Factors influencing the space use of a nonhunted population of eastern wild turkeys

Abstract

Wild turkeys (Meleagris gallopavo) have been an economically and culturally important game species in North America for many decades. Recent declines in abundance and productivity in several populations of wild turkeys, have caused widespread concern among researchers and managers. After near extinction in the early 1900's followed by successful restoration efforts in the late 1900's, researchers are focused on preventing populations of wild turkeys from declining again. Male wild turkeys are the only game bird in the contiguous United States hunted during their reproductive season, however, there are many aspects of male reproductive ecology that are not well understand. Because male wild turkeys use a polygynous-promiscuous mating system and do not participate in nesting or brood-rearing, wild turkey research has mostly focused on female reproductive ecology, leading to a gap in knowledge regarding male reproductive behaviors. Because hunting pressure can affect the spring behaviors of wild turkeys, it is critical to conduct research on male wild turkey reproductive behaviors in a nonhunted population. Because most populations of wild turkeys are hunted in the United States, the opportunity to study nonhunted populations is rare. In this study, I tracked the movements of 19 male eastern wild turkeys (Meleagris gallopavo silvestris) during the spring mating and summer non-mating seasons of 2020 and 2021 on the Savannah River Site near Aiken, South Carolina, in order to assess seasonal space use of male wild turkeys in a nonhunted population. In addition, I looked for evidence of cooperative courtship and kin selection operating in this population. I used dynamic Brownian Bridge Movement Models to estimate daily and seasonal ranges. Median daily mating season ranges of 100 percent of males were larger than median daily non-mating season ranges, and 83 percent of males had larger mating season ranges than non-mating season ranges. Linear mixed effects models showed season to be an important predictor of both daily range size and distance between consecutive nightly roost location. Only one male exhibited temporal autocorrelation in daily range size during the mating season. While 33 percent of males exhibited temporal autocorrelation in the size of daily non-mating season ranges, all but one had [less than or equal to] 2 significantly autocorrelated days. Males did not exhibit observable differences between seasons in the intensity of aggregation of daily locations compared to seasonal locations, and there was significant daily variation in both seasons. The lack of temporal autocorrelation and variation in daily aggregation intensity in both seasons indicates that male wild turkeys may not use space within their seasonal ranges differently between mating and non-mating seasons. I conducted a proximity analysis and calculated relatedness of male dyads to determine if there was evidence of cooperative courtship and kin selection operating in this population. I identified six pairs of first-order relatives (full siblings or parent-offspring), three pairs which were trapped together and three which were trapped separately. While I only had GPS data for two pairs of first-order relatives, they exhibited opposite behaviors. One pair traveled together throughout the study period and one pair never traveled together, indicating that cooperative courtship via kin selection may not be an obligate behavior for wild turkeys on the Savannah River Site. Additionally, one unrelated pair stayed together throughout the breeding season, indicating that kin selection may not be the only explanation of cooperative courtship in this population. This research highlights the need for future studies that focus on how courtship behaviors may differ across subspecies and habitat types.