The need to be eaten: Balanites wilsoniana with and without elephant seed-dispersal

Abstract

This study demonstrates that elephant seed-dispersal is vital for Balanites wilsoniana (Zygophyllaceae), a forest canopy tree with no other effective dispersers. Non-dispersed seeds suffered high mortality (84%) and low germination (3%). Elephants were reliable at visiting fruiting trees (46%), ingesting available seeds (55%) and dispersing the fruit crop (26%). Compared with unpassed seeds, seeds passed through an elephant's gut had improved germination (54.9% vs. 2.9%) and reduced time to germination (82 vs. 132 d). Given predation rates under parent trees, elephant gut passage is expected to improve absolute germination by 66%. When this change in germination is divided by germination of unpassed seeds, elephant gut passage is expect to improve relative germination by as much as 4000%. Although post-dispersal predation occurred in dung containing B. wilsoniana seeds, dispersed seedlings were abundant. Compared with seedlings under parent trees, dispersed seedlings had greater survival and height. Dispersed seedlings survived in a diversity of environments, thrived under high-light conditions, and were negligibly affected by post-dispersal density. Although elephants are not essential for B. wilsoniana germination, their actions greatly increase seedling establishment and move a large proportion of seeds. This high degree of effectiveness, together with very low non-dispersed seed survival, provides strong evidence that B. wilsoniana is dependent on elephants for its long-term persistence.

Working with mahouts to explore the diet of work elephants in Myanmar (Burma)

“…There is no evidence of any plant completely dependent on Asian elephants for seed dispersal. Such narrow mutualisms are exceptional in nature but have been described for African elephants and Balonites wilsoniana (Chapman et al 1992;Cochrane 2003;Babweteera et al 2007); and suggested for greater one-horned rhinoceros and Trewia nudiflora (Dinerstein 1988). Asian elephants can disperse seeds by endozoochory over long distances (CamposArceiz et al, unpublished).…”

Does Gut Passage Affect Post-dispersal Seed Fate in a Wild Chili, Capsicum annuum?

“…Our study, based on an examination of gut treatment, provides few studies comparing removal of passed and non-passed seeds, or seeds embedded or non-embedded in feces, do not yield a clear or consistent picture of any impact of gut passage on seed predation (Andresen 1999, Bermejo et al 1998, Cochrane 2003, Fricke et al 2013, Mártinez-Mota et al 2004, Roberts and Heithaus 1986. Furthermore, at least some observed impacts from these studies are inconsistent between seasons (Mártinez- Mota et al 2004) or within a season (Andresen 1999).…”

Feeding patterns of elephants at the Atherstone Collaborative Nature Reserve

“…crude proteins) occurs at a greater rate in the presence of elephants (Scholes & Mennell, 2008). Additionally, elephants promote seed dispersal and germination (Cochrane, 2003).…”