Predation strongly limits demography of a keystone migratory herbivore in a recovering transfrontier ecosystem
Cite this dataset
Watson, Fred et al. (2022). Predation strongly limits demography of a keystone migratory herbivore in a recovering transfrontier ecosystem [Dataset]. Dryad. https://doi.org/10.5061/dryad.0k6djhb3f
Abstract
Large herbivore migrations are imperiled globally; however, the factors limiting a population across its migratory range are typically poorly understood. Zambia’s Greater Liuwa Ecosystem (GLE) contains one of the largest remaining blue wildebeest (Connochaetes taurinus taurinus) migrations, yet the population structure, vital rates, and limiting factors are virtually unknown. We conducted a long-term demographic study of GLE wildebeest from 2012–2019 of 107 collared adult females and their calves, 7,352 herd observations, 12 aerial population surveys, and concurrent carnivore studies. We applied methods of vital rate estimation and survival analysis within a Bayesian estimation framework. From herd composition observations, we estimated rates of fecundity, first-year survival, and recruitment as 68%, 56%, and 38% respectively, with pronounced inter-annual variation. Similar rates were estimated from calf detections with collared cows. Adult survival rates declined steadily from 91% at age 2 years to 61% at age 10 years thereafter dropping more sharply to 2% at age 16 years. Predation, particularly by spotted hyena, was the predominant cause of death for all wildebeest ages and focused on older animals. Starvation only accounted for 0.8% of all unbiased known natural causes of death. Mortality risk differed substantially between wet and dry season ranges, reflecting strong spatio-temporal differences in habitat and predator densities. There was substantial evidence that mortality risk to adults was 27% higher in the wet season, and strong evidence that it was 45% higher in the migratory range where predator density was highest. The estimated vital rates were internally consistent, predicting a stable population trajectory consistent with aerial estimates. From essentially zero knowledge of GLE wildebeest dynamics, this work provides vital rates, age structure, limiting factors, and a plausible mechanism for the migratory tendency, and a robust model-based foundation to evaluate the effects of potential restrictions in migratory range, climate change, predator-prey dynamics, and poaching.
Methods
See journal paper.
Usage notes
Comma-separate-value (CSV) files. Can be opened by many software applications.
Funding
World Wide Fund for Nature
The Bennink Foundation
National Science Foundation of Sri Lanka, Award: IOS1145749
DOB Ecology
Gemfields Inc.
Painted Dog Conservation Inc.
Dazzle Africa
Norman Carr Safaris/Time & Tide
Tusk Trust
Rob and Kayte Simpson
Milkywire
U.S. State Department Fulbright Program
Wildlife Conservation Network
European Union through IUCN Save Our Species