Research on the Nine-banded Armadillo in Illinois
The range of the nine-banded armadillo (Dasypus novemcinctus) spans most of the tropical and subtropical regions of both North and South America. As adults, these animals are solitary and tend to avoid each other. In areas where the density of nine-banded armadillos is high, the shells of adults show signs of physical confrontation. These signs include scars produced by the claws of other individuals. Nine-banded armadillos act as hosts for several species of parasites and infectious agents specific to armadillos, yet they are known reservoir hosts for at least two zoonotic diseases: leprosy and Chagas disease.
Overall, the success of these animals is, in part, the result of reproductive strategies, chance and adaptations to new environments. Two features of their reproductive biology make nine-banded armadillos prolific animals. The first feature is their delayed implantation, which suggests that the embryo does not necessarily implant in the uterine wall following fertilization. Second, this fertilized egg undergoes further splitting upon cell cleavage, a phenomenon known as polyembryony; as such, from a single fertilized egg there could be at least four viable pups. Other factors that may ease their survival and dispersion include the lack of predators and competitors.
The reproductive strategy of the nine-banded armadillo, coupled with the absence of major predators, facilitates their survival into adulthood. The four pups will live in close association until the end of their first year of age. At that point each will disperse to become an independent, solitary adult.
During dispersal events, individuals from a single litter move to new habitats, avoiding areas already used as a home of adult armadillos. Furthermore, encountering an adult forces the displacement of at least one pup into newer territories. The Federal Aid in Wildlife Restoration research project under way at Southern Illinois University-Carbondale aims to document the routes and velocity of dispersion of the nine-banded armadillo in Illinois. We expect armadillos use riparian habitats along rivers and creeks as corridors of dispersion, and that the rapid population growth in the southern counties of Illinois will generate a continuous northward stream of immigrants.
Armadillos will be fitted with radio transmitters to identify their pathways of dispersion and estimate their velocity. The results of these efforts will assist wildlife managers and the public identify areas where armadillos are likely to appear first. This information will enable wildlife officials to allocate resources to minimize conflicts between wildlife and the general population. In addition, our efforts will include the screening of armadillo carcasses for endoparasites, such as the etiological agents, or disease-causing organisms, of leprosy (Mycobacterium leprae) and Chagas disease (Trypanosoma cruzi). The goal of this effort is to detect focal points of these infections to prevent contraction of the disease by members of the public and professionals working in the handling of wildlife.
Dr. F. Agustin Jiménez is an Associate Professor in the Department of Zoology at Southern Illinois University-Carbondale. He earned his doctorate at the University of Nebraska, and his research interest focuses on the historical relationships among nematodes and their mammalian hosts across the neotropics.