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Abstract Theory predicts that trophic specialization (i.e. low dietary diversity) should make consumer populations sensitive to environmental disturbances. Yet diagnosing specialization is complicated both by the difficulty of precisely quantifying diet composition and by definitional ambiguity: what makes a diet ‘diverse’?We sought to characterize the relationship between taxonomic dietary diversity (TDD) and phylogenetic dietary diversity (PDD) in a species‐rich community of large mammalian herbivores in a semi‐arid East African savanna. We hypothesized that TDD and PDD would be positively correlated within and among species, because taxonomically diverse diets are likely to include plants from many lineages.By using DNA metabarcoding to analyse 1,281 faecal samples collected across multiple seasons, we compiled high‐resolution diet profiles for 25 sympatric large‐herbivore species. For each of these populations, we calculated TDD and PDD with reference to a DNA reference library for local plants.Contrary to our hypothesis, measures of TDD and PDD were either uncorrelated or negatively correlated with each other. Thus, these metrics reflect distinct dimensions of dietary specialization both within and among species. In general, grazers and ruminants exhibited greater TDD, but lower PDD, than did browsers and non‐ruminants. We found significant seasonal variation in TDD and/or PDD for all but four species (Grevy's zebra, buffalo, elephant, Grant's gazelle); however, the relationship between TDD and PDD was consistent across seasons for all but one of the 12 best‐sampled species (plains zebra).Our results show that taxonomic generalists can be phylogenetic specialists, and vice versa. These two dimensions of dietary diversity suggest contrasting implications for efforts to predict how consumers will respond to climate change and other environmental perturbations. For example, populations with low TDD may be sensitive to phylogenetically ‘random’ losses of food species, whereas populations with low PDD may be comparatively more sensitive to environmental changes that disadvantage entire plant lineages—and populations with low dietary diversity in both taxonomic and phylogenetic dimensions may be most vulnerable of all.
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This content will become publicly available on April 1, 2026
Water economics of African savanna herbivores: How much does plant moisture matter?
Abstract Water is an essential and often limiting resource that pervades all aspects of animal ecology. Yet, water economics are grossly understudied relative to foraging and predation, leaving ecologists ill‐equipped to predict how the intensifying disruption of hydrological regimes worldwide will impact communities. For savanna herbivores, reliance on surface water can increase exposure to predators and competitors, and thus strategies that reduce the need to drink are advantageous. Yet, the extent to which increasing dietary water intake while decreasing water loss enables animals to forego drinking remains unknown.We studied water budgets of sympatric African savanna antelopes that differ in size, bushbuck (Tragelaphus sylvaticus, ~35 kg) and kudu (T. strepsiceros, ~140 kg). We hypothesized that both species compensate for seasonally declining water availability by increasing consumption of moisture‐rich plants and reducing faecal water loss, and that these adjustments are sufficient for small‐bodied—but not large‐bodied—herbivores to avoid spending more time near permanent water sources as the dry season advances. We tested our predictions using temporally explicit data on antelope movements, diets, plant traits and drinking behaviour in Gorongosa National Park, Mozambique.Water content declined between the early and late dry seasons in roughly half of plant taxa consumed by antelope. Although both species reduced faecal water loss and shifted their diets towards relatively moisture‐rich plants as the dry season progressed, dietary water intake still declined. Contrary to expectation, kudu reduced selection for surface water in the late dry season without adjusting total time spent drinking, whereas bushbuck increased selection for surface water.We developed a generalizable approach for parsing the importance of dietary and surface water for large herbivores. Our results underscore that variation in surface‐water dependence is a key organizing force in herbivore communities, that simple allometric predictions about the behavioural and ecological consequences of this variation are unreliable. Understanding wildlife water economics is a research frontier that will be essential for predicting changes in species distribution and community composition as temperatures rise and droughts intensify.
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- PAR ID:
- 10611323
- Publisher / Repository:
- Journal of Animal Ecology
- Date Published:
- Journal Name:
- Journal of Animal Ecology
- Volume:
- 94
- Issue:
- 4
- ISSN:
- 0021-8790
- Page Range / eLocation ID:
- 670 to 681
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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