Comparisons Between Nine-Banded Armadillo (Dasypus Novemcinctus) Populations in Brazil and the United States

Rev. BioI. Trop. 46(4): 1173-1183,1998 www.ucr.ac.cr www.ots.ac.cr www.ots.duke.edu Comparisons between nine-banded armadillo (Dasypus novemcinctus) populations in Brazil and the United States W. J. Loughry and Colleen M. McDonough Department of Biology, Valdosta State University, Valdosta, GA 31698-0015, U.S.A. Fax: 912-333-7389; email: [email protected] Received 21-1V-1998. Corrected 1O-Vl11-1998. Aceptado 20-Vl11-1998. Abstract: We compared characteristics of a population of nine-banded armadillos (Dasypus novemcinctus) studied in the southern United States with a population found in the Atlantic coastal rainforest of Brazil. Adult armadillos in Brazil weighed less than those in the U.S., but when weight was accounted for, did not differ in other measures of body size. However, juveniles in the U.S. were proportionately bigger than those in Brazil. Armadillos in Brazil were less abundant (numbers sighted per h of observation) and were active later at night than those in the U.S. Adult sex-ratios were male-biased in both populations: Finally, there was no significant difference in the incidence of litterrnate associations observed in the two populations, but groups of juveniles (which included non-litterrnates) were observed more frequently in the U.S. Many of these differences may be due to the fact that armadillos are hunted extensively in Brazil but not in the United States. Key words: Dasypus novemcinctus, armadillos, Brazil, United States, population differences. Many charactersitics of animal Breece and Dusi 1985, Redford 1985, Sikes et populations vary intraspe~ifically, presumably at. 1990, Lippert 1994). Females give birth to as the result of adaptation to conditions that litters of genetically-identical quadruplets in vary geographically (Lott 1991, Foster and the spring (Newman and Patterson 1910, Endler in press). Comparisons of populations Patterson 1913, Storrs and Williams 1968, inhabiting different areas can yield insights Prodohl et at. 1996), with litters first emerging into the evolutionary forces generating from their natal burrows from late spring differences between populations. In addition, through the summer (Loughry and McDonough the extent of intraspecific variation provides 1994). Juveniles (young of the year) remain in information on how generalizable data from close proximity, foraging together and sharing one population are to populations in other parts the same burrows through some of their first of a species' range. summer (Taber 1945, Galbreath 1982, Nine-banded armadillos (Dasypus McDonough and Loughry 1995, Prodohl et at. novemcinctus) are found from northern 1996), but litters appear to break up (due to Argentina to the southern United States dispersal or mortality) by the fall (McDonough (Humphrey 1974, Wetzel1982, 1985,Taulman and Loughry unpublished data). and Robbins 1996). They are relatively asocial, The above account. is potentially burrowing mammals (Newman 1913, problematic because almost all of this Galbreath 1982, McBee and Baker 1982), that information is derived from studies performed are mostly active at night (McDonough and in the northern-most part of the species' range Loughry 1997a), and feed primarily on insects (i.e., in the United States; reviews in Kalmbach (Kalmbach 1943,Clark 1951,Fitch et at. 1952, 1943, Taber 1945, Talmage and Buchanan 1174 REVISTA DE BIOLOGIA TROPICAL 1954, Galbreath 1982, McBee and Baker the analyses reported here we pooled data over 1982). Nine-banded armadillos have only the entire four year period for comparison with recently colonized the U.S. (Humphrey 1974, those collected in Brazil. While this makes the Taulman and Robbins 1996), so data from U.S. data set large in comparison with that from these studies may not be representative of Brazil, it seems appropriate because we are populations in more ancient parts of the interested in average differences between the species' range, living in the kinds of two populations, rather than transient conditions under which the species differencesdue to yearly variation. However,to presumably evolved. Comparisons with non- insure that pooling was appropriate, we North American populations of D. performed separate comparisons of each year's novemcinctus are required to determine if this data from Tall Timbers with the Brazilian data is a legitimate concern. In this study, we and obtained exactly the same pattern of results. addressed this issue by collecting data on a Data collection followed procedures population of nine-banded armadillos located developed during the Florida study in northern Florida (Loughry and (McDonough and Loughry 1997a, Loughry McDonough 1996, McDonough and Loughry and McDonough 1998). In both populations, 1997a) and, using the same methods, a we censused the property during both daylight population located in the Atlantic coastal and evening hours (200 days for a total of 2273 rainforest of Brazil. These two data sets person-hours of field time in the U.S., in provide an opportunity to examine the Brazil, 108 days and 958 person-hours). A question of how similar armadillos are in daily census typically lasted 4-6 h and was these two widely separated locales. While conducted by walking or driving along trails or our data are not an exhaustive account of the roads on each property. Spotlights and miner's population attributes of armadillos in either lamps were used to observe animals after dark. location, they allow at least a preliminary The total linear distance censused was assessment of the extent of intraspecific approximately 25 km at each site. A rotating variation that can occur in D. novemcinctus. schedule of observations was used, such that a portion of the entire sampling area was MATERIALSAND METHODS censused each night, followed by another portion the next night, and so on until the Data on Brazilian armadillos were entire area had been sampled. This schedule collected from 20 January-l June, 1996, at the was then repeated for the duration of the field Po~o das Antas Biological Reserve (5500 ha), season. Both sites were comprised of a variety located approximately 70 km north of Rio de of habitat types (in Brazil: rainforest, swamp, Janiero. The reserve contains one of the largest grassland and disturbed habitats, see Dietz et remaining fragments of Atlantic coastal al. 1997, Loughry and McDonough 1997, in rainforest and is the site of conservation efforts the U. S.: hardwood hammocks, wetlands, to preserve the golden-lion tamarin fields and upland pine areas, Brennan et al. (Leontopithecus rosalia, Kleiman et al. 1986, 1998). Visibility to the sides of roads and trails Dietz et al. 1997). Data for the u.S. come from varied considerably depending on habitat type. a four year (1992-1995) study of armadillos While we did not attempt to measure located on the Tall Timbers Research Station visibilities systematically in the two locales, it (1600 ha), near Tallahassee, Florida (see was our impression that they were relatively Loughry and McDonough 1996, McDonough similar overall. Thus, the total area sampled at and Loughry 1997a). There was some year-to- each site was roughly the same. year variation in the characteristics of the We attempted to capture armadillos Florida population (Loughry and McDonough observed during censuses with large dip nets 1996,McDonough and Loughry 1997a), but in attached to a 1.5 m pole. In Brazil, we also LOUGHRY & McDONOUGH: Comparisons between annadillo populations 1175 used live-traps placed in the mouths of active juvenile D. novemcinctusappear very similar to burrows. Once caught, animals were sexed, adult D. septemcinctus. Thus, our data on weighed, and marked for long-range juvenile abundances and the timing of activity identification by gluing unique colors and may be slightly biased by the inclusion of some shapes of reflective tape on various parts of the data from D. septemcinctus. This is unlikely to carapace. A small tissue sample for genetic be a large problem because D. septemcinctus studies was taken from one or both ears using was relatively rare on the reserve and typically an ear-notcher. These notches were taken from found in differenthabitatsfromD. novemcinctus different locations on the ears of different (Loughry and McDonough 1997). In addition, individuals, further contributing to most observations of juvenile D. novemcinctus identification of particular animals. Animals were from animals that had been captured, were markedfor permanent identification using marked and subsequentlyresighted. ear tags and, in the U.S., with passive Using the data collected by these methods, transponder (PIT) tags. Five body size we compared five characteristics of our two measurements (all in cm) were obtained from populations. (1) We compared morphology by all captured animals: (1) tail base = the analyzing differences in body weight and body circumference of the tail at itsjuncture with the size measurements with t-tests. Body size body near the pelvic shield of the dorsal measurements are correlated with body weight carapace; (2) tail length =the length of the tail (Loughry and McDonough 1996), so we from the base to the tip (animals who were performed a second analysis of body size missing a portion of the tail were not differences using an ANCOVA in which body measured); (3) front carapace = the length of weight was the covariate. For both sets of the anterior edge of the scapular shield of the analyses, we averaged data for individuals carapace (i.e., at thejuncture with the head); (4) with multiple measurements (except where the front band =the length of the posterior edge of animal changed age groups, e.g., data for an the scapular shield; and (5) back band = the individual first caught as a juvenile then length of the most posterior movable band. subsequently as an adult were not averaged but Animals were assigned to age categories based treated as independent points). Although on weight (McDonough 1992, 1994, Loughry armadillos may exhibit some sexual and McDonough 1996) as juveniles (young of dimorphism (McDonough 1992), we pooled the year, < 2.5 kg), yearlings (2.5-3.5 kg), or data for males and females in these analyses adults ( > 3.5 kg).

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