DOI: 10.5061/dryad.280gb5mpk
title: Home-site fidelity and homing behavior of the big-headed turtle Platysternon megacephalum

description: Site fidelity refers to the restriction of dispersal distance of an animal
 and its tendency to return to a stationary site. To our knowledge, the
 homing ability of freshwater turtles and their fidelity is reportedly very
 low in Asia. We examined mark-recapture data spanning a 4-year period in
 Diaoluoshan National Nature Reserve, Hainan Province, China, to
 investigate the site ﬁdelity and homing behavior of big-headed turtles
 Platysternon megacephalum. A total of 11 big-headed turtles were captured,
 and all individuals were used in this mark-recapture study. The site
 fidelity results showed that the adult big-headed turtles (n = 4) had a
 71.43% recapture rate in the original site after their release at the same
 site, whereas the juveniles (n = 1) showed lower recapture rates (0%).
 Moreover, the homing behavior results showed that the adults (n = 5) had
 an 83.33% homing rate after displacement. Adult big-headed turtles were
 able to return to their initial capture sites (home) from 150–2400 m away
 and precisely to their home sites from either upstream or downstream of
 their capture sites or even from other streams. However, none of the
 juveniles (n = 4) returned home, despite only being displaced 25–150 m
 away. These results indicated that the adult big-headed turtles showed
 high fidelity to their home site and strong homing ability. In contrast,
 the juvenile turtles may show an opposite trend but further research is
 needed.
description: Field studies were
 conducted in the Diaoluoshan National Nature Reserve, Hainan Province,
 China, within an altitude range of 500–1050 m a.s.l. from 2015−2019
 (except 2017). Population density of the big-headed turtle was 1.65
 individuals per km in our study area, and they have been less affected by
 hunting in recent years under the strict management of the nature reserve
 (Xiao et al. 2021). Long cylindrical nylon cages (length: 60 cm, diameter:
 33 cm; baited with dried fish) were arranged along the stream at an
 interval of ~30 m. The traps were set for a total of 3 days and checked
 every morning. After capture, the carapace length of each individual was
 recorded, and their sex and age group were determined. Females and males
 with mean carapace lengths of more than 100 mm and 130 mm, respectively,
 were regarded as adults (Sung et al. 2015a). For identification, captured
 turtles were uniquely marked on their marginal scutes, with care to avoid
 injury. Marked individuals were released at their capture sites (original
 or home sites) or a translocation site for the site fidelity experiment
 and then recaptured at their original site or release site throughout the
 year, as well as during subsequent years. Translocation sites were not
 randomly chosen; they were, instead, the original sites of another turtle
 (Figure 2) under two presumptions: 1) that different individuals of the
 same species would prefer similar habitats, and 2) that the habitats of
 the translocation sites would be similar in habitat types and
 characteristics of the original sites. We calculated the recapture rate as
 the ratio of the times the turtles were recaptured in the original sites
 and the total time of recapture. This recapture rate was used as an
 indicator of site fidelity, where a high recapture rate in the original
 site would indicate a high site fidelity. In the homing behavior
 experiment, the recapture rate in the original site was used as the homing
 rate. In addition, the geographic coordinates of the original and
 translocation sites were determined using a hand-held global positioning
 system unit and the trajectory distance along the streams to represent the
 distance between the original and translocation sites. For adults, the
 translocation sites were 150–2400 m away (except 35 m for one individual),
 which is beyond an adult home range distance (97 m; Sung et al. 2015b),
 whereas juveniles were released 25−150 m away. At the end of the
 experiment, all cages were removed to avoid harming the local wildlife,
 and all recaptured individuals were released at their original
 sites.