Coupled population dynamics of two Neotropical marsupials driven by mesopredator's abundance

Abstract

According to the mesopredator release theory, when top predators are eradicated from an area, mesopredators become overabundant. Didelphis aurita is the largest marsupial in the Atlantic Rainforest, and it occurs in higher abundances in the absence of top predators. This mesopredator has similar ecological requirements to the sympatric marsupial Metachirus nudicaudatus. Considering the similar requirements, and that D. aurita is about three times the size of M. nudicaudatus, our hypothesis is that the increase in D. aurita's abundance may negatively affect M. nudicaudatus' population. To test this hypothesis, we conducted a two-year capture-mark-recapture study in an area in the Southeast of Brazil where top predator community is depauperated. The relationship between the population dynamics of these two marsupials was analyzed by including abundance of D. aurita and environmental conditions as explanatory variables of the population parameters of M. nudicaudatus. We observed that all demographic parameters of M. nudicaudatus fluctuated over time and responded negatively to D. aurita abundance. Our conclusion is that, at least on a monthly timescale, the interspecific relationship with D. aurita seems to influence more M. nudicaudatus' population than any other environmental covariate. These findings suggest that mesopredator release can promote negative effects on population parameters of other species within the same trophic level. Considering that top predators are no longer present in most of the remaining Atlantic Rainforest fragments, the marsupial D. aurita has become a key species in this biome, with relevant consequences arising from its interspecific interactions. K E Y W O R D SAtlantic Rainforest, capture-mark-recapture, Didelphis aurita, mesopredator, Metachirus nudicaudatus, POPAN

Dimensões Ecológicas, Geológicas e Humanas em Estudos de Longa-Duração no Parque Nacional da Restinga de Jurubatiba, Rio de Janeiro.

“…Estudos clássicos no Hemisfério Norte demonstraram, por exemplo, como a abundância de lebres é influenciada pela densidade de linces e vice-versa, sugerindo uma forte associação entre as flutuações populacionais de presas e predadores (Elton 1924(Elton , 1927. Já na Mata Atlântica, a abundância do gambá Didelphis aurita tem sido proposta como um possível fator regulador importante das comunidades de pequenos mamíferos, uma vez que este marsupial poderia atuar como competidor e/ou predador de outras espécies com porte corporal similar ou menor (Ceotto et al 2009, Moura et al 2009, Kuhnen et al 2019). Entretanto, as implicações dessas interações interespecíficas para a estruturação das comunidades de pequenos mamíferos da Mata Atlântica ainda são pouco compreendidas.…”