Plant‐Mammal Interactions in Tropical Bolivian Forests with Different Hunting Pressures

Abstract

We studied plant‐animal interactions and vegetation structure in two geographically close tropical Bolivian forests subjected to different hunting intensities. We hypothesized that reduction of mammals openface> 1 kg in an “intensively hunted forest,” compared with an “occasionally hunted forest,” should correlate with decreased seed predation and seedling trampling, increased seedling survival and density, and decreased tree‐species diversity at the seedling stage in relation to the adult stage. The occasionally hunted forest held 1.7 times as many mammalian species as the intensively hunted forest. As predicted, predation of Astrocaryum murumuru seeds was 34.2% lower in the intensively hunted forest. Similarly, trampling of model seedlings was 5.4 times lower and seedling survival was 1.15 times greater in the intensively hunted forest than that in the occasionally hunted forest. But the intensively hunted forest displayed lower seedling densities and a higher ratio of seedling diversity to tree diversity than did the occasionally hunted forest. Reduction of peccaries from the intensively hunted forest may explain much of the between‐site differences in seed predation, trampling, and seedling survival. Lack of consistent differences in seedling density and diversity could mean that reduced granivory and trampling may be counteracted by reduced seed dispersal. The reduction of mammalian populations may produce a complex mosaic of forest patches with distinct degrees of structural change, depending on the intensity of defaunation.

Defaunation affects Astrocaryum gratum (Arecales: Arecaceae) seed survivorship in a sub-montane tropical forest

“…observ.). Most of the seeds and seedlings of any species in areas disturbed by rooting were killed (Roldán, & Simonetti, 2001;Aliaga-Rossel, pers. observ.).…”

“…Moreover, the effects of medium size rodents are difficult to determine and may depend on the composition and density of species within the forest (Donatti et al, 2009). Different forests close to human settlements will have different degrees of changes in wildlife composition, and such variation should result in different seed removal patterns and survivorship, causing changes in the dynamics of Astrocaryum seed removal across different scales within patches (i.e., near higher adult density) and ultimately influencing the structure and the composition of the local forest (Roldán, & Simonetti, 2001;Beckman, & Muller-Landau, 2007;Donatti et al, 2009;Holbrook, & Loiselle, 2009 …”

“…Many tropical wildlife including mammals, birds and insects are known seed predators (Smythe, 1989;Dracxler et al, 2011). Therefore, the composition of the animal fauna in a forest will have different impacts on seed survivorship, and the removal of medium to large mammals by over-hunting or habitat loss, will have different effects on tree populations and the structure of the forest (Roldán, & Simonetti, 2001;Silman, Terborgh, & Kiltie, 2003;Wright, 2003;Beckman, & Muller-Landau, 2007;Galvez, & Jansen, 2007;Holbrook, & Loiselle, 2009;Dracxler et al, 2011).…”

Mammals of Cabo Blanco: History, diversity, and conservation after 45 years of regrowth of a Costa Rican dry forest

“…The effects of mammal populations on seed dispersal and seed predation can be evaluated in several ways, including comparisons of seed and seedling survival where different levels of hunting have occurred, or exclosure experiments that eliminate different size categories of seed or seedling predators. When seeds are protected from mammalian access, there may result a secondary effect of increased seedling recruitment (Dirzo and Miranda, 1991;Wright et al, 1999) or decreased seedling recruitment (Asquith et al, 1997;Roldan and Simonetti, 2001), depending upon the relative importance of seed predation versus seed dispersal by the excluded mammals (Brewer et al, 1997;Beckman and Muller-Landau, 2007). …”

Home range and habitat use by pacas in a montane tropical forest in Bolivia

“…Pacas are found in mangroves, semideciduous forests, riparian vegetation and sites with dense undergrowth, always near water sources (Pérez 1992;Guzmán-Aguirre 2008;Wallace et al 2010). They tolerate, and even do better in non-intensively-cultivated land (Roldán and Simonetti 2001;Guzmán-Aguirre 2008;Parroquin et al 2010). Using tracks and fecal surveys at Sierra Tabasco, Mexico, Guzmán-Aguirre (2008) found that pacas prefer primary forest over secondary forests and fallows; he never found paca signs in croplands.…”