Research about California, Florida

USGS2019

Assessment of bird exposure to lead at Tyndall and Beale Air Force Bases, 2016–17

Soil contamination by lead (Pb) from past small munitions training on Beale Air Force Base, California, and Tyndall Air Force Base, Florida, may result in adverse effects for passerine birds that utilize the locations. A study was conducted during 2016-17 by the U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service and U.S. Air Force, at both Air Force Bases (AFBs) to assess the risk of bird exposure to Pb. Two different methods were used to estimate exposure. The first was analysis of blood and feather samples collected from birds captured on both AFBs, and the second was food chain modeling using data on Pb concentrations in dietary items (invertebrates and seeds) collected from both AFBs. Lead concentrations in blood and feathers for birds captured at Beale AFB indicate low exposure and risk; potential toxicity is possible based on blood and feather data for birds from Tyndall AFB. Food chain modeling utilizing dietary contamination indicates a risk likelihood of up to 35 percent at Beale AFB and up to 34 percent at Tyndall AFB. Lead exposure from incidental soil ingestion increased risk likelihood at both AFBs and is a significant uncertainty in this risk assessment. A companion data release for data collected during this project can be found at https://doi.org/10.5066/P92YXMQ2 .

California, Florida↗

USGS2016

Feline immunodeficiency virus cross-species transmission: Implications for emergence of new lentiviral infections

Owing to a complex history of host-parasite coevolution, lentiviruses exhibit a high degree of species specificity. Given the well-documented viral archeology of HIV emergence following human exposures to SIV, understanding processes that promote successful cross-species lentiviral transmissions is highly relevant. We have previously reported natural cross-species transmission of a subtype of feline immunodeficiency virus, puma lentivirus A (PLVA), between bobcats ( Lynx rufus ) and mountain lions ( Puma concolor ) in a small number of animals in California and Florida. In this study we investigate host-specific selection pressures, within-host viral fitness, and inter- vs. intra-species transmission patterns among a larger collection of PLV isolates from free-ranging bobcats and mountain lions. Analysis of proviral and viral RNA levels demonstrates that PLVA fitness is severely restricted in mountain lions compared to bobcats. We document evidence of diversifying selection in three of six PLVA genomes from mountain lions, but did not detect selection among twenty PLVA isolates from bobcats. These findings support that PLVA is a bobcat-adapted virus, which is less fit in mountain lions and under intense selection pressure in the novel host. Ancestral reconstruction of transmission events reveals intraspecific PLVA transmission has occurred among panthers ( Puma concolor coryi ) in Florida following initial cross-species infection from bobcats. In contrast, interspecific transmission from bobcats to mountain lions predominates in California. These findings document outcomes of cross-species lentiviral transmission events among felids that compare to emergence of HIV from nonhuman primates. IMPORTANCE Cross-species transmission episodes can be singular, dead-end events or can result in viral replication and spread in the new species. The factors that determine which outcome will occur are complex, and the risk of new virus emergence is therefore difficult to predict. Here we use molecular techniques to evaluate transmission, fitness, and adaptation of puma lentivirus A (PLVA) between bobcats and mountain lions in two geographic regions. Our findings illustrate that mountain lion exposure to PLVA is relatively common, but does not routinely result in infections communicable in the new host. This is attributed to efficient species barriers that largely prevent lentiviral adaptation. However, the evolutionary capacity for lentiviruses to adapt to novel environments may ultimately overcome host restriction mechanisms over time and under certain ecological circumstances. This phenomenon provides a unique opportunity to examine cross-species transmission events leading to new lentiviral emergence.

California, Florida↗

USGS2009

Estimating cause-specific mortality rates using recovered carcasses

Stranding networks, in which carcasses are recovered and sent to diagnostic laboratories for necropsy and determination of cause of death, have been developed to monitor the health of marine mammal and bird populations. These programs typically accumulate comprehensive, long-term datasets on causes of death that can be used to identify important sources of mortality or changes in mortality patterns that lead to management actions. However, the utility of these data in determining cause-specific mortality rates has not been explored. We present a maximum likelihood-based approach that partitions total mortality rate, estimated by independent sources, into cause-specific mortality rates. We also demonstrate how variance estimates are derived for these rates. We present examples of the method using mortality data for California sea otters ( Enhydra lutris nereis ) and Florida manatees ( Trichechus manatus latirostris ).

California, Florida↗