Land management alters traditional nutritional benefits of migration for elk

Abstract

Ungulates typically migrate to maximize nutritional intake when forage varies seasonally. In western North America, however, increasing numbers of ungulates reside on low‐elevation winter range year‐round rather than migrating. These residents often occupy irrigated agricultural areas, but it is not known whether the nutrition provided by agricultural land exceeds that gained by migration. We evaluated the nutrition available to a partially migratory population of elk (Cervus canadensis) in west‐central Montana where some individuals summered on low‐elevation agricultural lands, whereas others summered on traditional higher‐elevation ranges. We sampled elk forage plants from ground plots and adult female elk movements from global positioning system (GPS) collar locations during late summer for 2 years. We tested for differences in the nutrition provided by 11 vegetative communities commonly available to elk in the Rocky Mountains and the nutrition available in areas used by individuals whose behaviors ranged from residency to migration. We found the nutrition available to elk decreased along the continuum from resident to migratory behavior, contrary to our hypothesis that all behaviors would provide access to equivalent forage quality. The relatively small summer home ranges of migrants suggest other factors (e.g., decreased competition) may compensate for their lower nutritional value, because the size of a home range is often inversely related to its fitness benefits. We found irrigated agriculture provided the highest forage quality in low elevations, but recently burned (1–6 yr prior) dry forests at higher elevations provided forage quality approximately equivalent to that of irrigated agriculture. Excluding elk from irrigated agricultural areas should therefore reduce nutritional incentives for elk to reside at low elevations year‐round. Additionally, fire in higher‐elevation dry forests may temporarily increase forage quality for elk and improve nutritional benefits of migratory behavior. Our results indicate land management practices can affect nutritionally mediated fitness benefits of differing behaviors in partially migratory populations of ungulates. © 2018 The Wildlife Society.

Characterizing population and individual migration patterns among native and restored bighorn sheep (Ovis canadensis)

“…As GPS technology continues to enhance our ability to track and map animal migrations, there are an increasingly large number of seasonal migrations that do not fit within traditional definitions (Dingle & Drake, ). Rather than adopt a dichotomous classification (e.g., resident or migrant), seasonal migrations are being increasingly interpreted along a behavioral continuum (Barker, Mitchell, Proffitt, & Devoe, ; Cagnacci et al, ; Sawyer et al, ). Our results expand on this approach through recognizing not only variation in geographic distances, but also variation in elevational distances within and among populations.…”

Conserving transboundary wildlife migrations: recent insights from the Greater Yellowstone Ecosystem

“…; Barker et al . ). Lower carnivore numbers caused by hunting and lethal control to protect livestock, combined with limited elk hunting access on some private lands, may compound the benefits of a resident lifestyle (Haggerty and Travis ; Middleton et al .…”

“…In addition, the proportion of long-distance migrants in some partially migratory herds in the GYE appears to be declining (White et al 2010;Middleton et al 2013;Cole et al 2015), although it is not clear to what extent natural causes (eg predation, periodic drought) versus anthropogenic changes are driving these declines. Near the GYE frontier, irrigated hayfields may provide resident elk populations with a competitive advantage, or incentivize migrants to become resident Barker et al 2019). Lower carnivore numbers caused by hunting and lethal control to protect livestock, combined with limited elk hunting access on some private lands, may compound the benefits of a resident lifestyle (Haggerty and Travis 2006;Middleton et al 2013).…”

Native forage mediates influence of irrigated agriculture on migratory behaviour of elk

“…Additionally, given the relatively high nutritional quality of early seral-stage vegetative communities(Barker, Mitchell, Proffitt, & Devoe, 2019), managing disturbances to maintain a mosaic of early-successional vegetative F I G U R E 2 Results of best-supported model explaining migratory behaviour of 308 elk in 16 herds across southwestern Montana, USA, 2006-2016, and smoothed histograms of the raw data. Additionally, given the relatively high nutritional quality of early seral-stage vegetative communities(Barker, Mitchell, Proffitt, & Devoe, 2019), managing disturbances to maintain a mosaic of early-successional vegetative F I G U R E 2 Results of best-supported model explaining migratory behaviour of 308 elk in 16 herds across southwestern Montana, USA, 2006-2016, and smoothed histograms of the raw data.…”

“…). Fire management(Barker, Mitchell, Proffitt, & Devoe, 2019) and timber management Elk were increasingly likely to migrate rather than remain resident as forage varied more predictably (panel a).…”