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Updated: Jul 11, 2026
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Predicting the Effectiveness of Population Replacement Strategy Using Mathematical Modeling
Published on: July 4, 2007
Irruptive population dynamics in Yellowstone pronghorn.
P J White1, Jason E Bruggeman, Robert A Garrott
1National Park Service, Yellowstone National Park, Wyoming 82190, USA. PJ_White@NPS.gov
Summary
Pronghorn (Antilocapra americana) in Yellowstone exhibited irruptive population dynamics, with growth influenced by density dependence and significant population crashes following culling and resource depletion. This study highlights irruption as a key pattern in large herbivore populations.
Area of Science:
- Ecology
- Wildlife Biology
- Population Dynamics
Background:
- Irruptive population dynamics are common in large herbivores but rarely studied with long-term data and minimal harvests.
- Pronghorn (Antilocapra americana) populations in Yellowstone National Park provide a unique dataset for analyzing population fluctuations over 89 years.
Purpose of the Study:
- To determine if the Yellowstone pronghorn population exhibited irruptive dynamics using long-term count and removal data.
- To analyze the influence of density-dependent and independent factors, including harvesting, on pronghorn population fluctuations.
Main Methods:
- Analysis of an 89-year time series (1918-2006) of pronghorn counts and known removals in Yellowstone National Park.
- Application of information-theoretic model comparison to density-dependent, density-independent, and irruptive population models (Leopold, Gompertz, Ricker, Caughley).
Main Results:
- Irruptive dynamics and density dependence were supported for 1918-1946, with growth slowing above 600 animals.
- Population declines occurred during a culling period (1947-1966), with models suggesting culls replaced density-dependent regulation.
- Post-culling, the population irrupted (1982-1991) to ~600, followed by a crash (1992-1995) possibly due to diminished forage, and then stabilized at a lower level.
Conclusions:
- Pronghorn population dynamics in Yellowstone align with the paradigm of irruption in high-fecundity large herbivores, influenced by favorable conditions and delayed density-dependent effects.
- Incorporating known removals into population models is crucial for accurately interpreting the dynamics of intensively managed wildlife populations.
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