Allometry of behavior and niche differentiation among congeneric African antelopes

Abstract

Size‐structured differences in resource use stabilize species coexistence in animal communities, but what behavioral mechanisms underpin these niche differences? Behavior is constrained by morphological and physiological traits that scale allometrically with body size, yet the degree to which behaviors exhibit allometric scaling remains unclear; empirical datasets often encompass broad variation in environmental context and phylogenetic history, which complicates the detection and interpretation of scaling relationships between size and behavior. We studied the movement and foraging behaviors of three sympatric, congeneric spiral‐horned antelope species (Tragelaphus spp.) that differ in body mass—bushbuck (26–40 kg), nyala (57–83 kg), and kudu (80–142 kg)—in an African savanna ecosystem where (i) food was patchily distributed due to ecosystem engineering by fungus‐farming termites and (ii) predation risk was low due to the extirpation of several large carnivores. Because foraging behavior is directly linked to traits that scale allometrically with size (e.g., metabolic rate, locomotion), we hypothesized that habitat use and diet selection would likewise exhibit nonlinear scaling relationships. All three antelope species selected habitat near termitaria, which are hotspots of abundant, high‐quality forage. Experimental removal of forage from termite mounds sharply reduced use of those mounds by bushbuck, confirming that habitat selection was resource driven. Strength of selection for termite mounds scaled negatively and nonlinearly with body mass, as did recursion (frequency with which individuals revisited locations), whereas home‐range area and mean step length scaled positively and nonlinearly with body mass. All species disproportionately ate mound‐associated plant taxa; nonetheless, forage selectivity and dietary composition, richness, and quality all differed among species, reflecting the partitioning of shared food resources. Dietary protein exhibited the theoretically predicted negative allometric relationship with body mass, whereas digestible‐energy content scaled positively. Our results demonstrate cryptic size‐based separation along spatial and dietary niche axes—despite superficial similarities among species—consistent with the idea that body‐size differentiation is driven by selection for divergent resource‐acquisition strategies, which in turn underpin coexistence. Foraging and space‐use behaviors were nonlinearly related to body mass, supporting the hypothesis that behavior scales allometrically with size. However, explaining the variable functional forms of these relationships is a challenge for future research.

Limited spatiotemporal niche partitioning among mesocarnivores in Gorongosa National Park, Mozambique

“…We used the following spatial covariates in our models: termite mound density, distance to water, tree cover, and lion activity. We determined termite mound density within a 1 km radius of the camera based on a LiDAR‐generated map of termite mound distribution (Daskin et al., 2023). We chose this radius because it falls within the span of reported home range estimates for our four focal species (Admasu et al., 2004; Baker & Ray, 2013; Begg et al., 2013; Roux et al., 2016).…”

Integrating functional traits into trophic rewilding science

“…Daskin et al. (2023) show grazing associated with fungi farming Macrotermes mounds by Tragelaphus spp. (spiral‐horned antelopes) declined with body size and was more seasonally variable—an indication of lower diet quality and lower overall selectiveness in forage quality of larger antelope.…”

“…Daskin et al (2023) show grazing associated with fungi farming Macrotermes mounds by Tragelaphus spp. (spiral-horned antelopes)…”

Mechanisms of individual variation in large herbivore diets: Roles of spatial heterogeneity and state‐dependent foraging

“…They are solitary but not aggressively antisocial, such that home ranges overlap and individuals often forage in close proximity (Estes, 1991). As strict browsers, bushbuck feed almost exclusively on trees, shrubs, and forbs to the exclusion of grasses (Daskin et al, 2022;Kartzinel & Pringle, 2020;Pansu et al, 2019bPansu et al, , 2022Potter et al, 2022). Bushbuck also use woody plants for concealment and are considered "dependent on thick cover" for predator avoidance (Kingdon, 1997, p. 352).…”

“…We analyzed these samples using DNA metabarcoding, enabling taxonomically precise measurement of diet composition and richness at the individual level (Kartzinel et al, 2015(Kartzinel et al, , 2019Pansu et al, 2019b;Pringle & Hutchinson, 2020). Bushbuck in Gorongosa show high fidelity to small (generally <3-km 2 ) home ranges distributed across two broad habitat types (Atkins et al, 2019;Daskin et al, 2022), which allowed us to evaluate the role of spatial resource heterogeneity at different scales (population level and partitioned by habitat affiliation) in generating individual diet differentiation. Further, bushbuck are nonseasonal breeders, leading to wide variation among individuals in reproductive status and associated nutritional condition (owing to the high costs of gestation and lactation; Cook et al, 2013).…”