Stud Neotrop Fauna & Environm (1997) Vol. 32: 7–11
0165-0521/97/3201-0007$12.00 © Swets & Zeitlinger
POPULATION D YNAMICS OF DIDELPHIS MARSUPIALIS IN NORTHERN COLOMBIA
Gregory H. Adler1 , John Jairo Arboledo2 and Bruno L. Travi3
of Biology and Microbiology, University of Wisconsin, Oshkosh, USA2University of Antioquia, Medellín, Colombia 3 International Centre of Medical Training and Research, Cali, Colombia Accepted: 24 January 1997
Received: 7 August 1996
ABSTRACT A population of the common opossum, Didelphis marsupialis, inhabiting a highly degraded agricultural area in northern Colombia was studied by live-trapping for over two years. Three transects were established in stripsof riparian vegetation within a matrix of agricultural crops. Sampling was performed once in October 1993 and then monthly from August 1994 through December 1995. Four population-level characteristics were estimated: abundance, sex ratio, age structure, and breeding activity. Abundance was very high at the beginning of the study but declined dramatically and then fluctuated at low numbers. Thesex ratio did not vary among high-abundance, decline, and low-abundance population phases, but there was a deficiency of females with young at high abundance and of adults during the decline. The impact of these characteristics on the population dynamics of D. marsupialis is discussed with special emphasis on reproductive traits. These characteristics may also contribute to the potential of D.marsupialis as a reservoir for a wide variety of infectious agents. KEYWORDS: Age structure, Colombia, Didelphis marsupialis, population dynamics, sex ratio.
INTRODUCTION The common opossum, Didelphis marsupialis, is one of the most abundant and ubiquitous mammals throughout much of the Neotropics. This species is extremely adaptable and is found in many different habitats throughout its rangeexcept arid regions (Eisenberg 1989; Emmons 1990). Life history traits are highly variable over the wide geographic range of D. marsupialis. For instance, in Colombia mean litter size in the highly seasonal eastern plains is 6.5, and in the aseasonal western pluvial forests is only
Correspondence to: Gregory H. Adler, Department of Biology and Microbiology, University of Wisconsin, Oshkosh, WI54901, USA. Fax +1-414-424 1101; e-mail: email@example.com
4.5, with respectively 2 and 3 litters per year (Tyndale-Biscoe & Mackenzie 1976). Litter size also varies latitudinally, with smaller litters being produced closer to the equator (Fleming 1973). Individuals are apparently nomadic and generally remain in an area for no longer than two or three months (Fleming 1972; Hunsaker 1977;Telford et al 1979; O’Connell 1979; Streilein 1982; Charles-Dominique 1983; Sunquist et al 1987), although O’Connell (1989) recorded a maximum residency of 530 days in Venezuela. The common opossum is omnivorous and eats a wide variety of animals, plants (Charles-Dominique 1983, Atramentowicz 1988, Julien-Laferriére & Atramentowicz 1990), and garbage around human habitations (Emmons 1990). Here wereport on the dynamics of a population of D. marsupialis inhabiting a highly degraded agri-
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G.H. ADLER ET AL.
cultural area in northern Colombia. D. marsupialis are of particular interest because they have been incriminated as reservoirs of infectious agents that are responsible for several important humandiseases (e.g., Hanson et al 1980; Arias & Naiff 1981; Travi et al 1994), including Chagas’ disease and cutaneous and visceral leishmaniases. The examined population-level parameters are discussed under aspects of large-scale fluctuations typical of this species (O’Connell 1989, Emmons 1990) and the role of opossums as reservoir hosts for infectious agents.
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