Recovery and germination of seeds of Dichrostachys cinerea and Vachellia tortilis following ingestion by ruminants

Abstract

The dispersal of seeds through herbivore ingestion, and their subsequent germination, are vital for tree recruitment in savannas. This study investigated how recovery, retention and germination of seeds of Dichrostachys cinerea and Vachellia tortilis pods fed to goats and sheep differ, and how seed condition (intact vs swollen) affects germination success. Animals were fed pods equivalent to 2.5% of body mass. Seed recovery from D. cinerea was significantly lower than from V. tortilis across both animal species, although retention time was longer for D. cinerea seeds. The proportion of germinated seeds and time-to-germination differed between the pod species, with D. cinerea seeds germinating in higher proportions and quicker than V. tortilis seeds. Gut passage enhanced germination success relative to controls in both animal species (χ² = 99.64, p < 0.001), demonstrating a role in breaking dormancy. Seed condition further influenced germination: swollen seeds had 84% lower odds of germinating compared to intact seeds. Gut passage substantially influenced seed fate, while differences between pod species may partly reflect associated nutritional traits, which warrants further investigation.