Influence of body size, topography, food availability and tree-fall gaps on space use by yellow-footed tortoises (Chelonoidis denticulatus) in Central Amazonia

Abstract

Habitat selection and extension of the area used by a given species may vary during different phases of its life and are often determined by the distribution and availability of resources throughout the landscape, such as food, breeding sites, and shelters. In this study, we assessed the influence of body size on the areas used by 21 individuals of the yellow-footed tortoises ( Chelonoidis denticulatus ) from January to June 2017 in a dense rain forest area in Central Amazonia. We also investigated whether individuals selected different ranges of terrain slope, elevation, areas with high food availability, or areas with treefall gaps that could be used for shelter or thermoregulation. We monitored tortoise movements using thread-bobbins, and sampled terrain characteristics, availability of potential food resources and forest gaps along the routes used by the tortoises. We also measured the same variables in plots distributed systematically throughout the study area to evaluate resource availability. Tortoises used an average area of 1.56 ha (SD = 1.51, min = 0.03, max = 6.44). The size of the area used was positively associated with the individual body size, but did not vary between sexes. Small individuals selected higher and flatter areas where the availability of fallen flowers was higher, whereas the area used by larger individuals did not differ from the natural availability of topographic traits and food in the region. Although tortoises did not select areas according to availability of tree-fall gaps, most larger tortoises were found sheltered under fallen trees (85%). Conversely, small individuals were mainly found hidden under litter (66%). Body size determined the patterns of landscape use by tortoises; larger individuals were mainly generalists, but small individuals occupied high and flat areas. The yellow-footed tortoise is endangered by hunting, illegal collection for the pet trade, habitat destruction and effects of climate change. Size-related differences in habitat selection should be taken into account in species-distribution models for the identification of suitable areas for reintroduction and the development of management plans in protected areas.

Adapting a Traditional Hunting Technique to Improve Capture Rates for the Endangered Yellow-Footed Tortoise (Chelonoidis denticulatus) during Ecological Surveys in Amazonia

“…The trap features were also designed for preventing possible injuries in the captured tortoises. As we observed, the subsequent behavior after capturing was similar between tortoises caught by trap and by active search in Tavares et al (2019). However, we highlight that the use of fish as bait may pose an impact on fish populations.…”

“…The end of the dry season coincides with the beginning of the fructification period in white flooded forests (Freitas et al 2003; Paim et al 2017), and fruits are the main component in the yellow-footed tortoise diet (Guzmán and Stevenson 2008; Jerozolimski et al 2009; Moskovits and Bjorndal 1990; Sobral-Souza et al 2017; Strong and Fragoso 2006), hindering the attraction of the baits. In upland forests, although Tavares et al (2019) did not find an influence of the fruit availability in the tortoise displacement within the wet season, Stevenson et al (2007) found that the peak of tortoise activity coincided to the season with higher fruit availability. The activity pattern may be an important factor influencing the efficiency for both trap and active search, and it is relevant to consider this when establishing the capture period to maximize the number of detections.…”

“…The research assistants participating in this study were local hunters specialized in hunting tortoises, and the same research assistants sampled the wet and dry seasons and built the traps for each site. Considering the species average home range of 0.8 km 2 (Tavares et al 2019), all sites were at least 1 km apart to guarantee independence between samples. We measured the maximum straight-line length (CL) of the carapace of all captured individuals and sexed individuals with CL > 250 mm.…”

“…We measured the maximum straight-line length (CL) of the carapace of all captured individuals and sexed individuals with CL > 250 mm. Individuals with CL ≤ 250 mm were considered as juveniles and were not sexed due to the absence of external morphological dimorphism (Rueda-Almonacid et al 2007; Tavares et al 2019). The study was approved by the Instituto Chico Mendes de Conservação da Biodiversidade (License SISBIO no.…”

Widespread Use of Traditional Techniques by Local People for Hunting the Yellow-Footed Tortoise (Chelonoidis denticulatus) Across the Amazon

“…Although there has been reported a generational erosion regarding TEK in the Amazon (e.g., loss of ethnobotanical knowledge, Reyes-García et al 2013), we did not find evidence of a change in TEK associated with tortoise hunting between generations in the studied localities. The techniques recorded require an understanding of tortoise distribution in the forest with regards to slope, elevation, and shelter (Tavares et al 2019), tortoise feeding behavior, or the location and phenology of specific fruiting trees attractive to tortoises (Wang et al 2011). However, all this TEK related to hunting techniques is not static, and future losses may still happen due to unpredictable environmental, social, and economic pressures to which local inhabitants are, and will be, continuously exposed (Álvarez 1997; Berkes 2008; Menzies and Butler 2010).…”