Spatial ecology of the giant armadillo Priodontes maximus in Midwestern Brazil

Abstract

The giant armadillo (Priodontes maximus) is the largest living armadillo. This naturally rare and poorly known species is endemic to South America and classified as “Vulnerable” by the IUCN. Here we explored aspects of the spatial ecology of P. maximus in Midwestern Brazil to gain insights on its ecology and biology to support conservation efforts. In 8 years, we identified 50 individuals of P. maximus and monitored 23 of them using telemetry methods. To characterize site fidelity and home range, we fitted individual continuous-time movement models and estimated Autocorrelated Kernel Density Estimates. We built a Structural Equation Model to evaluate how home-range area and daily displacement are related to each other, to sampling effort, and to individual characteristics. We estimated home-range overlap between pairs of different sexes using a bias-corrected Bhattacharyya coefficient. Finally, we formulated a canonical density estimation formula to characterize minimum population density. We gathered a total of 12,168 locations of P. maximus. The best-fitted movement models indicated site fidelity for all individuals and a median adult home-range area of 2,518 ha. Median adult daily displacement was 1,651 m. Home-range area scales positively with daily displacement and daily displacement scales positively with body mass. Median home-range overlap between pairs was low (4%) and adult females presented exclusive home ranges among themselves. Median minimum density was 7.65 individuals per 100 km2 (CI = 5.68–10.19 ind/100 km2). Our results are congruent with characterizing P. maximus as a generally asocial species, most likely promiscuous/polygynous, that establishes large, long-term home ranges, which grants the population a naturally low density. Spatial patterns and biological characteristics obtained in this study can be used to guide future conservation strategies for P. maximus in the Pantanal wetlands and elsewhere.

Highways are a threat for giant armadillos that underpasses can mitigate

“…This species occurs mainly in cis‐Andean South America (Figure 1) (Abba & Superina, 2010; Meritt, 2006). Giant armadillos are notoriously rare, have large exclusive home ranges and population densities are low (Noss, Pena & Rumiz, 2004; Silveira et al, 2009; Desbiez, Massocato, Kluyber, Oliveira‐Santos & Attias, 2020). Desbiez, Massocato, and Kluyber (2019) report that giant armadillos only have one offspring at a time, prolonged parental care and inter‐birth rates of up to three years.…”

“…Median adult daily displacement for giant armadillos ranges from 3.7 km in Bolivia (Noss et al, 2004) to 1.6–1.8 km in the Pantanal and Cerrado of Brazil (Silveira et al, 2009; Desbiez et al, 2019). In the pristine Pantanal, median adult home range estimate for giant armadillos was 2.518 ha (Desbiez et al, 2020). The large highway network that cuts the Atlantic Forest, Amazon, Cerrado and Pantanal (Fernandes et al, 2018), with increasing volumes of traffic, is increasing the effects of habitat fragmentation on giant armadillos.…”

“…The distance between the underpasses used by the animal on the BR‐101 was 1.4 km. This is a short distance relative to the area covered by an individual of this species (Desbiez et al, 2020). These records suggest that the structures may enable both sides of a highway to be part of the home range of one individual.…”

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“…Despite a wide distribution throughout South America, P. maximus is always rare (Meritt, 2006). In addition to low densities, the species is solitary, nocturnal and has fossorial habits, making it particularly difficult to capture and study in the wild (Desbiez et al, 2019c). For this reason, camera traps have always been a very important tool in P. maximus research (Leite-Pitman et al, 2004;Noss et al, 2004;Silveira et al, 2009;Porfirio et al, 2012;Desbiez & Kluyber, 2013;Aya-Cuero et al, 2015, 2017Quiroga et al, 2017;Esteves et al, 2018;Desbiez et al, 2019a, c).…”

“…The authors describe using "the dividing line between dark and light scales on the carapace and on the hind legs" as well as "the number of light scales per row from the lower edge of the carapace up to the dividing line" (Noss et al, 2004:47) to identify individuals. All later researchers using individual identification of P. maximus cite this publication, sometimes adding another identifying characteristic such as scars (Aya-Cuero et al, 2017) or the scales on the tail (Desbiez et al, 2019c). The purpose of this study is to clearly present and illustrate the different individual identification patterns that can be used in camera trap research to distinguish individual P. maximus as well as to assess their reproductive status and age class.…”