Chad Wilhite | USGS Science

USGS2026

Mortality in the Hawaiian Short-eared Owl (Pueo, Asio flammeus sandwichensis): Causes and spatial trends

Trends in wildlife mortality can be particularly challenging to identify in low-density species where mortalities are less likely to be detected or documented. The Pueo, or Hawaiian Short-eared Owl ( Asio flammeus sandwichensis ), is the only native raptor that breeds on all the main Hawaiian Islands. The Pueo is state-listed as endangered on the island of Oʻahu, but drivers of population dynamics are not well known, including causes of mortality. In this study, existing records from organizations across the Hawaiian Islands were compiled to evaluate the causes of mortality in Pueo. Here, 242 unique records spanning the years 1993 to 2024 from state, federal, and private organizations were evaluated for causes of Pueo death. Trauma due to collisions with vehicles, wind turbines, fences, and other human-made objects was the leading detected cause of death (62%) followed by emaciation (13%) and disease (6%), with 19% of deaths due to unknown causes. The islands of Hawaiʻi and Kauaʻi, both with relatively low human populations, had the highest total number of reported mortalities (n = 77, 32%). The highest number of recorded mortalities was in the month of July (16%), and mortalities were generally higher from June through August. Although our study has detection biases, our results are consistent with global studies suggesting that blunt force trauma from vehicles, wind turbines, and other infrastructure are potentially important sources of mortality in raptors. Similar to other studies, rodenticide effects and infectious disease were potentially underestimated as sources of mortality, because most birds did not undergo a full necropsy. Further, there may be confounding variables due to ad hoc data collection. Development of a state-wide system for reporting and recording wildlife mortality along with future studies that include necropsies may improve our ability to discern which sources of mortality may be mitigated.

Hawaii↗

USGS2024

Desert Tortoise translocation plan for the U.S. Department of the Army National Training Center and Fort Irwin Western Training Area

The U.S. Department of the Army proposes to commence military activity at the Fort Irwin National Training Center within the Western Training Area (WTA) and to translocate Mojave Desert tortoises ( Gopherus agassizii ; hereafter tortoise) that will be affected to the Western Training Area Translocation Site (WTATS). This desert tortoise translocation plan provides a timeline of activities, actions for which permits may be required, and guidelines for assessing the short-term and long-term success of this desert tortoise translocation. Importantly, the monitoring projects described are designed to document the ultimate effects of the Army's translocation action (not just inform future translocations elsewhere). Results from the translocation, corresponding monitoring, and research projects will inform future translocations throughout the Mojave Desert for expanding human development. The plan has three main objectives: (1) provide guidelines to achieve a safe, humane, and successful translocation of tortoises from the WTA, with minimal effect to resident desert tortoises at sites where translocated animals are released (recipient sites); (2) study translocated, resident, and reference animals (tortoises living near translocation areas but whose home ranges do not overlap those of translocated or resident tortoises) to learn as much as possible about the ecology, conservation, and management of the desert tortoise; and (3) define best management practices for successful translocation and provide metrics to evaluate success over multiple time scales, which we identify for the short- and long-term. The procedures to plan, implement, monitor, and study translocation of tortoises were written using terms and conditions outlined in the U.S. Fish and Wildlife Service Biological Opinion 2021 that described effects of the expansion of the military base boundary, as well as recommendations provided in the Desert Tortoise Recovery Plan (and 5-year review). We provide guidance on appropriate translocation timing and procedures, as well as on how tortoise ecology and habitat can best be studied to further knowledge on tortoise translocation. The plan provides analysis for landscape tortoise density and abundance estimates, suitable sites for translocation of tortoises, and short- and long-term metrics that are addressed and measured by specific monitoring and research projects that can be used to assess the success of translocation activities.

California↗