The dual role of ungulates in the post-ingestion seed fate of an invasive forest tree

Acacia species are widespread invasive plants in Mediterranean ecosystems, including in central Portugal, where they promote significant negative impacts. These species exhibit vigorous regeneration strategies, with seed germination being facilitated by scarification, which may be achieved with high temperatures during fires, and passage through animals’ digestive tracts. We conducted feeding trials with captive domestic goats ( Capra hircus ), red deer ( Cervus elaphus ) and wild boar ( Sus scrofa ) to evaluate the potential of these ungulates to disperse or predate Acacia seeds. Acacia dealbata seeds were fed to animals to examine post-digestion fate. Results were compared with manually scarified and control seeds. Fragmented and intact seeds were detected in the faeces of all animal species. Seed recovery rate differed between domestic goat (very low) and wild ungulate (higher and similar for red deer and wild boar) species. Seed germination, seed destruction, and T 50 (time required for 50% of seeds to germinate) were similar among the animal species. Germination did not differ from the control, whereas seed destruction was higher and T 50 was lower than in the control treatment. Manual scarification increased germination and reduced T 50 . Our results show that domestic goat, red deer and wild boar can act as both dispersers through endozoochory and predators of Acacia seeds. Despite this pathway likely being a minor contributor to the overall spread of Acacia trees compared to other vectors, management should prioritize the control of Acacia in areas frequently used by ungulates. Overall, contrary to initial expectation, seed fate was largely consistent across ungulate species, despite differences in body size and digestive strategies.