Printer Friendly

An evaluation of the nine-banded armadillo as predators of gopher tortoise and northern bobwhite quail nests in Florida.


Invasive species can have important consequences, both economically (Pimentel et al., 2005; Evans, 2009) and ecologically (Gurevitch and Padilla, 2004; Krajick, 2005; Pimentel et al., 2005), and are considered one of the greatest threats to imperiled species within the continental United States (Wilcove et al., 1998). Through competition or efficient predator strategies, they may disrupt established interactions within an ecosystem and thus potentially lower biodiversity (Gordon, 1998; Wilcove et al., 1998; Powell et al., 2011; but see Wright and Muller Landau, 2006). Because control or eradication of invasive species can be extremely costly and difficult (Epanchin-Niell and Hastings, 2010; Pysek and Richardson, 2010), it is important that the negative consequences of invasive species be assessed so that managers can prioritize our increasingly limited conservation funds.

The nine-banded armadillo (Dasypus novemcinctus; hereafter armadillo) is an example of a species which can cause significant economic and ecological damage and is considered invasive in both Florida and Georgia (FFWCC, 2011; GISTF, 2011). Prior to the early 1900s, the armadillos range was limited in the United States to southern Texas (Fitch et al., 1952; Humphrey, 1974; Taulman and Robbins, 1996); repeated translocations by humans to Florida and anthropogenic habitat modification have enabled the species to expand its range across the entire southeastern United States (Fitch et al., 1952). Despite their widespread distribution and the large number of public complaints resulting from armadillo foraging and burrowing activities (Bruggers et al., 2002; Mengak, 2003), there is a relative paucity of literature pertaining to the foraging habits and the potential effect of armadillos on native species or communities in areas where introductions have occurred. Foraging armadillos could affect the abundance of native wildlife through two primary means: competition or predation. While no published reports confirming competition are known, one author (CM) has observed armadillos chasing striped skunks in Texas and received anecdotal reports of skunk populations declining after armadillos had moved into an area. Similarly, we are aware of few quantitative reports of the effects of armadillo predation on abundance of native species. Nine-banded armadillos are considered to be general omnivores (Redford, 1985), feeding predominantly on beetles, earthworms, millipedes, and fly larvae (Fitch et al., 1952; Sikes et al., 1990). They also feed opportunistically on small vertebrates (see review in McDonough and Loughry, 2008) and eggs of a variety of ground nesting species of conservation concern including sea turtles (Engeman et al., 2003, 2005), gopher tortoises (Gopherus polyphemus, Douglas mad Winegarner, 1977; Smith et al., 2011), and northern bobwhite quail (Colinus virginianus, Staller et al., 2005). Gopher tortoises are considered threatened by the IUCN (IUCN, 2010), the state of Florida (Gruver and Murphy, 2011) and the state of Georgia (Jensen, 2009). Bobwhite quail are considered near threatened and declining by the IUCN (IUCN, 2010).

The frequency of armadillo nest predation is difficult to determine because armadillos sometimes visit nests previously depredated by other species, resulting in blame for nest predation in instances where they were not the primary predator (Drennen et al., 1989; Engeman et al., 2005). Armadillos may be attracted to the remaining eggs or to the invertebrates feeding on the decaying remains of previously depredated nests (Drennen et al., 1989). Although armadillos have been documented as nest predators, much remains to be learned about how armadillos find these nests and the impacts of these nest visits. What cues do armadillos use to identify nests? Are armadillos typically primary or secondary predators? Do armadillos frequently depredate nests at sites where potential prey occur at low densities? To answer these questions we used a series of captive and field experiments in north Florida to assess armadillo attraction to eggs of two species of conservation concern: the gopher tortoise (hereafter tortoise) and the northern bobwhite quail (hereafter quail).



We captured 12 armadillos by use of long handled dip nets from Jul. to Nov. 2009 at three different locations in north Florida: Joe Budd Wildlife Management Area (JBWMA, 30[degrees]30'30" N, 19[degrees]32'84" W), North Florida Research and Education Center (NFREC, 42[degrees]32'30" N, 39[degrees]35'84" W), and Tall Timbers Research Station (TTRS, 24[degrees]39'30" N, 32[degrees]12'84" W). Captured individuals were transported to an experimental facility at the NFREC where they were held separately during testing for no more than 14 d before being released at their capture site. This protocol was approved by the University of Florida IACUC protocol #200801663 and a permit was issued from the Florida Fish and Wildlife Conservation Commission.

Our experimental facility consisted of six adjacent outdoor pens (3 holding, 3 experimental), each measuring 3.1 m x 3.1 m. The six pens were surrounded by a chain link fence and covered by shade cloth to protect captive armadillos from predators and extreme temperatures. Pen walls were constructed from 1.8 m x 3.1 m chain link fence panels with metal roofing material attached to those sides with which armadillos came into contact. Panels were buried 0.9 in to prevent armadillos from escaping via burrowing. A removable door was situated between each holding and its adjacent experimental pen to enable voluntary animal movement between the two. A layer of landscape fabric and ~8 cm of topsoil were placed in each experimental pen and replaced before experiments were performed with each new individual. Holding pens contained fresh hay for bedding and half of a plastic pet carrier for shelter. To ensure that individuals were acclimated to captivity and in foraging mode while in experimental pens, individuals were allowed 2 d to acclimate before any experiments were performed, and one or more experiments for a concurrent study comparing the attractiveness of food materials was performed prior to initiation of experiments for this investigation (Ober et al., 2011). Water was provided ad libitum and food was provided each night after completion of experiments.

We conducted three types of experiments to evaluate which nest cues elicited interest from armadillos. In every trial, each test material was placed at a randomly-selected location in experimental pens at least 60 cm from any wall and 45 cm from other test materials. To evaluate the relative likelihood of armadillos serving as primary or secondary nest predators we presented two intact and two cracked quail eggs to each armadillo. To assess the ability of armadillos to perceive cues from nest materials we presented two bowls containing tortoise egg shells and soil from a tortoise nest mound, two bowls containing soil from a tortoise nest mound, and two bowls with soil collected far from any active tortoise nest mound to serve as a control. Soil from tortoise nests was used to evaluate if chemicals such as secretions deposited by the female during laying might attract armadillos to the nests. To evaluate armadillo preferences for various types of eggs we presented one whole quail egg, one whole tortoise egg, and one whole chicken egg.

Quail eggs used in these experiments were attained from local farms and chicken eggs were obtained from a local grocery store. Unhatched tortoise eggs and soil from active tortoise nest mounds were collected from Reed Bingham State Park in South Georgia. The tortoise eggs and soil samples were kept frozen until use. All eggs and soil were handled with disposable gloves to avoid confounding the experiments with human scent.

During each armadillo's captivity, a maximum of two trials per experiment were performed, with one to three experimental trials per armadillo per evening depending on their emergence or participatory interest. Experiments were performed between 1900 and 0100 with illumination from battery powered infrared lights (CCTV 48 LED Camera Infrared Illuminator Night Vision). Armadillo behavior was recorded for analysis using a Sony Handycam DCR-SR85. Recording began when the door between the holding and experimental pens was removed to allow free access to the experimental area.

The relative interest armadillos had for test materials was quantified from videos using two behavioral metrics: (1) order of contact and (2) time elapsed to first contact. Order of contact was the order in which armadillos first contacted each test material. Time elapsed to first contact was the number of seconds from pen entry to contact with the test material. These two metrics were chosen because we believe they provide the most accurate reflection of each individual's ability to find various types of eggs. Although similar, the discrete vs. continuous nature of these variables could reveal subtle differences in armadillo perception that one parameter alone might not capture. Trials were ended when a period of 5 min elapsed after an armadillo last contacted a test material, indicating a lack of interest in all test materials. If any test materials were not contacted before the end of an experiment, they were recorded as being the last item(s) contacted and were assigned a time elapsed to first contact equal to the duration of the entire trial.

Data collected from experiments with captive armadillos were analyzed with R version 2.8.1 (R Development Core Team, 2009) using linear mixed effects (LME) models (Pinheiro and Bates, 2000) to account for repeated measurements within each trial and for each animal. Response variables, order of contact and time elapsed to contact, were log or square-root transformed to meet LME model assumptions of normality. In addition, armadillo breeding season (Jun.-Aug. = breeding; Sept.-Nov. = post-breeding) and distance between the entrance of the experimental pen and the test materials (hereafter distance) were included in models as fixed effects; therefore, our full model contained test material, season, distance, and the cross-product between test material and season. A reduced model was created by removing whichever variable explained the least amount of variability and was compared to the full model using a log-likelihood ratio test. If the resulting P-value was >0.05 this process was reiterated until significance was attained or no explanatory variables remained (Diggle et al., 2002).


To further examine the role of armadillos as primary versus secondary nest predators we conducted a field study with artificial quail nests (n = 78) from 25 Jun. to 16 Aug. 2010 at JBWMA (3 locations) and NFREC (1 location). These sites contained populations of both quail and armadillos. At each study site, we delineated habitat appropriate for nesting quail in Arc GIS and then randomly selected sites for each artificial nest within this area. Randomly-selected nest sites were located [greater than or equal to] 250 m from any other active artificial nests. While wearing latex gloves, artificial nests were created at the base of thick bunchgrass and fashioned with surrounding grasses. A Moultrie (Game Spy i40) or Cuddeback (NoFlash) trail camera with infrared flash capability was mounted on a post within 3 to 6 m to monitor for nest visitors. The first visitor to each artificial quail nest was counted in the subsequent analyses. Seven artificial nests were placed weekly at one or two study sites and checked every 3 d. Each nest was removed after depredation or a maximum of 7 d. Each artificial nest site was randomly assigned one of three treatments: intact (6 whole eggs), cracked (6 cracked eggs), or urine (6 cracked eggs with approximately 10 mL of raccoon urine (Procyon lotor) sprinkled next to the eggs). Both the cracked and urine treatments were intended to mimic a nest depredated by a prior visitor, with the cracked treatment providing cues from the eggs only, and the urine treatment providing cues from both the eggs mad a common predator of nests (Drennen et al., 1989; Engeman et al., 2005; Staller et al., 2005).

To evaluate which type of artificial quail nests elicited visitations from all potential nest predators, we used general linear models (GLM) with quasibinomial errors. These GLMs function as contingency tables but are more robust than traditional Chi-square tests when counts are low (i.e., <5) or sampling is unbalanced (Crawley, 2007). Infrequent nest visitors (black bear, bobcat, crow, and tortoises) were excluded from this analysis. The number of visited nests and the number of unvisited nests (a two vector response variable also known as the binomial denominator; Crawley, 2007) was modeled with nest type (intact, cracked, urine), study site, and visitor species as predictor variables.

We used a similar approach to determine which visitors functioned as regular predators of eggs. For this analysis only visited nests were included (all species). Again, we modeled the binomial denominator (visited, unvisited) by visitor species, egg depredation (none, partial, complete), and their interaction. We compared this model to a reduced model where the least common visitor was grouped with the intercept. Comparisons were performed using log-likelihood ratio tests where significance indicated that the most parsimonious model had been identified (Diggle et al., 2002).



Results of the first experiment with captive armadillos (n = 8 ind, n = 8 trials, [bar.x] trial duration = 12.5 min) indicated no preference for either cracked or intact quail eggs (Table 1). There was no difference in order of contact between the two types of eggs (P = 0.27) ; however, eggs located closer to the entrance were contacted before eggs located further from the entrance (P = 0.03, Table 2). Similarly, time to first contact was not significantly different between cracked ([bar.x] = 6.08 min, 95% CI from 3.38 to 9.56 min) and intact quail eggs ([bar.x] = 7.19 min, 95% CI from 4.22 to 10.94 min, P = 0.39, Tables 1 and 2); but eggs located closer to the entrance were contacted earlier (0.03 min per foot, 95% CI from 0.00 to 0.12 min, P = 0.05), Tables 1 and 2). Neither metric was related to season (Table 1). Similarly, the second experiment in captivity (n = 10 ind, n = 20 trials, [bar.x] trial duration = 22.7 min) indicated there was no difference in order of contact among the tortoise nest materials (P = 0.52, Table 1). Also, the time to first contact was not significantly different between control soil ([bar.x] = 2.46 min, 95% CI from 1.10 to 5.52 min), nesting soil ([bar.x] = 2.70 min, 95% CI from 1.20 to 6.05 min), or nesting soil with egg shells ([bar.x] = 1.84 min, 95% CI from 0.82 to 4.11 min; P = 0.22; Tables 1 and 2). Neither metric was related to distance from the pen entrance or season (Table 1).

Finally, the third experiment (n = 6 ind, n = 10 trials, [bar.x] trial duration = 19.0 min) revealed no distinct preference among the three types of eggs (chicken, quail, tortoise), as measured through order of visitation (P = 0.75, Table 1). Time to first contact was not significantly different between the chicken ([bar.x] = 19.72 min, 95% CI from 9.71 to 33.24 min), tortoise ([bar.x] = 15.0 min, 95% CI from 6.5 to 27.0 min), and quail egg ([bar.x] = 20.47 min, 95% CI from 10.24 to 34.21 min, P = 0.37, Tables 1 and 2). Neither metric was related to distance from the entrance or season (Table 1).


Visitation rates to artificial quail nests in the field differed significantly among study sites and among egg treatments (P < 0.01, Table 3). More specifically, although there was no significant difference between visitation rates to cracked quail eggs (62%) and cracked quail eggs treated with raccoon urine (88%; P = 0.37), visitation rates to both these types of nests was higher than visitation rates to nests with intact eggs (24%; P < 0.01).

Raccoons (n = 11), opossums (n = 7), and unknown visitors (n = 15) were the significant predators of eggs (P = 0.02; Table 4). Raccoons and opossums completely destroyed 86% to 90% of the nests they visited whereas complete depredation by rodents and unknown visitors occurred at approximately 50% of the nests they visited (Table 4).

Armadillos were the primary visitor to only three of the 78 artificial nests, and secondary visitor to only one nest. All of the visitations by armadillos occurred at a single location, the magnolia tract of JBWMA (Table 3). Whereas two of the three nests visited first by armadillos were depredated completely, based on still photographs we are confident that depredation was the result of subsequent visiting raccoons.


Previous research has shown that nine-banded armadillos can be important predators of several ground nesting species. Engeman et al. (2005) found that 49% of marine turtle nests at two locations in Florida were depredated by armadillos. Armadillos were responsible for 16% of quail nest failures at Tall Timbers Research Station in north Florida and Pebble Hill Plantation in southwest Georgia (Staller et al., 2005) and one gopher tortoise nest failure at Joseph W. Jones Ecological Research Center in southwest Georgia (Smith et al., 9011). Contrary to these findings, however, armadillos at our study sites (JBWMA and NFREC) were the primary, visitor of only 4% (n = 3/78) of artificial quail nests and did not appear to consume any eggs during these visits. Furthermore, captive armadillos did not exhibit any preference among chicken eggs, quail eggs, or tortoise eggs; nor did they express attraction behaviors towards tortoise egg shells or soil removed from tortoise nests. Because we used tortoise eggshell fragments and tortoise eggs frozen after they failed to hatch, we recommend that future research further investigate armadillo interest in active tortoise nests, preferably at varying densities. Our overall results are consistent with a concurrent research project where we demonstrated that armadillos showed stronger attraction live worms (Lumbricus terrestris, Pheretima hawayanus, and Eisenia fetida) and crickets (Acheta domesticus) relative to chicken or quail eggs (Ober et al., 2011).

We also found that armadillos do not appear to use cues from prior depredation events to find either quail or tortoise nests. In captivity, armadillos did not contact broken quail eggs any earlier than intact quail eggs as measured by both order of visitation and time to first contact. Contrary to the suggestion by Drennen et al. (1989) that armadillos may "clean up unhealthy eggs," captive armadillos did not contact soil with tortoise egg shells earlier than tortoise nest or control soil. Likewise, free ranging armadillos were equally likely to visit artificial quail nests with whole eggs, cracked eggs, or cracked eggs treated with raccoon urine (Table 3). Given that all of the artificial nests visited by armadillos were subsequently visited by at least one other species, and that other studies have found multiple species visiting individual quail or marine turtle nests (Drennen et al., 1989; Engeman et al., 2005; Staller et al., 2005), it seems probable that armadillos have in the past been misidentified as the cause of nesting failure; though less likely for Staller et al. (2005) who used video cameras instead of tracks to identify nest predators.

Armadillos are thought to be opportunistic foragers because of their diverse habitat selection (McDonough and Loughry, 2005; Gammons et al., 2009) and prey selection (Fitch et al., 1952; Sikes et al., 1990; McDonough and Longhry, 2008). The armadillo's apparent foraging plasticity and seasonal dietary shifts (Fitch et al., 1952; Sikes et al., 1990; McDonough and Loughry, 2008) could serve as an optimal foraging strategy. Individuals that develop a search image for nutrient rich food items such as eggs could outperform individuals selecting prey based on availability alone as long as these nutrient rich food items occur at abundances high enough to make searching for them profitable. While we did not specifically test the armadillos' ability to develop a search image, we anecdotally observed learned foraging behavior in captivity. For example, most individuals did not immediately recognize dog or cat food provided daily as a potential food source and ignored them. However, once individuals had consumed these foods, many immediately consumed them upon presentation. Similarly, some armadillos were able to recognize and process eggs (particularly chicken) more quickly over the course of the trials whereas other individuals never seemed to identify these as potential food sources (Ober et al., 2011). These captive results confirm observations in the field (Bushnell, 1952; Breece and Causey, 1973) that some armadillos readily feed on quail eggs whereas others encounter and disturb nests but do not recognize the eggs as a potential food item. The development of search images could explain why armadillos appear to be predators of ground nesting species in some areas and not others. Staller et al.'s (2005) study sites had relatively high densities of quail; therefore, a search image for these seasonally abundant nests would be more advantageous to resident armadillos at these sites than to those residing in the study areas we used for our field experiments where nest densities are low. On the other hand, predation of nests of quail or marine turtles may have been high in other studies due to high availability in comparison to other potential prey items (Engeman et al., 2005; Staller et al., 2005). In either case, our results suggest that armadillos are unlikely to threaten species of conservation concern in places where their nests occur at fairly low densities, but we cannot rule out the possibility that armadillos learn to consume eggs in areas where nest densities are high.

Predation rates at our artificial nests were similar to those reported in other studies (review in Coppedge et al., 2007). Consistent with other studies in the southeastern U.S. (Rollins and Carroll, 2001; Staller et al., 2005), common visitors of depredated artificial nests at our study site included the raccoon (26%), opossum (17%), and rodents (10%) (Table 4). We did not observe a single depredation by snakes even though a study performed in close proximity found that snakes were the most important predator of actual quail nests (29%; Staller et al., 2005). The absence of snake depredation which we observed is more likely an artifact of our methodology than an actual absence of snake depredation. Snakes may rely on cues from incubating females (i.e., heat or scent) to detect nests; cues which would not be present at our artificial nests (Weatherhead and Blouin-Demers, 2004). Alternatively, our use of still cameras rather than video surveillance could explain our inability to detect snakes as nest predators. Even with video surveillance, snake and rodent depredation can be difficult to detect because of the small size of these predators and their ability to enter nests from areas other than the entrance (Staller et al., 2005). We found evidence of this at one artificial nest where a tunnel created in the grass led to the rear of a depredated nest, but no predation event was captured on camera. It is interesting to note that all of the nests for which we could not identify a predator possessed cracked quail eggs.

Because whole, intact quail eggs are difficult for small rodents to penetrate (Roper, 1992; DeGraaf and Maier, 1996) and because snakes infrequently depredate artificial quail nests (Marini and Melo, 1998; Thompson and Burhans, 2004; Weatherhead and Blouin-Demers, 2004) we believe that rodents were likely responsible for the high percentage of nests with unidentified predators (36%). Rodents, therefore, may be important and previously unrecognized, secondary predators of quail nests.

Although our results pertaining to the visitation rates of snakes and rodents should he interpreted with caution, we believe that the visitation rates amongst mesomammals, especially armadillos, are meaningful. Biases for artificial nest studies typically arise from the use of artificial eggs, eggs from non-study species, or nests made of artificial materials (Davison and Bollinger, 2000; Rangen et al., 2000). To our knowledge, no study has investigated differences in predation rates between real and artificial nests where natural nesting materials and eggs from the species of interest are used; nor has any study documented a bias between real and artificial nest predation by mesomammals. Nevertheless, because we were unable to mimic parental scent, presence, or nest defense, our results from the field should be interpreted with the knowledge that artificial nest studies can be biased (Wilson et al., 1998; Davison and Bollinger, 2000; Moore and Robinson, 2004) and future research should compare armadillo depredation of quail and tortoise nests among areas with varying densities of these species' nests.


Our results from experiments with captive and free ranging nine-banded armadillos indicate that armadillos are not likely to threaten the persistence of quail or tortoises in our study area. Captive armadillos did not exhibit a strong attraction to either tortoise or quail eggs, and our experiment with wild armadillos and artificial quail nests support these findings. We believe that the high predation rate of nests by armadillos in some regions may he related to the high density of nests at these locations. It is possible that armadillos could impede recovery of species that have limited nesting areas, rely on a few productive nesting grounds, and rely on immigration for species persistence or repopulation. We suggest that nest predation of threatened species should be monitored at highly productive sites and predator management implemented on a local scale when warranted.

Acknowledgments.--We thank S. Wright, IC Torrington, J. Loughry, and A. Brock for their tireless assistance with armadillo capture, video analysis, and data collection; Chet Powell, Jennifer Glover, and colleagues at Reed Bingham State Park for collection of tortoise eggs and soil; C. Riddle for his assistance with ArcGIS. Our research would not have been possible without D. Francis and J. Cox facilitating access to Joe Budd Wildlife Management Area and Tall Timbers Research Station, respectively. We are grateful for the funding provided by the Southern Region IPM Center through the Enhancement Grants Program.


BREECE, G. ANN M. CAUSEY. 1973. Armadillo depredation of "dummy" Bobwhite Quail nests in southwest Alabama. Proc. 27th Ann. Conf. Southeast. Assoc. Game Fish Commis., 1973:18-22.

BRUGGERS, R. L., R. OWENS, AND T. HOFFMAN. 2002. Wildlife damage management research needs: perceptions of scientists, wildlife managers, and stakeholders of the USDA/Wildlife Services program. Internat. Biodeter. Biodegrad., 49:213-223.

BUSHNELL, R. I. 1952. The place of the armadillo in Florida Wildlife Communities. M.S. thesis, Stetson University, DeLand, Florida. 55 p.

COPPEDGE, B. R., L. G. TALENT, AND D. M. ENGLE. 2007. Effects of olfactory attributes and size of egg on rates of predation of artificial ground nests in tallgrass prairie. Southwest. Nat., 52:453-460.

CRAWLEY, M. J. 2007. Proportion data, p. 569-591. In: The R book. John Wiley & Sons, Ltd, West Sussex, England.

DAVISON, W. B. AND E. BOLLINGER. 2000. Predation rates on real and artificial nests of grassland birds. Auk, 117:147-153.

DEGRAAF, R. M. AND T. J. MAIER. 1996. Effect of egg size on predation by white-footed mice. Wilson Bull., 108:535-539.

DIGGLE, P. J., P. HEAGERTY, K. Y. LIANG, AND S. L. ZEGER. 2002. The analysis of longitudinal data. 2nd ed. Oxford University Press, Oxford, England.

DOUGLAS, J. F. AND C. E. WINEGARNER. 1977. Predators of eggs and young of gopher tortoise, Gopherus polyphemus (Reptilia, Testudines, Testunidae) in southern Florida. J. Herpet., 11:236-238.

DRENNEN, D., D. COOLEY, AND J. E. DEVORE. 1989. Armadillo predation on loggerhead turtle eggs at two national wildlife refuges in Florida, USA. Marine Turtle News., 45:7-8.

ENGEMAN, R. M., R. E. MARTIN, B. CONSTANTIN, R. NOEL, AND J. WOOLARD. 2003. Monitoring predators to optimize their management for marine turtle nest protection. Biol. Conserv., 113:171-178.

--, --, H. T. SMITH, J. WOOLARD, C. K. CRADY, S. A. SHWIFF, B. CONSTANTIN, M. STAHL, AND J. GRINER. 2005. Dramatic reduction in predation on marine turtle nests through improved predator monitoring and management. Oryx, 39:318-326.

EPANCHIN-NIELL, R. S. AND A. HASTINGS. 2010. Controlling established invaders: integrating economics and spread dynamics to determine optimal management. Ecol. Lett., 13:528-541.

EVANS, E. A. 2009. Economic dimensions of the problem of invasive species (IFAS FE386). University of Florida, IFAS Extension document FE386, Gainesville, Florida. Available online at http://edis. Accessed 19 May 2011.

FFWCC. 2011. Nonnative Mammals. Available online at mammals/. Accessed 19 May 2011.

FITCH, H. S., P. GOODRUM, AND C. NEWMAN. 1952. The armadillo in the southeastern United States. J. Mammal., 33:21-37.

GAMMONS, D. J., M. T. MENGAK, AND L. M. CONNER. 2009. Armadillo habitat selection in southwestern Georgia. J. Mammal., 90:356-362.

GISTF. 2011. Invasive mammals of concern in Georgia. Available online at mammals.html. Accessed 19 May 2011.

GORDON, D. R. 1998. Effects of invasive, non-indigenous plant species on ecosystem processes: Lessons from Florida. Ecol. Appl., 8:975-989.

GRUVER, B. J. AND C. MURPHY. 2011. Florida's endangered and threatened species list. Florida Fish and Wildlife Conservation Commission. Available online at Threatened_Endangered_Species.pdf. Accessed 9 Jun. 2011.

GUREVICH, J. AND D. K. PADILLA. 2004. Are invasive species a major cause of extinctions? Trends in Ecol. Evol., 10:470-474.

HUMPHREY, S. R. 1974. Zoogeography of the nine-banded armadillo (Dasypus novemcintus) in the United States. Bioscience, 24:457-462.

IUCN. 2010. IUCN Red List of Threatened Species. Version 2010.4. Accessed 9 Jun. 2011.

JENSEN, J. B. 2009. Species profile for Gopher Tortoise, Gopherus polyphemus Daudin. Georgia Department of Natural Resources. Available online at Accessed Jun. 9 2011.

KRAJICK, K. 2005. Ecology--Winning the war against island invaders. Science, 310:1410-1413.

MARINI, M. A. AND C. MELO. 1998. Predators of quail eggs, and the evidence of the remains: Implications for nest predation studies. Condor, 100:395-399.

MCDONOUGH, C. M. AND W. J. LOUGHRY. 2005. Impacts of land management practices on a population of nine-banded armadillos in northern Florida. Wildl. Soc. Bull., 33:1198-1209.

-- AND --. 2008. Behavioral ecology of armadillos, p. 281-293. In: S. F. Vizcaino and W. J. Loughry (eds.). The Biology of the Xenarthra. University Press of Florida, Gainesville, Florida.

MENGAK, M. T. 2003. Wildlife damage management education needs: survey of Georgia county FASAT agents. Proc. Wildl. Dam. Manage. Conf., 10:7-15.

MOORE, R. P. AND W. D. ROBINSON. 2004. Artificial bird nests, external validity, and bias in ecological field studies. Ecology, 85:1562-1567.

OBER, H. K. L. W. DEGROOTE, C. M. MCDONOUGH, R. F. MIZELL III, AND R. W. MANKIN. 2011. Identification of an attractant for the nine-banded armadillo, Dasypus novemcinctus. Wildl. Soc. Bull., 35:421-429.

PIMENTEL, D., R. ZUNIGA, AND D. MORRISON. 2005. Update on the environmental and economic costs associated with alien-invasive species in the United States. Ecol. Econ., 52:273-288.

PINHEIRO, J. C. AND D. M. BATES. 2000. Mixed-effects Models in S and S-plus. Springer, New York, USA. POWELL, K. I., J. M. CHASE, AND T. M. KNIGHT. 2011. A synthesis of plant invasion effects on biodiversity across spatial scales. Am. J. Bot., 98:539-548.

PYSEK, P. AND M. RICHARDSON. 2010. Invasive species, environmental change and management, and health, p. 25-55. Annu. Rev. Env. Resourc., 35:25-55.

R DEVELOPMENT CORE TEAM. 2009. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Anstria.

RANGEN, S. A., R. G. CLARK, AND K. A. HOBSON. 2000. Visual and olfactory attributes of artificial nests. Auk, 117:136-146.

REDFORD, K. H. 1985. Food habits of armadillos (Xenarthra: Dasypodidae). In: G. G. Montgomery (ed.). The evolution and ecology of armadillos, sloths and vermilinguas. Smithsonian Institution Press, Washington, D.C. 429-437.

ROLLINS, D. AND J. P. CARROLL. 2001. Impacts of predation on northern bobwhite and scaled quail. Wildl. Soc. Bull., 29:39-51.

ROPER, J. J. 1992. Nest predation experiments with quail eggs: too much to swallow? Oikos, 65:528-530.

SIKES, R. S., G. A. HEIDT, AND D. A. ELROD. 1990. Seasonal diets of the nine-handed armadillo (Dasypus novemcinctus) in a northern part of its range. Am. Midl. Nat., 123:383-389.

SMITH, L. L., D. A. STEEN, M. L. CONNER, AND J. C. RUTLEDGE. 2011. Effects of predator exclusion on nest and hatchling survival in the gopher tortoise. J. Wildl. Manage., In Press.

STALLER, E. L., W. E. PALMER, J. P. CARROLL, R. P. THORSTON, AND D. C. SISSON. 2005. Identifying predators at northern bobwhite nests. J. Wildl. Manage., 69:124-132.

TAULMAN, J. F. AND L. W. ROBBINS. 1996. Recent range expansion and distributional limits of the nine-banded armadillo (DaSypus novemcinctus) in the United States. J. Biogeog., 23:635-648.

THOMPSON, F. R. AND D. E. BURHANS. 2004. Differences in predators of artificial and real songbird nests: Evidence of bias in artificial nest studies. Conserv. Biol,, 18:373-380.

WEATHERHEAD, P. J. AND G. BLOUIN-DEMERS. 2004. Understanding avian nest predation: wily ornithologists should study snakes. J. Avian Biol., 35:185-190.

WILCOVE, D. S., D. ROTHSTEIN, J. DUBOW, A. PHILLIPS, AND E. LOSOS. 1998. Quantifying threats to imperiled species in the United States. Bioscience, 48:607-615.

WILSON, G. R., M. C. BRITTINGHAM, AND L. J. GOODRICH. 1998. How well do artificial nests estimate success of real nests? Condor, 100:357-364.

WRIGHT, S. J. AND H. C. MULLER-LANDAU. 2006. The future of tropical forest species. Biotropica, 38:287-301.



LUCAS W. DEGROOTE AND HOLLY K. OBER (1) Department of Wildlife Ecology and Conservation, NFREC-Quincy, University of Florida, 155 Research Road, Quincy 32351

COLLEEN M. MCDONOUGH Department of Biology, 1500 North Patterson Street, Valdosta State University, Valdosta, Georgia 31698


RUSSELL F. MIZELL, III Department of Entomology, NFREC-Quincy, University of Florida, 155 Research Road, Quincy 32351

(1) Corresponding author: e-mail:
TABLE 1.--Model comparisons for the three captive experiments (exp)
comparing armadillo interest in (a) cracked versus intact northern
bobwhite quail eggs, (b) control soil versus soil and egg shells from
gopher tortoise nests (eggs) versus soil from tortoise nests with no
egg shells, (c) domestic chicken eggs versus bobwhite quail eggs
versus gopher tortoise eggs. Armadillo interest is measured by order
of contact and time elapsed to first contact. Independent variables
include testing materials (T), season (S), distance from the entrance
to the experimental pen and testing material (D) or the intercept (1).
Significance is based on log likelihood ratios (log lik) and indicates
that the prior model explains significantly more variability

Experiment    Behavioral Metric   model           df        AIC

a             order of contact    T*S + D          9        86.55
                                  T + S + D        8        84.59
                                  T + D            7        83.18
                                  D                6        82.40
                                  1                5        85.65
              time to             T*S + D          9       231.28
              first contact       T + S + D        8       229.30
                                  T + D            7       227.50
                                  D                6       226.23
                                  1                5       227.99
b             order of contact    T*S + D         11       345.18
                                  T*S             10       343.19
                                  T + S           8        341.92
                                  T                7       340.18
                                  1                5       337.49
              time to first       T*S + D         11       363.59
              contact             T*S             10       362.19
                                  T + S            8       362.40
                                  T                7       362.02
                                  1                0.5     361.05
c             order of contact    T + D            7        60.45
                                  T                6        58.74
                                  1                4        55.30
              time to first       T + D            7       249.06
              contact             T                6       247.53
                                  1                4       245.50

Experiment    Behavioral Metric   model        log lik    P-value

a             order of contact    T*S + D       -34.28
                                  T + S + D     -34.30      0.84
                                  T + D         -34.59      0.44
                                  D             -35.20      0.27
                                  1             -37.82      0.02
              time to             T*S + D      -106.64
              first contact       T + S + D    -106.65      0.87
                                  T + D        -106.75      0.66
                                  D            -107.11      0.39
                                  1            -108.99      0.05
b             order of contact    T*S + D      -161.59
                                  T*S          -161.60      0.90
                                  T + S        -162.96      0.26
                                  T            -163.09      0.61
                                  1            -163.74      0.52
              time to first       T*S + D      -170.80
              contact             T*S          -171.10      0.44
                                  T + S        -173.20      0.12
                                  T            -174.01      0.20
                                  1            -175.52      0.22
c             order of contact    T + D         -23.23
                                  T             -23.37      0.59
                                  1             -23.65      0.75
              time to first       T + D        -117.53
              contact             T            -117.76      0.49
                                  1            -118.75      0.37

TABLE 2.--Model coefficients and 95% confidence intervals for the
three captive experiments  comparing armadillo interest in (a) cracked
versus intact northern bobwhite quail eggs, (b) control soil
(control) versus soil and egg shells from gopher tortoise nests (eggs)
versus soil from tortoise nests with  no egg shells (nest), (c)
domestic chicken eggs (chicken) versus bobwhite quail eggs (quail)
versus  gopher tortoise eggs (tortoise). Armadillo interest is
measured by order of contact and time elapsed to  first contact.
Independent variables listed are those that were significant after
model reduction; distance  from the pen entrance to the test material,
and testing materials

Experiment       Metric        Variable    Coefficient       95% CI

a            Order of          Cracked         1.28        0.59, 1.98
             contact           Intact          1.60        0.90, 2.30
                               Distance        0.20        0.02, 0.38
             Time to first     Cracked         6.08        3.38, 9.56
             contact           Intact          7.19       4.22, 10.94
                               Distance        0.03        0.00, 0.12
b            Order of          Control         3.90        2.99, 4.82
             contact           Eggs            3.27        2.36, 4.19
                               Nest            3.85        2.94, 4.77
             Time to first     Control         2.46        1.10, 5.52
             contact           Eggs            1.84        0.82, 4.11
                               Nest            2.70        1.20, 6.05
c            Order of          Chicken         2.05        1.43, 2.66
             contact           Tortoise        1.89        1.28, 2.50
                               Quail           2.05        1.44, 2.66
             Time to first     Chicken        19.72       9.71, 33.24
             contact           Tortoise       14.98       6.48, 27.00
                               Quail          20.47       10.24, 34.21

TABLE 3.--Primacy visitors to three types of artificial quail nests: 6
whole eggs (whole), 6 cracked eggs  (cracked), 6 cracked eggs
sprinkled with raccoon urine (urine), as recorded by trail cameras in
North  Florida during 2009. Other primary visitors included a black
bear, bobcat, crow, and gopher tortoises


Treatment   Location    armadillo   opossum   raccoon   rodent

cracked     magnolia        1
            main                                 1        1
            NFREC                      1         1        1
            office                               2
urine       magnolia        1          2         3
            main                                          2
            NREC                       1
            office                     2         2
whole       magnolia        1                    1
            NFREC                                1
            office                     1
Total                     3(4%)      7(9%)    11(14%)   4(5%)


Treatment   Location    other   unknown    none

cracked     magnolia               1         3
            main                   1         2
            NFREC                  4         2
            office                 2         3
urine       magnolia
            main          1                  2
            NREC          1        2         3
            office                 5
whole       magnolia                         3
            main          1                  3
            NFREC         1                  5
            office                           8
Total                   4(5%)   15(19%)   34(44%)

TABLE. 4.--Egg depredation at artificial quail nests in North Florida
during 2009, listed according to primary nest visitor. Total
depredation excludes nests where no eggs were consumed. Significant
visitors are indicated by; (P = 0.02)

Visitor      None   Partial     Complete       Total

armadillo     1                    2           2 (5%)
bear                               1           1 (2%)
bobcat                             1           1 (2%)
crow                   1                       1 (2%)
opossum                1           6           7 (17%)
raccoon                1          10          11 (26%) *
rodent                 2           2           4 (10%)
tortoise      1                                0 (0%)
unknown                7           8          15 (36%) *
Total         2       12          30          42
COPYRIGHT 2013 University of Notre Dame, Department of Biological Sciences
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2013 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Degroote, Lucas W.; Ober, Holly K.; McDonough, Colleen M.; Mizell, Russell F., III
Publication:The American Midland Naturalist
Article Type:Report
Geographic Code:1U5FL
Date:Jan 1, 2013
Previous Article:Foraging response of Erethizon dorsatum and Lepus americanus to specialized and generalized predator scents.
Next Article:Habitat use by the alligator snapping turtle (Macrochelys temminckii) and eastern snapping turtle (Chelydra serpentina) in Southeastern Missouri.

Terms of use | Privacy policy | Copyright © 2019 Farlex, Inc. | Feedback | For webmasters