Ontogenetic and seasonal shifts in movement and habitat selection of the alligator snapping turtle (Macrochelys temminckii)

Abstract

We aimed to discern the seasonal movement patterns, home range sizes, and microhabitat associations of subadult Macrochelys temminckii in a West Tennessee population. Because this population was previously monitored (i.e., telemetry and habitat use) as juveniles after the initial release in 2005, studying the movement ecology and habitat use of the same released cohort 12 years later allows for unique comparisons between hatchling and subadult ecology. We used radio telemetry to collect movement and microhabitat data of 16 subadult M. temminckii during one year. Our results suggest that seasonal and ontogenetic variation in movement patterns and habitat selection occur within a cohort of M. temminckii. Compared to juveniles, subadults used deep slough areas with high overstory tree cover and had larger home ranges (100% minimum convex polygons [MCP]). Additionally, as subadults, the mean distance moved (m) varied among seasons and furthest during summer. Subadults used deeper water, with higher temperatures and significantly more tree canopy cover, than random locations. Overall, the home range estimate for subadults (mean MCP ± SE; 1.64 ± 0.57 ha) was greater than for juveniles (0.044 ± 0.021 ha). These home-range estimates and habitat usage patterns were similar to subadults in other studies. The seasonal and ontogenetic variations suggest that habitat heterogeneity is critical to sustain populations of introduced M. temminckii.

Home Range and Habitat Use of Translocated Alligator Snapping Turtles (Macrochelys temminckii) in an Extensive River System

“…Vol. 22, Special Issue 12 confiscated adults and captive-reared juveniles and subadults (Hyder et al 2021, Kessler 2020, Moore et al 2014. Our findings indicate the Alligator Snapping Turtle is more of a habitat generalist than previously thought and will use a diversity of both lotic and lentic aquatic habitat types, as long as they provide an abundance of emergent and submerged structures, overhead canopy cover, and suitable water depth profiles.…”

“…The success of translocations depends on several factors, such as understanding the ecological requirements of the species and eliminating the original cause of the species decline; a well-planned monitoring program to assess success will help researchers collect information to adapt and improve management moving forward (Dodd and Seigel 1991, Fischer and Lindenmayer 2000, Germano and Bishop 2009, Griffith et al 1989). The long-term measure of success for translocations that are designed to augment or supplement existing low-density populations is the production of stable populations with low extinction risk in the future (Bubac et al 2019, Germano and Bishop 2009, Hyder et al 2021). For long-lived species with low population-growth rates, such a goal may take decades of difficult research effort to assess.…”

“…However, that study was conducted in a small, man-made impoundment (4.4 ha, 5.7-km channel) separated from the main river channel, and thus movements and home-range sizes may have been limited due to lack of access to linear river channels and further habitat (Moore et al 2014). Since Alligator Snapping Turtles typically move widely between preferred core sites along the linear corridor provided by river channels (Harrel et al 1996, Hyder et al 2021, Moore et al 2014, Riedle et al 2006, Sloan and Taylor 1987), and no published study has yet evaluated whether translocation for this species would be effective in an open, expansive river that might pose significant challenges for translocated turtles to successfully find each other and reproduce.…”

Big Turtles Start Small: Trapping Juvenile Alligator Snapping Turtles in South Mississippi and Implications for Conservation

“…Spangler et al (2021) used radio telemetry to track hatchling Alligator Snapping Turtles in southeastern Oklahoma, and they found that hatchlings settled in shallow water areas with abundant cover after a short dispersal period. Hyder et al (2021) investigated ontogenetic shifts in habitat use in a juvenile cohort of reintroduced Alligator Snapping Turtles in western Tennessee. Compared to data collected when the juveniles were first released, these turtles were utilizing deeper habitats and had larger home ranges as subadults.…”

A Standardized Field Method and Habitat Suitability Model to Assess Reintroduction Sites for Alligator Snapping Turtles

“…In response to the decline and disappearance of many Alligator Snapping Turtle populations in Oklahoma, a head-start program was established at Tishomingo National Fish Hatchery in 2000 with the goal of restoring populations in rivers and other suitable wetlands where the species has been extirpated and to supplement small populations that are unlikely to persist without intervention. Head-started juvenile turtles produced from the program and similar programs have been released in Oklahoma (Anthony et al 2015, Moore et al 2013), Illinois (Dreslik et al 2017), Louisiana (Dreslik et al 2017, Glorioso et al 2020), and Tennessee (Hyder et al 2021, Ream 2008).…”