Research, part of a Special Feature on Effects of Roads and Traffic on Wildlife Populations and Landscape Function Large Gaps in Canopy Reduce Road Crossing by a Gliding Mammal

Roads and traffic reduce landscape connectivity and increase rates of mortality for many species of wildlife. Species that glide from tree to tree may be strongly affected by roads and traffic if the size of the gap between trees exceeds their gliding capability. Not only are wide roads likely to reduce crossing rates, but mortality may also be increased if gliders that do cross have poor landing opportunities. The road-crossing behavior of 47 squirrel gliders (Petaurus norfolcensis) was investigated in southeast Australia using radio-tracking. The proportion of gliders crossing one or both roadways of a freeway where trees were present or absent from the center median was compared to that at single-lane country roads (control). The proportion of gliders crossing the road at control sites (77%) was similar to the proportion that crossed one or both roadways at the freeway with trees in the median (67%), whereas only a single male (6%) crossed the freeway where trees were absent from the median. The frequency of crossing for each individual was also similar at control sites and freeway sites with trees in the median. The almost complete lack of crossing at sites where trees were absent from the median was attributed to the wider gap in canopy (50 - 64 m vs. 5 - 13 m at sites with trees in the median). This suggests that traffic volume, up to 5,000 vehicles per day on each roadway, and the other characteristics of the freeway we studied are not in themselves complete deterrents to road crossing by squirrel gliders. This study demonstrates that retaining and facilitating the growth of tall trees in the center median of two-way roads may mitigate the barrier effect of roads on gliders, thus contributing positively to mobility and potentially to connectivity. This information will be essential for the assessment of road impacts on gliding species using population viability models.

[1]  L. Fahrig,et al.  Movement Patterns of Eastern Chipmunks (Tamias striatus) Near Roads , 2008 .

[2]  H. Mader,et al.  Animal habitat isolation by roads and agricultural fields , 1984 .

[3]  D. Kelt,et al.  Influence of roads on the endangered Stephens' kangaroo rat (Dipodomys stephensi): are dirt and gravel roads different? , 2004 .

[4]  Miriam Goosem,et al.  Effects of tropical rainforest roads on small mammals: inhibition of crossing movements , 2001 .

[5]  R. Wayne,et al.  FAST‐TRACK: A southern California freeway is a physical and social barrier to gene flow in carnivores , 2006, Molecular ecology.

[6]  J. Gibbs,et al.  Relative vulnerability of female turtles to road mortality , 2006 .

[7]  C.J.F. ter Braak,et al.  The effects of car traffic on breeding bird populations in woodland. Ill. Reduction of density in relation to the proximity of main roads , 1995 .

[8]  R. Alkemade,et al.  The impacts of roads and other infrastructure on mammal and bird populations: a meta-analysis. , 2010 .

[9]  L. Fahrig,et al.  Effects of Road Fencing on Population Persistence , 2004 .

[10]  Andrew F. Bennett,et al.  Gap-crossing by gliding marsupials: thresholds for use of isolated woodland patches in an agricultural landscape , 2003 .

[11]  S. Laurance,et al.  Effects of Road Clearings on Movement Patterns of Understory Rainforest Birds in Central Amazonia , 2004 .

[12]  G. Holland,et al.  Time-budget and feeding behaviour of the squirrel glider (Petaurus norfolcensis) in remnant linear habitat , 2007 .

[13]  J. Tash,et al.  An Approach Toward Understanding Wildlife-Vehicle Collisions , 2008, Environmental management.

[14]  P. Sunnucks,et al.  Beyond roadkill, radiotracking, recapture and FST - a review of some genetic methods to improve understanding of the influence of roads on wildlife. , 2010 .

[15]  B. D. Taylor,et al.  Gliding performance and its relevance to gap crossing by the squirrel glider (Petaurus norfolcensis) , 2009 .

[16]  S. Burnett,et al.  Effects of a rainforest road on movements of small mammals : mechanisms and implications , 1992 .

[17]  G. Merriam,et al.  Barriers as boundaries for metapopulations and demes of Peromyscus leucopus in farm landscapes , 1989, Landscape Ecology.

[18]  M. McCarthy.  Bayesian Methods for Ecology , 2007 .

[19]  Thorsten Wiegand,et al.  Fragmented landscapes, road mortality and patch connectivity: modelling influences on the dispersal of Eurasian lynx , 2004 .

[20]  Lenore Fahrig,et al.  The relative effects of road traffic and forest cover on anuran populations , 2008 .

[21]  Thierry Lengagne,et al.  Traffic noise affects communication behaviour in a breeding anuran, Hyla arborea , 2008 .

[22]  Katharina Tluk von Toschanowitz,et al.  Predicting when animal populations are at risk from roads: An interactive model of road avoidance behavior , 2005 .

[23]  J. Perry,et al.  Road effects on abundance and fitness of Galápagos lava lizards (Microlophus albemarlensis). , 2007, Journal of environmental management.

[24]  M. Fenton,et al.  The Effects of Roads on Populations of Small Mammals , 1974 .

[25]  Norris L. Dodd,et al.  Traffic Volume Alters Elk Distribution and Highway Crossings in Arizona , 2007 .

[26]  Kylie Soanes,et al.  Research , part of a Special Feature on Effects of Roads and Traffic on Wildlife Population s and Landscape Function Evidence that a Highway Reduces Apparent Survival Rates of Squirrel Gliders , 2010 .

[27]  Rodney van der Ree,et al.  Road upgrade in Victoria a filter to the movement of the endangered Squirrel glider (Petaurus norfolcensis): Results of a pilot study , 2006 .

[28]  L. Fahrig.  Effects of Habitat Fragmentation on Biodiversity , 2003 .

[29]  A. Coffin.  From roadkill to road ecology : a review of the ecological effects of roads , 2007 .

[30]  L. Fahrig,et al.  Effects of Roads on Animal Abundance: an Empirical Review and Synthesis , 2009 .

[31]  Ruud Foppen,et al.  The Effects of Car Traffic on Breeding Bird Populations in Woodland. II. Breeding Dispersal of Male Willow Warblers (Phylloscopus trochilus) in Relation to the Proximity of a Highway , 1994 .

[32]  A. Claridge,et al.  Recovering endangered populations in fragmented landscapes: the squirrel glider Petaurus norfolcensis on the south-west slopes of New South Wales , 2004 .

[33]  L. Fahrig,et al.  Do small mammals avoid roads because of the traffic , 2007 .

[34]  C. Patrick Doncaster,et al.  Roads as barriers to movement for hedgehogs , 2002 .

[35]  Rob Roy Ramey,et al.  Highways block gene flow and cause a rapid decline in genetic diversity of desert bighorn sheep , 2005 .

[36]  R van der Ree,et al.  Overcoming the Barrier Effect of Roads-How Effective Are Mitigation Strategies? , 2007 .

[37]  D. Marsh,et al.  Effects of roads on patterns of genetic differentiation in red-backed salamanders, Plethodon cinereus , 2008, Conservation Genetics.

[38]  G. Nachman,et al.  Simulating viability of a spadefoot toad Pelobates fuscus metapopulation in a landscape fragmented by a road , 2002 .

[39]  John Winter,et al.  Importance of canopy connectivity for home range and movements of the rainforest arboreal ringtail possum (Hemibelideus lemuroides) , 2007 .

[40]  M. Crane,et al.  Longevity in wild populations of the squirrel glider Petaurus norfolcensis. , 2006 .