Abstract
ABSTRACT The Greater Rhea (Rhea americana) is the largest (32–35 kg) flighless bird inhabiting grasslands and savannas of South America. Its diet comprises several fruit species, but the outcome of fruit ingestion (seed dispersal or predation) is largely unknown. We investigated the role of Greater Rheas in seed dispersal using fruit feeding trials with captive animals and seed germination experiments for 11 plants from the Brazilian savannas (Cerrado). We also performed a meta-analysis with a total 29 species included in seed germination experiments following fruit ingestion by Rheas. Rheas have a long gut passage time (GPT) (mean ± SD: 61.6 ± 13.5 hours), allowing them to carry seeds to long distances. In our experiment, seeds within heavier fruits and those with lipid-rich fruit pulp had shorter and longer GPT, respectively, which influences the potential distances of seed dispersal achieved. The impact of seed ingestion varied from seed destruction (for three species) to successful (three species) or faster germination (two species) compared to controls. Results were inconclusive for three species. Dispersal is done at the cost of considerable seed losses, probably due to prolonged seed abrasion inside the gut. Similar results were found in the meta-analysis. Given the consumption of many fruits combined with a long GPT and large home range, Rheas may influence the fate of a great amount of seeds for several plants. Current pervasive population declines of Rheas can disrupt these processes, affecting plant regeneration, particularly for species that depend on them for long-distance seed dispersal.
Published Version
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