Long Distance Seed Dispersal by Forest Elephants

Julia Knorr,Guichard Ndzeng Obiang,Mike Fay ,Shuyun Xiao,Joseph Okouyi,John R. Poulsen,Taylor Minich,Walter Mbamy,Justin P. Wright,Lee White ,Lingrong Jin,Connie J. Clark,Médard Obiang Ebanega ,Christopher Beirne,Colin Rundel,Melissa Baldino,Juliana Masseloux,Tanguy Nkoghe,Pete Morkel,Chase L. Núñez,Seokmin Kim

doi:10.3389/fevo.2021.789264

Abstract

By dispersing seeds long distances, large, fruit-eating animals influence plant population spread and community dynamics. After fruit consumption, animal gut passage time and movement determine seed dispersal patterns and distances. These, in turn, are influenced by extrinsic, environmental variables and intrinsic, individual-level variables. We simulated seed dispersal by forest elephants (Loxodonta cyclotis) by integrating gut passage data from wild elephants with movement data from 96 individuals. On average, elephants dispersed seeds 5.3 km, with 89% of seeds dispersed farther than 1 km. The longest simulated seed dispersal distance was 101 km, with an average maximum dispersal distance of 40.1 km. Seed dispersal distances varied among national parks, perhaps due to unmeasured environmental differences such as habitat heterogeneity and configuration, but not with human disturbance or habitat openness. On average, male elephants dispersed seeds farther than females. Elephant behavioral traits strongly influenced dispersal distances, with bold, exploratory elephants dispersing seeds 1.1 km farther than shy, idler elephants. Protection of forest elephants, particularly males and highly mobile, exploratory individuals, is critical to maintaining long distance seed dispersal services that shape plant communities and tropical forest habitat.

Highlights

Fruit-eating vertebrates play an important role in plant reproduction through seed dispersal (Levin et al, 2003)
To evaluate drivers of variation in seed dispersal distances, we modeled median seed dispersal distance, d, for each elephant as a linear model incorporating extrinsic and intrinsic factors as independent variables
Our estimates of mean gut passage time (GPT) are similar to estimates from previous studies of captive Asian (Elephas maximus) and savanna (Loxodonta africana) elephants that include both male and female adult individuals (Figure 2)

Summary

Introduction

Fruit-eating vertebrates play an important role in plant reproduction through seed dispersal (Levin et al, 2003). At local scales, seed dispersal increases plant fitness by potentially reducing competition between parent plants and their progeny and lowering the risk of density-dependent disease and predation (Janzen, 1970). Does seed dispersal promote community diversity (Harrison et al, 2013), it reduces species aggregation (Wandrag et al, 2017). Seed Dispersal and Forest Elephants scales, long-distance dispersal (LDD) links local populations within a metapopulation, facilitates gene flow, and promotes migration and colonization of new habitats (Cain et al, 2000; Nathan, 2006). The loss of large vertebrate seed dispersal services could compromise the survival of plant species that depend on range shifts driven by migration and colonization

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Results

Conclusion