers, but might benefit predators such as the golden eagle, which are adapted to feeding on adult jackrabbits. Research should also focus on other limiting factors that control the distribution and abundance of white-tailed jackrabbits.

A lack of studies has hampered understanding the scope and causes of decline of the white-tailed jackrabbit. We recommend that management agencies and conservation organizations critically evaluate the status of the white-tailed jackrabbit in their area of jurisdiction to provide frank evaluation of the species status based on current scientifically defensible data. In addition, we suggest that researchers study the feasibility of translocating white-tailed jackrabbits to prairie preserves within the species' former range where the species disappeared prior to grassland restoration. Managers could then operate such areas with the restoration of white-tailed jackrabbits in mind. Potential sites are many and include former habitats in The Nature Conservancy's 1,457-ha Nachusa Prairie Preserve in northwest Illinois, Dunn Prairie Preserve in northwest Missouri, and the U.S. Fish and Wildlife Service's Savanna division of the Upper Mississippi National Wildlife Refuge on the Minnesota–Illinois border. We recommend a range-wide genetic assessment of the phylogeographic structure of the white-tailed jackrabbit accompany possible translocation efforts to ensure appropriate source populations and to maintain historic genetic structure.

Supplemental Material

Please note: The Journal of Fish and Wildlife Management is not responsible for the content or functionality of any supplemental material. Queries should be directed to the corresponding author for the article.

Table S1. Museum records of white-tailed jackrabbit Lepus townsendii locations by institution as compiled from VertNet with accession numbers, states/provinces, coordinates, elevations (m), locations, sex, and year acquired.

Found at DOI: https://doi.org/10.3996/042019-JFWM-026.S1 (668 KB PDF).

Text S1. Review of the current (2020) status of the white-tailed jackrabbit Lepus townsendii by state and province.

Found at DOI: https://doi.org/10.3996/042019-JFWM-026.S2 (146 KB PDF).

Figure S1. Distribution of the white-tailed jackrabbit Lepus townsendii. Dots represent museum specimens collected during different time periods: 1800–1939 (yellow); 1940–1979 (blue); 1980–2018 (red); undated (white). The black line outlines the species' historical distribution based on museum records (Table S1, Supplemental Material) and information in the review of the status of the species by state and province (Text S1, Supplemental Material).

Found at DOI: https://doi.org/10.3996/042019-JFWM-026.S3 (1.36 MB PDF).

Table 1.

Extended.

Extended.
Extended.

Acknowledgments

We thank Kevin Stewart and Danica Cooke, New Mexico State University, for assistance compiling museum and literature records for the range map. We thank Jim Malusa for assistance with mapping. We thank Nichole Bjornlie, Wyoming Game and Fish Department; Steve Buback, Missouri Department of Conservation; Aaron Buchholz, Wisconsin Department of Natural Resources; David Budeau, Oregon Department of Fish and Wildlife; Laura Conlee, Missouri Department of Natural Resources; Jerrod Davis, Oklahoma Department of Wildlife Conservation; Brian Dhuey, Wisconsin Department of Natural Resources; Matt Eckert, Colorado Parks and Wildlife Department; Stefan Ekneras, U.S. Geological Survey; Sean Espinosa, Nevada Department of Wildlife; Mark Howery, Oklahoma Department of Wildlife Conservation; Corey Huxoll, South Dakota Department of Game, Fish and Parks; Pat Jackson, Nevada Department of Wildlife; Corey Jager, Oklahoma Department of Wildlife; Sara Kindschuh, Washington Department of Fish and Wildlife; Stan Kohn, North Dakota Game and Fish Department; Jeff Lusk, Nebraska Game and Parks Commission; Stan McTaggart, Illinois Department of Natural Resources; Matt Meshriy, California Department of Fish and Wildlife: Ken Morgan, Colorado Parks and Wildlife Department; Constance Millar, U.S. Forest Service; Matt Peek, Kansas Department of Wildlife, Parks and Tourism; Jeff Prendergast, Kansas Department of Wildlife, Parks and Tourism; Jason Robinson, Utah Division of Wildlife; Jon Runge, Utah Division of Wildlife; Jerry Shaw, Oklahoma Department of Wildlife; James Stuart, New Mexico Game and Fish Department; Mark Vieira, Colorado Department of Wildlife; Bryant White, Association of Fish and Wildlife Agencies; Sam Wilson, Nebraska Game and Parks Commission; Tim Woolley, Wyoming Game and Fish Department; Russell Woolstenhuln, Nevada Department of Wildlife; Simon Wray, Oregon Department of Fish and Wildlife; Greg D. Wright, Nebraska National Forests and Grasslands Bessey Ranger District. Their cooperation and contributions of state management data were essential to this paper. Richard Brown and Joe Medeiros provided photographs and Greg Beatty provided important information on the status of western-state raptors. We are especially indebted to the Journal of Fish and Wildlife Management Associate Editor and reviewers for their rigorous reviews of earlier drafts and for their thoughtful suggestions.

Any use of trade, product, website, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government.

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Author notes

Citation: Brown DE, Smith AT, Frey JK, Schweiger BR. 2020. A review of the ongoing decline of the white-tailed jackrabbit. Journal of Fish and Wildlife Management 11(1):341–352; e1944-687X. https://doi.org/10.3996/042019-JFWM-026

Competing Interests

The findings and conclusions in this article are those of the author(s) and do not necessarily represent the views of the U.S. Fish and Wildlife Service.