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. 2019 Feb 20;14(2):e0210180.
doi: 10.1371/journal.pone.0210180. eCollection 2019.

Long-term history of vehicle collisions on the endangered Nēnē (Branta sandvicensis)

Christopher A Lepczyk  1 , Jean E Fantle-Lepczyk  1   2 , Kathleen Misajon  3 , Darcy Hu  4 , David C Duffy  5
Affiliations

Long-term history of vehicle collisions on the endangered Nēnē (Branta sandvicensis)

Christopher A Lepczyk et al. PLoS One. .

Abstract

Millions of birds in the United States die annually due to vehicle collisions on roads. Collisions may be of particular interest for species of conservation concern, such as the endangered Hawaiian goose (Nēnē), which is endemic to Hawai'i. Using a nearly 40-year dataset of Nēnē road mortality in and around Hawai'i Volcanoes National Park, we sought to answer the following research questions: 1) has Nēnē mortality changed over time? 2) are there times of the year in which mortality is greatest and does it relate to specific events in the species' lifecycle? 3) does age at mortality differ over time, space, or sex? 4) given that existing mortalities appear to occur only in certain locations, do the number of mortality events differ across these locations; 5) does mortality rate show any density dependence? and, 6) are mortality rates related to numbers of visitors or vehicles? Between 1977 and 2014, a total of 92 Nēnē died from vehicle collisions; while absolute mortality increased over this time, the mortality rate remained the same. Similarly, average age of mortality increased over time, but did not differ by location or sex. Between 1995 and 2014, Nēnē population size and mortality rates were not correlated. Mortality was greatest in November and December (breeding season) and lowest in June. Most of the mortality occurred along just three stretches of road in and around the park, with the number of mortalities split about evenly inside and outside of the park. Furthermore, Nēnē mortality was unrelated to the number of visitors or traffic volume in the park. These findings suggest vehicle collisions are a growing concern for Nēnē, but that management actions to reduce mortality can be targeted at specific road segments and times of the year.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Hawai‘i Volcanoes National Park (HAVO) study region with major road segments.
Fig 2
Fig 2. Annual Nēnē mortality due to vehicles from 1974–2014.
Fig 3
Fig 3. Monthly Nēnē mortality summed over the 40-year period.
Fig 4
Fig 4. Age of Nēnē at time of mortality.
Because not all goslings could be aged to exact month we considered them all 0.5 years old.
Fig 5
Fig 5. Age of Nēnē at time of mortality compared to year when mortality occurred.
Fig 6
Fig 6. Total Nēnē mortality by road segment within the park and location of the segment inside or outside of the park.
Road segment lengths (km) are denoted above each bar.
Fig 7
Fig 7. Locations of Nēnē vehicle strikes.
Fig 8
Fig 8. Nēnē population size versus vehicle-related mortality.
See this image and copyright information in PMC

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