The worsening drought is beginning to affect the state's wildlife, drawing animals closer to roads and towns and triggering a big jump in calls to rescuers.

With all of NSW declared in drought, competition for grazing for kangaroos has intensified. Drying or dying trees have also cut the moisture available to marsupials such as koalas and possums, Christie Jarrett, vice chair of the Central West branch of the WIRES rescue service, said.

While farmers are often able to secure bales of fodder to keep their stock going, "wildlife gets the rough end of the stick" at times like this, Ms Jarrett said. "It's starting to affect animals more and more."

Based about halfway between Orange and Bathurst, Ms Jarrett's WIRES branch has registered a big rise in calls to treat kangaroos. So far this year, her team has rescued or had to euthanise 722 roos, up from 440 for all of 2016.

Drivers should pay special heed particularly at night as kangaroos gravitate to roadside in search of grass.