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Density Dependence in Large Herbivores Inhabiting an Insular Nature Reserve
Cornelius J Louw1, Francesca Parrini2, Jason P Marshal2
1Conservation Ecology Research Unit, Department of Zoology and Entomology University of Pretoria Hatfield South Africa.
Ecology and Evolution
|December 6, 2024
Summary
Ungulate populations in small grasslands show density-dependent regulation, with recruitment declining as populations grow. This suggests bottom-up processes primarily control these ecosystems.
Area of Science:
- Ecology
- Population Dynamics
- Wildlife Management
Background:
- Large-scale studies often overlook smaller spatial scales in ungulate population dynamics.
- Density-dependent responses to resource limitations are key drivers of population regulation.
- Small dystrophic grassland ecosystems require further investigation into their ecological dynamics.
Purpose of the Study:
- To investigate the temporal dynamics of ungulate abundance in a small grassland ecosystem over 20 years.
- To explore density-dependent responses at the population level and link them to demographic mechanisms.
- To understand the primary regulatory processes in grassland ecosystems.
Main Methods:
- Utilized annual ungulate counts and herd composition data over a 20-year period.
- Employed state-space modeling to correct population count data.
- Analyzed population growth and juvenile-to-adult ratios for density-dependent effects.
Main Results:
- Most ungulate populations exhibited an increase from low densities towards equilibrium.
- Evidence of density-dependent responses was found to shape population abundance dynamics.
- Juvenile-to-adult ratios showed density-dependent reductions in recruitment, indicating lower reproductive success at higher densities.
Conclusions:
- Grassland ecosystems with moderate annual rainfall appear to be primarily regulated by bottom-up processes.
- Density-dependent recruitment is a significant factor influencing ungulate population dynamics in small-scale ecosystems.
- Small-scale ecological studies are crucial for a comprehensive understanding of wildlife population regulation.
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