Effects of Small Rodent and Large Mammal Exclusion on Seedling Recruitment in Costa Rica¹

Abstract

We examined whether the experimental exclusion of large mammalian and small rodent seed predators had differing effects on seedling recruitment under natural seed rain conditions. In both primary and late‐successional secondary forested areas, exclosure experiments using natural seed densities were designed to assess seedling recruitment. To assess the differences in seedling recruitment, we monitored three exclosure treatments (1.2 m radius/1.5 m height) in two forest types (primary vs. late‐successional secondary forest): (1) fenced exclosures that excluded large mammals; (2) fenced exclosures that excluded both large and small mammals; and (3) open controls. Within each exclosure treatment, we marked and identified all seedlings at the beginning of the experiment (February 2001), followed the marked seedlings' fate for a year, and then marked and identified all new seedlings after a year. Two preliminary findings were generated from these data: for some tree species, small rodents and large mammals have differential effects on seedling recruitment, and the effect of excluding mammals did not differ with habitat type (primary vs. late‐successional secondary forest). These preliminary results highlight the need to examine further how the effects of small rodent and large mammal exclusion may affect species‐specific seed predation and seedling recruitment in a variety of habitat/land use types (e.g., primary forest, late‐successional forest, and early‐successional forest).

Seed predation of Araucaria angustifolia (Araucariaceae) in the Brazilian Araucaria Forest: influence of deposition site and comparative role of small and ‘large’ mammals

“…The role of mammals as seed predators and seed dispersers in the Neotropics was investigated focusing mainly on large-bodied species, like agoutis, pacas, and peccaries (DeMattia et al 2006). Nevertheless, some studies have highlighted the importance of small rodents as seed and seedlings predators in the Neotropics (e.g., Terborgh et al 1993;Sánchez-Cordero and Martínez-Gallardo 1998;Brewer and Rejmánek 1999;Brewer 2001;Vieira et al 2003;DeMattia et al 2004;DeMattia et al 2006).…”

“…The role of mammals as seed predators and seed dispersers in the Neotropics was investigated focusing mainly on large-bodied species, like agoutis, pacas, and peccaries (DeMattia et al 2006). Nevertheless, some studies have highlighted the importance of small rodents as seed and seedlings predators in the Neotropics (e.g., Terborgh et al 1993;Sánchez-Cordero and Martínez-Gallardo 1998;Brewer and Rejmánek 1999;Brewer 2001;Vieira et al 2003;DeMattia et al 2004;DeMattia et al 2006). Although being mainly seed predators these animals are also able to move seeds of some plant species without damage, therefore in a few cases acting as potential seed disperses as well (Magnusson and Sanaiotti 1987;Brewer and Rejmánek 1999;Briani et al 2001;Vieira et al 2006).…”

Experimental defaunation of terrestrial mammalian herbivores alters tropical rainforest understorey diversity

“…However, in some instances, for example when using small forest fragments or islands, effects of abiotic variables can operate as confounding factors [27]. Furthermore, available studies are of variable duration, ranging from a few months [28] to several years [29].…”

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

“…At Los Tuxtlas (Veracruz, Mexico), where midsized and large terrestrial vertebrates are dramatically reduced in number, Brosimum alicastrum seedlings create dense carpets beneath the parent tree (Dirzo and Miranda, 1990). At the other extreme, at Parque Nacional Corcovado on southwestern Costa Rica's Osa Peninsula, where mammalian seed predators are abundant, Brosimum costaricanum seedlings in a natural regeneration study were encountered only in exclosures that had been protected from both peccaries and small rodents (DeMattia et al, 2004(DeMattia et al, , 2006. Adult Brosimum alicastrum and B. costaricanum are both present at Cabo Blanco, but the fates of their seeds and seedlings have not been studied.…”