Radiotelemetry Survival Estimates of Lesser Prairie- Chickens in Kansas: Are There Transmitter Biases?

Radiotelemetry has provided wildlife biologists with a tool to estimate survival where fates of individuals likely are known. Analyses of known-fate data can yield accurate survival estimates if 5 assumptions are met. Two of these assumptions are rarely tested: that transmitters have no effect on survival of study animals and that right-censoring (i.e., any animal not located is as likely to be alive as dead) is random with respect to the survival of study animals. Using joint-models originally developed for live-encounter and deadrecovery data, we examined the potential for bias in survival estimates of radiomarked male lesser prairie-chickens (Tympanuchus pallidicinctus) in a 3-year study in southwestern Kansas, USA. Additionally, we examined the potential bias of right-censoring by comparing the return rates of known-fate and right-censored individuals. We captured 216 male lesser prairie-chickens and marked them with a combination of leg bands and a radio (n1⁄4 72) or leg bands only (n1⁄4 144). We applied joint-models to capture histories based on live-capture and telemetry data. The model best supported by the data indicated that 6-month survival was constant (Ŝc 1⁄4 0.679, SE 1⁄4 0.050) across radiomarked and banded birds. Eight of 16 (50%, SE 1⁄4 12.5%) right-censored birds not detected because of radio failure were subsequently recaptured, which was not different from the return rates for known-fate birds (23 of 59; 39%, SE 1⁄4 6.3%). Survival estimates of male lesser prairie-chickens in this study were not measurably biased by radiomarking, as their survival was greater than or equal to those of banded birds, and right-censored birds had similar return rates to those of known-fate individuals. Our results are encouraging because they indicate that 2 critical assumptions underlying analyses of known-fate data can be met with radiotransmitters and attachment techniques currently used in field studies of wild populations of lesser prairie-chickens. (WILDLIFE SOCIETY BULLETIN 34(4):1064–1069; 2006)