The Northern Yellowstone Elk: Density Dependence and Climatic Conditions

Taper, Mark L.; Gogan, Peter J. P.

doi:10.2307/3802877

Cited by 121 publications

(107 citation statements)

References 49 publications

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“…Thus, the estimated carrying capacity increased to between 20 000 and 25 000 elk (Taper and Gogan 2002). In addition, extensive fires during 1988 burned approximately onethird of the winter and summer ranges for northern Yellowstone elk (Despain et al 1989, Singer et al 1989).…”

Section: Introductionmentioning

confidence: 99%

Body condition and pregnancy in northern Yellowstone elk: Evidence for predation risk effects?

White

Garrott

Hamlin

et al. 2011

Ecological Applications

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Abstract. S. Creel et al. reported a negative correlation between fecal progesterone concentrations and elk : wolf ratios in greater Yellowstone elk (Cervus elaphus) herds and interpreted this correlation as evidence that pregnancy rates of elk decreased substantially in the presence of wolves (Canis lupus). Apparently, the hypothesized mechanism is that decreased forage intake reduces body condition and either results in elk failing to conceive during the autumn rut or elk losing the fetus during winter. We tested this hypothesis by comparing age-specific body condition (percentage ingesta-free body fat) and pregnancy rates for northern Yellowstone elk, one of the herds sampled by Creel et al., before (1962Creel et al., before ( -1968 and after (2000)(2001)(2002)(2003)(2004)(2005)(2006) wolf restoration using indices developed and calibrated for Rocky Mountain elk. Mean age-adjusted percentage body fat of female elk was similarly high in both periods (9.0% 6 0.9% pre-wolf; 8.9% 6 0.8% post-wolf). Estimated pregnancy rates (proportion of females that were pregnant) were 0.91 pre-wolf and 0.87 post-wolf for 4-9 year-old elk (95% CI on difference ¼ À0.15 to 0.03, P ¼ 0.46) and 0.64 pre-wolf and 0.78 post-wolf for elk .9 years old (95% CI on difference ¼ À0.01 to 0.27, P ¼ 0.06). Thus, there was little evidence in these data to support strong effects of wolf presence on elk pregnancy. We caution that multiple lines of evidence and/or strong validation should be brought to bear before relying on indirect measures of how predators affect pregnancy rates.

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Section: Introductionmentioning

confidence: 99%

Body condition and pregnancy in northern Yellowstone elk: Evidence for predation risk effects?

White

Garrott

Hamlin

et al. 2011

Ecological Applications

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“…Also, recent data (winter [2005][2006] show that calf recruitment on the northern range approximately doubled that of previous years (winters 2003-2004 and 2004-2005; [Lemke 2003], most of which are pregnant [Cook et al 2004]), and a substantial decrease of wolves during 2005 due to poor pup survival (Smith et al 2006b). Therefore, despite the relatively high elk calf mortality during our study, we do not expect the restoration of wolves to this ecosystem to extirpate elk or reduce them to consistently low numbers (i.e., ,4,000, which the population has been above during the last 4 decades; Singer et al 1997, White andGarrott 2005a) because of the demonstrated resiliency of the population after previous decreases in abundance due to management culls, hunter harvest, and winterkill, and the strength of density-related responses in survival and reproduction, potential functional and numerical responses of wolves, and use of alternate prey by wolves (Coughenour and Singer 1996, Taper and Gogan 2002, Varley and Boyce 2006.…”

Section: Expectations For the Northern Yellowstone Elk Populationmentioning

confidence: 99%

Elk Calf Survival and Mortality Following Wolf Restoration to Yellowstone National Park

Barber‐Meyer

Mech

White

2008

Wildlife Monographs

186

301

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We conducted a 3-year study (May 2003-Apr 2006 of mortality of northern Yellowstone elk (Cervus elaphus) calves to determine the cause for the recruitment decline (i.e., 33 calves to 13 calves/100 adult F) following the restoration of wolves (Canis lupus). We captured, fit with radiotransmitters, and evaluated blood characteristics and disease antibody seroprevalence in 151 calves 6 days old (68M:83F). Concentrations (x, SE) of potential condition indicators were as follows: thyroxine (T4; 13.8 lg/dL, 0.43), serum urea nitrogen (SUN; 17.4 mg/dL, 0.57), c-glutamyltransferase (GGT; 66.4 IU/L, 4.36), gamma globulins (GG; 1.5 g/dL, 0.07), and insulin-like growth factor-1 (IGF-1; 253.6 ng/mL, 9.59). Seroprevalences were as follows: brucellosis (Brucella abortus; 3%), bovine-respiratory syncytial virus (3%), bovine-viral-diarrhea virus type 1 (25%), infectious-bovine rhinotracheitis (58%), and bovine parainfluenza-3 (32%). Serum urea nitrogen, GGT, GG, and IGF-1 varied with year; T4, SUN, and GG varied with age (P 0.01); and SUN varied by capture area (P ¼ 0.02). Annual survival was 0.22 (SE¼0.035, n¼149) and varied by calving area but not year. Neonates captured in the Stephens Creek/Mammoth area of Yellowstone National Park, USA, had annual survival rates .33 higher (0.54) than those captured in the Lamar Valley area (0.17), likely due to the higher predator density in Lamar Valley. Summer survival (20 weeks after radiotagging) was 0.29 (SE ¼ 0.05, n ¼ 116), and calving area, absolute deviation from median birth date, and GG were important predictors of summer survival. Survival during winter (Nov-Apr) was 0.90 (SE ¼ 0.05, n ¼ 42), and it did not vary by calving area or year. Sixty-nine percent (n ¼ 104) of calves died within the first year of life, 24% (n ¼ 36) survived their first year, and 7% (n ¼ 11) had unknown fates. Grizzly bears (Ursus arctos) and black bears (Ursus americanus) accounted for 58-60% (n ¼ 60-62) of deaths, and wolves accounted for 14-17% (n ¼ 15-18). Summer predation (95% of summer deaths) increased, and winter malnutrition (0% of winter deaths) decreased, compared with a similar study during 1987-1990 (72% and 58%, respectively). Physiological factors (e.g., low levels of GG) may predispose calves to predation. Also, the increase in bear numbers since wolf restoration and spatial components finer than the northern range should be considered when trying to determine the causes of the northern Yellowstone elk decline. This is the first study to document the predation impacts from reintroduced wolves on elk calf mortality in an ecosystem already containing established populations of 4 other major predators (i. para determinar las causas del descenso del reclutamiento (de 33 a 13 crías /100 hembras adultas) tras la restauración del lobo (Canis lupus). Hemos capturado, marcado con radiotransmisores y evaluado las características de la sangre y la seroprevalencia de los anticuerpos a enfermedades de 151 crías 6 días (68M:83H). Las concentraciones (x, SE) de los indicadores del estado pote...

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“…To overcome such limitations, several authors (Zeng et al, 1998;Strong et al, 1999;Dennis and Otten, 2000;Taper and Gogan, 2002) have proposed the use of information criteria (IC) to choose the best among a suite of alternative models including both density-independent and density-dependent demographies. Generally speaking, ICs address the model selection by choosing the model that minimizes the product of the squared deviation from data and a penalization factor, which is an increasing function of the ratio of free parameters d to the size q of the dataset; the rationale for such a penalization is that an optimal trade-off should be found between the quality of data fitting and model complexity.…”

Section: Introductionmentioning

confidence: 99%

“…As a consequence of these restricting hypotheses, ICs are very often applied even if their constitutive assumptions are not strictly met. In the literature, the Final Prediction Error (FPE) and in particular the Schwartz Information Criterion (SIC) appear to be the most widely used by ecologists (Strong et al, 1999;Dennis and Otten, 2000;Zeng et al, 1998;Taper and Gogan, 2002).…”

Section: Introductionmentioning

confidence: 99%

Model selection in demographic time series using VC-bounds

Corani¹,

Gatto²

2006

Ecological Modelling

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The problem of distinguishing density-independent (DI) from density-dependent (DD) demographic time series is important for understanding the mechanisms that regulate populations of animals and plants. We address this problem in a novel way by means of Statistical Learning Theory (SLT); SLT is built around the idea of VC-dimension, a complexity index for classes of parameterized functions. Though VC-dimensions of nonlinear models are generally unknown, in the linear case VC-dimension actually corresponds to the number of free parameters; this allows one to straightforwardly apply the model selection framework developed within SLT, and called Structural Risk Minimization (SRM). We generate noisy artificial time series, both DI and DD, and use SRM to recognize the model underlying the data, choosing among a suite of both density-dependent and independent demographies. We show that SRM significantly outperforms traditional model selection approaches, such as the Schwartz Information Criterion and Final Prediction Error in recognizing both density-dependence and independence.

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The Northern Yellowstone Elk: Density Dependence and Climatic Conditions

Cited by 121 publications

References 49 publications

Body condition and pregnancy in northern Yellowstone elk: Evidence for predation risk effects?

Body condition and pregnancy in northern Yellowstone elk: Evidence for predation risk effects?

Elk Calf Survival and Mortality Following Wolf Restoration to Yellowstone National Park

Model selection in demographic time series using VC-bounds

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