Roads are one of the most severe threats to wildlife globally because of their pervasive and linear nature. Despite considerable attention afforded to road-effects on animals generally, little information is available concerning the specific impacts of road widening, also known as twinning or highway expansion. To address this gap, we monitored the abundance and distribution of large mammals adjacent to an 18-km section of highway in Ontario, Canada, that underwent expansion from a two-lane to a four-lane, divided highway, over 4 years. We expected to observe an initial decrease in large mammal track abundance and an increased distance from the highway, followed by a period of habituation during which track abundance and proximity to the highway would return to baseline levels. To quantify the effects of highway expansion, we monitored snow-tracks of three ungulates, two felids, and three canids on transects extending perpendicular and parallel to the highway. Our analyses revealed that proximity was species-specific and varied seasonally, but we found little evidence that the new four-lane highway alignment affected the movement ecology of large mammals in our study area. Limited increases in traffic volume could partially explain why we detected no change; however, traffic volume will rise. Although road widening is common for accommodating increased traffic volume, no studies have explicitly investigated its effects on animal movement ecology. Our findings suggest that increasing the footprint of existing roads, rather than building new roads, may be a suitable solution for accommodating increasing traffic with minimal impacts on adjacent large mammal communities.

道路由于其普遍性和线性性，是全球对野生动植物的最严重威胁之一。尽管通常对动物的道路影响给予了相当大的关注，但是关于道路拓宽（也称为孪生或高速公路扩张）的具体影响的信息很少。为了解决这一差距，我们监测了加拿大安大略省高速公路18公里段附近大型哺乳动物的数量和分布情况，这些哺乳动物在4年中从两车道扩展为四车道。我们预期会观察到大型哺乳动物的足迹丰度开始减少，与高速公路的距离增加，然后是一段习惯化时期，在此期间，足迹丰度和与高速公路的接近程度将恢复到基线水平。为了量化公路扩张的影响，我们在垂直和平行于高速公路延伸的横断面上监测了三个有蹄类动物，两个猫科动物和三个犬科动物的雪道。我们的分析表明，邻近性是特定于物种的，并且随季节而变化，但我们几乎没有证据表明新的四车道公路路线影响了我们研究区域内大型哺乳动物的运动生态。流量的有限增长可以部分解释为什么我们没有发现变化。但是，流量会增加。尽管拓宽道路是适应交通量增加的普遍做法，但尚无研究明确研究其对动物运动生态的影响。我们的发现表明，增加现有道路的足迹，而不是修建新道路，