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Surgically implanted transmitters are a common method for tracking animal movements. Immediately following surgical implantation, animals pass through a critical recovery phase when behaviors may deviate from normal and the likelihood of individual survival may be reduced. Therefore, data collected during this period may be censored to minimize bias introduced by surgery‐related behaviors or mortality. However, immediate post‐release mortalities negate a sampling effort and reduce the amount of data potentially collected after the censoring period. Wildlife biologists should employ methods to support an animal's survival through this period, but factors contributing to immediate post‐release survival have not been formally assessed. We evaluated factors that potentially influenced the immediate post‐release survival of 56 spectacled eiders (Somateria fischeri) marked with coelomically implanted satellite transmitters with percutaneous antennae in northern Alaska in 2010 and 2011. We modeled survival through the first 14 days following release and assessed the relative importance and effect of 15 covariates hypothesized to influence survival during this immediate post‐release period. Estimated daily survival rate increased over the duration of the immediate post‐release period; the probability of mortality was greatest within the first 5 days following release. Our top‐ranking model included the effect of 2 blood analytes, pH and hematocrit, measured prior to surgical implantation of a transmitter. We found a positive response to pH; eiders exhibiting acidemia (low pH) prior to surgery were less likely to survive the immediate post‐release period. We found a curvilinear response to hematocrit; eiders exhibiting extremely low or high pre‐surgery hematocrit were also less likely to survive the immediate post‐release period. In the interest of maximizing the survival of marked birds following release, hematological data obtained prior to surgical implantation of telemetry equipment may be useful when screening for optimal surgical candidates or informing appropriate response to mitigate potentially deleterious disorders such as acidemia. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

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Stress and physical exertion may affect the physiology and behavior of wildlife during and after capture, and consequently, survival following release. Such effects may reduce the quality and quantity of the data obtained from captured wildlife. We captured spectacled eiders (Somateria fischeri), a species listed as threatened under the United States Endangered Species Act, in western Alaska, USA, during spring 2018 for surgical implantation of satellite transmitters. We evaluated the efficacy of midazolam, a benzodiazepine sedative given at capture, to reduce stress and physical exertion. We dosed spectacled eiders with either midazolam (5 mg/ml, true x ¯ = 2.2 mg/kg intramuscular; n = 20) or saline (0.7 ml intramuscular; n = 20) at the point of capture. We assessed sedation level and collected blood samples upon arrival to the field surgery site and at anesthetic induction. We found that midazolam reduced mean corticosterone concentration by 29% and median lactate concentration by 30.3% at the mean arrival time (42 min post‐dosing) relative to the control group. These effects had abated by the mean induction time (99 min post‐dosing). Unexpectedly, blood pH was reduced in the midazolam treatment relative to controls at both arrival and induction, which likely resulted from sedative‐induced respiratory depression that was easily treated with intubation and mechanical ventilation, and administration of the reversal drug, flumazenil. Low blood pH was not associated with negative post‐surgical outcomes, as had been found in spectacled eiders with acidosis caused by anaerobic metabolism typical of physical exertion. Intramuscular injection of midazolam in the field effectively reduced stress and physical exertion in spectacled eiders prior to surgical implantation of transmitters. © 2021 The Wildlife Society.