Assessing physiological, behavioral and movement responses to Suprelorin implant delivery methods in free‐ranging eastern grey kangaroos <i>Macropus giganteus</i>

Overabundant populations of eastern grey kangaroos Macropus giganteus in peri‐urban areas pose ecological and social challenges. Current management strategies are often hindered by animal welfare and logistical concerns. This study aimed to assess stress responses of kangaroos to two contraceptive delivery methods. We assessed physiological and behavioral responses of females treated with Suprelorin (deslorelin acetate) implants delivered remotely as an alternative to the traditional capture‐treatment method. Sexually mature females were assigned to one of three groups: SC (4.7 mg implant via subcutaneous injection after capture), Dart (4.7 mg implant remotely via dart), and Control (no treatment or capture). We used a before–after control–impact framework to quantify stress‐induced response to both methods through assessment of changes in behavior (which may also indicate pain) and fecal glucocorticoid metabolite (FGM) concentrations. Additionally, we assessed changes in movement patterns using GPS collars. No significant changes in FGM concentrations, behavior or movement were detected across treatments or time periods. During the treatment window (5–9 April 2018), the Dart group displayed a temporary reduction in step length while the SC group shifted from nocturnal to crepuscular activity, with both groups returning to pre‐treatment patterns after the treatment window. The SC group showed weak evidence of increased vigilance and decreased grooming throughout the treatment window, though individual variability was high. Remote dart delivery avoids risk associated with sedation and capture and imposes fewer behavioral disruptions, presenting a safer alternative for administering injectable contraceptives to kangaroos in a peri‐urban area. Therefore, remote delivery offers a less invasive, more welfare‐friendly and practically advantageous option for managing overabundant populations. Future research should enhance the utility of remote delivery by addressing logistical challenges (e.g. identifying treated animals) and evaluating efficacy in other species. Adoption of remote delivery contraceptives in wildlife management policies could enhance ethical and practical management of overabundant populations.