DOI: 10.5061/dryad.qfttdz0h4
title: Ecological and behavioral mechanisms of density-dependent habitat expansion in a recovering African ungulate population

description: Major disturbances can temporarily remove factors that otherwise constrain
 population abundance and distribution. During such windows of relaxed
 top-down and/or bottom-up control, ungulate populations can grow rapidly,
 eventually leading to resource depletion and density-dependent expansion
 into less-preferred habitats. Although many studies have explored the
 demographic outcomes and ecological impacts of these processes, fewer have
 examined the individual-level mechanisms by which they occur. We
 investigated these mechanisms in Gorongosa National Park, where the
 Mozambican Civil War devastated large-mammal populations between 1977 and
 1992. Gorongosa’s recovery has been marked by proliferation of waterbuck
 (Kobus ellipsiprymnus), an historically marginal 200-kg antelope species,
 which is now roughly 20-fold more abundant than before the war. We show
 that after years of unrestricted population growth, waterbuck have
 depleted food availability in their historically preferred floodplain
 habitat and have increasingly expanded into historically avoided savanna
 habitat. This expansion was demographically skewed: mixed-sex groups of
 prime-age individuals remained more common in the floodplain, while
 bachelors, loners, and subadults populated the savanna. By coupling DNA
 metabarcoding and forage analysis, we show that waterbuck in these two
 habitats ate radically different diets, which were more digestible and
 protein-rich in the floodplain than in savanna; thus, although individuals
 in both habitats achieved positive net energy balance, energetic
 performance was higher in the floodplain. Analysis of daily activity
 patterns from high-resolution GPS-telemetry, accelerometry, and
 animal-borne video revealed that savanna waterbuck spent less time eating,
 perhaps to accommodate their tougher, lower-quality diets. Waterbuck in
 savanna also had more ectoparasites than those in the floodplain. Thus,
 plasticity in foraging behavior and diet selection enabled savanna
 waterbuck to tolerate the costs of density-dependent spillover, at least
 in the short term; however, the already poorer energetic performance of
 these individuals implies that savanna occupancy may become prohibitively
 costly as heterospecific competitors and predators continue to recover in
 Gorongosa. Our results suggest that behavior can provide a leading
 indicator of the onset of density-dependent limitation and the likelihood
 of subsequent population decline, but that reliable inference hinges on
 understanding the mechanistic basis of observed behavioral shifts.
description: This dataset comprises multiple data sources collected in
 Gorongosa National Park, Mozambique from 2015 - 2019, including: movement
 and activity data of waterbuck from custom-built GPS collars, individual
 body condition scores, DNA metabarcoding data of waterbuck diet, counts
 from aerial surveys of waterbuck presence (including historical data
 collection from 1969-1972), counts of ecto- and endo-parasites from
 waterbuck, road surveys of waterbuck demographic distribution, estimates
 of waterbuck energetic parameters from camera trap videos and established
 sources in the literature, and vegetation surveys from long-term, large
 herbivore exclosures and paired control plots.
description: Please see ReadMe files for additional information on data
 interpretation and usage.