Herpetology Notes, volume 14: 785-789 (2021) (published online on 18 May 2021) Home-range size and activity of the Red-footed Tortoise, Chelonoidis carbonarius (Spix, 1824) in a Brazilian coastal shrub area Patrícia Sayuri Shibuya1, Marcos Adriano Tortato¹, and Luiz Gustavo Rodrigues Oliveira Santos1,* Abstract. Animal movement studies may provide information for species management. Here, we studied a population of Chelonoidis carbonarius in a natural environment using GPS devices. We tracked five individuals (one female and four males) in 2014 and the average home range size was 1.57 ± 1.15 ha, ranging from 0.29 ha to 3.09 ha. The individuals were active throughout the day, with no peak-activity. Keywords. red-footed tortoise, movement, Testudinidae. Introduction 2009; Noss et al., 2013). A review by Slavenko et al. (2016) showed that the home range of chelonians was Understanding animal movement patterns are essential not influenced by the sex and social structure. Only to shed light on several ecological processes related to body mass exerted some influence, however it explains an individual’s spatial requirements (Mace and Harvey, relatively little of the variation in home range size. 1983; Loehle, 1990). These studies are important because As tortoises are ectothermic they rely on environmental they can provide supporting information for species heat sources for their body temperature and this conservation and management actions (Türkozan et al., dependence may restrict their movements and daily 2018). Home range, as defined by Burt (1943), is the activities (Porter et al., 1973, Falcón et al., 2018). Most area covered by an individual during its normal activities tortoises are diurnal and their peak activity usually such as food gathering, mating, and caring for juveniles. occurs during the early morning and late afternoon (Rose Thenceforth, researchers are trying to understand which and Judd, 1975; Douglass and Layne, 1978; Lambert, factors determine an animal’s home range size and shape 1981; Mazzotti et al., 2002; McMaster and Downs, (Powell, 2000). Several factors may influence the home 2013). Some tortoises become inactive or lower their range size of an animal, such as age (Kleeberger and movements on hot days due to the risk of overheating Werner, 1982; Davis and Ford, 1983), sex (Brown and (Hailey et al., 1984, Hailey and Coulson 1996), but Orians, 1970; Barret, 1990), body size (Slavenko et al., daily activity rhythm is also highly variable between 2016), habitat quality (Simon, 1975; Ruby and Dunham, seasons (Geffen and Mendelssohn 1989; Mazzotti et al., 1987), season (Geffen and Mendelssohn, 1988; Brito, 2002; Rouag et al., 2017) 2003), and population density (Alberts, 1993). Tortoises are reported to have defined home ranges Study species.—Chelonoidis carbonarius (Spix, 1824) and one of the factors that might influence the size of is a medium-sized tortoise that ranges from south-eastern their home ranges is the season, since some species have Panama to Venezuela, Guyana, Suriname, Colombia, smaller home ranges during winter, when they are less Ecuador, Peru, Bolivia, Argentina and Brazil (Rhodin et active (Eubanks et al., 2003; McMaster and Downs, al., 2017). This species is omnivorous and is influenced by the seasonal availability of food, consuming parts of plants such as flowers, fruits and leaves, invertebrates, vertebrates and fungi (Moskovits and Bjorndal, 1990; 1 Instituto de Biociências, Universidade Federal de Mato Grosso Jerozolimski et al., 2009; Wang et al., 2011). Females are do Sul, Rua UFMS, S/n - Cidade Universitária, Campo more active than males throughout the year, especially Grande - MS, 79070-900, Brazil. during the non-breeding or nesting season (Moskovits * Corresponding author. E-mail: [email protected] and Kiester, 1987). Furthermore, C. carbonarius is © 2021 by Herpetology Notes. Open Access by CC BY-NC-ND 4.0. more active during daylight, with a small increase in 786 Patrícia Sayuri Shibuya et al. the afternoon, especially in the rainy season (Noss et al., 2013). Here, for the first time, we deployed GPS devices on five Red-footed tortoises (Chelonoidis carbonarius) to provide descriptive information about home range size and activity of tortoises in a coastal shrub area in southern Brazil. Material and methods Study Site. We conducted the study in a coastal area within Serra do Tabuleiro State Park located in southern Brazil (27°52’27” S, 48°49’26” O). This Park is inserted in the Atlantic Forest ecosystem and has several phytophysiognomies: ombrophilous forests, highlands, mangroves and coastal salt shrubs (IMA, 2019). We carried out the study in a coastal shrub area which is composed of sandy coastal strips covered by herbaceous and arbustive-arboreal vegetation (Suguio and Tessler, 1984; Araújo, 1992). Capture procedure and radio-tracking. In 2014 we captured tortoises through diurnal active searching. Once an individual was found, we weighed, sexed and identified it with epoxy numbers attached to its carapace. Sex was determined based on external characteristics (e.g. concavity of plastron and longer tails in males). All tortoises received unique-frequency GPS transmitters (Modified i-gotU® G120 GPS logger). Each transmitter weighed less than 3% of the tortoise’s body mass and was fixed to the tortoise’s carapace using epoxy glue. GPS transmitters were setup to record relocations every five minutes. Home-range estimation and activity. We used the package “adehabitatHR” (Calenge, 2006) to estimate home range size, using the 95% fixed kernel density estimator (KDE) method and 95% Minimum Convex Polygon (MCP). The activity pattern was calculated using the median of distance moved at each hour during all days of the monitoring period (June – October 2014). Results We captured five adult animals: four males and one female. Body masses ranged from 3.51 kg to 4.80 kg (mean = 4.16 ± 0.52). The mean home range was 1.57 ± Figure 1. Home range, cumulative home range size and 1.15 ha: the largest and smallest estimated home ranges activity pattern of four male and one female adult Chelonoidis carbonarius in a coastal shrub area of southern Brazil. a) were both for males (3.09 ha and 0.29 ha, respectively) individual home ranges; b) cumulative home range; c) (Fig. 1A) (Tab. 1). Some home ranges have not activity; Dotted line: individual’s median of distance moved; stabilized yet which may lead to an underestimation of continuous line: population’s median of distance moved. home range size (Fig. 1B). Individuals showed uniform Home-range size and activity of the Red-footed Tortoise in Brazil 787 activities throughout the day (Fig. 1C), with no clear The tortoises monitored in our study did not follow activity peaks. the same activity patterns found in other studies, in which individuals were more active during the daylight Discussion throughout the year (Lambert, 1981; Mazzotti et al., 2002; McMaster and Downs, 2013; Rouag et al., 2017). Home range size estimated in our study (1.57± 1.15 ha) Although some studies showed some variations between was much smaller than other home range sizes reported sexes or seasons (Lambert, 1981; Mazzotti et al., 2002; in the literature: cocoa plantation (5.60±2.11 ha) (Borini McMaster and Downs, 2013; Rouag et al., 2017), they et al., 2014), Amazon (26.30±31.06 ha) (Moskovits do not apply to the results found in our study, since we and Kiester, 1987) and Chaco (124.47±177.18 ha) didn’t find the peak-activity of individuals. (Montaño et al., 2013). One of the factors that might One factor that can lead to a change in daily pattern have contributed to the variation in home range sizes activity is human disturbance. The home ranges of our found in these studies compared to ours is the shorter study animals are close to the park headquarters, which monitoring time. In this study we monitored animals for is also very close to the city of Palhoça, state of Santa an average of 66 days, compared to the other studies (12 Catarina, Brazil. Some studies revealed the effect of months and 10 months) (Montaño et al., 2013; Borini humans on wildlife activity, which some species alter et al., 2014), with one exception (51 days in Moskovits daily activity and are becoming more nocturnal to avoid and Kiester, 1987). The shorter monitoring time may human disturbance (van Doormaal et al., 2015; Gaynor reflect an underestimation of home range size, because et al., 2018). Another reason possible explanation we can the areas may not have (Seaman et al., 1999; Girard et take into consideration is that the study site is not within al., 2002; Boyle et al., 2009). the original distribution range of the species (Rhodin et Although Moskovits and Kiester (1987) monitored al., 2017). This can lead to behavioural differences in individuals for an average of 51 days, specimens from the use of space (Frantzen et al., 2001; Nussear et al., there had larger home ranges. This could mean that the 2012), since temperature ranges and food availability animals in our study move less, and one of the factors are different, animal foraging strategies could change may be the environment. The coastal shrub vegetation is (Nagy and Medica, 1986; Peterson, 1996). strongly influenced by topography, which can have very This is the first study to use GPS transmitters to narrow (4 m) bands of elevations (sandy cords) and bands estimate home range size of the Red-footed tortoise. of depressions (inter-cords) (Araújo, 1992). Inter-coords Through the use of GPS, it is possible to obtain a large areas are subject to flooding, remaining flooded for at number of accurate locations per individual without least 6 months a year. Flooded areas might decrease the weather constraints (can be taken independently of area available for foraging (Crawshaw, 1991), leading season, weather, time of day) (Rodgers et al., 1996; to smaller home ranges than non-floodable areas (Bravo Dussault et al., 2000).