Population Dynamics of Two Sympatric Rodents in a Variable Environment: Rainfall, Resource Availability, and Predation

Precipitation plays an important role in the dynamics of species found in arid and semiarid environments. However, population fluctuations generally are driven by a combination of multiple factors whose relative contribution may vary through time and among species. We monitored fluctuations of speci...

Full description

Saved in:
Bibliographic Details
Published in:Ecology (Durham) 2009-07, Vol.90 (7), p.1996-2006
Main Authors: Previtali, M. Andrea, Lima, Mauricio, Meserve, Peter L., Kelt, Douglas A., Gutiérrez, Julio R.
Format: Article
Language:English
Subjects:
Animal and plant ecology
Animal populations
Animal, plant and microbial ecology
Animals
Biological and medical sciences
bottom-up regulation
Climate change
Demecology
density dependence
Ecology
Ecosystem
El Niño
ENSO
Food availability
Foxes - physiology
Fundamental and applied biological sciences. Psychology
General aspects
Mammals
north-central Chile
Octodon degus
Owls
Phyllotis darwini
Plants
Population density
Population Dynamics
Population ecology
Precipitation
Predation
Predators
Predatory Behavior
predator–prey interactions
Rain
Rodentia - genetics
Rodentia - physiology
Rodents
semiarid habitat
Strigiformes - physiology
sympatric rodent species
Time Factors
time series
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Precipitation plays an important role in the dynamics of species found in arid and semiarid environments. However, population fluctuations generally are driven by a combination of multiple factors whose relative contribution may vary through time and among species. We monitored fluctuations of species in three trophic levels for >17 years at a semiarid community in north-central Chile. The region is strongly affected by the El Niño Southern Oscillation, resulting in high variation in rainfall that triggers dramatic changes in food resource availability, with strong effects on upper trophic levels. We focused our analyses on the role played by endogenous and exogenous (climatic) factors on the dynamics of two important rodent species in the community, Octodon degus and Phyllotis darwini. We documented population fluctuations of several orders of magnitude in response to wet and dry episodes of different strength and duration. P. darwini reached similar maximum densities, regardless of the duration of high-rainfall events, whereas O. degus showed additive effects of multiple wet years. Time series diagnostic tools revealed oscillations with a 5-year periodicity in rainfall, which may be the cause of the same periodicity and a weak second-order signal observed in the rodent dynamics. However, the dynamics of both rodent species were dominated by strong first-order processes, suggesting an important role of direct density dependence. Intraspecific competition, expressed as the ratio of rodent density/rainfall (or food resources) explained more than two-thirds of the variation in the population rate of change, whereas less than one-third was explained by lagged rainfall (or food resources). We detected no significant effects of predation. Our results contribute to a growing number of examples of dynamics governed by the combined effect of density dependence and climatic forcing. They also reveal strong bottom-up regulation that may be common in other arid environments.
ISSN:0012-9658
1939-9170
DOI:10.1890/08-0405.1