Effects of resource dispersion and site familiarity on movements of translocated wild turkeys on fragmented landscapes
Highlights
► We tested the site familiarity and resource dispersion hypotheses on wild turkeys. ► We monitored movements of 130 translocated turkeys using radio telemetry. ► Home ranges of turkeys increased with increasing habitat fragmentation. ► We did not find evidence supporting site familiarity hypothesis.
Introduction
Fitness advantages of an animal may increase as its site familiarity increases. Site familiarity helps animals to avoid predators and consequently enhances survival (Clarke et al., 1993). For instance, occupying an unfamiliar area can lead to increased predation in ruffed grouse (Bonsana umbellus; Yoder et al., 2004). Also, eastern chipmunks (Tamias striatus) in familiar locations took less time to escape predators than did those in unfamiliar locations (Clarke et al., 1993). Additional to decreased predation risk, migratory birds having high site familiarity often increase reproductive success with nest site philopatry (Péron et al., 2010, Piper et al., 2008, Ward and Weatherhead, 2005). Moreover, site familiarity facilitates formation of social groups in birds (Snell-Rood and Cristol, 2005) and may help new group members with less familiarity to escape predators and acquire resources (Péron et al., 2010). Therefore, site familiarity may have fitness consequences through influencing habitat use and movements of animals.
Anthropogenic disturbances have greatly fragmented animal habitats, resulting in loss of habitat and increasing dispersion or patchiness of food and other resources (Fleishman and Mac Nally, 2007). The resource dispersion hypothesis (RDH) predicts that increased dispersion of resources in fragmented habitat would increase home ranges of birds and mammals (Johnson et al., 2002, Macdonald, 1983). For instance, increased dispersion of acacia trees (Acacia spp.) increases territory sizes and movements of white-throated magpie-jays (Calocitta formosa) to acquire sufficient resources (Langen and Vehrencamp, 1998). Furthermore, habitat fragmentation increases risk of predation in eastern wild turkeys (Meleagris gallapovo silvestris, hereafter wild turkey) (Thogmartin and Schaeffer, 2000). However, it is unknown if increased predation of wild turkeys results from increased movements in fragmented habitats.
Habitat fragmentation and loss have become one of the main causes of population declines and extinctions of endangered or threatened species (Fleishman and Mac Nally, 2007). Translocation is an important approach to restore endangered and threatened species (Wolf et al., 1996). However, translocation inherently introduces animals to unfamiliar environments. Translocated noisy miners (Manorina melanocephala) and African elephants (Loxodonta africana) showed increased movement and exploration in unfamiliar habitats (Clarke and Schedvin, 1997, Pinter-Wollman, 2009). Animals relocated from their home ranges probably experience increased exposure to predation (Jacquot and Solomon, 1997). Survival of translocated animals to reproduction is important to establish and sustain translocated populations. Therefore, understanding effects of site familiarity on movements and home ranges of translocated birds in fragmented habitat is important to planning the restoration of avian species.
Wild turkeys, the largest galliform in North America, exhibit nest site and habitat fidelity (Badyaev and Faust, 1996, Miller et al., 2001). Wild turkeys are very mobile and require mature forests as habitat (Dickson, 2001, Miller et al., 1999, Porter, 1992). Wild turkey populations suffered from precipitous declines in the late 1800s through the early 1900s due to overharvesting and habitat loss throughout their range (Dickson, 2001). Wild turkeys were restored throughout their range, including the southern United States (the South), with wild turkeys translocated from remnant wild turkey populations in the 1950s–1970s (Dickson, 2001). These restorations increased sizes of wild turkey populations in the South to over 2 million birds in 1999 from an estimated 200,000 birds in 1959 (Dickson, 2001). Success of wild turkey restorations may indicate the great ability of wild turkeys to cope with unfamiliar environments. However, few studies have investigated effects of site familiarity and resource dispersion on movements and home ranges of translocated wild turkeys in fragmented habitat. Therefore, we tested: (1) the site familiarity hypothesis that increased site familiarity after release would reduce home ranges and decrease movements of translocated wild turkeys (Clarke et al., 1993, Heidinger et al., 2009) and (2) the resource dispersion hypothesis that more dispersed resources in fragmented landscapes would result in larger home ranges of wild turkeys. Alternatively, wild turkeys may increase home ranges to augment resource availability or energy acquisition, i.e. habitat productivity hypothesis (McNab, 1963). We predicted that home range size of wild turkeys was related positively to within home range plant biomass. We also predicted that newly translocated wild turkeys that joined social groups of existing wild turkeys would benefit from the site familiarity of the existing wild turkeys and exhibit similar movements (Péron et al., 2010, Snell-Rood and Cristol, 2005). Studies of responses of translocated wild turkeys to unfamiliar, fragmented habitat not only advance understanding of the adaption of mobile avian species to new environments, but also provide information to guide habitat management for restoring species. Therefore, our findings of effects of unfamiliar environments and habitat fragmentation on movements of translocated wild turkeys provided insight into the future restoration of endangered and threatened avian species.
Section snippets
Study sites
We conducted our study at 2 sites (hereafter north and south sites) about 17 km apart in the Mississippi Alluvial Valley in Quitman County, MS, USA. Wild turkeys were once abundant throughout our study region but were nearly extirpated as bottomland hardwood forests were converted to agriculture (Leopold, 1929). Recent reforestation implemented through Wetland Reserve Program and Conservation Reserve Program since 1985 may provide potential habitat for wild turkeys (King and Keeland, 1999,
Results
Populations of translocated wild turkeys peaked at 39 and 32 birds at the north and south sites, respectively, in March 2009 and 35 and 36 birds at the north and south sites, respectively, during spring 2010. Overall, we radio-tracked 130 turkeys for 9542 radio-track days and obtained 10,238 locations to compute movement distances and home ranges by site, season, and gender.
Discussion
We found no evidence supporting the site familiarity hypothesis for translocated wild turkeys. Movement distances and home range sizes were similar between birds released in 2009 and 2010, as was mean daily distance moved among birds that died and lived during the 2 months post-release in 2010. In contrast, we found evidence supporting the resource dispersion hypothesis (RDH) with turkeys at the more fragmented south site having greater movements and larger home ranges than wild turkeys at the
Conclusions
Our data supports the resource dispersion hypothesis that wild turkeys use larger home ranges and move longer distances in more fragmented habitat, but did not support the site familiarity hypothesis for movements and home ranges of wild turkeys translocated to highly fragmented habitat. Additionally, home range sizes of wild turkeys were related positively to CV in the NDVI and total NDVI within individual home ranges of wild turkeys. Resource heterogeneity may increase movements and home
Acknowledgements
We thank R. Hardman, M. McKinney, H. Cooper, D. Ohlrich, J. Rodgers, E. Wengert, and B. Winter for assistance with field work. Drs. D.A. Miller and B.D. Leopold read an early draft of our manuscript and made helpful comments. We are grateful to anonymous reviewers for their helpful comments on our manuscript. Mississippi Department of Wildlife, Fisheries, and Parks (MDWFP) conducted turkey captures and translocations and provided field housing for this study. We are grateful to R.A. Carson, Jr.
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